Gamma and the Coordination of Spiking Activity in Early Visual Cortex

SummaryGamma components of the local field potential (LFP) are elevated during cognitive and perceptual processes. It has been suggested that gamma power indicates the strength of neuronal population synchrony, which influences the relaying of signals between cortical areas. However, the relationship between coordinated spiking activity and gamma remains unclear, and the influence on corticocortical signaling largely untested. We investigated these issues by recording from neuronal populations in areas V1 and V2 of anesthetized macaque monkeys. We found that visual stimuli that induce a strong, coherent gamma rhythm result in enhanced pairwise and higher-order V1 synchrony. This is associated with stronger coupling of V1-V2 spiking activity, in a retinotopically specific manner. Coupling is more strongly related to the gamma modulation of V1 firing than to the downstream V2 rhythm. Our results thus show that elevated gamma power is associated with stronger coordination of spiking activity both within and between cortical areas.

► Elevated gamma LFP power indicates enhanced spiking synchrony in V1
► More coordinated V1 spiking activity results in stronger coupling with V2 neurons
► Coupling is influenced more by coordinated V1 activity than V2 gamma fluctuations
► Gamma reflects the coordination of intra- and interareal spiking activity