Preprint available

[Simon R. Schultz]

The following paper has been accepted for publication in Proceedings of
the Royal Society Series B: Biological Sciences, and is available in
preprint form:

"Correlations and the encoding of information in the nervous system",
S. Panzeri*, S. R. Schultz*, A. Treves+ and E. T. Rolls*

* Department of Experimental Psychology, University of Oxford,
  South Parks Rd., Oxford OX1 3UD, U.K.
+ SISSA - Programme in Neuroscience, 34013 Trieste, Italy

------ Abstract: ------

Is the information transmitted by an ensemble of neurons determined
solely by the number of spikes fired by each cell, or do correlations in
the emission of action potentials also play a significant role? We
derive a simple formula which enables this question to be answered
rigorously for short timescales. The formula quantifies the corrections
to the instantaneous information rate which result from correlations in
spike emission between pairs of neurons. The mutual information the
ensemble of neurons conveys about external stimuli can thus be broken
down into firing rate and correlation components. This analysis provides
fundamental constraints upon the nature of information coding -- showing
that over short timescales, correlations cannot dominate information
representation, that stimulus-independent correlations may lead to
synergy (where the neurons together convey more information than they
would considered independently), but that only certain combinations of
the different sources of correlation result in significant synergy
rather than in redundancy or in negligible effects. This analysis leads
to a new quantification procedure which is directly applicable to
simultaneous multiple neuron recordings.

This paper may be downloaded from the web page
http://www.cogneuro.ox.ac.uk/~schultz/corrinfo.html, in either
compressed postscript or PDF format.

-- 
Simon Schultz, D.Phil.
Visiting Fellow, Psychobiology Laboratory,
Division of Psychology,
Building 38, Australian National University,
Canberra, ACT 0200, Australia.
Phone: +61-2 6279 9733   Fax: +61-2 6249 0499
http://www.cogneuro.ox.ac.uk/~schultz