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Board Members

Nai-Chang Yeh
Co-Director

Keith Schwab
Co-Director

Harry A. Atwater, Jr.
Julia R. Greer
James R. Heath
Nathan S. Lewis
Oskar J. Painter
Michael L. Roukes
Axel Scherer
Kerry J. Vahala

 

image Thanos Siapas
Professor of Computation and Neural Systems; Bren Scholar

B.S., Massachusetts Institute of Technology, 1990; M.S., 1992; Ph.D., 1996.

phone: 626.395.8809
location: 427 Beckman Institute
mail code: 139-74

Research Group |

Network Mechanisms of Learning and Memory

Our research focuses on the study of information processing across networks of neurons, with emphasis on the neuronal mechanisms that underlie learning and memory formation. By recording the simultaneous activity of dozens of single neurons in freely behaving animals, we study the structure of the interactions between the hippocampus and neocortical brain areas and the role of these interactions in learning and memory.

The hippocampus is a brain structure that has long been known to be critical for the formation of new memories. This hippocampal involvement is temporary as memories are gradually established in neocortical stores through the process of memory consolidation and their retrieval becomes independent of the hippocampus. During consolidation recently learned information is progressively integrated into cortical networks through the interactions between cortical and hippocampal circuits.

The direct experimental investigation of these interactions has been difficult since, until recently, simultaneous chronic recordings from large numbers of well-isolated single neurons were not technically feasible. These experiments became possible with the advent of the technique of tetrode recordings in freely behaving rodents. Large-scale tetrode recordings provide a powerful technology for studying networks of neurons because they allow (a) reliable isolation of single neuron activity, (b) significant yield, enabling the simultaneous monitoring of large numbers of neurons, and (c) long-term stability of individual neuron recordings over many days, a property critical for studying the neuronal basis of learning.

Using this technique we record the simultaneous activity of large numbers of cortical and hippocampal cells during the acquisition and performance of memory tasks, as well as during the sleep periods preceding and following experience. Our goal is to understand the organization of cortico-hippocampal interactions in the different behavioral states, and work towards identifying the neuronal mechanisms according to which newly learned information is integrated into brain circuits. Furthermore, we investigate the cellular and molecular basis of network interactions by analyzing the effects of pharmacological and genetic manipulations on the organization of ensemble neuronal activity. Our experimental work is complemented by theoretical studies of network models and the development of tools for the analysis of multi-neuronal data.

 

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