cognitive neuroscience of perception_1_preliminary (1)

8/9/2019 Cognitive Neuroscience of Perception_1_preliminary (1)

1/38

The Cognitive Neuroscience of Perception

Onur Güntürkün


2/38


3/38

Rules of Perception

At any point in time, countless stimuli are detected by our sensorysystems and compete for our attention. If our attentional systemwould not be limited, we would not need a process of stimulusselection. In this course we will present some of the rules thatgovern our selection.

This process of selection is composed of two maor systems!

The "rst is the bottom-up system. It is stimulus#driven and thusrelies on the properties of the input $brightness, salience, si%e,movement etc.&. 'e attend to them whether we want to or not.(ottom#up attention depends on the properties of the ascending

sensory pathways.

The second is a top-down system. It is goal#driven and relies onpast learning and the current motivation. 'e know what we arelooking for. Top#down attention is mostly mediated by prefrontal

and basal#ganglia systems.Desimone, R. and Duncan, J., Neural mechanisms of selective visual attention, Annual Rev.Neurosci. 1995. 18:193-.


4/38

com!etitive

selection

Retinal eccentricit"


5/38

Auto Arm


6/38

Auto Am!el


7/38

Auto Amsel


8/38

Auto Aster


9/38

Auto

Alster


10/38

Auto

Auster


11/38

Take home message: #ur visual resolution dramaticall" dro!s $ith retinaleccentricit": $e onl" see a tin" fra%ment of our vision in hi%h resolution.

rods

cones

rods &luminace sensitive'

cones &color sensitive'

d i s t r i ( u t i o n

o f r o d s a c r o s s

r e t i n a


12/38

Take home message: )ince cones are rare in the !eri!her", our !eri!heralvision is to some e*tent color-$ea+.

d i s t r i ( u t i o n o

f c o n e s a c r o s s

r e t i n a


13/38

com!etitive

selection

ltrashort memor"



14/38

o$ $e ma+e saccades


15/38

Ultrashort-Term Memory (or Sensory Memory)

N !

" # C

P $

1 sec.

% & '

T '

* S

% & '

T '

* S

1 sec.

N !

" # C

P $

5 ms

)!erlin% /., 190. he information availa(le in (rief visual

!resentations. 2s"chol. ono%r., 4 & 1 1 , 6hole No. 98'


16/38

he shorter the dela", the hi%her the !ro(a(ilit" that $e re!ort the full dis!la".

Take home message: 6e have an ultrashort memor" that vanishes after afe$ hundred milliseconds. 2ro(a(l" this ultrashort memor" &sometimes also

called sensor" memor"' 7%lues saccadic ima%es into a coherent and lar%e

!icture. 6e are deceived to thin+ that this lar%e !icture &$hich is mostl"

constituted (" our sensor" memor"' is actuall" $hat $e see.


17/38

Take home message: ltrashort

memor" seems to $or+ li+e a (lac+(oard:s"m(ols overl"in% other s"m(ols erase

the !revious ones. ou can $rite and

erase on this (lac+(oard.

N +

' # ,

P

N +

' # ,

P

1 sec.


18/38

com!etitive

selection

A $irin% dia%ram for stimulus selection

ltrashort memor"



19/38

o$ visual attention $or+s

tectum o!ticum

&su!erior colliculus'

nudsen, ;.


20/38

.pc.pc.mc.mc

Tectum opticumTectum opticum

>isual in!ut from a certain !oint in s!ace

All o(?ect attri(utes $ithin this !oint in s!ace are hi%hli%hted &and !ossi(l" (ound'


21/38

.pc.pc.mc.mc

>isual in!ut from a certain !oint in s!ace

Tectum opticumTectum opticum

A 7$inner-ta+e-all com!etition for visual attention

i l fi ld


22/38

1 e c t u m

visual field

c e l l u l a r a c t i v i t "

time

6e record from thisneuron

i l fi ld


23/38

1 e c t u m

visual field

c e l l u l a r a c t i v i t "

time

6e record from thisneuron


24/38

o$ visual attention $or+s

Take home message:

" creatin% a 7$inner-ta+e-all s"stem, onl" fe$ &ma" (e

even onl" one' visual o(?ect is !rocessed in the visual

s"stem. his o(?ects then ca!tures all of our attention. his

selection is done /ottom up/ottom up &by the relative saliency of the

stimuli ', or (" top 0o1n !ro?ection &by the forebrain that isable to modulate the tectal dynamical field and thereby the „winner-take-all“ connectivity '.

All this is done (" tin" mid(rain structures. )o, donBt (e

corticocentric.


25/38

com!etitive

selection

)"na!tic $ei%hts of ascendin% streams


ltrashort memor"



26/38

Instruction! )ook for the luminancechange*

)+inance O-Ientation )O#+nilateral )O#(ilateral

time

// ms

. / / m s

0/ ms

Synaptic 1eights of ascen0ing streams&courtes" of =hristian este'

1 r r o r r a t e $ 2 &

este, =., 6ascher, ;., /CntCr+Cn, #. and Dinse, . R., eature s!ecific e((ian learnin%

(iases attentional selection, =urrent iol., 11, 1: 840-88


27/38

Induction of neuronal plasticity by passive, sensorystimulation

)+inance O-Ientation )O#+nilateral )O#(ilateral

time

// ms

. / / m

s

0/ ms

51 rials

2ost 1

9 min

)timulation

aseline

2ost

h

2ost 3

1


28/38

Ri%ht side &stimuliated'

Eeft side

3igh and low fre4uency training results in an increase or adecrease of perceptual detectability.

F

F

F


29/38

he difference is due to a hi%h freGuenc" &E2-li+e' or lo$-freGuenc"

e*!osure &ED-li+e' to the relevant feature. hus, s"na!tic stren%thenin% or

$ea+enin% of (ottom-u! !ath$a"s drives our !erce!tion.

etc. in.

5 sec

5 sec

H

etc. in.

1 H

ED-li+eE2-li+e

Take home message! 5ompetitive mechanisms of sensoryselection can be tuned in a speci"c way and for lengthy periodsof time by synaptic strengthening $)T6#like& or weakening $)T7#

like&. Thus, we can train our perceptional system for ceratin


30/38

com!etitive

selection



ltrashort memor"


com!etitive

selection

eature selection


31/38

ind the lon% $hite vertical (ar

find the inverted letter find the non-inverted letter

reisman A. /ormican ). 1988. eature anal"sis in earl" vision: evidence from search

as"mmetries. 2s"chol. Rev. 95 : 15-8

Take home message: At some !oint (et$een in!ut and res!onse,

o(?ects in the visual in!ut com!ete for re!resentation, anal"sis, orcontrol. he com!etition is (iased, ho$ever, to$ards information that

is currentl" relevant for (ehavior. Attended stimuli ma+e demands on

!rocessin% ca!acit", $hile unattended ones often do not.


32/38

com!etitive

selection



ltrashort memor"


com!etitive

selection

eature selection

ocus attention on sou%ht ima%es


33/38

2refrontal =orte*

33


34/38

2refrontal =orte*

)hort term memor" consists of t$o neuronal entities:

1' An active %rou! of neurons that re!resent the stimulus. his %rou! ismostl" located in sensor" associative cortical areas. #n its o$n, this

%rou! $ould dis(and after a $hile.

' A %rou! of !refrontal neurons that +ee!s the visual associative neurons

in the ventral tem!oral corte* active as a %rou!.

1

34


35/38

6hat do $e o(serve in !refrontal corte* durin% short term memor" I

Dela" !eriod

35

2refrontal neurons are activated $hen the relevant stimulus

disa!!ears. hese neurons are !ossi(l" the cellular correlate of

short term memor".


36/38

Remem(er this or%et it

36

-ose 8, 5olombo ., 9eural correlates of e:ecutive control in the avian brain. 6)o;(iol. //0 $/


37/38

D o p a m i n e

A cortical landsca!e of thou%hts

37

Durste$itH, D., elc, . and /CntCr+Cn, #., A neurocom!utational theor" of the do!aminer%ic

modulation of $or+in% memor" functions, J. Neurosci., 1999, 19, 84-8.

Summary


38/38

38

K Our visual resolution dramatically drops with retinal eccentricity!we only see a tiny fragment of our vision in high resolution and wesee it color#weak.

K 'e have an ultrashort memory that ?glues@ these saccadic imagesinto a coherent and large picture.

K ;timuli compete at brainstem level by a ?winner#take#all@ system,such that only few obects are processed in the ascending sensory

systems. These few obects capture all of our attention. Thisselection is done both by bottom up $by the relative saliency of thestimuli&, andor by top down proections.

K 5ompetitive mechanisms of sensory selection can be tuned in aspeci"c way and for lengthy periods of time by synaptic

strengthening $)T6#like& or weakening $)T7#like&.

K At some point between input and response, obects in the visualinput compete for representation, analysis, or control. Thecompetition is biased, however, towards information that iscurrently relevant for behavior. Attended stimuli make demands on

i it hil tt d d ft d t

Summary

cognitive neuroscience of perception_1_preliminary (1)

Documents