The relationship between visual memory and the P300 in families with schizophrenia
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KeywordsSchizophrenia Sustained Attention Visual Memory P300 Latency Neuropsychological Measurement
Patients with schizophrenia and their unaffected relatives exhibit significant P300 amplitude and latency abnormalities in conjunction with neurocognitive deficits. Both the deficits in the P300 and neurocognition suggest that these indexes may be potential endophenotypes of the disorder. Few studies have examined the relationship between the P300 and neuropsychological measurements of sustained attention, visual memory and current intellectual ability in schizophrenia and these studies provide inconsistent results. The aim of the present study is (a) to examine which cognitive impairments the P300 reflects in schizophrenia and (b) to investigate the relationship between neurocognition and the P300 in families with schizophrenia in order to examine if these may be potential endophenotypes of the disorder.
Materials and methods
95 patients with schizophrenia (35 females, 60 males), 149 of their non-psychotic unaffected first-degree relatives (91 females, 57 males) and 69 unrelated healthy controls with no personal family history of psychosis (39 females, 30 males) were assessed both in a P300 oddball paradigm and neuropsychological measurements such as the WAIS-R (Wechsler, 1981), response tendency of the Conner's Continuous Performance Test (Conners, 1995), immediate and delayed visual recall of The Wechsler Memory Scale-Russell's version (Russell, 1975). STATA 9.0 (STATA Corporation, College Station, TX) was used for the statistical analysis of data.
Significant P300 amplitude reductions and prolonged latencies were found in patients and their unaffected relatives independent of current general intellectual ability, education and age. There was a significant effect of sustained attention (response tendency), on the P300 amplitude reductions of patients and their unaffected relatives. Immediate visual recall had a significant effect on the P300 amplitude reduction of patients and their unaffected relatives, while there was no effect of delayed visual recall. There was no significant effect of immediate and delayed visual recall on the P300 prolonged latencies of patients and their unaffected relatives. Sustained attention did not have a significant effect on the P300 latency, but after controlling for its effect the differences between the groups disappeared.
The findings of the present study suggest that the P300 amplitude reduction that patients and their unaffected relatives exhibited reflected impairments in effortful attention and in the use of short-memory processes (e.g. encoding) that involve the visual modality. The findings also suggest a dissociation between the P300 and delayed visual recall in patients and their unaffected relatives. Although it is less clear from the present findings, the prolonged P300 latency does not seem to reflect impairments in sustained attention and visual memory processes in either patients with schizophrenia or their unaffected relatives. The P300 amplitude reduction seems to be a potential endophenotype of schizophrenia
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