Responsiveness to repeated speech stimuli persists in left but not right auditory cortex.
Activation of the auditory cortex habituates with repeated stimulation. While behaviorally adaptive in most circumstances, decreasing auditory responsiveness could interfere with speech perception. We therefore tested whether auditory habituation differs for speech and non-speech stimuli and for left and right auditory cortex. We examined seven right-handed subjects in whom we had determined left-hemispheric language dominance by event-related blood flow assessment. We recorded magnetoencephalographic-evoked responses to trains of four sine tones or vowels and measured the decrement from the first to the last stimulus of the response component about 100 ms after stimulus onset (N1). For the sine tones there was a decrement in both hemispheres. Conversely, for vowels there was significant attenuation of the auditory decrement in the left compared with the right hemisphere (p=0.017). This left-hemisphere persistence in auditory responsiveness to vowels demonstrates that the human brain processes speech stimuli differently than non-speech stimuli and that the left-hemisphere plays a dominant role in this speech-specific auditory processing.
Teismann
Inga K
IK
Department of Neurology, University of Münster, Albert-Schweitzer-Str. 33, 48149 Münster, Germany.
Sörös
Peter
P
Manemann
Elisabeth
E
Ross
Bernhard
B
Pantev
Christo
C
Knecht
Stefan
S
D000161:Acoustic Stimulation / Q000379:methods; D000222:Adaptation, Physiological / Q000502:physiology*; D000328:Adult; D001303:Auditory Cortex / Q000033:anatomy & histology / Q000502:physiology*; D001306:Auditory Pathways / Q000033:anatomy & histology / Q000502:physiology*; D002560:Cerebrovascular Circulation / Q000502:physiology; D005072:Evoked Potentials, Auditory / Q000502:physiology; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006185:Habituation, Psychophysiologic / Q000502:physiology*; D006801:Humans; D007807:Language Tests; D015225:Magnetoencephalography; D008297:Male; D011930:Reaction Time / Q000502:physiology; D013067:Speech Perception / Q000502:physiology*