Vigilance in Schizophrenia and its Disruption by Impaired Preattentive Selection: A Dysintegration Hypothesis

Introduction : The study determined, simultaneously, whether major deficits of schizophrenia (sustained and selective attention, slow information processing, slow motor responding) are independent or related to each other. Methods : An auditory vigilance task (Pigache Attention Task, PAT) required a button-press to targets during four 5-minute subtests (slow diotic, fast diotic, slow dichotic, fast dichotic, analogous to four versions of the continuous performance test). Twenty schizophrenics on the first test-occasion of a double-blind, placebo controlled, crossover study were compared to 11 healthy subjects. Also, all 28 fortnightly testoccasions were analysed to quantify the schizophrenia deficits more precisely and the PAT was evaluated in a larger group of 86 healthy subjects. Results : Schizophrenics were significantly impaired on all task parameters versus healthy subjects. The patients' errors were independent and additive (grand mean components: basic task 36%, including a 9% time-on-task component; speed increment 26%; dichotic increment 38%). Errors, latencies, and psychosis severity were mutually correlated. Conclusions : The performance of all subjects confirmed a quantitative Vigilance Decision Model. The PAT impairments in schizophrenia suggested that rival options (e.g. thoughts) redeployed or suppressed attention away from the task, indicating a dysfunction of pre-attentive selection processes. Brain mechanisms are discussed and a new dys integration hypothesis of schizophrenia is proposed.