Induced electrocorticographic gamma activity during auditory perception. Brazier Award-winning article, 2001.
OBJECTIVE
To define the spatial, temporal, and functional characteristics of induced gamma (>30 Hz) activity during functional activation of the left superior temporal gyrus.


METHODS
Electrocorticographic (ECoG) recordings were made in 4 clinical subjects during auditory tone and phoneme discrimination tasks, and event-related changes in the ECoG band power were calculated. The topography and temporal sequence of event-related power changes in different gamma bands were contrasted with those of auditory evoked potentials (AEPs), and with those of event-related power changes in the alpha band (8-12 Hz).


RESULTS
Auditory stimuli induced a broadband power augmentation that included 40 Hz, as well as higher (80-100 Hz) gamma frequencies. The topography of gamma augmentation was similar, but not identical, to that of the AEP, and was more focused than that of alpha power suppression. Its temporal onset coincided with the N100, but outlasted it. Phonemes produced greater gamma augmentation than tones, while a similar difference was not observed in the N100.


CONCLUSIONS
Auditory perception induces ECoG gamma activity not only at 40 Hz, but also in higher gamma frequencies. This activity appears to be an index of cortical activation that reflects task-specific processing in the human auditory cortex more closely than the AEP or alpha power suppression.
Department of Neurology, The Johns Hopkins University School Of Medicine, N. Wolfe St., Meyer Building, Baltimore, MD 21287-7247, USA. ncrone@jhmi.edu
N E
NE
Crone
D
D
Boatman
B
B
Gordon
L
L
Hao
D000293:Adolescent; D000328:Adult; D001307:Auditory Perception / Q000502:physiology*; D001363:Awards and Prizes; D002540:Cerebral Cortex / Q000033:anatomy & histology / Q000502:physiology*; D004569:Electroencephalography / Q000379:methods*; D004827:Epilepsy / Q000503:physiopathology; D005072:Evoked Potentials, Auditory / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010700:Phonetics; D013057:Spectrum Analysis; D013997:Time Factors