Synchronous Chaos and Broad Band Gamma Rhythm in a Minimal Multi-Layer Model of Primary Visual Cortex

1. PLoS Comput Biol. 2011 Oct;7(10):e1002176. doi: 10.1371/journal.pcbi.1002176.
Epub 2011 Oct 6.

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

Battaglia D(1), Hansel D.

Author information:
(1)Max Planck Institute for Dynamics and Self-Organization, Göttingen, Germany.

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, analysis of Local
Field Potentials (LFPs) across different experiments reveals considerable
diversity in the degree of oscillatory behavior of this induced activity.
Contrast-dependent power enhancements can indeed occur over a broad band in the
gamma frequency range and spectral peaks may not arise at all. Furthermore, 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. We show that the strength of the inter-layer
coupling crucially affects this spatiotemporal structure. We predict that layer
VI inactivation should induce global changes in the spectral properties of
induced LFPs, reflecting their slower temporal decorrelation in the absence of
inter-layer feedback. 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.

DOI: 10.1371/journal.pcbi.1002176
PMCID: PMC3188510
PMID: 21998568 [Indexed for MEDLINE]

Conflict of interest statement: The authors have declared that no competing
interests exist.

Auteurs Bordeaux Neurocampus