1. learning vs plasticity

2. reinforcement learning vs supervised learning

3. circuits: VOR & OKR

4. open vs. closed loop controllers

6. plasticity: cerebellar LTD

5. learning: adjusting the FF controller

frequencyfrequency

E E

H

LRMR

abducens nucl.

vestibular nucl.

oculomotor nucl.

semicircularcanals.

MLF

VORCircuit contraipsi

PPRF

Motor NeuronsRm =

eye position (deg)

From Fuchs & Leschei 1970 From Robinson & Keller 1972

0-75-150 75 1500

100

200

300

eye velocity (deg/s)

r / k = = 0.25 sviscoelastic time constant

Ro = 100 sp/s

Ro

r 1 (sp/s) / (deg/s)

+ rĖ

k 4 (sp/s) / deg

+ kE

-45 -30 -15 0 +15 +30 +45

350

300

250

200

150

100

50

0

firi

ng f

requ

ency

(sp

ikes

/s)

E

Pursuit System(Gaze Velocity Purkinje Cell)

EpMotor

NeuronE + Ė

NeuralIntegrator

(NPH for H INC for V)

Eout

Extra-OcularMuscle

-H

Vestibulo-OcularReflex (VOR)

Saccade System(Burst Neurons in PPRF)

Er

Final Motor Pathway

Ein

?

Integrator Lesion: Effects

Cannon & Robinson 1987

Planes of the Semi-Circular Canals

horizontal anterior posterior

Excitatory Motions for the SCC’s on the left.

from Carpenter, fig. 2.7

from KS&J, fig. 33-9

cochlear n.

vestibular n.

vestibulo-chochlear n.

foramen magnum

Angle at which the plane ofthe anterior semicircular ductcrosses the midsagittal line

cochlea

semicircular ducts:

anteriorhorizontalposterior

internal acousticmeatus

left right

DTN/NOT LTNMTN

D+antU+postH ipsiversive

EIRabbit OK (Afferents)

stimulus speed (deg/sec)

direction selectivity

1010.10.01 inferior

posterioranterior

superior

canal: horizontal anterior posterior

Accessory Optic System

data from Simpson 1984

VN

NPHINC

Ė

E

MN

E

I+

AOS/NOT

InferiorOlive

Cerebellum

climbing fibers

mossyfibers

SCC

errorsignal

Rabbit OK(adjusting VOR gain)

Final Motor Pathway

The normal VOR

Spectacles to change VOR gain

Steve Lisberger

VOR before and after learning

Miles & Fuller, Brain Res. 80:512-6, 1974

Learning in the feedforward controller for saccades

Tim

e du

ring

ada

ptat

ion

expe

rim

ent

Straube et al. J. Neurophysiol. 77: 874-895, 1997.

Double steps of target speed for studying learning in the feedforward controller for pursuit

Kahlon & Lisberger, J. Neurosci. 16: 7270-7283, 1996.

Sequence of a pursuit learning experiment

Kahlon & Lisberger, J. Neurosci. 16: 7270-7283, 1996.

LEARNING

FeedbackController

~100 msretinalinputs

GoalFeedforward

Controller Eyeball+ eyemovement

I.

G.

SensedVariable

VORSaccadesPursuit

HII

•

•

-EII

•

•

VNSC, PPRF

MT, DLPNFMP

General Scheme for Motor Learning

e.g. AOS

to eye musclemotor neurons

VRN

FTN

inferiorolive

GCGC

inhibitoryinterneurons

HGVP

parallel fibers

climbingfiber

inhibitionexcitation

mossy fibers

after Lisberger 1998

sites oflearning

I.

H.

Cerebellar Circuit

(ipsi)

(contra)

The learning rule:“Marr-Albus-Ito” or “Floccular” Hypothesis

Version 1: operational

retinal slip

vestibularinformation + contra I

.. ipsi H gain

CF + PF LTD

Version 2: synaptic plasticity

after Linden & Connor 1995

heterosynaptic LTD

associative LTD

homosynaptic LTD

PC

CF

PF

cerebellar LTD

Long Term Depression

PLC

PIP2

DAG

IP3

NO

cGMP

LTDInduction

PKC*

after Linden & Connor 1995

Parallel Fiber: H(glutamate)

.

Ca++

Ca++

Climbing Fiber: I(PC depolarization)

.

AMPA Na+

mGluR1

Na+

Ca++ Ca++

HGVP

Cerebellar LTD