Stimulus-dependent correlations and population codes

TL;DR

This paper investigates how stimulus-dependent correlations among neurons influence the information encoding of neural populations, revealing that such correlations can both carry and modulate information, with effects depending on their relationship to firing rates.

Contribution

The study demonstrates how stimulus-dependent correlations can significantly modulate neural population information, highlighting conditions where they enhance or impair encoding.

Findings

Stimulus-dependent correlations can carry information directly.

Correlations increasing with firing rates can enhance population information.

Strong spatial decay of correlations can diminish the benefits of stimulus dependence.

Abstract

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.