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People/Faculty
Ann M. Graybiel, Ph.D.
Walter A. Rosenblith Professor of Neuroscience

Department of Brain and Cognitive Sciences
Building: 46-6133
Lab: Graybiel Lab
Email: graybiel@mit.edu

Neural Basis of Implicit Learning and Action Strategies
Much of our normal behavior depends on learning how to perform sequences of acts so smoothly that we can carry them out with minimal conscious effort. This type of learning is crucial for maximizing cognitive function. We depend on it to free us to think and to react to new events in the environment. Much evidence suggests that the basal ganglia are centrally involved in this type of learning, variously known as procedural, implicit or habit learning. But what is the type of neural processing that lets us transform behaviors into habits? And how do we break them once they are formed? The goal of research in the Graybiel laboratory is to answer these questions.

The basal ganglia function as part of a distributed network (including cortical areas), in which the frontal cortex and basal ganglia operate in loop circuits in the acquisition and performance of habits. Our lab is interested in identifying the neural plasticity that occurs in these cortico-basal ganglia loops during acquisition, and the neural encoding that mediates subsequent performance of the behavioral routines. We use two experimental approaches to focus on these issues. First, we record chronically with multiple tetrodes (four-channel electrodes) from ensembles of neurons in the striatum and cortex of rats and mice as they undergo training in learning tasks such as T-mazes and then as they perform these tasks after learning. We find large-scale and long-lasting changes in the response properties of striatal neurons as the learning process takes place and find that they occur at the population level. We also record from the frontal cortex and striatum of macaque monkeys as they learn motor tasks and then perform them "automatically" as routines. We find specific neural modulation patterns in the cortex and striatum as the monkeys shift cognitive strategies during learning. Again the activity modulation occurs at the population level. Therefore, the Graybiel lab can track shifts in behavioral state during habit learning by monitoring the dynamic changes in ensemble activity that occur in cortico-striatal networks.

The second approach is to seek molecular events that mark the stages of procedural learning and to discover links between these molecular markers and the physiology. We map early response genes for initial clues to identify relevant circuits, and have cloned novel striatum-enriched genes to allow transgenic approaches to studying habit learning.

DeCoteau WE, Thorn C, Gibson DJ, Courtemanche R, Mitra P, Kubota Y, Graybiel AM. (2007) Learning-related coordination of striatal and hippocampal theta rhythms during acquisition of a procedural maze task. Proc Natl Acad Sci U S A. 2007 Mar 27;104(13):5644-9.

DeCoteau WE, Thorn CA, Gibson DJ, Courtemanche R, Mitra P, Kubota Y, Graybiel AM. (2007) Oscillations of local field potentials in the rat dorsal striatum during spontaneous and instructed behaviors. J Neurophysiol. 2007 Feb 28

Tippett LJ, Waldvogel HJ, Thomas SJ, Hogg VM, van Roon-Mom W, Synek BJ, Graybiel AM, Faull RL (2006) Striosomes and mood dysfunction in Huntington's disease. Brain.130:206-221. Brain Abstract

Barnes, T. Kubota, Y., Hu, D., Jin, D.Z., and Graybiel, A.M. (2005) Activity of striatal neurons reflects dynamic encoding and recoding of procedural memories.
Nature. 437:1158-1161

Our most recent publications can be found at the lab website:

http://web.mit.edu/bcs/graybiel-lab/pub.html