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 sustai ned attention/vigilance measurement. However, though the key index of vigil ance impairment is the decrement of sensitivity over time during the test p eriod, only few studies have examined whether schizophrenics show a larger drop in CPT performance than do healthy controls. 48 schizophrenic inpatien ts and 48 controls were investigated with the Munich CPT (480 visual stimul i, 25% target stimuli, one stimulus per second). Stimuli were degraded by r andomly inverting 40%, 41%, 42%, or 43% of the pixels. Results were calcula ted separately for three consecutive trial sections. Additionally, PANSS ra tings, medication, and other clinical data were documented. Schizophrenics show a vigilance decrement over time, controls show a vigilance increase. D ifferential vigilance changes were not related to the level of stimulus deg radation. Schizophrenics performed worse than controls only at the lowest d egradation level. While overall sensitivity correlated negatively with the dose of atypical neuroleptics and benzodiazepines, vigilance shifts over ti me correlated negatively with the dose of typical neuroleptics. Furthermore , sensitivity was related to the cognitive PANSS syndrome, number of admiss ions/duration of illness. Differential sensitivity decrements of schizophre nics 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 examina tion of the relationship between sustained attention/vigilance decrements a nd clinical features of schizophrenia is suggested.