I. MEJ!ASOMATIO PHO'M)R%OQTORS A I D 'PHlSIR PROPSRTIB8

A. tooaliaation of the photoreoeptorr

When l i g h t re8 ohone on the netaroma, there war oonmiderc

able eleotr ioal a o t i r i t y e l io i ted i n the ventral nerve oord

i n the neroromatio xvgion, Thir responme t o l i g h t per r i r ted

even when the outiole of the metasoaa war rmoved and the nerve

oord was isolated from the animal showing that the nerve oord

i s direat ly sensit ive t o l igh t , To looal ise the region of

photosensitivity, i n the ventral neme aord, the e lea t r ioa l

aot ivi ty war reaorded from the exposed ventral nerve aord subjeoting

different regions of i t to illumination separately, The ventral

nerve oord of raorpion o o n s i r t ~ of a ahain of seven f ree abdominal

ganglia of whloh the f irst three are lodged i n the memoromr and

the r e s t f ~ u r i n the metaaoma (Big, 1). I t was evident that the -- - _- --- abdominal g-lia i n the metasomatlo region, e ta r t iag from the

fourth t o the eeventh ganglion are photo~ensit ive. I n addition

to t h i s , the telsonio nerve6 whiah merge from the last

abdominal aanglion and i n n e n e t e the s t ing apparatus were a l r o

found to be photoreoeptivs, An attempt was made t o fur ther

examine whether photoreaeption i s oonfined t o m y one p a r t of the

ganglion, For t h i s purpose, the l e f t and r ight halve8 of the

ganglion were illuminated separately using a narrow beam of

l i g h t of threrhold intensity. The other half of the ganglion

whioh was not illuminsted was oovered we11 with blaak paper to

prevent any r t ray l i g h t from reaohing tha t part , The s ixth

? 8 X r a r u mhordng the r o r p h o l o ~ ~ of the o.ntral

nortourn my.*- (After Babu, 1965).

abdominal cFne_lion war releoted fo r thir -purpore r inse

i l l u r i n a t i o n of this g-lion very often yielded gead responses

oorpared t o other grrnglia i n the roorpion 4. f u l v i ~ e r I whioh

w u used f o r t h i s rtudy, ?he 8o t iv i ty w8r reoordeb from both

wore found t o be mort clonveaient f o r plaaing hook eleotroder, I t

war obrerved t h a t both the l e f t and right halve0 of the g.aglion

oould evoke a o t i r i t y i n the vent ra l nerve oord on photio

stimulation, l o r i g n l f i o m t differanoe war observed i n tho

threshold in tens i ty required f o r exoi tat ion of the two halves of .

the ganglion, But i t oan be r i r u a l i s e d that the above method,

although l i m i t s the general rurfaoe area o f ' t h ~ ~ gazqglion exposod

t o l ight , doer not prevent the l i g h t from rerahing other p a r t s

of the ganglion due t o i n t e r n r l re f leo t ion wlthin the t issue.

Therefore, e f f o r t r were rade t o i ~ o l a t e the ' t l o halve8 of the

ga.nglion by making a ve r t ioa l inoir , ion using a f i n o roalpel,

One half of the g m i o n w8r expored t o light m d the other half

was eiaher oovered rrith a s t r i p of - b l a ~ k paper parlring i n between- . .

the two reparated halves o r ~ o m ~ l e t ~ ~ ieol8ted and removed from

the nerve oord. lhim very of ten resul ted -ia oomplete reduotion

of a l l ao t iv i ty i n the vent ra l nerve oord. However, from few

ruooersful greparat ionr , i t war evldqnt that both the l e f t and .- right halroe of the ganglion our e l i o i t a o t i v i t y i n the~ vent ra l

nerve oord, Thlr a l s o &re8 an indioat ion that there may be more

thur one photoreoaptor unit wlthln 8 ganglion. During tho oourme

of the l8t.r rtudy alrs two m d on one oooamion three primary

neuronr oould be rpotted i n the ventral norre oord on

i l l u l n a t i o n of a a i q l e photomenritive ganglion i n a prep*

ration, Although tho ex8at aumber of the primary reoeptor

neurons preaont i s not very olear, i t a8n be raid tha t there a re

a large number of them w i t h a minimum of ten i n the ventral

nerve cord of soorpion, Boon i n arayfish reoent s tudier

indioated the preaenoe of a number of primary photorensit ire

neuronr ( ~ i l k e n a and Larimer, 1972). The photosenaory neurons

i n orayfish are a l so known t o be dis t r ibuted i n both halves of

the nerve cord (~eanedy, 19638), The telaonia nerves of

soorpion were found to be sensi t ive to l i g h t a l l along t h e i r

length a tar t ing from imed la te ly por ter ior to the seventh ganglion

upto and inoludiag the t e l roa where they a re known to ramify

(Babu, 1965). This aleo ahor8 t h a t the te3roaio aerves themaelves

ore aenr i t iv r t o light and the rasponses enoountrred a re not due

t o in terna l refleation, The l a t t e r poaaibi l i ty would apply i f

illumination of the telaonia nerves immediately pos ter i s r to the

reventh ganglion alone were t o evoke rerponaes w h l & i s not true.

The above studiaa were repeated i n s , f u l r i ~ e r 11 and

4. ,gravimmus, The resultr of these studiea did not d i f f e r

from the previour findings. But rome differenaer were obaervad

i n the r e l a t ive aena i t i r i ty of the photorearptive regions i n

different aninalr,

Photorooop tor r e n r i t i r i tx

Pho ra la t ive r e n e i t i r i t y of dif ferant region8 within the

motarona in tennr of the thrashold l n t s n r i v roquired f o r

oxoitation wee, found t o d f f fa r i n a given animal, 2he threshold

in tenr i ty mosruremontr were madm by reoordiag the oleoOrioa1

aot iv i ty from 2-3 oonneotiver In animals dark adapted f o r reveral

minuter (20 to 30) a f t e r oaoh t e s t flarh, Tho re la t ive r e n r i t i r i t y

of a given region war oleo found t o notably d i f fo r i n d i f farent

anlrnrlr, The r ix th abdominal grurglion and aometimea the f i f t h

ganglion ware found t o be most often more r e n s i t i r e than the

other regions i n the roorpion f u l v i ~ o 8 I. I n oontra8t to th ia ,

the teleonio nerves were found t o ba most r e n s i t i r e to l i g h t

i n Che soorpion 8, grarimanur, The data i 8 prerented i n ?able 1,

It oan be reen tha t i n 8, f u l v i ~ a g (11) the to l ronia nerve8 a re

a l r o quite sens i t ive t o l i g h t unlike i n g, f u l ~ p o r (I), but

them 18 no oignlfioant difforenoe i n the r o n r i t i r i t y of t h r

ganglionio rogionr usd the te l ronlo reglon, Howoror, i n a l l there

animal6 studiod, the fourth abdominal g w l l o n mr found t o be

l e a s t ren8i t ive and r e l a t ive ly higher in tene i t ios warm roquirod

fo r exoitation,

It war a lso obrorved that the threehold in tens i ty required

to stimulate a given region varied within a rsnge from proparation

to preparation, 3omo preparations relrponded very well a t

oonridorably low i n t e n r i t i o s rrhilo higher i n t e n r i t i e r WON

raquired f o r roma proprraOionr. Alro, monitoriag the a o t i r i t y

from thare photoreoeptorr rrr not alwayo suooeoaful i n a l l

0.- r h o d a g dlifaraaaor i n Um rm8itIrit)r e i a e nt-

aaulrr plotom-tom i n diffarcrat 8paoiar of raorpion.

Vrluar indiarta tha poror~rtyo of Ilriralr wharo 8 throrhold

intrrrmity of 33 lux or la88 rrr roqwirad. - indiartor

higher intsnrit ior nlro required Tho n r u l t r .ru i ror r

tota l o i 45 rith 15 be&@-- to arab amup. Tha

raluar are oarraotad to tho naammt *ole ntmber,

8.10. S i t @ of rtimulation Abdorinal g8ngli8 'JCelronio --- a a m

p n p a r a t i o m . I n view of thir and i n view of the f ao t t h a t the

l e v e l of rpontaneoua e l e o t r i o r l ao t iv i ty i n the ventral nerve

oord of roorpion exhibi t8 a oiroadion rwth (1~80, 19641

Ve~&ataohe* 1971), i t war thougbt t h a t the time of the day

m q be playing an important ro le i n deteminlng the s e n s i t i v i t ~ of

there reoeptors. Moreover, oiroadian ohmgae i n the r e n s i t i r i t y

of the median and l a t e r a l eyes of the r o o q i o n Androotonur

her been raoently reported (Ple i r rner , 1968, 1972). H e n the

r e n s i t i v i t y was found t o inoreare by 3 t o 4 log unit8 i n the

eve-. The p o r s i b i l i t y of r e f l e c t i o n of a oiroadian rhythm

i n this reoeptor ryetern war exmined by measuring tho threehold

in tens i ty required t o e l i o i t response from t h e 6th abdominal

ganglion a t d i f f e ren t time i n t e r v a l s (Table 2). The time period

shown i n the t ab le denotes the time of dlaeeation. Observations

were made onoe the animal war prepared and t h e photoreoeptor

neuron8 were looated, not giving muoh time f o r de te r io ra t ion of

the preparation, beoaune the threehold in tens i ty war o f t en found

t o inorease i n old preparations. S imi la r deoreaae i n the

s e n s i t i v i t y with time ha8 been reported f o r the exoised o o e l l i

of Linulur (Barlow and Waglon, 1971).

A s i t i s er idsnt from t h e t a b l e ( l a b l e 2) , no oorre la t ion

wa8 observed between the time of the day and the e x o i t a b i l i t y

of the photoreoeptors. Howevar, tha tedmlque involving the

use of chroniaally Implanted eleotroder simllar t o that anployed

by f y l o r (1970) f o r studying the a m d t i v i t y ahanger i n t h e

oreyfiah internouroar would be desirable ,

Dat. rhodng photonoaptor rrnritirity a t dlffarant t i re inbrrcrlr

of the day in 4. I. Ntuber~ ahow the peroen$ye of

I n i r l l 8 . A t o t a l of LOO miram warm ured, a0 at @.ah time

intern1 shoran. Boluas i n braohrts iadloate $he lowart l ram hold

intardty required tn Luxr

Tluarhold TSme of the b~

0. Blra t r iaa l a o t i r i t s i n the nhotorraeptor nruronr

Ihr o leot r ioe l a o t i r i t y of the phot orroeptor nruronr war

reoorded from the ganglia as we11 ar from the oonneotiver and the

1, Pat te rn of rrsponrer t o liah*t

Spontaneous a o t i r i t y undrr oontinuous darkners war

obrened i n about 506 of tho photoreoeptor u n i t s r tudled (Big. 2) ,

Thia upontaneour a o t i r i t y i n the dark oould be obaemed i n the

in tao t nerve aord a r well as when the nerve aord war oompletsly

i ro la t rd . The u n i t s were deaided to be primary photoreaeptora

since applioation of drugs l i k e niootine d i d not abolish the

responses, Moreover, the reeponre aharsoter i s t ior inoluding f the f rrquenoy of d i aoharge were wore oonsi s t en t on repeated

rtimulation unlike i n the interneuronr where the r6spon8as ware

found t o be more lab i le . One of the units (Pig. U) dlsaharged

rrfth a nearly uniform r a t e of about 4 impulses/are, Sometimes,

8 rhythm10 a c t i v i t y wherein periods of a o t i r i t y a l t e r n a t e rrlth

r i l e n t phames was obsrrred (big. 28). However, few u n i t s appeared

t o be s i l e n t i n the abrenoe of photio input. On il lumination,

tonio a o t i r i t y was e l i o i t e d (pig. 3) whish often pr ra i r t ed through-

out the prriod or i l lumination whijh I a r t e d f o r two or mom

recondrr. Suoh u n i t s i n whiah the a o t i r i t y inoreared with t h e

onret of l i g h t may be ra id t o give an "onw response. I n oontrast

to th ia , them war a o t i t i t y rvoked i n a receptor u n i t rsith t h e

Pig. 2: 8pontanoou8 r o t i t L t y i n p h o t o n w p t o r nouroru

from i r o l r k d n o m oord.

At U n i t r i t h noarly unifonn bisohar#o fnqfronojr

i s o l a k d f r o m tbo l o f t tolmonio norr..

P): U n i t oxhibi t ing q i k o a o t i r i t y d t h a l t o m a t i n g

a i l a n t phaser loaatod in tho 4 e abdorizaal

gur(lli0n.

Tinet 0.5 8.00

Pig. 3: Romponnor of a i l a t photozaooptor a w r o a r looatod

i n tho 6- rbdoninal &-lion (A) and the 4$h

abdominrl -lion (B) t o p h o a o 8 t i m u l r ~ o n .

P i . 4 W O f f W roarpanee f r o m a r i l o n t photoroooptor ual*

from the 6- abdorinr l g w l i o n .

!Elrot 0.5 8.0.

oarra t ion of the p-santed light s t i r u l u r (big. 4). Thir type

of raoponsa o8n be oal lad 88 tha wof iw reapoxma a8 daaoribad by

E u t l i n a (19%). R a a p t o r units which wera q o n t m e o u ~ ~ ao t l r e ,

axhibite6 4 tonio inoreare i n the frequenoy of ptllrar with photio

r t imulat ion (Pig. 5). Ona u n i t war upontaneoualy dlsoharglng

with a frapuenoy of about 5 irpu18a~/reo. The unit a t ta ined a

maximum frequenay of about 1 2 i.pulros/aeo. about two s%oonds

a f t e r the o m e t of. l i g h t (Pig. 5) The frequenoy of disoharge

gradually ilaoreared ead reaohed tha o r ig ina l l eve l about 5.5 raoonds . l a t a r .

It was alsa obaelme'b tha t the photoreaaptor neurons of ten

exhibited a tandenay t o disoharge i n t h e fonn or doublets 'on

photia r t imulat ion (Bigrr. 3, 5, 6 and 7). One photoraoeptor unit

looated i n the rerenth g a w l i o n was found t o disoharge spontaneously

with a frequenay of about 3 spiker/seo. ( ~ i g . 6A). This a o t l r i t y

aonsisted of s ingle spikes. It was in t a r e s t i ng t o note ' tha t the

un i t began t o diaoharge i n t h e fonn of doublet6 when one of the

h a i r s on the te laon was moved forwards ( ~ i g . 6B) a s we11 a8 when

r t lqu la ted w i t h l i g h t ( ~ i g . 60). The me- frequmoy of spikes

inoreared t o 5/sea. on t a o t i l e s t imulat ion and near ly 4/8e0. on

photia stimulation. It was observed tsat these doublets oannot

be a l i o i t e d when the unit was l ight ad;erpted.. SonJeevo RedQ (1969)~

during hlr s tud le r on t he t a o t i l a h a i r s on the te laon "- ~ o n c l ~ ~ i ~ o i ~ demonstrated that the .if a ran t neuronr f I

t o l roa io hairs terminate i n the 7th ganglion whare thc

Pi(. 58 Bompoaro of a mpostur.ou.l~ r o t i v a photoroaaptor

uait fror tho 5- abdominal ganglion t o pho.4io

r t i r u l r t i o n . Booor4 B i r oonUnurtion of A.

68 Boaponrar of a rpontaaooumly a o t i r o photoma8ptor

unit f r o m tho 7 t h abdominal 6 u l i o n t o aocahaalorl

mad phot ia rtiruli. 'Pho uni* rpoat.naou8l.y bir-

ahrrgod rin&e mpikor 110 the dark (A) . md in

the f o r r of doublet8 on r o e h u r i o r l r t i r u l a t i o n o f

8 hair on -0 tol-n (B) urd a l r o oa phat io

r t i r u l a l i o n (a). There war ur in i t ia l b u r r t of

rp ikar on rovwreat of the hair.

FIG. 5

-

P i g . 78 Itmrpen80r of r photonoaptor unit (-80 maen %n

P i g . 3) $0 inolrrr8Ing inton8itima of l ight .

Eotm *at tho latonay of roopoara doororma8 and

dimehargo iraqumnqy inorarmor with in8roaro i n

the light intonmity i n waomrsirm roaordm. Alao

not* that athor unit8 u o mxoitod rt highar

i n t a n r i ~ . . m f l i ght .

Pig. Ua Omh ahowing th. r o b t i o n botwo81a -a iPtm.i$y

of U&t and $ha lat.noy of ro.polrma o i photo-

roorg tor unit.

?is. 8 B r O r r p h rhowin( *ha ralat ion batraoa tho intondty

mad duration of li&t mtirulua -ah o m o l i o i t

rampon80 f r o m a photenaeptor unit.

Both obmomtioam ware fmm tha unit moan in

Piguse 7.

Pi(. Wr Qrrph a h o w tho rolrtioa betwoon Wo b t e ~ i 8 y

of light and the r e u l froquoney of d i rahu(a in

8 r i l o n t photoroaoptor mlt 1oort.b i n the 6th

abdominal mi-. 2he l i gh t r t i r u l u r laa tod f o r

10 reo, The n o m froquonoy of diroharge 2 roo.

a f t o r tho i l r i$ i r t ion of a a f i r i t y was noarurcrd

over r poriod of 5 800.

Pig, 9Ba Graph rhoring me ro l r f ion betwe= the intomi*

of l i gh t r t i r u l u r m d the maximum fraqueaoy of

diroharge i n tho s a e pho$oruoeptor u n i t i r o l r t e d

i r o n a0 6ah ganglion.

P i g . 108 Iamponra f ror a d l e n t photosooeptar? naurra

irolatad fror tha 5- abdominal g-liaa t o

photio rtimuletion showlng adaptation to light.

. Eota the gradual dearorre i n bho dirthrrga

ire quanoy.

Pig. 11: Orrph rhoring tbe ramponre o f a epontmaou.ly

aotive photonoaptor unit IsolaPed iron tiha

7- (mglion to light and mubraqueat adaptation

t o light. Tima u i r indioatar Ohe t i r a r i t a r

tha in i t ia9 ion o f Uat atirulur. Light ramulur

laotad far 7.5 8.0.

Pig, 128 8pootral monaitiri~y of ra.trraomatio pho*

raeep0orm, Tho aurvea rra nomalimed by

rottiag the point rt 568 nr equal to 100. Ihe

r a x l m u m mlrponmo i s neaarrod i n tanra of Oh@

r.iriaur dl.ahrrge imqwnoy. 8ensitirifq i o

a e n d p r a o a l of $he threohold intonalty.

The valuer rapresent tho reur 2 8. D. of 14

d.t.rmbaationae

r o t i r l t y i n unitre More in te res t ing was the burst pa t te rn v e y

often notioed i n the photonaeptor interneurons (pig. 17),

gighly pat terned burst ao t iv i ty was more oomr~only seen i n un i t s

igolated from 2-3 a d 4-5 oonneotives, It oan be notioed from

the reoord (big, 17B). that the number of m i k e s i n a burst varied

frola 23 t o 33 with the buret a*athdL varyirrg between 250 to 350

mseo, The i n t e r b u r s t i n t o n a l ( l r t #pike of one burst to the 1st

spike of the next buret) varied from 0,82 to 1,g reo, There

did not appear to be any oorrelat ion between the burst duratAon

o r t h e number of epikea i n a burst and the in te rburs t in t e rva l ,

The unit a o t i r i t y was aleo aharaoterised by an interesting

in t raburs t pa t t e rn (Pig. 17C). The burs ts were always preoeded

by a l a rge spike, The i a t e r r p i k e in te rva l within a burst a l so

varied oharaoter iet ioal ly , The in te rva l s were shor ter during the

initial bur r t period, ranging from 1 2 to 1 3 in te rva l s and

gradually inoreased thereaf te r , The l a s t i n t e r v a l was o f t en the

l a r g e s t ranging from 20 t o 60 mseo, This i s very muoh s imi lar

t o the buret a o t i v i t y reported i n the Pal-B neuron of the

eartropod Heliasma t r l r o l r i s recently ( ~ a t e r end Kaneko, 1972).

The burs t r o t i v i t y i n t h i s Pal-B neuron which could be modulated

by photio, t a o t i l e 'and other in#uts was aleo oharaoterised by

rhort in$errpike in te rva l s during the in i t ia l burs t period and

i n t e n a l e of inoreasing duration during the r e s t of the burs t

period, The number of spikes i n the short i n t e r v a l phase was

-1.r than i n the l a t e r p a r t of the burs t 88 notioed i n the

rerent exmple. The p a t t e r n of a o t i v i t y i n t h i s neuron ahanged'

Pi&. 16: Unltr exhib%tlng irregular ro t iv t tp with rafasmoe

t o m i k e irequonay rr well 8 8 the apiko intarvale

A: Butrrt ro$ ir i ty i n a unit d t h about 5 rplkerr/

burrt,

B: Buret aoti.rity i n a unit rl th about 23 bo

35 rpikse/burst,

a: Reeord t o ahow tho rpika prttenr in a mingle

burrt irr tha unit roen in reoord 0).

on rt i .ul8tion ( roe p. 6 4 ) It 18 l ikely tha t ruch unit.

exhibiting patterned a o t l r i t y , i so la ted from the 2-3 end 4-5

oonneotiter a r e lower-order interneurons beoause, s tudies on the

aentral oourse of the photorvoeptor u l t e grerented l a t e r

(p, 64 ) ahowed that a number of photoreosptor un i t s terminate

i n the 3rd and 4th abdominal ganglia, It has been dieoursed tha t

the lowe-order neurons are aharaoterired by patterned a a t i r i t y

ra ther than the higher-order interneurons whioh tend to exhibit

a random aot iv i ty (Horridge, 1968). However, &ether t h i r

8 o t i r i ty i r from lower-order interneurons o r more oentra l neurons

ouulot be deoided unlesr ao t iv i ty 18 6imultaneously reoorded from

uoaeesive levels , sinoe the spatial looation may not r t r i o t l y

e f l eo t th? functional hierarohy of these neurone,

B, Responses of ~ o n t a a e o u a l u inao t i r e interneurons

About 60$ of the interneurons studied were found to be

pontaneously inaotive. Three types of unit8 oould be diet inguirhe(

opendlng on their responses t o illumination, There were un i te

(Ishibiting an *onW response, disoharging when presented wlth a

h t atimulur ( ~ i g , 18). One uni t (~ig, 18A) responded with a

g l e opike on illuaaination, But i n some unite, the 8o t iv i ty

I i n i t i a t e d with l i g h t and the un i t oontinued to respond ,

wughout the peklod of photio stimulation and a160 a f t e r the

au lur war off (Pigs, 1 8 B and 1%). These un i te may be apt ly

,led *on-with* neuron# 8s ruggerted by Pieron (1965). gome I 98 exhibited *ofin rrrrponre, only diroharglng when the 8timulur

Pig. 188 A. A r i l a n t unit romponding r i t h a r inglo rpiko

t o photlo r0imulatlon.

B, A r i l a n t unit dl rohuglng on photio ram-

lat ion. Boto that tha unlt dirohargor through-

out the period of Il lumination and r l s o

o o n t i n u ~ r t o dlraharae a f t e r the rSlndlur 18

off*

Raoord O i r oonfinuation of B*

Tirot 0.5 sea.

Pig. 198 A. W O f f W rorponro of a s i l o n t unl t o o n r I r # ~ of

a r ingle rpiko *on the l i g h t r t l a u l u r 18 off ,

Also note that there i s another unit rrhioh

dirohargos d t h the onsot of light.

B. W O f f ~ nrponao of two dif forant unit8 n&lob

disohargo with ion. rpikar when tha l i g h t r t b u l u r

is off. Tha two t raaor show 8 o U r i t y f r o m those

two unit6 nonitorad betwoen the 2nd and 3rd

g W i a (uppor t raee) a d 3rd and 4@a 4 r s g l i r

(lower trrae).

2I la t 0.5 800.

FIG. 10

0- : ;

FIG. 19

-

ohmgar from l ight t o b.rknesrr 'Phe larger units i n Figures 19A

m b 2OA r r r a found to diraharge with a single spike every t ine

the l i g h t r t inulur war off, Two different units from erne

preparation om be reen t o respond rimultaneoualy to oesration *

of l i g h t r t inulus i n Figure 19B, The rerponse latenay wae greater

for the la rger unit than f o r the rmaller unitb The aot ivi ty from

there two units could be monitored between 2nd and 3rd granglia

r e well a s between the 3rd and 4th ganglia (see p, 60 ) , The

t h i r d group of neurons which nay be oalled aa "on-off" neurons were

found t o be aotivated both ndth the onset of l i g h t and i t s

oeesation ( ~ i g , 20), The mnaller uni t seen i n the reoord (pig, 20A)

axhibited a transitory rerponse, oonsieting of few spikes when

the l i g h t wae on and again diaoharged but with a higher frequenoy

( i n i t i a l l y 12/sece) &en the l igh t etimulus wao off, A similar

response i s also seen i n another unit which responded with 2 o r

3 impulees to l i g h t on and disoharged a t a r a t e of about 11 to

1 2 spiker/seo. fo r a period of about one second when the l i g h t war

off ( a g e POB), . Two types of u n i t s oould be reoognired depending upon the

duration of t h e i r responres, There were phardo uaitr oharaoterisrd

by a brief response oonsiating of only a few or even a single

spike even at suprathreehold l i g h t in tens i t i e s of long duration

(%nm unlt of figura 18). and "off" uni ts of f igures 19A,B and 20A).

In oontrast to this, there were other units uhioh were b n i o

erhibiting a surtained disoharge i n re6ponse to l i g h t throughout

Fig, 201 U n i t 8 exhlbi#ng "On-Offa rerponrer. Note the

rompanre iron a larger unit aonristiag of 8

aingle spike d e n the l i g h t ramulur i r Wofiw

in A. The lar t reoord irr oontinuation of

raoord B.

the period of illumination Woh l a r t e d f o r re re ra l reoondr end

sometineta nearly half 8 h u t e ( f igs , 18B, 19A and 21),

A l u g e number of there interneuronr were ohareoterised by

8 marked after-dleoharge, One unit oontinued t o dlsoharge even

a f t e r the oessation of l i gh t stimulus f o r about three seoondr

(Fig, M A ) , Another s i l e n t un i t responded t o l i g h t etimulation

with a latenoy of about 2, 6 eeoonds and oontinued to disobarge

throughout the period of stimulation which me a s long a s about '

23 seoonds and there was an after-disoharge whioh l a s t ed f o r .

about 9 eeconds a f t e r the rtimulua w a s off (Pig. 21). The

frequenoy of dieoharge gradually inoreared and reaohed a manurn

of about 8 to 10 apikes/rec, about 10 reoonds a f t e r the i n i t i a t i o n

of l i gh t stimulus, The dleoharge frequency then deareaeed

gradually and was maintained around 3 to 5 irnpulaea/sec, duting

the r e s t of the period, About 10 t o 1 2 aeoonds were required

f o r the oomplete ceeeiation of the l i g h t i n i t i a t e d ac t iv i ty a f t e r

the stimulus wan off. I n general, the after-discharge lae ted

longer when the in tens i ty of l i g h t presented uae greater,

Depending on the temporal pat tern of the reeponaes t o

photio r t inu la t ion , two type8 of interneurons aould be dietinguishe

I n eoae un i t s , the disaharge e l i o i t e d by l i g h t exhibited a tonio

inoreaee i n the frequenoy over a period (~ig. 21) while some units

erhibited m instantaneour high frgquenoy diechar@ followed by

adaptation (big, 18B). However, this dis t inot ion tea not alwrye

Pig, 21: turtrined aour i ty elioi*ed i n a rilont unif

on photio rtirulrtion, l o t @ r i t e ~ d l r a h a r g e

-oh lartod for about 9 raa. The figure

represontr r rlngXe aontinuous maord read f r o m

top to bottoa,

P i . 221 Berpoarer of r i l a t unit ta phoao rtiruli

of two d i f f e r a t irrtenritier. 'Pha intmri$y

of l ight rkLmulur -8 User i n B than i n A,

m e riddle ~ c l 0 r d i r oontinuation of lnaord A,

lo t* that *err i r 8 gradual inanare i n the

biraharge frequnay i n A and .a lnrtortaneoue

high fnquaaay diroharga i n B,

FIG. 22

Pig. 2'31: Beeponre of a 8poat.1~00umly 8et iva Wt t o Ugbt

rhowing inoro88e in the diroharga frequaaoy on

pho ti o r t i ru la t ion .

A: Spontureour ao t i r i ty .

B and 0: A o t i r i w on photia rtimulatlon.

Raeord a i r o ~ t i n u a t i o n of reaord Be

Pig, 24: Oraph .howlag the inorearo i n the frequsncry of

rhor te r intervals i n a .ponta~soualy a o t i r e unit

on photlo r t i ru la t ion . Spike in te rv8 l r sangiw

frar 80 t o 90 u a o . were daainant during

apontaneour dirohareo (A). Spike Interval8 of

l e r r than 50 area. b e o u e mom oomon on p h o a o

rtimulatiorr (8). Zhe data $8 from the uait 8a.n

i n Pigun 25.

r a t e of about 4 to 5 rpiker/reo, On illumination of the 6th

gmglion the disoharge f requenoy at ta ined a maximum ra te of

about 11 impulrer/seuc a i o h las ted fo r about 2 seoondr, a f t e r

a long latenoy of about 4 reoond. (pig. 25C). The frequenoy of

d&soharge ranged f h m 5 to 8 apiker/seo, during m a t of the

period whioh i n olore t o the spontaneous rate, But the pattern

of ao t iv i ty ahanged soon a f t e r photio stimulation and the unit

r t a r t ed diaoharglng i n the form of doublets whila the apontaneoua

i o t i v i t y oonsisted of single apikea, The interapike in terva l

gradually increased a f t e r the stimulus ' off' and the or iginal

pattern of single spikes rar regained ( ~ i g , 250).

It was observed that some units s t a r t dlroharging i n the

form of bursts when presented with l igh t , A unit was found t o

be apontaneoualy disoharging a t a low frequenoy of about 2 to 4

@ikee/aeo. (Pig, 26). When there was photia input, buret ao t iv i ty

was observed a f t e r a latenoy of about 1,l reconds, The frequenoy

of bursts wen i n i t i a l l y high ( 5 bur$aeo.) and daoreaaed l a t e r t o

about 3 bursts/see, %oh burst oonristed of. about 3 to 4 rpikes,

The unit again starteed dieoharging i n the form of single spikes

when the l i g h t m a off,

8lmllar buret aotivi ty wao also observed i n another

8pontaneously aot ive unl t on photlc stimulation (pig, 27)r In

$hi8 unit burst a a t i v i t y war e l io i t ed and the aplke frequenoy

inoreared both with the onret of l i g h t and i t 8 oeaaatioab This

i@ U81060~8 t o the w&r-offfl reaponres dasoribed e a r l i e r i n

P i g , 25: 0-• in tha aotirity pattern of l rpon8&oourl~

aot i te unit 0n phoaa stimulation,

A Spontaneour ao9ivi ty i n uait ooarirtbg

of single mpikem,

B, A o U r i t y i n m e m a 6 hanit rhoring a tandonoy

t o biroharge in the form of doublet8 on

photio rtimulation. Reaord C is ooatinuation

of B. 'Phe reoord also &our aat ir i ty i n

mother unit uhiah exhibit. a burst of .piker

with light r$irulus on and 8 oaaller burrt

rri* l ight off,

U(, 28: Multiple .pike a a t i r i v 8 l io i t86 %a a

rgon*ureooml~ r o t i r a unit on pho#a r t i ru la t len .

Hote r i w l e mp%ker mappear enoe the lie* rtimulur i r off. m e 2nd moor6 i r aoa#lw.Uon

of the firrt.

Cia. 278 Multiple .pike ro#ri*y e l io i t ed i n a

rpontrneouml~r a a a r e unit b o a d t h m e onmet

of l ight mtirulur aad i t 8 oarration. Hote *at

r in4le .pike a o t i r i t y reappaarm a f t e r r brief

pariob o f r u l t i p l a mpilce ao#rity. %he reoorrll

n o o r d i a eontinuation of the flrmt.

'ig. 28s Deorerae i n the burat frequalrcry in r

mpont~ooualy dimahrrging unit on photio

rtimulatioae

Be A u a r i t y on phoacr stirnulatien. Bota

the inareame i n m a ia0arburmt intervrl,

Also note that a o 0 i - w in uertaln other

.pontmeou8ly r e t i r e unit8 get8 inh ib i t ed

w i t h l i g g h t *

Also ma@ Figure 29,

Pig. 29: l i f e a t of photio r t i ru la$ ion on the p a t t e r n oi

a o t i r i t y i n a 8 p o a m o u r l p a o t i r e unit e r b i b i t i q

b u r r t a o t i r i t y rean i n Ngure 28.

A - Spontaneou aot iwlt r .

B - AotiritJI on photio rtirulatioa.

I. H $ r t o g m r -owing inore88e i n the r a m

number of rpiker on photio r t i rula t ion. Valuer

&ow tha aman ef 8 nrooeraire b u r 8 t e . D e

If. Graph rh@w%ng iaazoara i n the bur r t daurtion

on photio r t i au l r t ion .

111. Hirtsgrar rhorlng inoreare i n We n e w harrt

i n t e r v a l a8 a r e r u l t of photio r t i r u l r f i o n .

Value8 ind ioa te t h e mean of 7 maooearire

i n t e r n 1 8 2 S.0.

IV. Hirtogrrra mod- deorerre la the burr$

frequenoy on photio r t i r u l 8 t i o a .

InhibiUon of apontaaeoum r o a d * in turitm on

photio r W 8 t i o n .

Pig. 301 Spontureoum 8 o t i r i Q in a onit (A) i n driah tohe

rpika in*@& inora8mam ramulting i n 8 deoreare

i n tbe dimoharge fraquanoy on photio mtirulation (B).

Mote bh8t a o t i r i v 18 el loi tad i n a milant onit

on photlo mtinulation i n rooord B. Reoord 0 t o B .how 1

/ de~raaae i n the d~moharaa trapuanoy on,photio

r t i r u l r t i o n i n )rro differant unit#. Reoord D Am

oontinwtion o f 0. 'Pha unit a o t i r i t y i r rupa~-

impomad on tho l ight rig- i n a and P.

Pig. 31; Oraph ahowing i n a r e u e i n the irequanay or

longer mpika AntarvaXr i n 8 rpontureoumly aotive

unit (mean i n fig. 3OA) on photie mtirulation.

input ma provided, Ohe ao t iv i ty war inhibited very moment8rily

( f o r l e s s then 1,5 roo.) followed by an inorease i n the l eve l of

a o t i r i t y md regaining of the or iginal rpike frequenoy,

But i n a number of unite, the ao t iv i ty wae t o t r l l y

arreeted with l i g h t input, The epontaneous ao t iv i ty i n a uni t

aoneirted o f about 5 opiker/reo, (pig, 3 % ) , This uni t beuame

s i l e n t with l i g h t (Fig, JD),

Another un i t exhibited spontaneous burst8 wlth 1 4 to 15

spikes i n eaoh burst ( ~ i g , 34B), The in terburs t in terva l varied

from 2 to 2,5 seo, When l i g h t was preeented to the 6th ganglion,

the burets were completely a r r e r t r d (Pig, 34B). The unit remained

e i l en t so long a s the l i g h t waa on and s o t i v l t y reappeared

immediately when fhe list wag off (pig, 3 4 ~ ) ~

Xet another example of buret ao t iv i ty whioh ge ts inhib i ted

wlth l i g h t i s seen i n Figure 35, The burets oonsisted of 30 to

35 spikee with .a mean burat i n t e r v a l of about 830 mseo, i n the

Qsrk, No burs ts were seen on photicr r t imulation of the 5th

ganglion, With euetained i l lumination, the burlst8 however

reappeared, The f i r a t burs t which reappeared was alwaya smaller

aoneiating of about 15 t o 16 apikss, The burst duration oon-

8equently deamasod from 1.5 sec, t o about 0.6 aec, However, the

number of spike8 a d the burat duration of euooessive burst8

inoroared wtil the o r i g i n a l pa t t e rn was attained,

Burst a o t i r i t y i n another u n i t oonailrtsd of typiosl ly 5

splkea with one o r two .p ike r ooourring i n between the burbta

Pig. 33: 9otal i u b i t i o n of a s t i t i * of r rpantaeott8ly

ro#ro tanit on phoUo rtirulrtion. The raocurd

sooord i 8 oantirruation of the f i r a t reeord

Pig. 34: 2oZ.l inhibition o f aol i i r i ty i n a'unit

npoatureour~ dir-ging in Obe f o a ef bmtlr.

Hot@ that U1e burat8 zaappmar on00 t h e rWmulu8

i a off irr reoord 0.

A Gpontureour .o#ri$y.

B & Oa AaMrity aa photio 8.tiirulation.

Reoord O i r a6ntiaurtioa of B.

f i re r 0.5 880.

( 6 , 6 The a o t i r i t y reen i n tho dark d ioqpeand on

p r o r i d o n of l igh t t o ah@ 7th ganglion (pig. 'j6B,C). $pilea

were reen i n the unit a f t e r the etiaulua war off and the buret

a a t i t i t y reappeared abou* 3 reoondr af t e r the etimulus woo off.

Bowever, these bursts oonrristod of only 4 spikes f o r a period

of about 10 to 15 reoonda a f t e r the aeesation of etlmulus.

I n one instanoe (Pig, 37) inhibi t ion was simultaneouely

reoordod from We prorynagtio (lower traoe) a8 well a s post-

synap t i o uni t s (upper traoe), 2he uni t s were spontaneously

active (big. 37A). 'Phere war no It 1 relationship between the

ac t iv i ty i n the two unite. The spike frequenoy i n the presynaptio

unit varied from 4 to 6 rpikea/rec, The apike frequenoy in the

poeOeynaptio unit was muah lower and was about 1 to 2 spike8/aeor

With photio input from the telsonio nerves, the spike aot ivl ty

i n the presynaptio uni t dlaappeared about one seoon& l a t e r

(pig, 37B). Aotlvity i n the portsynaptia unit a180 disappeared,

This inhib i t ion was maintained f o r a long time i n the uni t s even

a f t e r the rtimulue wae off, There was a poat-inhibitory rebound of

aot ivi ty (Fig, 37E) a i a h reappeared about 7 aeaonda a f t e r the

4 atimulua was off. The ireqyenoy of diecharge i n the grefjymptia

unit was now about 7 t o 9 spikea/seo, and that i n the poet-

rylzaptio uni t -8 about 4 to 5 spikss/eec. TIM spike frequenoy

deareared t o a lower l e v e l of about 3.5 seoonbs l a t e r (pig, 37]P)*

I t was evident tha t the r a t i o of poatayneptio t a pm8ymptio

@piker inareared when the frequenoy of diroharge i n the pre-

a w p t i o unit W80 greater.

?is. 35: dpantmeour a o t i r i t y i n a rrnit u o n r i r u oi

long burrtr whiah ge t i lrhibited on p r o r i r i a n

of li@at. 'Phe bara t r reappeared about 6 roe.

l a t e r . Row -at $here b u r r t r -&oh ro rppeand

a r e mhorter than t h o apontureous burst.

Pig. 36: Patterned b u r r t aaWri$y i n r ?anit nhioh ga t s

t o t a l l y i a h i b i tad an p ro t i s ion of llgh*.

A: Sponteaeour bu r s t ro0 i t i ty .

B & 01 Inhibition of burr$ a o t i r i t y on photia

stirrulatien. 0 $8 oontinuation o f B e

Da B u r s t a o t i t i t y i n t h e unit whioh reappeared

about f roo. after the l i g h t rtimulw m a

off.

Tima: 0.5 860.

Pig. 3 7 Irhibition of opontaneaur asti** in two

Qiffaront M t r oa pmljrion of li@at.

A t a P roprormt a a o n t i ~ e t m reoord. &owor

trroo mhorm ao$iri*y iP li p s a ~ 1 ~ p - 0 uaAt

f r o a l e f t 5 2 oonneotite. Upper trroa rtrowa

r a t i r i t y i n r portrgnrptio unit fro^ l o f t 1-2

aoanooUva. l o t @ port-inhibitory oxoi*atioa

ia Arrow inUoakr uhrn light 8 t i ~ u l u r

$8 off ,

Oae p-t ieakrra obrerred dth m inoreare i n the

i n t e n d t y of l ight -8 the momiWrat of unit& A t hi@er

i a t o n r i t i e r of l ight l u g e 2 amber of unit8 wen found to reapwid

than a t lower i a t e n r i t i e 8 ~ We froquanay of diroharge i n ona

unit om be rean t o be inoreared fro8 5 rplker/r#o. t o about

10 rpiker/reo, dth ph0a0 input (pig, m)e mth UI iIl0ma8@

i n the l ight intenri ty , i n addition to inoreared aot l r i ty i n thir

unit, there war mother la rger unit (b ) q p e a r i ~ about 1,2 reoondr

a f t e r the i n i t i r t i o n of list (pig. %B),

Similarly, In mother rpontuleourly r a t i r e unit la'

(Pig, Na), the apika frequenoy inorearad from about 6 to 7

@ e r / a e o to about 9 l o 10 impulrer/rro. d t h phoOio input.

Aao$her larger r i l e a t unit cbl diraharged with a latenay of

about 2 reoondr, When the interui ty of l i gh t 00inulur war

inoroared a t h i r d r#l1 larger unit 1 a1 rrr 8lre exoited a f t e r

a latmnoy of about 1.) recondr a f t e r the rtlmulue war on (fig. m), With fur ther inarerre i n the etlmulur - in tmr i ty , yet another unit

-hioh n r larger thra the other 3 unite -8 aot i ta ted (pig. Jdl).

thur i t i r otident t h r t there i r r@arui.trent of larger and Ur@r

unltr at hi@@? i n t m d t i e r b

Another p h m w n o n o l e u fmm P i p r o 38 $8 the inonare

i n the irequanay of @piLee d t h inareare i n t h e Intarrity of list.

m r l l o r unit rlhiah had a rpontmeour dirahrrge of about

?%a. Rompoarom of unit8 t o inarorr ing in tuzr iMo8

of l i#ht .

A t U n i t ( a ) oxhlbit ing rpont.nooum r o t i v i t y i n

rhioh tho dirohrrao froquonay inororrob d t h

ugh*.

B t Rooorl rhowing f u t h o r inororro i n tho dl*

ohargo froquonoy of tho rpontraoourly aot ivo

UPit ( a ) m d O f b i t I t i 0 ~ 01 IrDothor 8 i l O E k t

unit (b) on r t i r u l r t i o n w i t h a highor intonri*y

of l ig th tm

O t o Bt Suooorriro rooordo rhow rorponror af

uaitr to muooosrively inorer r ing light inton-

s i t i o r . l o t o t h e inororre in t he Qircrhu60

froquanoy of r mpontmeou8ly r a t i t o uPit 1.1

@a& inoroar. i n the li@t i n t o n r i w ,

U r o note that r a t l r i t y is o l i o i t e d in -08

d i f f o r m t ailmab unit., t b t , ta t aad Id,.

-01 0.5 800.

Pig. 398 O w h rhowing tho ~ 1 8 t i 0 ~ 1 b @ f ~ a a the iPt@~iv of l ight r u r u l u r and We dlrahrr@o froquonoy t&

a rponturoouely r a u r e unit, 1Phe detr i o from tho

rpontmoourly ro4ive uait tat reon i n rooordr 0 .

t o E of Pigure %.

3 t o 4 opikarJrae. Usohaxgad a t a r a t e of about 10 t o 1 2

rpikar/raa. d t h photio input (Pig. W ) . A* l hi@@? inte-ity

of li@t, tho dirahwga fraqpuray i n the rbm unit inareared t o

about 20 irpulrar/rao, (Fig. XB), Similarly, wotha r

rpoataaaourly a o t i r a unit '8' dirohuging at a rat@ of about

6 t o 7 Upulrar/rao. %n darknarr dirohargod at a ra t e 3f about

9 t o 10 impulrer/rao. *an l ight r t inu lu r war prarontad with a

l a k n o y of about 2 raoondr (Pig. N O ) . When the l i gh t i n t e n d t y

war inorearad by abou* 0.5 timer, 3he unit diroharged rrim a

nuimum fraquanoy of about 1 4 rpiker/sao. (pig. 38D) . m a n tha

l ight in tonr i ty war inorearad by naarly three amor, the aaxinum

fraquenoy a t ta ined inoraarod t o about 23 impulser/reo. (pig. 3 8 ~ ) .

The r e l a t ion batwean a e m i k e fraquanoy i n the unit 'at 8nd light

intcmsf$y i r mprarantad i n Figure 39. It am al ro be roan that

the unit tbl diroharaad a t h a low fraqurnoy of about 2 i .pulrar/

r a ~ , a t 101ar U t e n d t y (f ie. 380) and d t h a m r x i m u m fraguenoy

of about 20 ingulrar/rao. at highor i n t e n r i v (fig. WB).

Iaoreara i n the fraquanoy o f rpike disohrrge with

Intanri tJ om U r o ba r e m i n mother ualt (pig. 40). The

fraquenoy of diraharge one raoond a t t a r the i n i t i a t i o n of l i g h t

1 t i a ~ 1 u a W.8 found t o be l.l//rro. a t a lower fntenaity (pig. 40*),

12/rro. a$ a r l i @ t l y highrr i n t m r i t y (pig. 408) a d about

l o . a t r t i l l bigha . inlmrit). (?%(lo 4W)

One aon ph~amanon obrrrrad mr the baorerre i n the

latonay of rarponrr with inaraara i n a a i n t m r i t y of Ugbt.

Pig. 408 Ba8ponmam of a rilant unit t o inurardng

lntanritiar of li&t. 2he intanrity of l ight

rtirulua inormamod from A to 0. let@ ma

daaraare i n the rsaponra lafamy and .loo the

inoreama i n the dieoharge inqusnoy at hiaer

l ight IntenrIMae.

Pig. 41: Beoordr rhodng increase in the reapozme

latanay of a silent unit to euooemrire Ught

mtiruli of higher intslrcri t ies , Tha izatanri*

of l ight etimulus inorerred from A t e 0.

Hot. that the Cisaharga fraqpenay inomasae

w i t h inorerl~a i n the rtimul~cr intanmity.

The Mit rbt airoh.rgod ria a I r t m o y or about 800 mroo, rt

a l r r a r intonmi* (fig. BD), Iho l a tmoy d r o n u a d t o about

SO0 mrro. a t a U a a r i a l a n r i t y ( r ig , B l ) r S i r i l a r l y tho

latonoy or mmponn of unlt rot 8 l ro daorearad from 1.3 rao, t o

about 0.9 rao. wlth rs inoraara in tho li&t i a t a y i t j . tho

latonoy or rarporuo ai m a other uait (Pig, 40) r l r o our ba

raon t o daororre tram 560 nrao, t o 500 ma80 a d f laa l ly t o

300 .roo. d t h ruooeorira inara r ra r i n tho l ight intoneitye Thir

rorporua latanoy may bo durn t o the d d . y at m a noop to r l a n l ,

the oonduotioa tina;ar roll a8 due t o the g q l i n i o dolay. The

daoraara i n the rosponra latanay obrarred rdth i n o n r r a in the

intonrriQ my be dua t o phmoaam egorating a t the maaptor lava1

o r at tho rylupra o r boU.

Iioraror, rhea *a raoeptor war r t inu la tad .rop@ataAly, the

latanoy of rarponra a 8 obeamad t o inorarra with inororra i n a 0

in t ans i ty of l i gh t , The rarponro latanay of a uai t inoraarad

from 360 nraa, t o 2.64 roo, wlth a Initial inororra i n tha

r m u l u r i n t a n r i w urd t o about 3 roo, with fur thar inorarra

in the list (Pig, 41). It o m ba obramad that the IF@QUII~W of

8piL;ar olsntiauad t o inoraara with in t an r i t y of i l lwr inr t ion ,

Orrc, i n to ro r t i ng o b r e m t i o n was the bspondonw of tha . . 18 t0~0y of naponre from oontra l un i t e bn the r i t a of photio

8Mmulation, m a delay war rhorliar f o r r t inu la t ion of a o n m t a r i o r

Pu t8 of the n o t r r o m oomprrad t o ahat of nore por ta r io r par t8

m a 88 a 0 k l roaAo aervae. Tho rooordr ( ~ g . 42) &ow 8 unit

nr f e u d t o bo u a i t o d on i l l u r i n r t l n g a e 6a urd tho 7UI

the talronio nerve# ath auoaasrively lnomar-

in( in ten r i t i e s of light.

. D t o P I Rarponres of the r m e uul t t o r t i ru-

l a t ion of the 7th 8bdoarin.l ganglion with

0 t o I t Responaar of the 6-8 unit t o st ia\ laUon

of tha 6th abdominal ganglion nl$h auooeraivoly

inareasin& in tans i t io r of l igh t ,

!?ha three diffaraat ln tene i t ies of l i g h t ueod ware

kept aonetant f o r rtImulaOion o f diffarent mglonr.

Sea !Caxt,

J: Reaponre of the uait t o s ~ u l t a n a o u r r-u-

l a t i o a of the 71rh aad 6th abdominal gangli8.

The l igh t in tanr i ty w a d war same a s tha t urad

i n raoordrr H and L. Bote t ha t the rosponra

latanuy i r rhortar thus tha t f o r the illturination

of the 7th ganglion (B) or tho 6th ganglion (H)

lndiridually with tihe o u e light intarmi*.

Pig. 431 O q h ahoffing tho lateaoy of roaponmo oi a

ri loat uait (.em i n Ng. 42) to phoUo 8-

la t ion o f the tmlmonio nerror (A), tho 7ta

8 b r a r i ~ l gaql ioa (b) mid tho 6- alp-

m i o n (0) in rrlatioa to the interuity r i

l ight . Hot@ $ha* tho mrpoaro l a $ a q

60onraer rdth irrororae i n tho iatonaitj of

right an& rlro -at a t a given intonr&ty, i t

i r loart for Oh0 rMrulatioa of the 6-

ga@ion and W u m for th. rtirulaUon of tho

tolron%a norve8.

? 4 4 CPryph mhorinq: tho ra lr t ioa botrooa tho rnrpoamo

lrtonay o f m irtemauzon (mom i n 42)

aad the r i t e o f photie at i tulrt iop. Mrtraoo

-8 indiortor ma birtrmao botraan $ha d t o ef

phetio rt irulrt ion whiah -04 aad tho r i t a of

reoorung alriah war k8pt aonrturt.

8b- # 8 4 i a u w i l l u the te lmnto n e m r . ?he Wt did

not reerpond to rti.ulrUea of the 4W or thi 5- ganglia. The

t h n e re(Jionr wore r t h u l a t e d indiriQally with dif f o m t

in tonr i t i e r of light. htrr a a n nr taken t o protar t le-

of l i g h t t o other part8 of the name cord, rh i le illumbrtiag

on@ photormri#te regionr The latenoy of naponre a t a given

in tenr i ty war dlfieront f o r the photio r t iaulat ion of the 3 ngiona

It" n r l e a r t f o r &e illumination of Obe 6th ganglion, meater

f o r the 7th g q l i o n aad nuinum for the telronio n e n e r (Pigre 42

md 43). The latenay i n all the oarer dearearer with m inoreare

i n the intenri ty of list (big. 43)r The la temy deoroared f r o m '

2,2 8eOo t o l r ' l j reo, at the .(IJdmum intenrity wed fo r the

otinulation of the telronio n e n e r (Pigr. 4241 t o 0) 4X)r 'Phs

reeponre lateaoy rmged iron 1.3 reo. to 0.56 reo. to a similar

range of intensi ty of light on rtlmulstion of the 7m abdominal

gurglioa (Pigar 42D te bl 43B)r 111 0a8O of the 6th ganglion, the

reaponre latenoy r q o d from 1.14 re00 t o Ob47 rreo. under rinilrr

oonditionr ( l i g r , 420 t o I) *)%I). When the 6tb a8 well a8 Oha

7th 8 b d a i r u 1 mi8 r a r e rimultmrourly illuminated (Pig. 42J),

the la$mroy dearerred t o aa even l e r r e r value of about 340 rreo.

'the dliferonao i n the latonoy of responee from the rme wit

on r t i ru la t ton of the mriour rogCionr of the oord may be h e t o

a difiormoe i n $ha numbex of r p p r o r involved i n addition t o

a@ diifermoor i n tho aonduotion time. The r e q o n r i Utenoy

Of tho u i t in rrlr$ien t o the d i r tmoe involrob betwoen *e

#it@ ef aUru la t ion a d the d t e of rooording i r plotted i n Pig. 440

If tha lateacry Ufieruaaer r a re sol* h a to the d i f iannoaa i n

tha oonduotion d i r tmoe r a r u l t m t plot oan ba axpaotad to ba

l i n a u -oh i r not tnre. It o m be r a m that tho differonor

i n the lateaoy W u a r for photio r t lnulat ion of the two abdomlml

ganglia i r r a m l o r indioating that $he diiferanae t r y be &a

t o the diffaranoa i n the oonduotion time. But the latenoy 18

oonridarebly gmata r f o r the illumination of the telron labloating

that mora number of ryrugrar m y be i ~ t 0 l t 8 d i n the pathry uhioh

the photia input fro. the teleon fo l lor r ,

It aur a l ro be r a m a t the frequanoy of dirohatga inareared

with in tenr i ty (Pige 42). A 1 tha 8 u i r u ~ i a t a n d t y urad, tha

dirohargr fraquaaay i n Bha uaif war about 1 t o 2 rpiker/rro.

f o r tha r t i .ulat ion of $ha talronio n a n a r , about 4/reo, f o r

r t l ~ u l a t i o n of the 7th m i o n md about 10/reoe f o r r t i ru la t ion

of the 6th gag l ion@ %hare mr alro a s8oond m a l l e r unit exoitad

on rtimulating the t r l ron io n a n a r , This urit war not axoitad

on illumlacrtion of e i the r the 7th or the 6th gmglion.

There a l ro appearad t o be d i f f e r a t unit8 rasponding to

different ranger of li@t i n t m r i t y , A large unlt war found to

raspond d t h f a r #piker at thrrlhold inaenrity (rig. 451.). With

ul inoraare i n the l i gh t in tur r i tp , oertain marllor units were

a180 u o l t e d and they dirohar#rd a t 8 mam ra te of J opikrs/seo.

-la the la rgar unite oontinued t o dlsaharga with few rrpiker

(Pig, 45B). With fur ther inorear@ i n the light intanri ty , the

la rger unlt rerpondad d t h a ringla #pika and the m a l l a r unit

? 5 Reoordr rhodng d l i f @rant unit# -*onding t o

d i f f a r m t i n t e n d t l a a of light rtlmull, Pra

l i g h t iP9enrlt~r lnoraaaad from A t o D. Mote that

onlf largo rplker are a l ia i tad at the lowart

light 1at.nrity uaad (A) m d only ma -11

8pika8 at t b o h i a e r t light intenrity (D) , A t

iatamediate l i g h t in taar i t ias (B and 0 ) both

the uni t r tempondad.

rerpoabed with a frequenw of 7 rp%ker/roo~ (pi$. 450). a* 8

r t i l l highor light i n t m e i t y , the l a r a e r unit fa i l ed to *

ranpond and tho m r l l e r vllrit 8loao diaaharged a t a ra te of about

t o &ow a r t not all unit8 rorponded to inorease i n the i a t e n r i t y

of l i g h t d t h an inoreare i n bhe d iaaharp irepuenoy,

A la rge number of uni te exhibited adaptation on surtr ined

i l luniaat ioa. !Cha rate of abaptation rs r iod over a r ide rango

i n differcurt unitr. Some uni t8 8r dasaribad ea r l i e r (Bigor 18,

19, 20 and 45A) rerpondod with very few apikor to l igh t stimulation

rulgiag from 1 t o 5 or 6 ~ i k 0 8 . 'Phe uni te 8oon got adapted and

no reaponre war obrened *en illwpination aontinued. Some unit8

were ex9remely rlow in adaptation and rewonbed with a prolongad

tonio dlrohorge often with an 8 f t e r diaoharge f o r long ~ o r i o d r

(Pig. 21). ?he freqpenoy of bisaharge a f t e r a t ta ining the arxlmum

d e 0 ~ 8 l b d v@ry 8101l~r However, i t me eoaetimer obrerved that

there u'ir a t ranr ient reaponae a t low i n t m s i t i r r and a more

wstalned a o t i r l t y a t higher i n t e n d t i e s of i l l l u i l u t i o n (amaller

unit8 in Fig. 43).

Adaptation i n 2 W t r i r shorn i n big, 46. O u m A ahow8

8 re la t ive ly tart adrgUng unit and ourve B r o p m r m t r a o t i r i t y

k a #lowly adap.pting unit, l ither 8 u n l O seturnod t o the p r c

t ~ a i t 8 t 0 r y r tak of m t i v i t y a f t e r adaptation (pig. 461) o r 8

Pig. 468 Graph rhorring 8Q.ptation to light of two diffet.at

uaitr out of whieh ona i r a f8.t adapting unit (A)

and one i r 8 r l o w adapting unit (B). A r r o w r

iadiorta uhan tho l ight rtiruli we- on urd off.

Pig, 47: Oonduaaon reloalty in throe different photo-

maoptor interneurona. Tha diotuzoe batroon

the mito o f rtiaula0ion and the site of

reearding ram 12 nu (A), 18 n (B) W

7.5 mr (O),

i n the ran*& ae r re osr4 of rosrpioa (0. J t e 5.0 m/rao.)..

A 8L.il.r -0 (2.5 k 5 ./rro.) n r a l ro n p o r t e d f o r unit8

in the polyahaetr r i f q ( B U ~ ~ O O L , 1948).

ReoorUng of rorponrer fron tha internmronr alone doer

not @V@ a oolrplete p i o t u r ~ of the 0entr.l input* Thanfore,

a a t i r i t y i n the p r i n a q reoeptor @Or 88 well a r a e l n t e r n e ~ ~ ~ n r

may aot upon were dmultrpoeourly roaorded r o r t h i r purpere,

e leo t r ioa l r t i r u l a t i o n war l o y e d rinoa rtlmulur pa raae ten

oould be oontmolled nrah b e t t e r than when light war ured f o r

r t laulat ion. The photorroeptor k u r o n r whioh were i ro la ted by

oarefully tearing the oanneotiver were e l eo t r i oally stimulated

uriag n a t a l mioroeleotroder and a o t i r i t y reoorded fron thm ar re11

ar other uaitr may r o t upon i n tthe oord.

A 1: 1 aorrerpondenae of the prerynrptio and portrynapua

rerponrer -8 obrerveb at rome junotion~. B8eh impulre i n the

reoeptor unit e l i o i t r d a rin&le Impuloe i n the interneuron (pig.

4 U t o 0). However, ene t o many nlationmhip war 8lso obeened

md a ringla r p U e e l i o l t e d 3 t o 4 rpiker in the p o r t r p p t i a

b e ( D ) The oent r r l delay varied from l e r r than

1 mare. t o nearly 15 area. (big. 58). Thir d e l . ~ ~ war manly

the a p p t i o delay due t o the olore proximity of the two noe*n((

@leotroder.

Pig. 48: A & B: Rargonra fro8 photorcrorgtor amwar isolated

i ron tha 7th g.rrglion (lowar $ m a ) and pert- mynap t i 0 neuron8 (upper t n o a ) t o a lao t r ioa l pulrar dalirarcad to the photoraaeptor a m m n r ~ I o t a 1 to 1 rarponsa of *a p o r t r p a p t i o ualtr.

0: Rarponra of a photorooaptor unit i ro la tod f r a tho 6th -@ion (lowar t r roo) and r p o r h rynaptia unit (uppar trrroa) t o an a l aa t r i a pulra dal i rarad t o the photoroooptor wit ohawing 1 t o 1 re la t iomhip batworn the rot i+i ty in tha ~ W O UPItb.

D: Aoti r i ty i n 8 ghotaraoeptor neuron i ro l a t ed from t h e right t a l roa io nerra (uppar t r roa) and r portrynaptio unit (lowar traoa) uhiah ra8pondod with numbor of irrpulrer i n rarponra t o @.ah lmpulra in the photoroooptor unit o l io i t ad by an a l a a t r i o pula@.

I t Rerponra of an interneuron to o lao t r laa l rMau- l r#on of r photeraooptor unit i r o l r t o d from tha l o f t ta l ronio nerve. Splkcsr i n the photoraoaptor unit imaadiatalp followad 4ha a l eo t r ioa l gu l ra r end ara not raan ia tha figura. Mote 4he Baoraua i n $ha rorponro latanay t o ruoaaeri ta pulser. 2ha raaordr r r a t o ba ra rd fmm top t o bottom.

Zham uam U r e ov%&anoa of i8alUtrtioa at there jurrotioar.

P i g w e W ahour 8 unit rhiob i r rponturaour4 ixmot in , Tho

wit war aotivatod on p r o r i r i o a ef l ight t o the to l ronio narver.

Zhe unit U r o rampendad t o a l ao t r io8 l r t i r u l a t i o n of tho l o f t

t a l ron io name. 'Pha pu l ra r wn dal i ra rad a t i n t e r n 1 8 of

200 rroo. Tho firrt pulra f a i l a d to a l i o i t m y r o t i r i t y . The

raooad puI.10 a l i a i t a d 8 rpiko rftmr 8 l r t m o y of noarly about

37 rrao. The t h i r d pulre a l i o i t o d 8 rpika & t a r about SO nreo.

Tho fourth pulro e l i o i t o d two rpikas and -a 18tonoy daom8rad t o

nearly 20 rrao.

m a oourra of m a photoraaoptor unitr i n the n a n a oord

war r b d i a d by rrimulturaoual~ raoording tha a o t i r i t y from tha

Mitr a t d l f farent lava18 of the n a n a oord, The primary U t 8

ra re i r o l a h d f r o m ma ooanaoUrar by taar iag the f i b m r , It war daoidad that a givan unit t a a i n a t a r i n r euaglion by the

i 80 t t h a t tharo war no r t r i o t oorreopondmnoe batwaen the r o t i r i t y

of the photoreoeptor unit and the r o t i r i t y i n any of the port-

g ~ l i o n l o units, Ih8n *en them war I t 1 oorrerpond@noe i n the

ao t iv i ty i n two leva18 of the narva oord, the unite oould be

d i f fa ran t i r t ed by the differenoer i n the mhape of the q i k a and

rpike height (pig, 48B) and somrtimae by the long oantral delay

involvad (]rig, 48A,O). It war almo o b s r n m l that the r o t i r i t y

i n the unit i d l a d t o e l i a i t MJ a o t i f i t y i n m y of the units

i n the pos*#uae;lionio oonneotivar a f t e r applioation of alootine.

On@ 8 i g a i f i 0 ~ n t observation war tha t the primary photo-

raoeptor uni t8 were almym found to amoend toward8 tho anter ior

s ide and thare -8 no eridanoe of m y of the photoreoeptor units

daroending portariorly. Ihe oourre of the photoreoeptor units

i n the v a n t r u nerve oord i 8 8ahemrtioally rapresentad i n

Figure 49, Prom t h i a f igure i t i r erident tha t the photoraoeptor

neurona loortad i n the vrr iour ganglia rroond up the aord and f a l l

off 8% differant lora l r . The unit8 appaarad t o t ravel through

one t o W e e qangl ir d t h o u * my r m p r a r , Tha neuron6 of the

7th g w l i o n ~~~~~d t o t r r v a l 8 longer d i r turor oonp.red to

units i n other par t@, passing through two or three gmgli8.

g 49: Suhomrua r~rementatton o f the oentrrl crotume

of the photorecroptor nouroam in $ha wntr8l

nerve oord,.

1 Ab- t o 7 Abdg: = 1 t o 7 abdaPrinal (CIIIQClla.

Sn - Olemental nerve*

'Pn - Telmoaia nerve.

9he photorawi#ve f ibre8 loaatod i n tho t r l ronio nervor won

faturd t o araand and te.ia8te in Oh0 7th -ion whioh they

ontor.

A large number of neuron8 i n the rent- n e m oord wora

f w d to bo exoitod on photio 8timulation of the motaroutio

photorooeptorr rhowiw &at thi8 input i m wel1,repmmented i n

the oontral nonour syrtem, Tbir war orpedal ly orident when tho

aot i r i$y war rooordod fro. tho who10 oonneotlros (Pig, 50), Uhm

the rerponrer to illuarinrtion were ri8ultanoourly roaorded from

two hal te r of tho ventral nerve aord i t wa8 otident that the

rotfvi ty i n the two br l te8 very muah oorreapondo with eaoh other

md there -8 oonriderable phare re l8 t l0nrhig~ Thur tho rorponro

from the l o f t oonneotlve (lowor traoe) and the right oonneative

(upper t r roe) between the 2nd and 3rd q-ia o m be sera i n tho

rooord A (pig. 50), Similarly, t h e roqonree from the l e f t

(lower b o u ) m d right (upper bem) oonneotfver between a0 l r t

md 2nd ganglia aan be seen In the rooord B (pig, 5 0 ) , 'Phi8

indio8tor that them am para l le l pathways excited simultmeourly,

I t 10 a l r o porsible $hat ool l r te ra l r of unite in one 00me@#v@

axoito uaitr in the other oaanoetive. Bxistonoe of suoh pa r s l l e l

pa thaye i n a number of i n r r r t o b n t i r $0 knom ( H ~ r d d 8 0 , 1968).

!Wr 8imilariQ in tho reaponre8 i ron two halres of the nerve

oord r$$mulatod to r ti* of the porr ib i l i ty of he tarolateral

@*i8ulation of unite, 2he poeribi l l ty of atinulation of unite

oae oonaootive by unit8 i n the o o n t n l 8 t r r 8 l aonneotive wu

rNUed, ?or a i r pur)oao Iha r o t i r i t y war rimult.nrourly

%able 501

A8 Rompon808 from liho l o f t ( l o r o r traoo) .pd tho -&ht

(upper traoo) oonnootiror botwom tho 2nd a d 3rd

ganglia t o photia input f r o m tho rotaroaa.

B8 Romponre8 from tho l o f t ( l o r o r t raao) and tho fiat

(uppor traoo) oonnootiror botroan tho l r t md a d

g-lia to photio input from the r o t a r m a e

l o t o tho pharo r e l a t i o n botroon tho aoMr i ty i n tho .ti-

h8lr08 of t h e norre 00rd8 i n both -0 ro00rd8e Aot i r i ty

18 ruporimporob on the lie* niga83 i n 4he l o r o r t r roo r

of A md Be

0 & Dt Aotivity i n -0 l o f t 3rd oonnootiro b o f o n

photio r t i r u l a t i o n (0) and during photio

r t i a u l a t l o n (D) mhoang tho oxoi ta t ioa of

l a rge aumbor of aouronr by photia inpu.ti.

Tho a o t i r i w war rooordad from wholo

oonnootiror in .11 oaror.

Tirot A and B - 0,s roo.

0 ma P - Oao rweop - 15 rroo.

reoerded fro8 the aaaending turita in oontral8ter.l oonneoMnr

a t different l e r e l r of the norre oerd 88 rhom i n the diwru

( g 1 ) AoUrity fmm Ohe right 6 5 aoaneotire (lover traoe)

urd the l e f t 3-4 oonoertive oan be reen i n the moord A (pig, 52).

'Lhe r ight 3-4 aonneotivo md the l e f t 4-5 aonneotive 88 well a8

m e l e f t 2-5 eonneotirer were revered, About 2 to 3 unite

rerponded t o phoUo rtimulation of the 6th ganglion md 3 to 4

units i n the poster ior 4 t o 5 eomeotive. I t i s o le r r that the

rroending w i t r i n the S-4 oonneotive are e i w e r symptioally

aotivated i n the 4th g w i o n o r they m a y be W t r a i a h ororr

over from one aide of the ventral nerve oord t o the other aide.

Suoh a d i r t r ibut ion of f i b r e r i n the ventral nerve oord of

moorpion ha8 beon reported ( ~ a b u and Venkataohari, 1966).

Horerer, none of t h e rerponding un i t s i n tho two oonneatirer

r e r a b l e d eaoh other i n t h e i r #pike oharaoterirt ioa and mere

war no r t r i o t oorrerpoadmoe between th6 a o t i r i t y i n the unit8

of the two ooaneatirer, 'Phis ruggertr that the unite i n the

5-4 ooaneotire a re 8yaaptioally sot ivatad i n the 4 t h ganglion,

Reoord B (Fig, 52,) rhonr response from u n i t s ia the fight 2-3

ooaaeotire (upper t r a m ) rQioh r6oeirer exoitation from units i n

the l e f t 3-4 aonneatite ( loner traoe) af ter autting the r ight

3-4 rad l e f t 2-3 uoaaeo#rer.

ehe number of u n i t e i n a aomeatire r@asiTlng exaltation

from the po8ter ior @ ~ n * r . l a t e m l oomeoti ter -6 aounted by

ilol8tirrg f ibre8 i n tht oonneotire in to f ine bundler and r e a o r b i q

rerpoawr f r o m eaah bundle r rp r ra te ly t o photio rtimulation

Pig, 518 Oiagrau rhoring a@ ar-ement tor rooordiw

the oxoitation of areendin$ oontral8tor.l

unitr aad ororring over of photio input towardm

the right (A) m d l e f t (B) halrer of tha @ o ~ d . R1 t o R3 - Recording electrodes

. i t o r other oonaaotiror of $ha oord war@ out 88 dareribad bafora.

It #a a d d o a t from ruoh rtrrbiar that the input from I h m

ra taroaa t io photoroooptor8 ororoar m a r f rm ona d d a of tha'

ren*ral name oord t o &a othar r i d@ a t r r r iour l a n l s . Ar

exoi tat ion f m n porWrior aontrrJ8tar.l ooaaeotiror appaarad t o

be more aoanon batwean the g w i 8 2 and 4 than i n the anter ior

p a r t of the oord batwen tho ruboarophyeal ganglion and tha '

2nd g8aglioa. fha input war ale0 obrarrad t o ororr over

raquant ir l ly nore than onoe i n tha ruooarrive g u y l i r i n mat -a 4

aroanding unitr nhiah raoa i t e exoitation frm tha postar ior

oon t ra la t a r r l unit8 i n Wrn axoitab unitr i n the anter ior

eon t r r l8 ta r s l ooaaaati+aa Thir ruggartr t h a t $her@ i r axtanriva .

r u i f i o a t i o n o f unit8 and divarganoo of photio input from the .

arlaromatio photorroeptorr. 2hihir a180 dononetrater tha p k r n o a

of 8 lrddar-l lka name oord i n roorpion vdrioh i r so o m o n r ~ o n g r t

the 8r*hropodr (Horridge, 1968).

Although the ditergenoe of input i e a la i r ly evident, there

n r rurartihelear oonrlilerceble degvas of oonvergence obrar red

It war o b r a m d that the phot io input from v a r i w r p h o t o r m d t i r r '

8rear of vent ra l nome oord i n ths metaroma aonverbad onOo h e

8-a interaauron. 8uah i n t ernmaron8 a ra obvt ourly roueiring

azoi ta t ien from r number of primary photomeaptor unit& the . . PQrribi l i$y of tha r m a photoraorptar neuron awoeiting photio

fnpa a t d i f f o r m t loo% i n the vent ra l n e m oord d&n(l i t 8

Data ahocrdng the number of tuPit8 reoeiriry exoiWtion frm the

porterior oontr8lrteral aonneo#ver a t different level8 of the

ventral nerve oord an photio rtlmulation and arordlog over of

the rmrory input froa the n6tarout io photoreoeptorr, The 6th

abdominal 6mglion war raleated for photio rtiaulation,

Dimation of srordng 610. of Yeuz number of Maxinu. number over of the phetio input prep* units, Vrluer of unit8 ob- -------------- ration# oorrooted to rerved i n 8

@XU- the ne8rort propamtion. ??a To ad. rholc num3rr.

Left 5-4 4-3 1 4 Left 6 3 Right 5 2 14 Left 5 2 f ight 2-1 18 lieit 2-1 Ria0 1-808 16

Ri@t 5-4 t o l e f t 4-3 t o fight s-2 12 3 4

Pig. 528

At Beoord ahorin# ex&tr t ion o i r a o n t r a l a t e r r l

unit i r e l a t e & iror t h e l a i t )1.4 e o ~ e a t i v e (upper

t m e e ) by r o t l r i t y fn tha right 6 5 aoaneetive

(lower t r r a e ) on photio m#rulation.

B: Reoord mhowing the exa l t a t i on of u n i t s i n We

right 2-3 ooanaatita by units i n the l d t 5-4

oonneatite on ghotio rtiraulr#on, Hot. that

there a r e three unit8 i n -0 upper t r r o a w h I &

raoelve a x a i t r t i o n f r o m the por ter%or o0ntr.r

lateral oonneo t i r e .

A a t i t i t y i r muperimpomad an m a l i g h t dp.1

in the lower t r r a a 8 ef the tw recrorbr,

Tina: 0.5 880.

FIG. 52

rooeptorr 8ad proridin# photio atimuli a rpanta ly to $ha

t .r iour rb4- mi8 md tbe telrollio lumea. Suah

rtudfer d id not r a t aa l tba proranom of any primary neuronr

drioh o m be eroitad by photio rtimulation a t more than ona

l o a w i n the vantrr l nerve oord.

A rurit war found t o biaaharge a t a low fraquonoy of about

1 to 2 qilcaa/raa. (?igb 53). The unit b a r n to dlroharga

wlOh 8 vary high fraquenay of about 20 to 25 rpikaa/rao. *on

the 6th ganglion war i l luninatad (Pig. 5%). Tha unit diaohargad

with a frequanoy of about 1 2 to 16 spike@ whan the 5 t h ganglion

war il luninatad with light of r u e intanri ty (pig. 5D). men

$ha 4th ganglion war illuninatad, the unit dioahargad with a

fraquonoy of about 5 to 9 rpikaa/rea. (pigr 530) although tha

intensity of light amployad m r the ram@ i n 8l1 the three 08rar.

Another unit rooairing input from the 6th and 7th ganglia

88 well 88 the telronia name8 ha8 already baen prorentad (rig. 42).

But at 8 given intonri ty , the frequanoy of dieoharge. for tha

illunlnatiion of the &roe d l f f e r m t raglona war dir t inot ly

different end mr highart f o r the illumination of the 6th gmglien

md l e r r t for the ta l roaio narver. The Iatanoy of responrra from the

unit alao ta r lad aa axplainad marlier (1)igr. 43 and 44) and war

leaa t whm the 6th aanglion n a illuminated and meriaum uhen tha

te l roaio narrar warm i l lua i ru tadr fhur .Ithaugh thara 18

t ~ o n r r r ~ e n ~ a , tha individuali$y of the input appear. t o ba maintainad

$0 roma axtentb

Pig. 338 Berponrer from a mpoatureoumly -tire \mi$ to

photio mtbrulatian of the 6th abdominal

ganglion ( A ) , 5m guyl ion (B) urd the 4 t h

g;uyllion (a).

Time: 0.3 re@.

Pig . 548 Re#ponrer fro8 tro milent uaitr to phoaa

r ~ m u l a t i o a of $he 6th (m(~1ion (A). The

two unit8 fai led t o respond when the 5 t h gmglion

wa8 illuaiaa$ed.

FIG. 53

-

FIG, 54

.

A -bar di ~ t e ~ ~ ~ ~ H r o a lso 100atod w h l & r e ~ o n d o d

t o photia in)ut iro8 only one of tho photoroaritivo loo1 i n tbo

rant& n e n o oorb, 2ho M O O ~ ~ (?I&. 54A) rho- two unit8

*oh wora exoitod on i l luminating the 6th lion, I e i t h o r

of Wore uniCr oould bo exoitod on illuminating tho 5 t h -ion

(Pig. 54B) o r any olhor p a r t of tho aord,

8 m e of tho photoraoeptor intornouronr woro found t o t r a i o l

uonridorablo d i r tmoor along tho name oord, ofton oonduoting

through two or mom gaaglia, To oremino the prosenso of unit8

travelling through grrr(y1ia without torainating i n thorn, t h o

an te r io r moat i p d 1 a t r r . l oannootive war dorheathad and rororod

j u r t por tor lor 40 the ruboorophagoal ganglion, Zhe f i b r e r wore

i r o l a t o b from a i r oonnoativo by oarefully pulling them rri* tho

holp of a p a i r of tino loraopr, A a t i r i t ~ r war r inul tmrour ly

reeordod fmm eaoh of there unit8 and from $he intorneuron

i r o l a t o b more por ter ior ly whioh respondr t o photia input, When

$hero rrr oxaot It1 oorrerpondonoo i n the a o t i r i t y i n tho

porrtrriorly irolaCod unit and any of the unit8 i ro la t ed i n the

U t o r i o r ocoanootiro and when m e spike uharaatoriatlor a l r o

wero tho rum, it war dealdab that tho a o t i r i v raoordod at two

let018 i r from t h e 8-0 unit. TMr was f u r u e r oonfirmed by

providing ur e l o o t r i o pul re a t e i t h e r levols and 8imultmooudly

rooording from b o a tho l e t o l r , 'Phe r u e rlootrodas r o n e d

b)b for r t inula#on and reoarding, Thore n.6 eanoelUtion of

Oulror r r h a tho ram4 unit war rtimulated, Whsn none of tho unit8

i ro la t ad Fn the m t a r i o r 8or t 8 o a n a a ~ v a oould be deoidad to be

the rema rr am one i ro la tad p o r t e r i o r u , U a mama prouadun

war rapmatad wlth .nomar 8onnaotiva more olorar to the

unit i rolatad, Suoh r tudier ahowad that a number of intar-

nauronr eonduot tbrough two t o throe suooaarive g w l i a ,

P i g u n (Pig, 351) ahor8 ana unit t ravel l ing through the 2nd

8 w l i o n and mother tanit t r a v e l l i w through .bhe 2nd and the

l r t ganglia (big, 55B). Pigure 43 a lso rhowr two uaitr the

a a t i t i t y i n whioh oould be monitored between the l o t and 2nd 88

wall 88 between the 3rd 8nd the 4 t h ganglia showing tha t the uni t8

pars through the 3rd arid 2nd ganglia without terminating i n them,

Two aore u n i t s t r av r l l lng through the 3rd ganglion has already

been prerented (pig, lgB),

Pram the formgoing aooount i t i s olear tha t the photia

input from the matasom ha8 r ignif iosnt o a n t r u affeote influanoing

a u t i r i t y i n a la rge number of intemreuronr whlah traverae along

the ventral aerve oord r ight upto the nrboarophegeal ganglion,

Thir oonapiauous affao9 of the photio input on the oentral

nauronr ruggartr that i t may be reprerented i n the brain a s well,

To exaaine this, a a t i r i t y from u n l t u i n the rupraoesophageal

&anglion war reoorded uring tungatan mloroelaotro%es, The

raoordr (?la. 56) show a a t l r i t y i n brain unltr (upper traoe) a r

wall am i n the ventral name oord oonneotives i n the nesoroma

monitored rbultasraouoly. One unit i n the brain (A) was found

t o dirohrrga only whon thara warm two olorely opaoed spikes i n

Pig. 55; Bm.poarmm of two Prritr -ah eenduot

the mooond @urgliea (A) and mmaonb and f i r a t

gmglir (B) to phatio laput.

A: Upper traoe - AatititJI naordmb from

l e f t 1-2 ooonma~rm.

&owmr trrom r Aativity reaorded from

l e f t 2-3 oannaatitm.

B; Upper trram - Aetiri ty raoarded fram

l e f t l a t ooanmatire.

Lower trram - A o t i v i t y reaosded from

a l o f t 2-3 eoanmatite.

Pig. 56:

A t Aotivity a l i o i t a d in r aait %A t he b e ( a p p n

t r roa) urd i n tha right f i r a t oorraeotire (lower

trrrua) on photio a t i r u l r t i o n of the 6- abQmbml

g-ion.

Bt AoUrity a l i o i t a d i n asother unit i n the b r a

(uppar t r r a a ) nhiah i 8 axoite4 by r o t i r i w irr

r unit from the l a i t 2-1 aoaaaotire (lower t r roe )

on photio s t i r u l r t i o a of $ha 7th rbdoa%nrl

( y u y l i oa..

0: Aot i r i ty 81ioit .d in yet motha r unit ia trhe

b r r i a (upper t r roe) by a unit in the l a i t i i r a t

oonneatita of t h e rmtral nerve aord ( lever trrrae).

Beoordr A urd B a r e ftoa a. I a ~ d

O $8 f ror H. farip.. 11.

tho r ight f i rr t oonnartiva (lowar ~MOI) . AnoUar u a i t i n tha

b r a i n (11) ru found to dir&.rga la an U o r t l a 1 murnar f o r

@very largr #pika i n the l a r t 1-2 oormeotiva, -la rna l l a r uni t r

i n tha mama oonaaotira f a l a d t o a l i o i t #piker from thir unit ,

A 111 rarponae was a l r o obrened i n mother brain unit, f o r

arary impulra la the l e f t first oonneoUve (0). Howaver, f i r a t

f a r #piker f a i l ad t o e l l o i t any ramponre from the b r a i a unit.

From thlr it i s olear $hat +he ratarolratio photio input is

rapramentad i n the brain. But the aentral area8 wlthin tha brain

whioh a re influenoad by m a photio input i s not blear a t prarmt .

Tha af faot of photio rtimulotion of the abdominal phode

raeaptora on the aotirity i n motor f i b r a r war ale0 e x a n a d miam

ur, input ao widely repraronted i n the nemoua ay8tem 18 moat

l ika ly to influanoe tha a f r a r m t aot lv i ty 8180, To study the

effaranO a o t i t i t y , +aot iv i ty from unite i ro l s t ed from tho regaantal

nerve# was monitorad. The d i r t r ibut ion of efferant f ibre8 i n tha

ragmental nerve8 of soorpion ham been d~eor ibed e a r l i e r

(Venkateohrri and Babu, 1970). It was inOerasting t o f ind that a

l r r g a numbar of motor uni te ar le ing from t h e tariour abdominal

ganglia ware axoitad by t h i s photio input* A 6pontaaeourly

inaat ive r o t o r unit i n the venf r a l n a n e of the l e i t f i r s t

ra-antal nerve rrlriag irom the i irrt abdonrinal ganglion was

axoitab oa i l lud ,na t ion of the 6th ganglion (pig. 57A). When

oonneatira batwem the name oord md the ruboarophrgarl

8~@.on war ratamd, $ha rerponrcr from this motor unit t o photio

? 57: Brcritation of r e t o r -to by photia inputi i r o n

A: Reaponre from a no tor trait i r o l a t e d f r o m .the l e f t

l r t relpentdl nerve (upper t r8ae) on photia

r t i r u l r t i o n of fhe 6- abdorfxml ganglion, Sower

t r a a e rhowr remponrem from the l e f t f i r r t

oonneatfve of .Oh8 nerve oord.

B t Beeponre from another motor unit i n thr aame

reqprental neme a f t e r i r o l r t i n g the nerve oord

from We aephalothorrfio nerve macro, l o t 9 *at

-8 r o t o r Wt rlbioh prerlously ranpondad t o l igh t

i n reoard A f a i l e d roepond now.

0: Reaponam of a m o t o r unit i r o l r t o d from the meeoad

right regrenta l nerve to photio r t i r u l a t i e a of the

7- abdoarinrl gmgl ioa (upper t raae) , &ower t raoe

mhowr aa t i r i *y e l i o i t e d i n the ria$ S-4 aoaneotire

by the 8-0 rPirulu8.

Mote that thm latenoy f o r i a i t i a t i o n of a s t i v i t y i n the r o t o r unit@ 18 g rea t e r Wmn that f o r the lnitirti@n of r o t i r i t y i n the nerve oar& oonneo#ver.

input ~ u ~ d r a i r ahow th.t tho motor unit war n o o i r i a g

oxel tat ion troll oor t r in hi@@? aentror in the oaphalothoraoia

norto u r r . b o t h o r motor aouron in tho raao norro, uhloh oould

not bo eroi tob by photio iaput oar l ior , now roopondad t o light

inpu* f r o . tho 6th g w l i o n (Pig. 57B). It i r probablo that

tho unit war toooiring inhib i t ion from the higher oontro, and

honoo $ r i l e d t o rorpond i n m Fntaat proparation, fah ib i t ion

o f r o t i r i t p i n efferuat f i b r o r i n reorpion ha8 alro been rho-

e a r l i e r by Venkataohari md h b u (1970). Similar oephalio

inh ib i t ion ha8 born very wall demonstratad t n a number of insoot8

. ad i n other rniaalr (Bullook and Horridge, 1965). Thir ao to r

u n i t mr found t o beoome s i l e n t again about 4.2 rooondr a f t o r tho

a o t i r i t y war i n i t i a t e d by photia input (pig. 57B), But another

ao to r unit exhibited mare surtained e o t i r i t y w h l o h l re tod through-

out the period of Illumination (3 roo.) md ale0 oontinued a f t e r

the l i g h t rtimulur was off (Pig, 570). Thir motor uni t appoarod

t o be d i roa t ly exaitod by tho r r o o n d i ~ uni te rinoe 80lrering a 0

anter ior aonnootiro d id not intorforo with i ts rerponre t o

photio InpuO.

On0 8$gaifioan% o b s o m t i o n ms tha t the photio input to

the n e t a r o u t i o gurglfr oould induoo bonding motemontr of tho

te lron (Pig. 58). Ar evident from the fi(luro (pig. 59), tar

( e p e e e f bending and tho r a t e of bmding n r f @und t o drpend

on tho i n t o m i t y of l ight . a r n t r of bondtag r r fartrr and

u@ Qeweo of bending war grer%or a t higher i n t r a a i t i o a of l i gh t

Pig, 588 Piotura rho- photoktrutio r o r r u r t of $ha

$el80&& -oh i 8 a l i o l t e d by the phoUo input

f ror tha ratamoarr.

A Pornition of the $ e l m a betore photlo r#mulrtian.

B: Oorit ion of tha te l ron after photio r t i r u l a U o n

of the r 8 t a . o ~ .

Fig. 59: Beaordr mhowiryl the noromant of the t a l r o a

on photia mtlaulation of We re ta roar , Ziorar

tram mhorr liet rt i ru lua . Upper t r r a o ahom

tha maramant of tha t a l r o n roai tosad udng a

l i q u i d potantionater. 'Pba intenr i$y of liat

ured war graa ta r la B than in A, Hota tha t

the urpl i tude of more man^ of tho t e l r e n 18

poster r.ti higher l ight intarmi*.

than at lower in tanr i t ia r . It mr howatar obrarvab Ohrt the

l i g h t i n t a m i t y required t o a l i o i t tbir rarponao war muoh

highar (70 lux) eonpuad t o that raqu ind to a l i o i t aotiri$y

ia tha photoraorptor nowonr.

Rargoaram wera alao raaordad from tha motor uni te

innamatlag U e t e l roa to i l lua lna t ion of the aataromatio photo-

raooptor8, Pigura 60 show a o a v i t y i n 8 rpontmeourly aativa

motor uni t la the l e f t ta l roaio nerve. The uait whiah war

dlroharged at a r a t e of about 3 rpiker/#eo, on photio mtimulation

of the 7th ganglion, Illumination of the talronio nerve i t s e l f

d i d not influenoe the a o t i r i t y i n thir unit.

It i s obviour *at a memory input m y not only in flu an^

funotioning of O h m narroum system by direat ly proriding .bha aanrory

information but a l r o nay great ly exert influenoe by intaraotinq

riU other input8 uhathar o r not tha input i e effeatlve by i t a a l f

i n i t 6 rotion, Thir i r due t o Oha phenonenoa of oonverganoa .tld

aoonomy of f i b r e s obrerved i n a number of arthropod8 (Horridga,

1968). In view of $he la rge numbar of intarneuron8 influonoad

by abdominal photio input, a t l e a r t @@me of then om ba

Oxpaated t o be rarviag i n other gathwa$w 80 wall, h m d l i q

i n f o n n t i o n other than photio rlao, To axaainr th la porr ib i l i ty ,

.Qtirity in i d m U f i e d rnitr war rtubied r p l o y i n g a nunbrr of

rtimuli, both photio aad non-photio+

It m a i a t e m r t i n g Oo f i n d rul t r i rodrl unit8 rtrioh

r@Q@!ided t o more thur one nodrlity. Oar unit erhibitad a rpon-

* ~ e o u r burr* r@tiri8 (pig. 6U). Zha b u r r t r oonriated of 23 *O

Pig . 608 R8aponra fraa a rotor rurit i n tha l a f t talmonio

nerve t o photio at irulation of th8 7 U m i o n ,

FIG. .60

-

JJ r p t l o r oaah and the borr t d m t i o n ru l lod from 250 to 350 mreo.

rean bur r t in t e rva l '8 found t o be about 1.9 reo, (re* a l r o

Pig, l7B,0), There p a m e t e r r re ro f o w d to be aoarly uniform

over a 1- pedod unber buknerr. Aotiri ty i n thir unit war

nodlf i rd both on gentLy touehing the body wall of the f irr t

metaroratio regnent on tho r igh t sido (big. 61B), and photia

r4inulation of tho 5 a m i o n (Rtg, 610), On meohmioal

r t i n u l r t i o n of the body w a l l , We burat duration war prolonged.

Tho first buret e l i o i t e d a f t o r maahmioal rtimulation uonaisted

of 90 rpikea and l a r t e d f o r as long a8 about l a 2 eeo. The

ruooeeding bursta were m r l l o r than the first burat but def in i te ly

l a r g e r than the epontaneous burstr, Photio stimulation of the

5 t h ganglion a l r o had a s imilar effeot i n prolonging the bursts.

3he f i r s t burst l a r t e d f o r about 520 mreo. and oonsirted of about

64 spike8 (Pig, 610). The mean in terburs t in terva l was found t o

inorease from a value of about 1.9 reo. to about 2,2 t o 2.3 moo.

on moahsaioal and photio atimulation, It i r olear from the

f igurea ( ~ % g r * 62 t o 64) tha t both mouhanloal llrtimulation of the

body -1 of the l a 4 metaronatlo llregaaent m d photio atimulation

of the 5 U I ganglion have a s i a i l a r effect an the a o t i r i t y of M e

neuron in that there war a tendmay f o r an inorease i n the n u b o r

of apikerr/burat (Pig, 62) and therefore an inorease i n the burr*

d u r ~ t i o n (Fig. 63) and alro .n inoroa8s i n the in terburs t

in t e rva l (Pig, 64); In botb the ins tmoer , the or iginal pa t te rn

of a a t i f i t y n t u r n e d 5 ta 6 reaondr . i t o r rtimulation,

Fig, 618 Reaponme8 of M intarneuron t o e l e e t r i a a l

atimulat%on of the 4th l e f t regrental m r v a

rad photio r t i r u l a t l o n o f the 5 t h rbaor inr l

gax@ion,

At 8pontaa~our aot ivi ty i n tihe unit oanmirting

of bucmta,

Ba A o t i v i t y i n tha unit an touohing the body

wall of the f i r a t m ~ t a a o u U o aegmont.

Or Aa$iviw i n tho mame unit on photio

at imulrt ion of the 5- abdoainrl g a q l l o n ,

l o t e %he inorease A n the number oi eplk~s/burmt

and burst duratiion on meahaaioal a@ well a8

photio atimulrtian. Alao aeo Bigurom 62 t o 64,

FIG. 61

r

Be Aotiriw oa touohiag the body wall

of tho rot.rorr,

0 , Aotititr on phoWo rtirulr#on OS

the 5th abaorinal ganglion.

Hot* that there i r an inareare irr t h a

number of rpfker/burrt (?is. 62).

inerrearo in ma burrt dura t ion (?%go 63)

and inoraaro in Phe rean burst interval

(?$go 64) a -w U w ~ U 88 ph0Oi 0

rthulation. %ha valu.8 i n IFlg. 64

bdi@a$O IeM ~f 6 8~@0e l l%t@ i ~ t e - 8

+ SeDe -

laotlur! i r r tenuursr war 8 l ro e b r e m d to exhibit 8

apontraarum burr* ao#ri*y ( P i g . 6%). We mean duration of

buret8 r u found t o be a b d 90'mreo. %ah burrt ooarirted

of rbetat . l l t o 16 rgtker. 'Phe brurrt frequenay war found t o be

about l/rreo.. md t h i interburat in terva l varied from 0,9 tio - 1.1 ~000ndr On e l e o t r l o Q r t in r l a t lon o f the r i g h O 4 t h

tho mean burr t duration dooreased s l ight ly to about 80 mseo. urd

the number o f q l k e r / b u r r t tended t o be m a l l a r (11 to 1 2 mpUe8). *

The irequanay of bur r t r on ths other hapd inoraassd t o about

1 3 btan;./10 ma. and the mem buret I n t e r n 1 deorearrd t o abaut

870 mseo, Thir e f t e a t of e1rotrIa.l r t inulat ion war auuH

pronounoed when 8 high frequenay of r t i ru la t ion (40 pulrer/reoond)

-8 sagloyed, (fig. 650). The nwrber of apiker/burrt ran&@ - . from

7 t o 9 m d the bur r t r 18stod f o r @bout 30 mseo. Burrt frequenoy

Inoreased a r m furMer iro about 2 .bursf6/seaond and t h o mean -

in terburs t i n t e r n 1 dearerred t o about 475 nsea. Photlo

rtimulatlon of tae 7th ganglion (Pie. 650) also hnfluenoed' a o t i r i t y

i n the unit i n the sane fashion, There war a deorsrro I n *ha

number of .pikam/burrt t b about 7 t o 9 ' q i k e r &d %n the me-

burat dura$ton whioh war now about 400 msao, The frequency of

bur r t r 8 l r o inoroared t o about 16 burotr/lO roo. .nd the mean

iaterburrt htorrrr l . doonasad t o 660 nseo. Thur to aum8fise,

t h e n n o . 8 tanilenoj for 8 deoreare i n the number of rpikee/

b-t (nr. 66). doorrarr i n Phe buret d u n t i o n (fig. 671,

9. Aatiri* la the unit on olootrieaA

rtirula#on of Oh. right 4th dor8.l

rolpeatal M W ~ at r irequanay of

4 pulror/reo.

D. R ~ ~ o ' M ~ of tho uni* t o photio mamulatian

of tha 7th rbda inr l m i o n .

l o t @ that thm numbor of rgiker/burrt &ad

the burr* QreUon 4aorarra on alaatx?%errl, u

wall rr photio r$irtalatioa. .'

Ngr . 66 t o 69: Ohmga in 80Mr i ty pa**aSn ia

iatamcnrroa arhibiang r)antrPraou bur$

r o a v i t y ( r a m i a n~. (s), on I- l r t i e n *

Bi.Aotir itr an a1eatrlo.L rlimulatioa af

$ha right 4th Qorral 8a0.aat.l aerra

inom88a i n tha fraquenoy @f burr t r (Pig, 68) and deorerre i n the

.am bur r t i n t a m (Ngr 69)e

Xat mother intarneuron rrr found to haw' 8 wide

raoaptiva f f e ld (pig, 70)r 'Phi8 unit w8r 8 l ro ohanatar i rad

b r bur r t r o t i r i t y but r88 not rpontmaourly rot i t@. Burrt

r a t l t i t y oould ba a l io i t ad i n ahir unit by rn~ l of the following

r t i m u l i t

1, Yaahuaioal 8 ~ a u l r t f o n of m 1pr i lo tor . l hair on the

2, Meahaniool r t i a u l r t i o n of 8 oon$rrlataral hair on

tha raoond t.il ramant (Big, 70B)r

3, Yoraan;t of the t e l r e a (Pig* '000).

4, T r p p w tha tabla on whioh the preparation 18 aouatad

(Fig, 'lop),

. ' 51 Photio 8t i .ulat ioa of the 7th -ion (Pig. 701) m d

2he r o t i t i t y a l i o i t e d by the vafiour stimuli rrr found t o

ba d i f fe ren t t o roae axtent (?able 4), The 8eur ia$arburrt

i n t e r n 1 war l a a r t f o r banding of the ta l ron (0.57 rao, ) urd

8u&mtu for photio r t imalr t ion of the 7th g.1ULioa (1.5 8eo.).

m a frrpurnoy of burr t n r found t o ba alwayr na8rly l/rao. axoapt

on boadin(l the t e l ron when i t r r found t o be about 2 burrtr/rao.

The amber of apikar par burr* n r not r i l p i f l o a t l j diff@sOnt

f o r *a -dour stimuli and it varied from 3 t o 6 rpikar.

tuciour stimuli, Tha in ta r r i ty of li&t urad crad the r w $ u d e

81 0 8 t W u l lo. of YO- ~ ~ W ~ O J T lo. ---------- apikar/ iater- of burrtr

f oo-photio ?hetie b u r t burr t

1. P o m r d di 180+ "1 4 to 6 10 4 l./8@00 .ant of .rr pri- l r t a m l hair en .Oh@ 1rt BOW 86aaU0 I@*@ILte

2. lorward d i ~ p l 8 0 e - 5 1.25 I/raa. mant of 8 aontrrc l r t a r a l hair on tha 2nd ma- romatia seflant.

3. Banding of -a 3 $0 5 0.57 2/r@a0 trl son.

4. 28pping the tabla 0n60.

Shining l ight 4 $0 5 10 5 1/8000 on tha 7th #an& i on. Shining l ight 4 t o 3 10 0 1/b@0. on a e 6th g8nglion.

8. Movement of oontr-terrl hair on 4 to 5 1.05 1/8@0. the 2nd nataromaUo rmigrmt m d rimalturaour ill\rasination of 7$h tmnliaa.

Fig. 708 Booordr rhodry burrt a a t l r i t y e l i o i t e d i n a

rul.triredrl interneuron in rorponro t o rrriour

r t i r u l i . Ba-pg of tho i n lUa1 burr* of

.piker at tha begbaing o f .Oh@ lnoordr A D

repromon$ bhs Wne of tho onrat of Ohe

raahaaiarl rtimuli. Iiower liraeaa of 1 and P

indioate li*t rtirulur. Sea text.

I n t o n r W u l r , tho rorponro l a t o a q rrhioh rrrr about 1.0

and 1.89 roo, f o r tho r t i m l a t i o n of tho 6th md 7th g w l i a

roapoatitoly (?I#, 701 md ?), droroarod t o about 0.46 roo. rhea

both tho 6th and 7th gm4lir mn raiaulrtod r i .ul turrour4 dth

a Ugh3 of r m a i n t o n r i v rrod f o r i l lu r in r#~ t h m gWi#lir

indlvidually ( f i g . 71). Thlr dooaaro i n latonoy my bo duo

t o f a a i l i t a t i o n oaatwring at rpnrpror,

Oao a i g n i f i o m t f o a h r e of tho mrrponrr from thir unit

-8 adaptation. !tho bwrtr, onoo o l i a i tod by dirplaamont of

8 h d r , l a r t o d for a mrdrur porlod of about 8 roo. a f t o r uhlah

tha uait rtoppod dieahax&- f r r in(r W.8 period r reoond

rtlmulur t o the same h r i r or d i r p l a o r o n t of .bho other hrir

f r i l o d $0 e l i o i t tho hrrrt r o t i d t y . !l!hlr poriod when tho unit

booomer inoxoitablo following a period of a o t i r i t y m o d fro8

25 t o 30 roo. But pho9iu rt imulation o f oithor tho 6 t h o r tho

7#3 ganglion oould ruooaarfully crliait ao#ri ty during thir period.

Thir ruggrr t r that the seneory information from the hrirr i rpia(o

on tho o u r pathway *oh i s ruoaegtiblo f o r ad8ptrtion. Bu9 tha

photio wut agporrr t o roroh the unit through mothor path*

wbioh i r available md *oh i s not affeotob by input from tho

hag#, would rot rr r merrurr t o Onalre OUoo08#ful hmdlirrg

of information even i n tho prorenoe of otihor oenrory input nhioh

18 l i k e l y t o oawe adaptation i n the Wtr .

If. BaZIVI OURAS bX@HIFf O U O B 03 2HB YEqASOYIZIO

PHOTOWSQEP'POR%

phot io b&av%our of tbo mi*

night and -main photone6a0irr (hrrin# tho r o r t of the dry

( l u ~ r l r h n a md RaoB 1971). I n n a h l n B there animal8 litr i n

deep burrora underneath stoner during tho dy and emerge out of

t h e i r burrorr a t duek i n t o the open a rea whore they r tml l

during tho ear ly hour6 of the night i n rearoh of food, 8aorpionr

hato a l so boon ahom t o oxhibit marked p o r i t i t e t h i l p o b u i r ,

rquoedng through o n r i a o r ( ~ a v o r y , 1959). Theroton, i t may

be e i t h e r the photonogatire bohatfour or the pori t ivo thigmo-

t a a t i o behariour or bolsh -ah aro roaponsiblo f o r driving the

rnimalr i n t o the burrow#. But Oop.lakrlrhnr Beddy (1966) har

oloarly demonrtrated that the p h o t o n ~ g a t i r ~ rorponse and not the

th igaotaa t io behaviour i r mainly rrrponriblo f o r roleot ion of

burrow8 although the l a t t o r may reinforoe the fornor, Aburhuar

(1964) while atudyiag the e f f e a t r of 0Ombinati0~0 of d i f f o r a r t

onvlroruontal f r o t o r s on the behariour of the roorpion Eoiqr\lr

-rrtdrtur a l r o coslaluded that tho l i @ b faotor prebo.inator

over o thar f ra tor r . ?roa t h i a i t i r e + i d e ~ t mt tho photo-

roooptora play an i n p o r t m t ro le i n the behariour of the min.l.

But it i r not known uhother t h i n general information aboub bho

rtrte of i l lumination is relayed through the oyor or the

abdominal photonaoptorr o r both.

brtraooular photonoeptorr have bean mhom t o

r igni f lour t ly inf luenre the boharlour of a larue number

of animals, 2he s t i ak l a r e a t $guroriug a r r m e r a stiok pos twe

during the day a d beoour a o t l r e and feedr a t nlght. Thir

behadour has beea shorn t o oontinue to rome extent @en

the eyer a re oauteriaed ( ~ o d d m and O o l d r i t h , 1972). Light

inhib i ted arousal i n ruoh blinded miarls a lso rhodng that the \

e:iraoaular photonoeptorr om medlate the response. The

ro le of ex t rare t ina l pathways i n mediation of a number of

photokinatio and phototaotio responses i n a number of War18

har been already mmtlonod (p. 11 ) . To e x u i n e the ro le of eyer md the abdomhal photo-

reueptorr i n the photio behatiour of the soorpion the rniaaalr

were plroed i n uhoioe ohmberr (pig, 72). These ohmbere

uonristod of no tangu la r g lara oontainera aonrist ing of two

ha l re r separated by an opaque p a r t i t i o n of blaak oard board.

Proris ion was made i n this p a r t i t i o n f o r the f r e e pasrage of

a ~ h a l r from one half of the ohamber to the other half, One of

the halves war oompletely pr inted blrak on the outer side, The

uonteinrr war oorered over wlth 8 glarr p la te one half of whioh

war a l so pr inted bla& Four nrah oontainers were w e d dth

24 rnimals eaoh, belorrging to both the sexes. The oontainer 1

oonristed of normal untreated animals. Oontainer 2 uonsisted

of urimalr i n w h l u h the metarorrt lo photoreoeptorr were uolraple9ely

bloaked from reoeit ing any l i gh t , bor this purpose mall narrow

? 2 m8grm #lroWAq the ah0%08 ehambor8 ~ 8 . d for

rtu4yingl tho phototratio behariour of

moorpioam.

A - Dark chsmber

B - Light chamber

b w r (5 t o 8 I d imeta r ) of a i f l o i r n t 1-h (10 to 50 m r )

N1I ~ d @ Out 0f 0 @ U q h U @ &@at8 008tad w i t h 5 b 4 008atlg8

o f bladt Indian ink. m a r e b y 8 wan rlippad orar the netarolra

m d t i e d with f i n e 8- thread at .bha juaotioa of maroraa

urd tha nat8rou. N r junotion mr a l ro raalod uia a mrrm

r t r i p of adharive tap@ printad blrok dth Indirn ink, Thara

b y 8 were very l i g h t and did not hinder my noromantr of the

&a4l, Oha .third aontalnar ooarirted of animal8 i n whioh tho

ryor were blooked from l ight* lhro nathodr ware amployad for

this, I n one r a t oonrlrting of 1 2 rni.al.8, the ayor r a m

painted over d t h non-1ath.l blaak paint (Ariua O i l Paint goe

Ltd,), After the first 008ting dried up a raaond ooabing war

given to ensure that there would be no li&t leaking into the

8 Tho whole of the orphalothor8z lodqing a e median and

l a t e r a l eyer were p e i n k d over, In another re$ of 1 2 aninalr

plaoed i n the raoe aontainer, U e eyer war@ mutar irad uring

f i n @ r t a e l naablsr heatad rad hat ju r t brfora r au te r iu t ion ,

Although painting was ruaoaariully ured f o r impairing the photio

input from tha ayar, t h i s uould not be usad for tho aataro8atio

photoraoeptora rinoe there rrrr oraaking a d ohippiiq of the

ooating of paint due t o the m o v m t r of the mrtaroaatia reqrmtr .

The four* aontainer oonrrirted of ani.8lr diere a l l the ayar

+om p a n t e d over aad the net8rom .I80 a o t r n d over ruah tha t

there i r no photio input t h r o w e i ther of than@ two photonoaptor

m,rtrre m e four oontainarr were i l lumimted with two f luorr rorn t

tuba l ight8 ( 4 f t . long) plaoed p a d l a 1 a t ria* -la8 t o the

low 8x08 of the ah r rben . Ihe reoond tube liet nhioh war

orer ly iag the darkor h a l t o r of tho ohmborr -8 ured t o eneure

mat thore would bo no difforonoer i n the temperature i n the two

Bal rer of the uherborr due t o i l l u r i m t i ~ n ~ Other i r o t o r r ruoh

88 the humidity woro aonrtant i n t h e two b l v e r of the ohuber r ,

Iho number of rnlarlr i n tho i l l u n i r u t o d p a r t of the oontainerr

( 3 lux) mr 0 0 ~ t 8 d at i n t o n a l 8 of two hours over a period of

revon oonreoutite d y r ,

The r o r u l t r re rg nuoh agrood with t h e r e s u l t 8 reported

o a r l i e r (~8mrltriahna and Rao, 1971) I n that bhe animal under

normal oonditiona were pho to r rn r i t ive betwecw 6 porn, and 1 2

nidaight ~ n d photonegativo during the r o r t of the dy (pig, 7 3 ) e

It i r evident that Uooking e i t h e r the eyes o r the metasomatlo

photoreooptors d i d not r b o l i J l t h e p a t t o m of photio behatiour

of t h e ur ioa l , l o o iga i f ioant differen08 was obsorved in tho

phot io behariour of tho raimala with eyer o w t e r i s e d m d

orrimrlr with eyer p r in ted over, Henoe t h o i r numbers a re

prerented together, When the ey08 a8 r o l l 8s the metasom8 woro

blookod, the animal t a i l e d t o exhib i t the normal pa t t e rn of

phot io behaviour and the d i r t r i b u t i o n of the .aimale rhored no

re la t ionehip botwom proferonoo f o r l ight o r dark ohamberr

a d t h e t i s o of the dy (Pig, 73D). Thlr a180 ehowr that the

nethob rnployed f o r blooking tho phot io input 8uooorriully

rbol i rh08 a l l phot ia input,

mm a hi@ i n t r n r i t y of i l l u n i r u t i o n (above 50 lux) -8

? A , 7)a Orrph mhorring tho photia brhrriour of .tha

a z a l s r l m a t di f forunt par%od8 of t he we %ha r o r t i o a l ax%# indioatam tha number of

a a l r preaant Aa tha light ebambar

oountad at irrtarrelm of two hour. over 8

period of maran d q 8 . A t o t a l of 24

an%mal8 we- usad i n aaoh aoatainar.

A. lo& a a i m U e .

Be A ~ i u l m i n w h l o h t he ratrmomr -8

bloekod f r o m raoair ing 1ig;htr.

a, MUA. i n a i o h tha aya. ~ i t h ~ l t

p r i a tod blralr o r amtaria8d.

D, A ~ I u l r r i n rrhiah al l the myam a m wall

r a the matrmmr was. bloolced f r o m

raaa i r ing my lie*.

promoak4 to the m b a l o %a tha feu aontabel~r , about 72 to

bOE Of th0 i]ll @8& 0f tha f ir84 Q O A - ~ ~ ~ M

axhibitad 8 taadoney k rurria In *ha d8sk ohanbar irrargaotiva

o f tha t w e of the by, m a rigaifiornoa oS nrah 8 behariour i r

not olaer. However, 4ha a n h a l a i n the 4th oon*.iner aonUnuad

$0 be randomly dirtrib\rtad 88 beforor

laorpions are known t o l i r e i n GrOPprr Sherefore, a

quastion om be mired mat the differanoar obrerrad i n the

dir t r ibut ion of animal8 i n the two halver of the oonbahmrr o r ~ l

not ba rolely due to diffarenoar i n i l luaination but there may b

o a r t a n rooial faotorr influenoing the i r dirtribu9ion. To

alinlnata any ruah rooial intar8oMon that would influgnoa *ha

d i r tdbu t ion of U o eJlimalr, o riagla 8aim8l was plooed ia .a*

of U a four aontaimrr. 2wo of the four a n i m a l 8 were S d a

rurd two were male. It war o b r e r r ~ d that mesa .a iaalr a l ro

baharad esaotly l ike the group of ania8I.r obrartad bafora, l h i r

#horn tihat roeial ia ta raoaoar do not intarSara w i t h the photio

bahariour of t h e an imla .

'Phr, tollowing aenalurionr may be dram iron th, rbora

obrervationr: (1) U t h a r UIe y a r or the meterom8Bic photo-

raaoptorr our madiate tha photio bahrriour of the roorpion

,rrhioh i n r o l r r r t i aa dapandant prafarenaar fo r l igh t m d dark

o o a d i t i ~ n r ~ (2) The mapound eyer and the rataromatie photo-

reoeptorr f om two r q 8 r a t e and indrpandmt photonoaptor

8 y r t r r oapabZe of indrpendantly influanoing %a beh.riour of

-a a. It i r po8dbla that i n n8tun m a r y r t a rainforoa

$ha other tn ~ o l l a o t i a ( r the photio i a i 0 ~ 8 U o n r (3) Tha animal raoairar photio input only through tha ndim md l a t e r a l ayar

u l d Oh@ net.r#.Uo photoraoaptorr and them are no other

photoronrit ire r t ruoturar other than Utara, (4) fha ma t a r o m t i

photoraoap tore arm ranr i t iva to l o r i n t onri t i e r of illuminatioa

ar l o r 88 3 lux i n an i a t a a t aaiaal although highar in ten r i t i e r

warm required to a l i o i t responrer from photoreoaptor neuron8

whila monitioriag the i r a lao t r ioa l ro t i r i ty .

B. R o 1 l of the aetaroma%io ~ h o t o r e o e ~ t o r s u%th r e f a r u a ~ q

The rala of renaory ryetear i n r a t t ing and maintaining the

@xoitabi l i ty lave18 in the oentral namour mystam i n addition

t o providing information about the phyrioal parma $are of tha

environmant i s wall knoun (Oohen, 1965). Thir oan tml axoi tabi l i ty

r t a t a i n turn detanriner the ganaral bahariour of Ohe an- i n

rala9ion t o the mtironaant. The importenom of the baokground

a o t i r i t y i n tiha ranrory ryrtamr i n the maintananom of the norm81

fuaotioning of tho nenour r y r t m h8r baen repeatedly beaonrtratad

( d l @ 1 9 6 1 Oohan, 1965) R m 8 k r i r h n . m d Bao, 1971),

'Pha porr ibla ro le of the mat8roaatio photoraoaptorr i n

influenoin8 the oentral exoitrtory r t r t e of the 8ninrl m e

axuinad. 'Pha defcuuire r t r ika rerponra of the animal u8e

ohoran or an inbioator of the genarrl axoi tabi l i ty of the smiarl,

Zhir mrpoara -oh i n w l v e r the rovment of the retaroma

t o r u d r $he r i t e of r t i n u l a t i o a i r i n i t i a t e d by tha raoaptorr

r m t t a r a d over the nrrfaoa of the l a g r and o0lrar partr of the

bodJ (3-8 m d B&bt&, 1967). ihir ootion of a e rting i r

r l r o ]mom t o p l w a s iga i f ioant ro le i n the bohariour of the

.niaaL, The mpl i tude of tha movement of the matarnoma in naponre

t o a neahaniaal r t i d u r mr reamred i n miaaalr i n the ab8enoa

of my photio input and ooapared with that in u r i m 8 l r n i n the

prasenoe of photia input from the mataroma and the eyes. The

amplitude of t a i l movement i n arah normal animala n i th both the

metasomatic photoreosptors and the median aad l a t e r a l eyer

funational war aonsidered t o represent 100$ tonurn of the 8nia.l.

lChe fourth leg -oh bar bean rho- to e l i o i t maximal t.il

reaponse aaapered to the other l e ~ m war ohosen f o r s t i r u l a t i o a ,

Zaahnique involving a marker nagnot similar t o that employad br

Bamakrishna and 8.0 (1970) war ueeb f o r ds l ivr r ing meohaaiorl

r t i n u l i of uniform rtrangth. The rapplitude o f the ta i l movemart

warr reaaured with the help of a l i q u i d potent imetar ,

%ram batohar o f 20 mimrlr aaoh warm usad f o r We purpore,

Tha r a m r rp l i tuda of tail rrrpoara t o 5 r a n u l i war maamred

from eaoh animal. Tha rtimtli ware rpaoad at i n t a r r r l r of on@

a . m a f i r r t batah of 8aImal.r aonsirted of nonral untraatad

-la, 1Pha saaond bat& of 8nim.la oonristed of anlmslr i n

whioh the median m d l a t a m l ayes ware oompletaly oauterisad

~ 8 i n g red hot neadler about 6 hour8 before fha experiment,

Data a h o r i l y &e role of ajar rsd #a matarma~a phatoneapton

in the oarOnl axai*ability of reorpion, 2hr W u e r n p n r a n t

the morn peroantrg. of the rerponrrfroa a to t .1 of hunbred

obuamtionr 2 S.D. The mean reaponre f r o m tho no& a n i u l r

reprerented lo* toaur.

$ Tonur

0. &&la of the n ~ t u o m a t i o nhotonoantorr i s the looornotop

Lhe extmooular photoreoeptorr hare been ohom t o play an

i8port .nt ro le i n the l o r r o t o r a a t i r i t y of a number of ruliaalr

(Hot fmma, 19701 Underwood and Momkor, 1970; AaLer, 1970, 1971)

Undarwood, 1973). Soorpion exhibit8 a oiraadian rhythm i n

the looomotor aotivi9g w h l o h inorearer around duak md remain8

high during the night followed by a period of inaot iv i ty during

the d y (~opal . l s r i shar Reddy, 1966). the ro le of metaromatio

photoreoeptors i n tha looomotor a o t i v i t y of roofpion i s not known

and the eons war examined by rtudying the looomotor a o t i r i t y

of the animal i n the prerenao and i n the abrenoe of photio input

from the aetrromatio photoreoeptorr.

The looomotor a o t i r i t y m a mearured using a teohnique

rimilsr t o that employed br l a y l o r (1958) and OopalaLrisha.

Reddy (1966). The loaomotor movmmntr of the mimala were raoorde

wlth the help of 8 ltymograph. A Ootal of about 30 anlmalr were

t r i ed , 'Ilhe median md l a t e r a l eyer of the an%mrls were owta r i r ed

aompletely and the mimr l r rubjeotad t o (1) normal l i g h t dark

period of 1 2 h o u r raoh, ( 2 ) oontinuour darknerr and (3) oontlnuou

light. ). fluoreroent l i g h t (5 lux) war ured f o r i l l w i n a ~ o n .

It war evident t h a t i n the rbrmoe of the eyer, the mimrlr

oontiauad to exhibit inorearad 8 o t i r i t y whioh rtarts batween

4 .nd ( p.m. and r e d m f o r a period of about 10 t o 1 2 hour.

A, Wul mbgeoted t o l ight f r o m 6 a.m. to

6 p.m. and to brrknarr from 6 pere to 6 r,r,

0, A n i m a l lubjeetmb t o oontinuow light.

l o t . that the r o t i r i t y o$ W r uriul i r

relr$%vely higher thur f n the other anlnmlr,

tooorotor ra t i r i ty o f uriaals on tha reraath d y

aftar the7 were mabjeoted t o the ~xgarimantrl

l ighbdrrk oondi$ionr rro prorantad*

U@t r u p m t i d ~ d fm 6 t o 6 pea* f 0 1 1 0 ~ d by

d.dm08l fin 6 pear t o 6 &Be (?ig. 7 4 ) . Under oomploto

bubror r , tho oirudira rbytbm r U l l p o r d r t a d md U r n n o no

ohuyo in tho p o d 0 4 of w e t of r o t i d t y or tho duration of

the inoroared aot i rLty oror a podod of om reek (He. 74B)

rho- that tho rbjtb. i r mdogmour. k r l i o r r tudiar r l r o

rhornd that tho l oomata r ao t iv i ty rhJlth. i a ondogatour urd

p o r d r t r f o r mom thua ono month undor oontinuour darlulorr i n

loorpion ( ~ o p a l a k r i lhru Rod*, 1966). Vndor oontinuour L l l r u i -

nation, ormthotyh tho oiraadiaa rhytba porristod, there mr a

rhlft i n tho onrot of a o t i r i t y j r ioh war dalayod by about one t o

two hours rhowi6 that l i g h t p l q r 0080 role i n ro t t ing tho

loomotor a o t i d t y rhfth. (Wg. 740). It i r . I00 orldsnt in.

~a r e r u l t s mat the notaroart io photoreaeptorr prorido ru f f io ioa t

pathway f o r this influsnor of l igh t on tho oiroadirn loomotor

8 0 t i r i t y rhythm of tho mi.& It om r l r o bo obronod that tho

l s r o l of r o t i r i t y i r r o l a t i r a l y highor i n blinded -.lo oxpo8rd

t o oontinuour i l lumia raon md lower i a .aiarlr kopt under

oontlnuour drrknorr hen aonprrrd to tho loomotor r e t i r i t y

of tho rn iul r w d o r normal list-duk oonditionr. ~ h o r o f o r r ,

i t i r otidont that oonrturt photio input f roa the motaroma

r e r a t 0 i n inonarod l o a a o t o r a o t i r i t y of the u r W e