Paper available: Coding in the cat LGN

[Ken Miller]

The following paper is available from 
ftp://ftp.keck.ucsf.edu/pub/ken/LGNPaper.pdf
or from
http://www.keck.ucsf.edu/~ken (click on 'Publications', then on
                               'Experimental Results')


Liu, R.C., S. Tzonev, S. Rebrik and K.D. Miller (2001).  "Variability
and information in a neural code of the cat lateral geniculate
nucleus."  This is a final draft of a paper that has now appeared as
Journal of Neurophysiology 86, 2789-2806.

Abstract:

A central theme in neural coding concerns the role of response
variability and noise in determining the information transmission of
neurons.  This issue was investigated in single cells of the lateral
geniculate nucleus of barbiturate anesthetized cats by quantifying the
degree of precision in and the information transmission properties of
individual spike train responses to full field, binary (bright or
dark), flashing stimuli.  We found that neuronal responses could be
highly reproducible in their spike timing (about 1-2 ms standard
deviation) and spike count (about 0.3 ratio of variance/mean, compared
to 1.0 expected for a Poisson process).  This degree of precision only
became apparent when an adequate length of the stimulus sequence was
specified to determine the neural response, emphasizing that the
variables relevant to a cell's response must be controlled in order to
observe the cell's intrinsic response precision.  Responses could
carry as much as 3.5 bits/spike of information about the stimulus, a
rate that was within a factor of two of the limit the spike train can
transmit.  Moreover, there appeared to be little sign of redundancy in
coding: on average, longer response sequences carried at least as much
information about the stimulus as would be obtained by adding together
the information carried by shorter response sequences considered
independently.  There also was no direct evidence found for synergy
between response sequences.  These results could largely, but not
entirely, be explained by a simple model of the response in which one
filters the stimulus by the cell's impulse response kernel, thresholds
the result at a fairly high level, and incorporates a post-spike
refractory period.


Ken
 
        Kenneth D. Miller               telephone: (415) 476-8217
	Associate Professor		fax: (415) 476-4929
        Dept. of Physiology, UCSF	internet: ken at phy.ucsf.edu
        513 Parnassus			www: http://www.keck.ucsf.edu/~ken
        San Francisco, CA 94143-0444