Decorrelation by recurrent inhibition in heterogeneous neural circuits

TL;DR

This paper investigates how heterogeneity in neural circuits with recurrent inhibition reduces correlations among neurons, with implications for understanding brain activity in regions like the cortex and basal ganglia.

Contribution

It demonstrates that synaptic heterogeneity is essential for inhibitory suppression of correlations and provides analytical results for correlation magnitudes and timescales in neural networks.

Findings

Correlations at zero lag are positive and scale as K^{-1/2}.

Inhibition rapidly suppresses correlations within a timescale of K^{-1/2}.

Model aligns qualitatively with physiological data from cortex and basal ganglia.

Abstract

The activity of neurons is correlated, and this correlation affects how the brain processes information. We study the neural circuit mechanisms of correlations by analyzing a network model characterized by strong and heterogeneous interactions: excitatory input drives the fluctuations of neural activity, which are counterbalanced by inhibitory feedback. In particular, excitatory input tends to correlate neurons, while inhibitory feedback reduces correlations. We demonstrate that heterogeneity of synaptic connections is necessary for this inhibition of correlations. We calculate statistical averages over the disordered synaptic interactions, and we apply our findings to both a simple linear model and to a more realistic spiking network model. We find that correlations at zero time-lag are positive and of magnitude K^{-1/2}, where K is the number of connections to a neuron. Correlations at longer timescales are of smaller magnitude, of order K^{-1}, implying that inhibition of correlations occurs quickly, on a timescale of K^{-1/2}. The small magnitude of correlations agrees qualitatively with physiological measurements in the Cerebral Cortex and Basal Ganglia. The model could be used to study correlations in brain regions dominated by recurrent inhibition, such as the Striatum and Globus Pallidus.