N400 abnormalities in unmedicated patients with schizophrenia during a lexical decision task.

Full Abstract

A lexical decision task was used to investigate semantic processing in schizophrenia. Eighteen unmedicated schizophrenics and 18 gender/age-matched controls were tested. Subjects were visually presented with pairs of words. The target word (S2) was either a non-word, semantically related, or unrelated to preceding word (S1). Subjects decided whether the S2 was a word or non-word. Event related potentials (ERPs) elicited by the S2, including N350, and the late positive component (LPC) were measured. The latency of the N350 was prolonged in schizophrenia. The N400 effect, measured by the mean amplitude (300-500 ms) from difference waves (unrelated word-related word, non-word-related word), was smaller in patients. Peak amplitude of the LPC was reduced and latency of the LPC was delayed in the schizophrenics. Behaviorally, control subjects responded much faster to related words compared to unrelated or non-words, while patients showed little difference in processing speed between word categories. A reduced N400 effect suggested inefficient utilization of the context, while prolonged latency of the ERP components suggested a general delay of semantic information processing in schizophrenia.

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Author information

Author/s: Hokama, Hiroto (H); Hiramatsu, Ken-Ichi (K); Wang, Jijun (J); O'Donnell, Brian F (BF); Ogura, Chikara (C);

Affiliation: Department of Neuropsychiatry, Faculty of Medicine, University of the Ryukyus, 207 Uehara, Nishihara, Okinawa 903-0215, Japan. hhokama(-atsign-)med.u-ryukyu.ac.jp

Journal and publication information

Publication Type: Journal Article

Journal: International journal of psychophysiology : official journal of the International Organization of Psychophysiology (Int J Psychophysiol), published in Netherlands. (Language: eng)

Reference: 2003-Apr; vol 48 (issue 1) : pp 1-10

Dates: Created 2003/04/15; Completed 2003/08/21; Revised 2004/11/17;

PMID: 12694896, status: MEDLINE (last retrieval date: 12/26/2008)

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MeSH headings (categories)

This article was linked to the MESH Headings shown below.

Adult
Brain - physiopathology
Brain Mapping
Case-Control Studies
Evoked Potentials - physiology
Female

Humans
Male
Reaction Time
Schizophrenia - physiopathology
Schizophrenic Psychology
Semantics

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