Effects of Instructions on the Early Stages of the Visual Perception of Verbal Stimuli in Health and Schizophrenia

We report here studies of the early stages in the selection of meaningful and meaningless verbal information in one implicit and two explicit tasks on the latency and amplitude of the P100 component of event-related potentials in healthy subjects (n = 99) and patients with schizophrenia in the first psychotic episode (n = 102). Schizophrenia patients displayed greater impairment to the passive perception of meaningful verbal information. Giving instructions made no difference to the properties of the P100 wave from those in healthy subjects. A decrease in the amplitude of the P100 component on perception of words in passive observation conditions seen in patients may be linked with the severity of hallucinations. The relationships of the P100 wave showed that provision of instructions, as compared with passive perception, decreased the time taken for primary analysis of stimuli in healthy subjects regardless of category and relevance, while this occurred only on reading pseudowords in schizophrenia patients. The results obtained here provide evidence of impairments to the automatic attraction of attention to the semantically significant content of verbal stimuli. The studies reported here demonstrated a link between the properties of the P100 wave and behavioral parameters.

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