Research

Overview

Our research draws on molecular genetics and experimental psychology. Molecular genetics is used to selectively manipulate neural circuits in mice. Experimental psychology is used to understand how these manipulations alter behaviors and the underlying cognitive and psychological processes. We apply these approaches toward several research questions.

Adult hippocampal neurogenesis

Adult hippocampal neurogenesis is conserved across many, if not all, mammalian species. And adult-born neurons appear to have important functional effects. Changes in the rate of adult neurogenesis correlate with clinically important variables. For instance, psychosocial stress potently suppresses hippocampal neurogenesis, while exercise, environmental enrichment, and virtually all antidepressant treatments stimulate adult hippocampal neurogenesis. Using targeted, inducible genetic manipulations in mice, combined with rigorous behavioral analysis, we aim to identify behaviors that are sensitive to the disruption of hippocampal neurogenesis, and then use those behaviors to elucidate the underlying cognitive processes that are modulated by adult neurogenesis.

Hippocampus and context memory

Context memories are multimodal memories of time and place that can be used for different purposes. A context can acquire emotional valence, such as in contextual fear conditioning, where a context acquires the ability to elicit fear. Or a context can help disambiguate the meaning of other stimuli, while remaining neutral itself. For instance, if one is driving down the highway at 80 mph, the sound of a siren may induce fear or anxiety; but if one is sitting in the living room, the siren is not likely to elicit an emotional response. The context (highway versus living room) determines how the siren is interpreted. We are interested in how these different uses of context memory are represented in the brain. Can they be localized to different subregions or longitudinal segments of the hippocampus? How do the neural representations over time?

The neural basis of interval timing

Interval timing is timing in the seconds-to-minutes range. Many different species -goldfish, birds, humans, and more- have the ability to accurately time intervals in this range. In associative learning, knowledge about the temporal relationship among stimuli is acquired very rapidly and informs the very first instances of learned responding within a training experience. For instance, in classical conditioning, animals typically learn not only to respond to the conditioned stimulus, but also when to respond. The conservation of this ability across species suggests that it has strong evolutionary value. We aim to identify the brain structures that represent time and to better understand how time governs basic learning processes such as acquisition and extinction of Pavlovian conditioning.