BINARY MAPPING OF CORTICAL SPIKE TRAINS IN SHORT-TERM MEMORY.
Mark Bodner, Yong-Di Zhou and Joaqun M. Fuster.
Department of Psychiatry and Brain Research Institute, School of Medicine,
University of California, Los Angeles.
APStracts 4:0029N, 1997.
ABSTRACT
Microelectrode studies in monkeys performing short-term memory tasks show the
sustained elevated discharge of cortical neurons during the retention of
recalled sensory information, as those tasks require. Cortical cells that are
part of memory networks are assumed to receive numerous inputs of excitatory
as well as inhibitory nature, local as well as remote. Thus, it is reasonable
to postulate that the temporal and spatial summation of diverse inputs on any
cell in an activated network will result in temporally discrete groups of
spikes in its firing. The activation of a network in active memory supposedly
increases the magnitude and diversity of those inputs and thus increases the
discontinuities and frequency fluctuations in the firing of cells in the
network. In this study we use a new method of analysis which allows the
quantification of firing discontinuities in a spike train. We apply it to
parietal cells recorded from monkeys during the performance of a tactile
short-term memory task. In our method, time is divided into bins of equal
duration, and the measure of discontinuities is the total count of the number
of transitions between consecutive time bins with and without spikes. The
results of the analysis show that in many of the cells studied,
discontinuities (transitions between spiking and non-spiking) reflect memory-
related activity obscured in the measures of raw spike frequency over a wide
range of frequencies. These cells show more firing transitions in active
short-term memory than in baseline (inter-trial) conditions.
Received 24 October 1996; accepted in final form 30 December 1996.
APS Manuscript Number J845-6.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 24 January 1997