15 - Cortical gamma-band activity during auditory processing: evidence from human magnetoencephalography studies

Summary

Introduction

Oscillatory synchronization in the gamma-band range (~30–100 Hz) has been proposed as a possible solution to the “binding problem,” i.e. the question of how the brain integrates perceptual features that are processed in distant cortical regions to generate a coherent object representation. Intracortical recordings in animals have demonstrated stimulus-specific synchronous oscillations of spatially distributed, feature-selective neurons (Eckhorn et al., 1988; Gray et al., 1989) that may provide a general mechanism for the temporal coordination of activity patterns in spatially separate regions of the cortex (Gray and Singer, 1989; Singer et al., 1997). In addition to visual feature binding, fast oscillations have been found to reflect modulations of arousal (Munk et al., 1996), perceptual integration (Fries et al., 1997), and attentional selection processes (Fries et al., 2001), and have even been proposed as a potential neural correlate of consciousness (Engel and Singer, 2001; Singer, 2001). In the middle of the last decade, the first studies of gamma-band activity (GBA) in human electroencephalogram (EEG) have relied on paradigms analogous to the early animal work (Lutzenberger et al., 1995; Müller et al., 1996). Since then, investigations using scalp EEG, magnetoencephalography (MEG), and intracranial recordings have supported the functional significance of fast oscillatory activity for a wide range of human cognitive functions. The present chapter will first provide a brief overview of the current state of human GBA research related to visual perception, selective attention, and memory.