Reaction time, symptom profiles and course of illness in schizophrenia

Abstract

Schizophrenic subjects perform more poorly than normal controls on a wide range of neurocognitive tasks. Some studies suggest that patients with persistent illness may have different patterns of cognitive deficits and different associations between cognitive deficits and symptom profiles compared with patients with fluctuating illness. This study uses simple reaction time, choice reaction time and Stroop tasks to explore the relationship between reaction time and symptom profiles in patients with fluctuating illness ( n=24), persistent illness ( n=17) and normal controls ( n=16). We tested the hypothesis that in patients with persistent illness, psychomotor poverty is associated with impaired initiation of activity, and that disorganization is associated with impaired selection in both persistent and fluctuating illness. There were no differences in the severity of symptoms in the patient groups. In the simple reaction time task, patients with persistent illness performed more poorly than patients with fluctuating illness and controls. Both patient groups performed more poorly than controls in the choice reaction time tasks. Psychomotor poverty was associated with simple reaction time in patients with persistent symptoms. Disorganization was associated with poorer performance on the choice reaction time task in both patient groups. These results suggest the possibility that persistent illness, negative symptoms, and impaired initiation may reflect dysfunction associated with enduring structural abnormalities. In the case of impaired selection processes and disorganization, our data indicate that these abnormalities occur in both persistent and fluctuating illness. This suggests that enduring brain damage might create a predisposition to impaired selection and disorganization, but these clinical features can also arise as a result of transient biochemical imbalance.