title: Neuromagnetic correlates of impaired automatic categorical perception of speech sounds in schizophrenia.
abstract: Schizophrenia is associated with dysfunction in language processing. At the earliest stage of language processing, dysfunction of categorical perception of speech sounds in schizophrenia has been demonstrated in a behavioral task. The aim of this study was to assess automatic categorical perception of speech sounds as reflected by event-related changes in magnetic field power in schizophrenia. Using a whole-head magnetoencephalographic recording, the magnetic counterpart of mismatch negativity (MMNm) elicited by a phonetic change was evaluated in 16 right-handed patients with chronic schizophrenia and in 19 age-, sex-, and parental socioeconomic status-matched normal control subjects. Three types of MMNm (MMNm in response to a duration decrement of pure-tone stimuli; a vowel within-category change [duration decrement of Japanese vowel /a/]; vowel across-category change [Japanese vowel /a/ versus /o/]) were recorded. While the schizophrenia group showed an overall reduction in magnetic field power of MMNm, a trend was found toward more distinct abnormalities under the condition of vowel across-category change than under that of duration decrement of a vowel or tone. The patient group did not show abnormal asymmetries of MMNm power under any of the conditions. This study provides physiological evidence for impaired categorical perception of speech sounds in the bilateral auditory cortex in schizophrenia. The language-related dysfunction in schizophrenic patients may be present at the early stage of auditory processing of relatively simple stimuli such as phonemes, and not just at stages involving higher order semantic processes.
authors.affiliation: Department of Neuropsychiatry, Graduate School of Medicine, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655, Japan. kasaik@bwh.harvard.edu
authors.forename: Kiyoto
authors.initials: K
authors.lastname: Kasai
authors.forename: Haruyasu
authors.initials: H
authors.lastname: Yamada
authors.forename: Satoru
authors.initials: S
authors.lastname: Kamio
authors.forename: Kazuyuki
authors.initials: K
authors.lastname: Nakagome
authors.forename: Akira
authors.initials: A
authors.lastname: Iwanami
authors.forename: Masato
authors.initials: M
authors.lastname: Fukuda
authors.forename: Masato
authors.initials: M
authors.lastname: Yumoto
authors.forename: Kenji
authors.initials: K
authors.lastname: Itoh
authors.forename: Ichiro
authors.initials: I
authors.lastname: Koshida
authors.forename: Osamu
authors.initials: O
authors.lastname: Abe
authors.forename: Nobumasa
authors.initials: N
authors.lastname: Kato
mesh_terms: D000328:Adult; D001308:Auditory Perceptual Disorders / Q000209:etiology*; D001332:Automatism; D001921:Brain / Q000002:abnormalities / Q000503:physiopathology*; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D008279:Magnetic Resonance Imaging; D015225:Magnetoencephalography / Q000295:instrumentation; D008297:Male; D010700:Phonetics; D012559:Schizophrenia / Q000150:complications* / Q000503:physiopathology*; D013067:Speech Perception / Q000502:physiology*