Disordered time perception has been reported in schizophrenia. We investigated time perception dysfunction and its neuropsychological correlates in patients with schizophrenia. Thirty-eight patients and thirty-eight age and sex matched healthy volunteers were compared in an auditory temporal bisection paradigm using two interval ranges (a 400/800ms condition and a 1000/2000ms condition). In the temporal bisection, subjects were required to categorise a probe duration as short or long, based upon the similarity with two reference durations. All subjects also completed a battery of neuropsychological tests measuring sustained attention, shortand long-term memory and executive function. In the 400/800ms condition, patients judged durations significantly shorter than did control subjects. Patients also exhibited decreased temporal sensitivity in both conditions. We found in both groups a negative association between temporal sensitivity and sustained attention for the 400/800ms condition, and between temporal sensitivity and long-term memory for the 1000/200ms condition. In patients, short-term memory performance was negatively associated with duration judgement in both conditions, while executive dysfunction was correlated to a general performance deficit in the 400/800ms condition. These findings suggest the possibility that time perception abnormalities in schizophrenia are part of neuropsychological dysfunction and are likely to adversely impact upon activity of daily living.
Executive cognitive impairment has been found in families affected by schizophrenia and is a putative endophenotype. We wished to explore its genetic basis further by studying the association between impairment and genetic loading for schizophrenia. We studied 30 schizophrenia patients with a family history of schizophrenia, 53 of their nonpsychotic first-degree relatives (familial), 32 patients with schizophrenia but no known family history of psychosis, 52 of their first-degree relatives (nonfamilial), and 47 normal controls. They were tested using the National Adult Reading Test (NART), Trails A and B, Verbal fluency tasks, and a computerized version of the Wisconsin Card Sorting Test (WCST). Familial, but not nonfamilial, relatives were impaired on NART, letter fluency, Trails B, and WCST total errors. They were inferior to nonfamilial relatives on letter fluency and Trails A. Both sets of relatives were impaired on Trails B controlling for Trails A, and on WCST categories achieved. There were no significant differences between schizophrenia patients with and without a family history. Our results suggest that executive deficits qualitatively similar to those seen in those with schizophrenia reflect familial susceptibility, even taking early IQ and education into consideration, consistent with a genetic mechanism.
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