Mechanisms of cortical high-gamma activity (60-200 Hz) investigated with computational modeling

Abstract

High-gamma activity (HGA) at frequencies 60-200 Hz have been observed during task-related cortical activation in humans [1] and in animals [2], and have been used to map normal brain function and to decode commands in brain-computer interfaces. To understand the role that HGA plays in both normal and pathological brain states, deeper insights into its generating mechanisms are essential. Because the neural populations recorded by LFPs and EEG cannot be comprehensively recorded at scales that are likely to be relevant, we used a biologically based computational model of a cortical network to investigate the mechanisms generating HGA. The computational model included excitatory pyramidal regular-spiking and inhibitory fast-spiking neurons described by Hodgkin - Huxley dynamics. We compared activity generated by this model with HGA that was observed in LFP recorded in monkey somatosensory cortex during vibrotactile stimulation. Increase of firing rate and broadband HGA responses in LFP signals generated by the model were in agreement with experimental results (see Figure ​Figure11). Figure 1 Comparison of high-gamma observed in vivo (AB) and simulated in the model (CD) during sensory stimulation for different stimulus amplitudes denoted G1, G2, G5 and G10. AC: average firing rate of neurons. BD: time - frequency maps of LFP signals.