Degraded Stimulus Continuous Performance Test Research Articles

Paranoid schizophrenia: non-specificity of neuropsychological vulnerability markers

During stages of remission, patients with paranoid schizophrenia seldom show severe attentional or information-processing dysfunctions, except in cases of long-term chronicity. The diagnostic specificity of four putative psychological vulnerability indicators of schizophrenia — the Span of Apprehension, the degraded stimulus Continuous Performance Test (dsCPT), the degraded stimulus visual backward masking task and the Wisconsin Card Sorting Test (WCST) — was examined in a group of patients with paranoid schizophrenia. Since no single test seems to identify all patients, the use of a combination of measures may be a useful strategy. Accordingly, the four tests were administered to 18 paranoid schizophrenic patients, 18 depressed patients and 18 normal subjects. Paranoid schizophrenic patients could be distinguished from normal subjects primarily on the basis of their performance on the backward masking task and secondarily by the dsCPT and the WCST. Paranoid schizophrenic and depressed patients could be differentiated to some extent by their performance on an information-mask condition of the backward masking task. Thus, of the four measures studied, only the degraded stimulus backward masking appeared to be a specific indicator of paranoid schizophrenia. © 1997 Elsevier Science Ireland Ltd.

Glucose metabolic correlates of continuous performance test performance in adults with a history of infantile autism, schizophrenics, and controls

Twenty-five schizophrenic patients, fourteen adults with a history of infantile autism, and twenty normal controls performed a test of sustained attention, the degraded stimulus continuous performance test (CPT), during the 35 minute 18-fluoro-2-deoxyglucose uptake period preceding positron emission tomographic (PET) scan acquisition. This is the first analysis comparing correlations between glucose metabolic rate (GMR) for selected regions and CPT performance. CPT performance differed in controls and schizophrenics, but autistics did not differ from either group. In controls and schizophrenic patients, task performance correlated with GMR in medial superior frontal gyrus and lateral inferior temporal gyrus, suggesting that activation of those regions is important in the normal performance of the task and that damage to those regions, which also showed low GMR in schizophrenics, contributes to the attentional dysfunction in schizophrenia. Also, schizophrenics showed negative correlations of task performance with anterior cingulate activity suggesting that overactivity of that region, which is involved in mental effort and whose GMR was low in our larger study of schizophrenia, impairs task performance in schizophrenics. Autistic patients showed negative correlations of medial frontal cortical GMR with attentional performance, suggesting that neuronal inefficiency in that region may contribute to poor performance.

EEG coherence of prefrontal areas in normal and schizophrenic males during perceptual activation

Multiple studies have demonstrated prefrontal dysfunction among schizophrenics. The prefrontal cortex does not function in isolation, but instead relies on extensive connections with other brain areas. Functional relationships between cortical areas were assessed by calculating the coherences between different scalp electroencephalogram (EEG) signals recorded from 13 unmedicated male patients with schizophrenia and 9 normal male subjects. Alpha-band coherences linked to prefrontal areas in schizophrenic patients were about the same as those of normal controls when subjects were cognitively "at rest," but they were reduced for certain electrode pairs in the former group when performing the degraded-stimulus continuous performance test. Most of these findings were not accounted for by changes in alpha power, suggesting that "cortical circuits" extending beyond prefrontal areas may be disrupted in schizophrenia.