Responses of the human auditory cortex to changes in one versus two stimulus features.
Neuromagnetic responses were recorded with a 24-SQUID magnetometer in two "oddball" experiments to determine whether mismatch responses to changes in single stimulus features are additive. In experiment 1, the one-feature deviants differed from standards in interstimulus interval (ISI) or frequency, and the two-feature deviants in both ISI and frequency. In experiment 2, deviants differed in duration, frequency, or both. All deviants evoked a mismatch field (MMF) with sources close to each other in the supratemporal auditory cortex. Except for the ISI deviants, the MMF sources were about 1 cm anterior to the source of the 100-ms response, N100m, to the standards. In the two experiments, MMFs obtained in response to the two-feature deviants resembled closely the sum of MMFs in response to one-feature deviants. The results suggest that the standards leave a multiple neuronal representation in the human auditory cortex. The particular neuronal traces of the representation react independently to changes in different features of sound stimuli.
Levänen
S
S
Low Temperature Laboratory, Helsinki University of Technology, Espoo, Finland.
Hari
R
R
McEvoy
L
L
Sams
M
M
D000161:Acoustic Stimulation; D000328:Adult; D001303:Auditory Cortex / Q000502:physiology*; D005072:Evoked Potentials, Auditory / Q000502:physiology; D005260:Female; D006801:Humans; D015225:Magnetoencephalography; D008297:Male; D009949:Orientation / Q000502:physiology; D011930:Reaction Time / Q000502:physiology