Stimulus-dependent
correlations and population codes
K. Josic, E. Shea-Brown, B. Doiron, and J. de la Rocha
The magnitude of correlations
between stimulus-driven responses of pairs of neurons can itself be
stimulus-dependent. We examine how this dependence
impacts the information carried by neural populations about the stimuli
that drive them.
Stimulus-dependent changes in correlations can both carry information
directly and modulate the information separately carried by the firing
rates and variances. We use Fisher information to quantify these
effects and show that,
although stimulus dependent correlations often carry little information
directly, their modulatory effects on the overall information can be
large. In particular, if the stimulus-dependence is such that
correlations increase with stimulus-induced firing rates, this can
significantly enhance the information of the population when the
structure of correlations is determined solely by the stimulus.
However, in the presence of additional strong spatial decay of
correlations, such stimulus-dependence may have a negative
impact. Opposite relationships hold when correlations
decrease with firing rates.
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