Research Projects

PROJECT SUMMARY The thalamic reticular nucleus (TRN), the major source of thalamic inhibition, plays essential roles in sensory processing, arousal and cognition. Receiving inputs from cortical and subcortical regions, this structure is strategically positioned to influence thalamo-cortical interactions. During quiescence, the TRN participate in sleep rhythm generation, sleep stability and memory consolidation, while in active states, TRN neurons contribute to sensory filtering underlying attention.

NEURONAL CIRCUITS FOR CONTEXT-DRIVEN BIAS IN AUDITORY CATEGORIZATION In everyday life, because both sensory signals and neuronal responses are noisy, important cognitive tasks, such as auditory categorization, are based on uncertain information. To overcome this limitation, listeners incorporate other types of signals, such as the statistics of sounds over short and long time scales and signals from other sensory modalities into their categorization decision processes. At the behavioral level, such contextual signals bias categorization by shifting the listener's psychometric curve.

PROJECT SUMMARY Goal-directed navigation often occurs in complex, large environments where the same goal can be reached from different starting point and through different routes which are often self-selected. The hippocampus is believed to play a central role in navigation yet it remains poorly understood how it supports the planning and execution of naturally emerging navigation patterns during goal-directed behaviors.

Project Summary Complex motor sequences are fundamental to many highly skilled behaviors, ranging from athletics to musical and vocal expression. Learning such complex movements requires both motor variability, to facilitate exploration important to reinforcement learning, and motor flexibility, to enable the adaptive modification of behavior in response to reinforcement signals. Studies of relatively simple skill learning, such as lever pressing or licking, emphasize that interactions between the motor cortex and the striatum are central to both exploration and reinforcement.

Project summary: Synaptic plasticity in brain structures like the hippocampus has been hypothesized to underlie an essential brain function - consolidating transient experiences into long-lasting memories. The importance of sleep for promoting long-term memory storage, and the disruptive effect of sleep deprivation on memory, have been appreciated for nearly a century. However, it remains unclear how sleep-associated changes in the activity of specific brain circuits contribute to synaptic plasticity in the hippocampus and other structures.

Project Summary/Abstract Sleep is necessary for all brain function and ultimately life. The core function by which sleep contributes to healthy cognition remains one of the great questions facing neuroscience. Recent theories point to powerful cellular rules, but these are controversial and have difficulty accounting for the effects of sleep in ethologically and developmentally diverse circumstances. We recently showed that cortical circuit dynamics are actively tuned to criticality, a computational regime that maximizes information processing.

Project Summary. Human and nonhuman primates are highly visual animals that are predominantly active during the daylight hours. Yet our understanding of the neural mechanisms supporting spatial navigation is largely based on studies of nocturnal, burrowing rodents with poor vision. Indeed, studies of human and nonhuman primates have already demonstrated that spatial positions can be encoded in the hippocampus exclusively by visual inspection of a scene (i.e. spatial-view cells).

Abstract To survive in dynamic environments, the nervous system must be able to generate flexible behavior — seamlessly weaving together past experience with the present context to achieve future goals. Our team of experts on the neural circuits of behavior will collaborate to reveal the neural mechanisms by which a mouse engages in specific processing of one sensory modality versus another based on task demands.

Learning desired actions from experience requires evaluating alternative actions by integrating the consequences assigned to each action over time. In the real world, actions and outcomes occur in complex sequences, and a continuous stream of events must be parsed into appropriate pairs of causative action and outcome before such pairs can be evaluated. However, how the brain solves this problem, known as temporal credit assignment (TCA) is unknown.

SUMMARY Adaptive behaviors emerge from neuronal networks by dynamically regulating functional connectomes. Based on an underlying anatomical connectome, a functional connectome is the configuration of effective synaptic connections that underlies a pattern of neuronal activity during a specific behavior. Unique combinations of neurons activate specific functional connectomes, thereby generating a behavior (a combinatoric code).