Dynamic Choice Behavior of Mice under Variable-Interval Reinforcement Schedules

Publikation: Bog/antologi/afhandling/rapportPh.d.-afhandlingForskning

In the context of studying foraging decisions in the lab, variable interval schedules for reward delivery have been proven speci cally useful. The optimal strategy under such schedules, called matching behavior, is to allocate choices among options according to the reward rates obtained. My PhD thesis addresses the underlying mechanisms of matching behavior from the novel perspective of decoupling time from trial structure. In this respect, my focus lies on how animals estimate and react to varying reward rates. To this end, I establish two versions of a trial-based, two-options dynamic matching task in mice. In the simple version reward rates are controlled solely by the probability of assigning a reward to an option. In contrast, in the delay version, reward rates are additionally manipulated by varying the initial wait intervals prior to the decision. I nd that, in the simple version, mice adjust their choice distribution dynamically to experienced reward proportions, as has been observed in other species. Hereby, mice seem to rely on both past rewards and choices leading to a mixture of alternation and perseverance. In the delay version, this balance between choice patterns is shifted towards perseverance upon longer wait delays. This suggests that mice are not only sensitive to relative, but also absolute reward rates demonstrating the signi cance of time in the decision process. Interestingly, my analysis reveals that this change in choice strategy can be mainly attributed to impaired choice integration, while reward integration remains una ected indicating independent integration processes over event histories. As a potential underlying mechanism, I test a recently developed reinforcement learning model, the double-trace model. This model captures and replicates the choice behavior signi cantly better than other reinforcement learning models o ering a decision process potentially shared across species.
StatusAfsendt - 31 jan. 2019

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