Sensory feedback mediated modulation of bout dynamics in larval zebrafish

Shenoy, Amey Sunil (2022) Sensory feedback mediated modulation of bout dynamics in larval zebrafish. Masters thesis, Indian Institute of Science Education and Research Kolkata.

Text (MS dissertation of Amey Sunil Shenoy (17MS064)) 17MS064_Thesis_file.pdf - Submitted Version Restricted to Repository staff only Download (4MB)

Abstract

Making correct decisions often requires organisms to accumulate evidence from their surroundings. This process becomes particularly difficult in an environment where the organism might receive different feedback from the same action. In such situations, making an effective choice reduces to successfully predicting the outcome of future choices and maximising this reward. This prediction requires continuously updating a behavioral policy by taking into consideration the history of past outcomes. This can be accomplished by computing a subjective value for a particular action and then updating it depending on the outcome of that choice like in a reinforcement learning system. I explore this paradigm in larval zebrafish exploiting its positive phototactic behavior to bias its left-right turn selection. We see that larval zebrafish utilise the change in light intensity that results from a particular bout to bias the orientation of the forthcoming turns. In a behavior task, where the action reinforcement probability is varied, we see that the zebrafish’s choice ratio matches the reinforcement ratio. Larval zebrafish, therefore, uses information about past rewarded and unrewarded swim events to update its behavioral policy and select the optimal motor output. Having established this behavioral paradigm in freely swimming and embedded larval zebrafish will eventually allow for whole-brain imaging and characterisation of the neural circuitry involved in this process.

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