Combinatorial analysis of sequential firing patterns across multiple neurons decoding memory of sequential spatial experience in rat hippocampus

There is broad agreement that the hippocampus is crucially involved in the formation of richly-detailed, long term memories of events in humans. A key aspect of such memories is the temporal order and spatial context of the events experienced. Evidence from a wide variety of behavioral and electrophysiological experiments indicates that the rodent hippocampal spatial memory system is a model system for studying this type of memory in humans. Here, we develop a new combinatorial method for analyzing sequential firing patterns involving an arbitrary number of neurons based on relative time order. We then apply this method to decode memories of sequential spatial experience in the rat hippocampus during slow wave sleep. Specificaly, rats are trained to repeatedly run through a sequence of spatial receptive fields ("place fields") of hippocampal CA1 "place cells" in a fixed temporal order. The spiking activity of many such individual cells is recorded before (PRE), during (RUN), and after (POST) this experience. By treating each place field traversed as an individual event, the rat's experience in RUN can be represeted by the resulting sequence of place fields traversed, and therefore by the activity of the corresponding place cells. Then to characterize the extent to which the sequential nature of the RUN experience has been encoded into memory, we search for firing patterns related to the RUN sequence in POST. To do so, we develop a method that statistically quantifies the similarity between any desired "reference sequence" (here chosen to be the RUN sequence) and arbitrary temporal firing patterns. We find that the RUN sequence is repeatedly re-expressed during POST slow wave sleep in brief bursts involving four or more cells firing in order, but not so during PRE.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Brain and Cognitive Sciences.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2003

Author dc:creator

• Lee, Albert K. (Albert Kimin), 1972-

Advisor dc:contributor.advisor

• Matthew A. Wilson.

• Brain and Cognitive Sciences.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/29932

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/29932