Global and Parallel Cortical Processing of Auditory Gamma Oscillatory Responses in Humans

Gamma oscillation is a physiological phenomenon that reflects higher cognitive function and parvalbumin-positive GABAergic interneuron function in animals. Gamma-band auditory steady-state response (ASSR) is the most robust index for gamma oscillation, which is impaired in patients with neuropsychiatric disorders. Although ASSR reduction is known to be selective for frequency and time, the neural basis of this phenomenon is poorly understood. We directly showed in the current study that ASSR is globally distributed among the temporal, parietal, and frontal cortices using electrocorticography (ECoG) recording from a wide range of the cortex in patients with refractory epilepsy. ASSR was composed of multiple neural circuits depending on frequency and latency. Importantly, late-latency ASSR was topographically organized along the dorsal and ventral auditory pathways according to frequency tuning characteristics. These results provide a neural basis of the frequency-time dependence of ASSR reduction in patients with neuropsychiatric disorders.