Electrophysiological insights into language processing in schizophrenia.

Department of Psychology, Tufts University, Medford, Massachusetts 02155, USA.
Psychophysiology (Impact Factor: 3.18). 12/2002; 39(6):851-60. DOI: 10.1111/1469-8986.3960851
Source: PubMed

ABSTRACT Deficits in language comprehension in schizophrenia were examined using event-related potentials (ERPs). Schizophrenic and healthy participants read sentences in which the first clause ended with a homograph, and the second clause started with a target word that was semantically related to the homograph's dominant meaning (e.g., 1. Diving was forbidden from the bridge because the river had rocks in it. or 2. The guests played bridge because the river had rocks in it.). Processing of the targets (e.g., "river") was expected to be primarily influenced by the preceding overall sentence context (congruent in 1; incongruent in 2) in healthy participants, but to be inappropriately affected by the dominant meaning of homographs (e.g., the "structure" meaning of "bridge") in sentences like 2 in schizophrenic patients. The N400 ERP component that is known to be sensitive to contextual effects during language processing confirmed these predictions. This showed that language abnormalities in schizophrenia may be related to deficient processing of context-irrelevant semantic representations of words from the discourse.

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    ABSTRACT: Thought and language disturbances are crucial clinical features in Bipolar Disorders (BD), and constitute a fundamental basis for social cognition. In BD, clinical manifestations such as disorganization and formal thought disorders may play a role in communication disturbances. However, only few studies have explored language disturbances in BD at a neurophysiological level. Two main Event-Related brain Potentials (ERPs) have been used in language comprehension research: the N400 component, elicited by incongruous word with the preceding semantic context, and the Late Positive Component (LPC), associated with non-specifically semantic and more general cognitive processes. Previous studies provided contradictory results regarding N400 in mood disorders, showing either preserved N400 in depression or dysthymia, or altered N400 in BD during semantic priming paradigm. The aim of our study was to explore N400 and LPC among patients with BD in natural speech conditions. ERPs from 19 bipolar type I patients with manic or hypomanic symptomatology and 19 healthy controls were recorded. Participants were asked to listen to congruous and incongruous complete sentences and to judge the match between the final word and the sentence context. Behavioral results and ERPs data were analyzed. At the behavioral level, patients with BD show worst performances than healthy participants. At the electrophysiological level, our results show preserved N400 component in BD. LPC elicited under natural speech conditions shows preserved amplitude but delayed latency in difference waves. Small size of samples, absence of schizophrenic group and medication status. In contrast with the only previous N400 study in BD that uses written semantic priming, our results show a preserved N400 component in ecological and natural speech conditions among patients with BD. Possible implications in terms of clinical specificity are discussed.
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