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| Research article summary (published 30 Dec 2001): |
Hemispheric lateralization of the processing of consonant-vowel syllables (formant transitions): effects of stimulus characteristics and attentional demands on evoked magnetic fields.
Full Abstract
It is still unsettled in how far temporal resolution of dynamic acoustic events (formant transitions) or phonetic/linguistic processes contribute to predominant left-hemisphere encoding of consonant-vowel syllables. To further elucidate the underlying mechanisms, evoked magnetic fields in response to consonant-vowel events (synthetic versus spoken) were recorded (oddball design:
standards=binaural/ba/, deviants=dichotic/ba/-/da/; 20 right-handed subjects) under different attentional conditions (visual distraction versus stimulus identification). Spoken events yielded a left-lateralized peak phase of the mismatch field (MMF; 150-200ms post-stimulus onset) in response to right-ear deviants during distraction. By contrast, pre-attentive processing of synthetic items gave rise to a left-enhanced MMF onset (100ms), but failed to elicit later lateralization effects. In case of directed attention, synthetic deviants elicited a left-pronounced MMF peak resembling the pre-attentive response to natural syllables. These interactions of MMF asymmetry with signal structure and attentional load indicate two distinct successive left-lateralization effects:
signal-related operations and representation of 'phonetic traces'. Furthermore, a right-lateralized early MMF component (100ms) emerged in response to natural syllables during pre-attentive processing and to synthetic stimuli in case of directed attention. Conceivably, these effects indicate right hemisphere operations prior to phonetic evaluation such as periodicity representation. Two distinct time windows showed correlations between dichotic listening performance and ear effects on magnetic responses reflecting early gain factors (ca. 75ms post-stimulus onset) and binaural fusion strategies (ca. 200ms), respectively. Finally, gender interacted with MMF lateralization, indicating different processing strategies in case of artificial speech signals.
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Author information
Author/s: Hertrich, Ingo (I); Mathiak, Klaus (K); Lutzenberger, Werner (W); Ackermann, Hermann (H);
Affiliation: Department of Neurology, University of Tübingen, Otfried-Müller-Street 47, Germany. ingo.hertrich@uni-tuebingen.de
Journal and publication information
Publication Type: Clinical Trial; Journal Article; Research Support, Non-U.S. Gov't
Journal: Neuropsychologia (Neuropsychologia), published in England. (Language: eng)
Reference: 2002-; vol 40 (issue 12) : pp 1902-17
Dates: Created 2002/09/04; Completed 2002/11/29; Revised 2006/11/15;
PMID: 12207989, status: MEDLINE (last retrieval date: 11/6/2008)
Sourced from the National Library of Medicine. Abstract text and other information may be subject to copyright.
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