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