Project Summary/Abstract Circuit mechanisms underlying evidence accumulation during decision-making Behavior across many types of decision-making is well described by the gradual accumulation of evidence toward one of multiple alternatives. Neuronal correlates of the accumulation of evidence during perceptual decision-making have been observed in many areas in the brain. Recent work in a rat auditory evidence accumulation task has identified a causal role for a number of brain structures, including the frontal cortex, basal ganglia, and the superior colliculus. These structures are highly interconnected to each other, indicating that understanding their interactions is necessary for elucidating the circuit mechanisms underlying decision- making. It is not known whether or how these structures interact with each other during decision-making. This project will address three questions regarding the interactions between structures implicated in decision- making: 1) Are the frontal orienting fields, a rodent prefrontal area, and the superior colliculus functionally independent during evidence accumulation? 2) How is the neural encoding of evidence transformed between the input and output nuclei of the basal ganglia 3) Does the the neural encoding in the frontal orienting fields and the superior colliculus depend on the basal ganglia? This project will address these questions through simultaneous optogenetic perturbation and electrophysiological recording across multiple brain areas. The results this project will likely provide detailed understanding of the neural circuits that support the gradual accumulation of evidence during decision-making.