HIGH-FREQUENCY BRAIN ACTIVITY - ITS POSSIBLE ROLE IN ATTENTION, PERCEPTION AND LANGUAGE PROCESSING

Coherent high-frequency neuronal activity has been proposed as a physi ological indicator of perceptual and higher cognitive processes. Some of these processes can only be investigated in humans and the use of n on-invasive recording techniques appears to be a prerequisite for inve stigating their physiological substrate in the healthy human brain. Af ter addressing methodological issues in the noninvasive recording of h igh-frequency responses, we summarize studies indicating co-occurrence of neuronal synchrony of single cells exhibiting rhythmic activity at high frequencies, oscillations in the local Field potential and dynam ics in high frequencies recorded using high-resolution electroencephal ography (EEG) and magnetoencephalography (MEG). We then review EEG and MEG studies of attention, perception, and language processing in huma ns indicating that dynamics in the high-frequency range > 20 Hz reflec t specific cognitive processes. Types of high-frequency (HF) activity can be distinguished according to their latency after stimulus onset, stimulus-locking, cortical topography and frequency. There appears to be a systematic relationship between specific cognitive processes and types of HF activity. The findings are related to recent theories abou t the generation of HF activity and their possible role in binding of stimulus Features. Dynamics of HF cortical activity reflecting higher cognitive processes can be accounted for based on the assumption that the elements of cognitive processing, e.g. visual objects and words, a re organized in the brain as distributed neuronal assemblies with defi ned cortical topographies generating well-timed spatio-temporal activi ty patterns. (C) 1997 Elsevier Science Ltd.