Stimulus-dependent augmented gamma oscillatory activity between the functionally connected cortical neurons in the primary visual cortex

Abstract : Neuronal assemblies typically synchronize within the gamma band (30-80 Hz) and are fundamental to information processing. Despite numerous investigations, the exact mechanisms and origins of gamma oscillations are yet to be known. Here, through multiunit recordings in the primary visual cortex of cats we show that the strength of gamma power (20-40 Hz and 60-80 Hz) is significantly stronger between the functionally connected units than the unconnected units within an assembly. Furthermore, there is increased frequency coherence in the gamma range between the connected units than the unconnected units. Lastly, the higher gamma rhythms (60-80 Hz) are mostly linked to the fast-spiking neurons. These results led us to postulate that gamma activity is intrinsically generated between the connected units within cell-assemblies (microcircuits) in relation to the stimulus within an emergent ‘50 ms-temporal window-of-opportunity’