Paper available: Integration and ISI variability in Cortical Neurons

[Ken Miller]

FTP-host: ftp.keck.ucsf.edu
FTP-filename: /pub/ken/integration.ps.gz
14 pages

The following paper, to appear in Neural Computation, is now available
by ftp.  The ftp site is
ftp://ftp.keck.ucsf.edu/pub/ken/integration.ps.gz
This and other papers can also be obtained from our http site:
http://www.keck.ucsf.edu/~ken


PHYSIOLOGICAL GAIN LEADS TO HIGH ISI VARIABILITY IN A SIMPLE MODEL OF
A CORTICAL REGULAR SPIKING CELL

Todd W. Troyer and Kenneth D. Miller
todd at phy.ucsf.edu, ken at phy.ucsf.edu

Keck Center for Integrative Neuroscience
Sloan Center for Theoretical Neurobiology
Departments of Physiology and Otolaryngology
University of California, San Francisco
San Francisco, CA 94143

ABSTRACT:

To understand the interspike interval (ISI) variability displayed by
visual cortical neurons (Softky and Koch, 1993), it is critical to
examine the dynamics of their neuronal integration as well as the
variability in their synaptic input current.  Most previous models
have focused on the latter factor.  We match a simple
integrate-and-fire model to the experimentally measured integrative
properties of cortical regular spiking cells (McCormick et al., 1985).
After setting RC parameters, the post-spike voltage reset is set to
match experimental measurements of neuronal gain (obtained from {\em
in vitro} plots of firing frequency vs.\ injected current).
Examination of the resulting model leads to an intuitive picture of
neuronal integration that unifies the seemingly contradictory
``$1/\sqrt{N}$'' and ``random walk'' pictures that have previously
been proposed.  When ISI's are dominated by post-spike recovery,
$1/\sqrt{N}$ arguments hold and spiking is regular; if recovery is
negligible so that spiking is triggered by input variance around a
steady state, spiking is Poisson.  In integrate-and-fire neurons
matched to cortical cell physiology, steady state behavior is
predominant and ISI's are highly variable at all physiological firing
rates and for a wide range of inhibitory and excitatory inputs.