Septal Regulation of Hippocampal Gamma (40-100 Hz) and Ripple (200 Hz) Patterns and Memory

University Of Connecticut, Storrs CT

Investigators

Abstract

Lay Abstract (0090451) The means by which large numbers of neurons (ensembles) effectively interact is not well understood. Recent findings demonstrate thousands of hippocampal neurons participating in specific fast-frequency patterns [theta-modulated gamma (40-100 Hz) and sharp wave modulated ripples (200 Hz)]. These in vivo patterns likely support the memory functions performed by the hippocampus and interconnected structures (e.g. medial septum). Local application of drugs into the medial septum of rats will be used to manipulate both memory formation and hippocampal electrophysiology. This project will determine the role of septal neurons in regulating gamma and ripple frequency patterns and the relation between these ensemble patterns and memory. The medial septum and the hippocampus are brain structures critical for episodic memory formation. While the functions supported by particular brain structures are fairly well understood, how large numbers of neurons effectively interact to support emergent function is not. The hippocampus exhibits specific patterns of activity during which thousands of neurons discharge in transient gamma (40-100 Hz) and ripple (200 Hz) frequency patterns. These patterns may play a role in organizing the discharge of individual neurons into ensemble patterns, similar to the manner in which the precise timing of miniature lights on a large scoreboard can create a coherent message or picture. What role these organizing patterns actually play in memory formation is not yet known. This project will manipulate gamma and ripple frequency patterns, and determine the effect on memory formation. The results are likely to advance understanding of the function of fast-frequency ensemble patterns.