our research
Dr. Madhav studies cognitive representations in the brain, specifically in the hippocampal formation. The neural correlates of these representations can be recorded as the activity of place cells, grid cells, and head-direction cells, among several other cell types. His lab will investigate how these representations are formed from sensory inputs, how they are flexibly modulated by task demands, sensory availability and behavioral states, and how they contribute to navigation and control of behavior. There will be two initial research thrusts;
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In a virtual reality ‘dome’ apparatus, rats will be trained to perform complex tasks that require the representation of non-spatial cues in addition to spatial variables. The study will examine how the topology of the representation, as decoded from high-density electrophysiological recordings, conform to the topology of the task-related cues.
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Both rats and human participants in head-mounted virtual reality will navigate a ‘maze’ apparatus. The study will examine how varying levels of information related to the task and goal will affect the behavioral strategies of these subjects. These strategies will be compared to robotic path planning, reinforcement learning and optimal control algorithms. In addition, the study will look for neural correlates of these algorithms in rodents using high-density electrophysiology.
The brain is a feedback control system, with a plethora of hidden states both persistent and plastic. Higher-order representations in the brain are influenced by sensory inputs and task perception, but are driven primarily through persistent internal dynamics. It is the gradual and continuous perturbation of these neural dynamics through sensory modification which could yield the answer to their structure and function.
Quantifying the algorithmic basis of spatial navigation is a challenge that has implications well beyond understanding how a rat can find its food in a maze. Cognitive representations are integral to learning and memory, and the brain regions housing them are affected through neurodegenerative dementias such as Alzheimer’s and Huntington’s diseases. Understanding spatial navigation in rodents is key to understanding problem solving and memory in humans, and likely illuminates a path to early detection and better management of chronic degenerative disorders.
