Bimodal response sensitivity and bias in a test of sustained attention contrasting patients with schizophrenia and bipolar disorder to normal comparison group.

This study examined response discrimination (d') and bias (likelihood ratio) differentials in a computer-generated test of auditory and visual attention functioning. Patients with bipolar disorder (n=42) and schizophrenia (n=47) were contrasted to a normal comparison group (n=89) in two conditions: (a) simple modal responsivity (auditory and visual stimuli) and (b) ipsimodal (auditory/auditory and visual/visual) and crossmodal (auditory/visual and visual/auditory) responding. The results of this study indicated that in the simple modal condition both subject groups showed differential modal preferences but in opposite directions. The schizophrenic group showed a significant visual over auditory preference, committing more auditory commission and omission errors than visual errors. The bipolar group displayed a distinct auditory over visual response preference, committing significantly higher number of visual omission errors. Response bias analysis indicates that both diagnostic groups adopted a more liberal response bias, whereas the comparison group assumed a more conservative approach. For all groups response sensitivity improved as response bias became more neutral. The modal switching results indicated that all three groups tended to commit more commission errors (false alarms) in the auditory crossmodal switching condition (visual/auditory) by comparison with the other switching conditions. Between group comparisons for this condition showed that the schizophrenic group committed significantly more commission errors than the other groups. No significant medication effects were detected.