Synchronous cortical gamma-band activity in task-relevant cognition

Widespread synchronous oscillatory activity, particularly in the gamma ('40Hz') band, has been postulated to exist in the brain as a mechanism underlying binding. A new method of examining phase synchronicity across multiple electrode sites in specific EEG frequency bands as a function of time was employed, in a conventional cognitive ERP paradigm in 40 normal subjects. A significant late post-stimulus gamma synchronicity response occurred for task-relevant stimuli, whereas for task-irrelevant stimuli no such response was evident. However, an early response was seen for both task-relevant and irrelevant stimuli. This is the first empirical demonstration that widespread synchronous high frequency oscillations occur in humans in relation to cognition. NeuroReport 11:669-675 (C) 2000 Lippincott Williams & Wilkins.