title: Differential brain activation patterns during perception of voice and tone onset time series: a MEG study.
abstract: Evoked magnetic fields were recorded from 18 adult volunteers using magnetoencephalography (MEG) during perception of speech stimuli (the endpoints of a voice onset time (VOT) series ranging from /ga/ to /ka/), analogous nonspeech stimuli (the endpoints of a two-tone series varying in relative tone onset time (TOT), and a set of harmonically complex tones varying in pitch. During the early time window (approximately 60 to approximately 130 ms post-stimulus onset), activation of the primary auditory cortex was bilaterally equal in strength for all three tasks. During the middle (approximately 130 to 800 ms) and late (800 to 1400 ms) time windows of the VOT task, activation of the posterior portion of the superior temporal gyrus (STGp) was greater in the left hemisphere than in the right hemisphere, in both group and individual data. These asymmetries were not evident in response to the nonspeech stimuli. Hemispheric asymmetries in a measure of neurophysiological activity in STGp, which includes the supratemporal plane and cortex inside the superior temporal sulcus, may reflect a specialization of association auditory cortex in the left hemisphere for processing speech sounds. Differences in late activation patterns potentially reflect the operation of a postperceptual process (e.g., rehearsal in working memory) that is restricted to speech stimuli.
authors.affiliation: Vivian L. Smith Center for Neurologic Research, Department of Neurosurgery, University of Texas-Houston Medical School, Houston, TX 77030, USA. Andrew.C.Papanicolaou@uth.tmc.edu
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Papanicolaou
authors.forename: Eduardo
authors.initials: E
authors.lastname: Castillo
authors.forename: Joshua I
authors.initials: JI
authors.lastname: Breier
authors.forename: Robert N
authors.initials: RN
authors.lastname: Davis
authors.forename: Panagiotis G
authors.initials: PG
authors.lastname: Simos
authors.forename: Randy L
authors.initials: RL
authors.lastname: Diehl
mesh_terms: D000328:Adult; D001288:Attention / Q000502:physiology; D001303:Auditory Cortex / Q000502:physiology*; D001931:Brain Mapping; D004292:Dominance, Cerebral / Q000502:physiology; D005072:Evoked Potentials, Auditory / Q000502:physiology; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D015225:Magnetoencephalography; D008297:Male; D010700:Phonetics; D010898:Pitch Perception / Q000502:physiology*; D012815:Signal Processing, Computer-Assisted; D013067:Speech Perception / Q000502:physiology*; D013998:Time Perception / Q000502:physiology*