In contrast to animal studies, relatively little is known about the functional significance of the early evoked gamma band activity in humans. We investigated whether evoked and induced 40 Hz activity differentiate automatic, bottom-up aspects of attention from voluntary, top-down related attentional demands. An auditory novelty-oddball task was applied to 14 healthy subjects. As predicted, more evoked gamma was found for the target condition than in the two task-irrelevant conditions. Since gamma band activity was not enhanced for novel stimuli, the evoked gamma response cannot be explained with a simple concept of stimulus arousal. Neither induced gamma nor the degree of 40 Hz phase-locking were different between the experimental conditions. Taken together, our data emphasize the role of evoked gamma band activity for top-down attentional processing.
1Cellular Neurobiology Group, Institute of Medicine, Research Center Juelich, 52425 Juelich
2Institute of Neurophysiology, University Hospital, Eppendorf, 20246 Hamburg
3Max-Planck-Institute of Cognitive Neuroscience, 04303 Leipzig
4Department of Biopsychology, Institute of Psychology, University of Magdeburg, 39016 Germany
CACorresponding Author: email@example.com
Received 20 September 2002; accepted 6 February 2003