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PSYC 318- Lecture#9
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- 1Research Question: Do rats with a history of cocaine use demonstrate as much insight as control rats do? (Over-expectation: compound probe)step 1: receive compound-cue A1V
a) V (light) says = it's associated with 3 pellets
b) A1(tone) says = it's associated with 3 pellets
i) Based on history of reinforcement animal assumes there're 3 pellets available.
ii) Not based on history of reinforcement, animal assumes 6 pellets available
Reason: b/c cues paired together for the first time - 22) Over-expectation: compound probe (1 day)S.G. = inc. time in food port w/ compound cue (60% instead of 50%).
Cocaine Animals = don't have over-expectation. (don't inc. percent time spent in food port)
Conclusion: animals don’t use model-based thinking & use reinforcement history.
Result#1: inc. amount of time in food port corresponds w/ an inc. OFC activity when A1V is presented (to S.G.???) vs. when A1 is presented in S.G.
Result#2: cocaine animals; no inc. in OFC activity and no inc. in amount of time spent in food port. - 33) Extinction of Over-expectation: compound training (3 days)Findings: compound cue A1V only gives 3 pellets, even though there is more expectation in sucrose animals
Result: punishment of neural circuits (i.e. dopamine neurones stop firing & punish recently active neural activity.
step 1: after 6 presentations of compound cue w/o reward inc. = behaviour extinguished (time spent in food port dec. & OFC activity returns to baseline) - 44) Under-expectation: extinction probe (1 day)Which cues lost value when the animal was punished for over-expectations?
Result: b/c cue V always produced 3 pellets, this prevented it from extinction
Hypothesis: A1 cue should get punished
step 1: Halfway through day, A1 was present alone (instead of A1V), follow by no reward.
Results: 1st time S.G. see A1 cue alone again, they have low expectations of reward (dec. time in food port & dec. OFC activity)
Conclusion: punishment occurred in response to value of A1
Cocaine rats don't change their neural activity/behaviour in response to A1 alone
Result: Cocaine rats can learn just fine; difference b/w S.G. is that they don’t show over-expectation to compound cues or under-expectation to presentation of single cue again - 5The animals that had the greatest over-expectation in phase 2, had the greatest under-expectation in phase 4 (when no reward was present)Interim conclusion: after experiencing compound cue, re-presentation of individual cues (A1) produces blunted reward expectation in drug-naïve rats, (dec. in behaviour & OFC neural activity)
Contrast w/ cocaine rats: never had an over-expectation effect (therefore don't show these effects)
General Observation: individual cue presentations, results in sudden changes in OFC responsiveness (correlates w/ sudden behavioural changes) - 6Why does a history of cocaine affect OFC activity during moments of over or under expectations?OFC neurone excitability is not fundamentally affected by cocaine use b/c it responds to single cues w/ direct reward relationship
Hypothesis#1: maybe following cocaine use, OFC alternates how it integrates info.
Hypothesis#2: Maybe neural activity is altered in circuits upstream of the OFC, this means info. received by the OFC is diff. in animals w/ & w/o a history of cocaine
General: reasons OFC neurons show diff. in compound-cue related neural activity after cocaine use = unclear - 7Can insight be restored?15 Hz optogenetic stimulation = OFC projection neurone's targeted w/ virus during compound cues presentation.
Stimulation: may restore OFC function & mice behaviour = under-expectation.
Cue A1 was first presented alone after compound cue training
Result: behaviour = no different during training (don’t run over to food port/ over-expectation)
As soon as presentation of compound cue stops & only A1 is presented rats expect less reward.
Conclusion: stimulating OFC during presentation of compound cue restored under-expectation of reward during subsequent presentations. A1 cue was punished. - 8Is the timing of the OFC stimulation important?Method: Repeat same optogenetic stimulation but stimulate b/w trials (random times, i.e. no food in bowl, no stimuli present)
Result: Restores behavioral response of under-expectation.
Conclusion: random stimulation seems to restore model-based calculations (that underlie compound cue-related under expectations of value) - 9Final conclusions:Why this works is unclear
Hypothesis: the stimulation somehow alters how OFC integrates incoming synaptic information & attributes value
Conclusion: this data suggests cocaine use somehow alters how the OFC works (simply stimulating this region at somewhat random times can effectively restore normal function & consequently model-based calculations)
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- Psychology Flashcards on PSYC 318- Lecture#9, created by Pascale Bockelmann on 02/02/2017.
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