e-mail: witali.duninbarkowski@ttuhsc.edu acat’2002, moscow, russia, june 24-28, 2002 great brain...

E-mail: witali.duninbarkowski@ttuhsc.edu

ACAT’2002, Moscow, Russia, June 24-28, 2002

Great Brain Discoveries: When White Spots Disappear?

Witali L. Dunin-Barkowski,

Institute for Information Transmission Problems,

Russian Academy of Sciences, Moscow, Russia Department of Physiology, TTU Health

Sciences Center, Lubbock, Texas, USA

Knowledge:

Finite or Infinite =

= Universe:

http://www.physiology.ttuhsc.edu/wldb/Witali/Witali.htm

Open or Closed

??

Understanding Brain:Fascinating but Finite Problem

The best known precedent: Walking

Simpler Problem: Flying

Exponential Growth in a Limited Space Microbes in a Jar

Task formulation:A microbe divides in two in a second (Tm=1 s). At the start of experiment (T(0)=0) there is one microbe in the 3 liter jar. In Tf=24 hours thejar will be filled with the microbes.Q.: How much time it would take to fill 1/2 ofthe jar? 1/1000 of the jar?

A.: T(J/2)=24 hrs- 1 s; T(J/1000)=24hrs-10 s

Understanding Brain: Finding a Time Constant

0

10000

20000

30000

40000

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31

T1/2 = 6.9 years

Topt = 23 years

Tpsm = 91 years

Society for Neuroscience Annual MeetingsNumber of Attendees (1970 - 2001)

Neural Mechanics:

The First Two Uncovered Mechanisms

1. Sensory Cortex

2. The Cerebellum

http://www.physiology.ttuhsc.edu/wldb

New Hopfield's Paradigm in Computational Neuroscience

1. J.J. Hopfield, C.D. BrodyProc. Nat. Acad. Sci., Vol. 97, No. 25, pp. 13919-13924, Dec., 2000.

2. J.J. Hopfield, C.D. BrodyProc. Nat. Acad. Sci., Vol. 98, No. 3, pp. 1282-1287, Jan., 2001.

Understanding the Brain: Role of John Hopfield

In 1982-1984 he has discovered NEUROMAGNETICS

Hopfield’s paper animal (HPA)

HPA

HPA: Mechanisms

Dunin-Barkowski W.L., Lovering A.T., Orem J.M., Vidruk E.T., Sirota M.G., Beloozerova I.N.Submitted to Computational Neuroscience Meeting, Chicago, July, 2002

HPA: experimental verification

Hopfield & Brody, 2001,Fig. 9

THE CEREBELLUM: 10 % OF THE BRAIN MASS

You CAN live without cerebellum

http://www.physiology.ttuhsc.edu/wldb

DETAILS ONLY:

90 % OF BRAIN NEURONS ? % OF UNIQUE BRAIN

FUNCTIONS

N

i

t

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tgtΠ

1

,d

exp)()()(

),()(d

)(dtett

t

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t,

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HT

tΠ

c

jt

t

j

j

(1)

(2)

(2`)

(3)

(4)

Mauk’s Equations (esp. (2) and (4))

Total synaptic inflow to climbing fiber cell (1), synaptic inflowfrom extra-cerebellar sources (2), and climbing fiber cell impulses (3) in a transient state of (left) and in the steadystate (right).

Density of climbing fiber cellfiring vs. phase of template signal(1) - transient, (2) - steady states.

How equalization works

Equalization is unstable when plasticity depends on ionotropics

1 and 2 as above; climbing fiber cell impulses are not shown: they are highly correlated with the phase of template signal all time. Red bar denotes short period of “attempted” equalization.

“Intracellular” record of the membrane potential of the model climbing fiber cell

Poincare plot of sequential intervals between CFC impulses

Intervals between CFC impulses vs. impulse order number

1 1001

))(()/1()(...)( IOC11 tCtgtg NN

Mm

gg mmN

m

...1

,,...1

Solution exists, when M

Nl

Plljj NjNlxwy ..., 1, ..., 1, , ;

Nj

Cjjkk NjNkyuz ..., 1, ..., 1, , ;

LN

LN

N

Pk

)1(

k

iikkk xLxz

1

)/1(

22 )/1( LN

N

N

P

V

V

V

V

m s e c

m s e c

m s e c m s e c

m sec

m sec

m sec m sec

m sec

m sec

m sec

m sec

a.

b.

m sec

m sec

HEP-TYPE EXPERIMENT IN NEUROPHYSIOLOGYDunin-Barkowski, Markin, Podladchikova, Wunsch, 1999

Minimal model: Mutual inhibition with accommodation

Accommodation: hot topic [Hopfield & Brody, 2001]

Respiratory Pattern Generator - is a first example of a physiological system, where the tentative physiological role of accommodation as a time-scale factor was first

proposed [Reiss, 1964].

Underlying mechanisms: Ca++-dependent potassium conductance (proposed for RPG in [Rybak, Payton &

Schwaber, 1997])

Respiratory Rhythms: Network vs. PacemakerMechanisms.

Intraneuronal Mechanisms and MuscleContraction: Ryanodine Receptors

Ca-dependent Ca release. Contraction demands large amounts of Ca.To make the process independent of extracellular Ca concentrations it is releasedfrom intracellular cisterns.

A fast mediator is needed to transfer eventsat the membrane inside the cell. The most convenient substance - Ca. Just as a signal,not as a catalyzing substance.

Ca-dependent K-channels: accommodation.Release of Ca from intracellular compartments produces cell inhibition. Three factors: (1) external excitation; (2) Ca-dependent K-channels; and (3) Ca-dependent Ca release acting in concert canprovide both conditional pacemakers and flip-flop oscillations.Network mode of operation depends on a single parameter: strength of inhibitory connections between opposing neuron pools.

Model 1 Model 2

In Vivo

Dunin-Barkowski W.L., Escobar A. L., Lovering A.T., Orem J.M., Submitted to Soc. for Neuroscience Annual Meeting, Orlando, Florida, November, 2002

Model 1

Model 2

Dunin-Barkowski W.L., Escobar A. L., Lovering A.T., Orem J.M., Submitted to Soc. for Neuroscience Annual Meeting, Orlando, Florida, November, 2002

We should also keep searching for new components andtheir combinations

The work is demanding and rewarding: We reveal ourselves.The final results are soon to come. Although, may be not so

soon, as one could hope:

Understanding the Brain: Operational Tools

We know a lot about the components

23 y. < Tfin < 91 y.