Differential sustained attention/vigilance changes over time in schizophrenics and controls during a degraded stimulus Continuous Performance Test

The Continuous Performance Test (CPT) is a widely used procedure for sustained attention/vigilance measurement. However, though the key index of vigilance impairment is the decrement of sensitivity over time during the test period, only few studies have examined whether schizophrenics show a larger drop in CPT performance than do healthy controls. 48 schizophrenic inpatients and 48 controls were investigated with the Munich CPT (480 visual stimuli, 25% target stimuli, one stimulus per second). Stimuli were degraded by randomly inverting 40%, 41%, 42%, or 43% of the pixels. Results were calculated separately for three consecutive trial sections. Additionally, PANSS ratings, medication, and other clinical data were documented. Schizophrenics show a vigilance decrement over time, controls show a vigilance increase. Differential vigilance changes were not related to the level of stimulus degradation. Schizophrenics performed worse than controls only at the lowest degradation level. While overall sensitivity correlated negatively with the dose of atypical neuroleptics and benzodiazepines, vigilance shifts over time correlated negatively with the dose of typical neuroleptics. Furthermore, sensitivity was related to the cognitive PANSS syndrome, number of admissions/duration of illness. Differential sensitivity decrements of schizophrenics and controls can be shown if suited CPT procedures are used. The need for basic research on experimental conditions of the CPT as well as examination of the relationship between sustained attention/vigilance decrements and clinical features of schizophrenia is suggested.