Increasing stimulus duration can normalize late-positive event related potentials in people with schizophrenia: Possible implications for understanding cognitive deficits

This study determined whether increasing stimulus duration for patients with schizophrenia normalized late Event Related Potentials (ERPs) associated with modulation of response to emotion-evoking stimuli. These ERPs are decreased in patients versus healthy controls when both view stimuli of the same duration. Subjects viewed pictures of hands and judged whether the events depicted were painful or non-painful. Pictures were presented to patients for 500 or 800 ms and to healthy controls for 200 or 500 ms. Participants were 19 adult outpatients meeting DSM-IV criteria for schizophrenia or schizoaffective disorder and 18 healthy controls, as assessed by the Structured Clinical Interview. ERPs to neutral stimuli during a 350-900 ms window following stimulus onset were subtracted from ERPs during this same response window to pain stimuli. The area under this difference wave reflected the degree of pain-related positivity and was the dependent measure for analysis. Patient late-positive ERP responses following 500 and 800 ms stimuli were highly similar to responses in healthy controls following 200 and 500 ms stimuli respectively. Patients and controls differed significantly when responses to 500 ms stimuli were compared. People with schizophrenia are known to process information more slowly than healthy people. Our results indicate that slowed early processing of sensory input may limit engagement of higher cognitive and regulatory processes in patients with schizophrenia. This may be one reason that self-regulation is compromised in patients, and may help explain why measures of slowed information processing account for so much variance in other cognitive deficits in schizophrenia.