[High freuquency oscillatory activity in the human brain]

Abstract

Synchronized neural activity in animal visual cortex in the frequency range above 20 Hz, the gamma band, has been proposed as a signature of temporal feature binding. More and more research in humans by means of noninvasive electrophysiological recordings was stimulated by these studies. Here, research on evoked and induced gamma band activity in human EEG and MEG mainly in the auditory and visual modality is reviewed and their role in perceptual processes, feature integration and language processing is discussed. In addition, research on the attentional modulation of gamma band activity is reviewed. In contrast to evoked gamma band activity, which occurs right after stimulus onset, induced gamma band activity can be recorded with a latency of 200 to 400 ms and a frequency range of 30 to 95 Hz. Cumulative consistent experimental evidence allows us to conclude that gamma band activity in the human cortex is related to neuronal information processing and cognitive functions, e.g. memory processes. The findings are discussed in the light of different functional theories of induced gamma band activity.