Vikram Gadagkar, PhD

A major goal of neuroscience is to understand how the brain produces behavior. But to produce complex learned behavior, the brain first needs to evaluate behavior. The central question that drives the Gadagkar Lab is: How do brains evaluate behaviors - both self-generated and the behaviors of others? Many of our socially relevant motor skills such as speaking or playing a musical instrument are not innately programmed but are acquired and maintained through a process of trial and error or reinforcement. First, during the practice phase, these complex motor sequences are learned by matching exploratory motor output to internal goals or templates. Second, these newly acquired sequences are performed to a socially significant target audience in a highly stereotyped manner. Third, the audience evaluates the performance, shows a preference for certain features like stereotypy and virtuosity, and provides feedback to the performer. These three stages of practice, performance, and preference serve the goal of learning motor skills critical for social life, yet we understand very little about the neural mechanisms underlying these processes.

The songbird, with its highly tractable song circuit, is an excellent model system to address this problem. The adult zebra finch song is a learned, stereotyped motor sequence, and juvenile finches learn to imitate their tutor’s song (the internal goal) by trial and error. Furthermore, male songbirds ‘practice’ their songs alone with the ultimate goal of ‘performing’ to a female. Female finches evaluate male songs directed at them and show a ‘preference’ for the most stereotyped and attractive songs. The goal of the Gadagkar Lab is to combine the advantages of the zebra finch courtship song system with state-of-the-art computational, theoretical, and experimental techniques to study how the brain implements reinforcement learning through the stages of practice, performance, and preference. Some of the questions we are currently investigating are: 1. What is the role of reinforcement during early critical periods of sensorimotor learning? 2. How does the brain switch between a state optimized for variability and learning to a state optimized for stereotypy and performance? 3. What are the neural mechanisms of female mate choice?