Synchronous chaos and broad band gamma rhythm in a minimal multi-layer model of primary visual cortex

TL;DR

This paper presents a minimal multi-layer model of primary visual cortex demonstrating how interactions between layers can produce synchronous chaos, explaining rapid decorrelation and broad gamma rhythms observed in V1 activity.

Contribution

It introduces a novel multi-layer cortical model showing how layer interactions induce synchronous chaos, accounting for fast gamma rhythm decorrelation in V1.

Findings

High contrast induces synchronous chaotic gamma oscillations.

Low contrast results in weakly synchronous, transient activity.

Synchronous chaos arises from coupled local inhibition and excitation mechanisms.

Abstract

Visually induced neuronal activity in V1 displays a marked gamma-band component which is modulated by stimulus properties. It has been argued that synchronized oscillations contribute to these gamma-band activity [... however,] even when oscillations are observed, they undergo temporal decorrelation over very few cycles. This is not easily accounted for in previous network modeling of gamma oscillations. We argue here that interactions between cortical layers can be responsible for this fast decorrelation. We study a model of a V1 hypercolumn, embedding a simplified description of the multi-layered structure of the cortex. When the stimulus contrast is low, the induced activity is only weakly synchronous and the network resonates transiently without developing collective oscillations. When the contrast is high, on the other hand, the induced activity undergoes synchronous oscillations with an irregular spatiotemporal structure expressing a synchronous chaotic state. As a consequence the population activity undergoes fast temporal decorrelation, with concomitant rapid damping of the oscillations in LFPs autocorrelograms and peak broadening in LFPs power spectra. [...] Finally, we argue that the mechanism underlying the emergence of synchronous chaos in our model is in fact very general. It stems from the fact that gamma oscillations induced by local delayed inhibition tend to develop chaos when coupled by sufficiently strong excitation.