Awarded in 2026
Home Department: Biology
Faculty Advisor: Mark Schnitzer (Biology and Applied Physics)

Title: Dopaminergic Control of Visual Perception: Circuit Mechanisms of Hallucinations

Abstract:
Hallucinations, seeing or hearing things that aren’t there, are a debilitating symptom in different neuropsychiatric conditions such as schizophrenia, Parkinson’s disease, Lewy body dementia, and drug-induced psychosis. Despite affecting millions of people worldwide, we still do not understand the brain circuit mechanism that cause them, which has prevented the development of targeted treatments. A common substrate across all these diverse conditions is the abnormal levels of striatal dopamine, a neurochemical involved in motivation, reinforcement learning and decision-making. Yet a fundamental question remains: how does striatal dopamine control what we perceive? According to the leading theory of how the brain processes what we see, visual perception can be understood as an active process in which the brain integrates external sensory evidence, with learned internal learned expectations. When learned internal expectations dominate, hallucinations arise, leading to confident visual percepts without corresponding visual sensory input. Using mice trained to detect faint visual signals embedded in noise (mimicking the perceptual uncertainty that precedes visual misperceptions in humans), we will combine cutting-edge multi-region two-photon imaging to record large-scale neuronal activity patterns and dopamine dynamics simultaneously across cortical and striatal regions, together with precise optogenetic control (a technique that uses light to switch neurons on and off) of dopamine signals to map the circuit mechanisms from dopamine dynamics to false visual perception. Specifically, this project will test whether dopamine distorts how the brain learns expectations about the world, or whether it corrupts how those expectations are weighted against the external sensory input in real time during perception. Crucially, these two mechanisms are not mutually exclusive, both may operate but at different timescales (acute vs chronic dopamine dysregulation), and distinguishing them predicts fundamentally different neuropsychiatric interventions. By resolving this question at the neuronal circuit level, this work will bridge systems neuroscience with computational psychiatry and optical engineering, reframing how we understand visual hallucinations to develop more targeted treatments across neuropsychiatric disorders.