Time perception and its neuropsychological correlates in patients with schizophrenia and in healthy volunteers.

Disordered time perception has been reported in schizophrenia. We investigated time perception dysfunction and its neuropsychological correlates in patients with schizophrenia. Participants comprised 38 patients and 38 age- and sex-matched healthy volunteers who were compared in an auditory temporal bisection paradigm using two interval ranges (a 400/800 ms condition and a 1000/2000 ms 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, short- and long-term memory and executive function. In the 400/800 ms 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 400/800 ms condition, and between temporal sensitivity and long-term memory for the 1000/200 ms 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 400/800 ms 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.

Neurocognitive basis of insight in schizophrenia.

People with schizophrenia have been categorised into three groups: those with full insight (aware, correct attributers); those aware of being unwell, but who misattributed their symptoms (aware, incorrect attributers); and those unaware of being ill (unaware). Cluster analysis of 'awareness of illness'and 'relabelling of symptoms'scores on the Schedule for the Assessment of Insight confirmed three distinct subgroups. The unaware group were impaired on executive and memory tests, whereas those in the aware, misattributing group were cognitively intact. Findings support an association between unawareness of illness and executive dysfunction, and highlight the separation of symptom misattribution from unawareness of illness.