Introduction

Our laboratory studies the function of the cerebral cortex, including how the cortex encodes and processes sensory information, and how it learns and adapts to patterns in the sensory world. We focus on the rodent’s primary somatosensory (S1) cortex, which is a major model system for studying cortical function. S1 cortex processes information from the facial whiskers, which serve as active tactile (touch) detectors analogous to human fingertips. We study how the whisker system extracts tactile information from the world, and how this information is dynamically encoded and processed by S1 circuits. We also study how S1 neurons and circuits are altered by recent sensory experience in order to store sensory information and optimize S1 processing according to behavioral needs.

Our goal is to understand basic principles of cortical information processing, information storage and learning, from the synapse to circuit to systems levels. Results from our studies will provide much-needed basic knowledge about brain function, and will enable better understanding of common disorders of cortical function and plasticity, including epilepsy, autism, Alzheimer’s disease, learning disability, and mental retardation.

Areas of current research

Synaptic Mechanisms for Cortical Map Plasticity. Cortical map plasticity is mediated at the cellular level by physiological changes at cortical synapses including long-term potentiation (LTP), long-term depression (LTD), and homeostatic plasticity, as well as by anatomical reorganization of cortical microcircuits and changes in intrinsic excitability of neurons. We work to identify specific sites and mechanisms of plasticity, and to understand how multiple plasticity mechanisms interact to drive overall changes in receptive fields and maps. Prior work from our lab helped establish that LTD at L4-L2/3 excitatory synapses underlies a major component of map plasticity, the activity-dependent loss of responses to underused sensory inputs. More recent work focuses on inhibitory microcircuits and excitatory-inhibitory interactions, which can both drive use-dependent changes in maps, and also contribute to map stability (homeostasis).

Sensory processing and coding in the whisker system. A major feature of sensory systems is that sensory detectors are actively moved to sample the environment (e.g., whiskers, fingertips, eyes, sniffing in the olfactory system). How the brain processes active sensory inputs is not understood. Rats actively sweep their whiskers at 5-12 Hz to detect objects and determine object location, surface features, and shape. We are currently performing several types of experiments to determine how tactile information is extracted by moving whiskers and processed and encoded in somatosensory areas of the cortex. These include behavioral analysis of whisker input during whisker sensation, multi-site neural recordings during active palpation and discrimination, and single-unit and whole-cell patch clamp recordings to determine how S1 neurons encode complex, natural whisker inputs.

Time and timing in sensory processing and learning. Precise timing is critical for sensory processing, from speech production and recognition to processing of visual motion, and disruption of rapid temporal processing may be the basic deficit in dyslexia and other language impairment. Recent work from our laboratory indicates that whisker inputs are encoded in S1 with high (~ 10ms) temporal precision, and that this precision is critical for accurate sensory representation and for plasticity. However, sensory behavior appears to reflect integrated input at slower time scales. We are currently testing how this temporal precision arises in S1, and its perceptual importance, with the goal of understanding the neurobiological basis for temporal processing deficits, and how they may be remedied. This work is done as part of the National Science Foundation-funded Temporal Dynamics of Learning Center.