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Inhibitory Cerebello-Olivary Projections and Blocking Effect in Classical Conditioning. J J Kim, D J Krupa, R F Thompson Science, vol. 279, 570-573 (1998). Test A alone Normal CR Test B alone Very little or no CR. CS A. CR. CS B. Blocking: Observed data. CS A. UR (A-US). US. - PowerPoint PPT Presentation
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Inhibitory Cerebello-Olivary Projections and Blocking Effect in Classical Conditioning
J J Kim, D J Krupa, R F Thompson
Science, vol. 279, 570-573 (1998)
Blocking: Observed data
CS A
US
UR(A-US)
• First CS (A) paired with US– A-US
• First CS (A) and second CS (B) paired with US– Compound conditioning
– AB-US
UR(AB-US)
CS ACS B
US
CS B
CRCS A• Test A alone– Normal CR
• Test B alone– Very little or no CR
Blocking: Interpretation
• If US is fully predicted by A (A-US), then adding B does not provide new information– Save on unnecessary computation
• Weaker pre-conditioning of A-US causes a stronger effect of B-US– Inverse proportionality of A-US and B-US
CS B
CRCS ACS B
CRCS A
Redundant
NMR = nictitating membrane response
Eyeblink Conditioning
Speaker (CS A)Light (CS B)
Air nozzle (US)
Thread to eyelid
Eyelid movement
measurement device
Eyelid closes(UR, CR)
Postulated eyeblink conditioning circuit
CS-US association(Purkinje cells in HVIspike when CR is learned)
Blockinginhibition
GABA antagonists (eg. Picrotoxin [PTX])prevent blocking
Interpositus nucleus
The question: Is this circuit correct?
Experiment 1: Procedure
• Standard classical conditioning– Tone CS
– Airpuff US
– Eye closing UR becomes CR during training
• 54 Purkinje cells recorded during conditioning– 31 in lobule HVI <--- most likely activity site for eyeblink conditioning
– 12 in anterior lobe HV, 6 in HVIIA, 5 in paramedian lobule
Experiment 1: Eyelid & Cell Responses
Naïve animals (5 cells) Trained animals (11 cells)
CS-US trials
US only trials
CR
No purkinje cell response
Purkinje cellspikes
UR
UR UR
Experiment 1:Control, Conclusions, Comments
• Control case: strictly unpaired tone and airpuff trials– 20 out of 45 cells responded to the airpuff with complex spikes
– Indicates that tone and airpuff must be paired for spike suppression
• Conclusion: as eyeblink conditioning occurs the inferior olive’s ability to convey US information to the cerebellum is suppressed– This is not really shown - just the involvement of Purkinje cells
• Comments– UR amplitude in response to US-only trials is higher for trained
animals: why?
Trained eyelid response to picrotoxin (PTX)
US only
CS + USbefore PTX infusion
CS + USafter PTX infusion
Purkinje cell spikes
No purkinje cell spikes
Purkinje cell spikes
CR
CR
UR
• 3 cells recorded• Well-trained
rabbits– how many?
• PTX injected into inferior olive
Experiment 2: Procedure
• Preparation– Rabbits implanted with guide cannulae above contralateral inferior olive
CS A
US
UR(A-US)
• Phase I: Tone-airpuff conditioning– 7 sessions, 1 per day (10 blocks x 10 trials)
UR(AB-US)
CS ACS B
US
• Phase II: Tone-light-airpuff conditioning– Simultaneously introduce one of two fluids:
• GABA antagonist: picrotoxin (PTX)
• Placebo: artificial cerebrospinal fluid (ACSF)
– 5 sessions, 1 per day (10 blocks x 10 trials)
CS B???
US
• Light-airpuff test– Light CS + airpuff US testing (B-US)
– 5 sessions, 1 per day (10 blocks x 10 trials)
Experiment 2: Test groups
• Main group– ACSF: 6 rabbits
– PTX: 12 rabbits
• Control group– 5 rabbits
Phase I Phase II Light-airpuff
Phase II Light-airpuff
Experiment 2: Results
Phase ITone CS
Light-airpuff testLight CS
Phase IITone + light CS
• Normal acquisition
• ACSF/PTX maintain response
• Control case similar to PTX
• ACSF shows blocking, then re-learning
BlockingControl case acquisition
• PTX does not affect UR amplitude
US-only
Partial response
Is the circuit correct?
• Experiment 1 --> something stops Purkinje cell spiking– Purkinje cell spiking correlated with CR
• PTX infusion in inferior olive restores Purkinje cell spiking– Inferior olive and GABA are involved
• Experiment 2 --> PTX infusion prevents blocking– PTX seems to prevent GABA inhibition of inferior olive
Blockinginhibition
Interpositus nucleus
Specific Comments
• Mechanism for inverse relationship between strength of A-US and B-US is not explained
• Slow acquisition during Experiment 2 light-airpuff test (compared to Phase I) not explained
• Decrease of blocking over time is not explained– Due to simultaneous extinction of A-US and acquisition of B-US?
The End
Cerebellar Cortex
(Ghez & Tach, 2000)
Molecular layer
Granule-cell layer
Purkinje cell layer
Parallel fibres
Climbing fibre
Purkinje cell
Purkinje cell axon
Mossy fibre
Golgi cell
Basket cell
Stellate cell
Granule cell
