Extensive research has demonstrated that schizophrenic subjects are slower than normal comparison subjects on a range of reaction-time tasks. Some investigators have also observed that schizophrenic patients exhibit larger intra-individual variability in reaction times when performing these tasks than do normal comparison subjects. This study, using a lexical decision choice reaction time (CRT) task, explored the relation of mean CRT and its intra-individual variability (CRT-SD) to psychiatric symptoms and to performance on executive-motor tasks in 26 medication-free schizophrenic out- patients and 17 normal comparison subjects. Schizophrenic subjects had both significantly slower and more variable CRTs which were unrelated to general intellectual abilities (IQ). Among schizophrenic subjects, both CRT and CRT- SD were significantly related to severity of psychotic symptoms, failure to maintain cognitive set, and poorer motor coordination and global functioning. After controlling for mean CRT, CRT-SD showed unique covariation with clinical symptoms (positive, disorganized and tension/hostility). Conversely, mean CRT showed unique covariation with the failure to maintain cognitive set and with stereotypic mannerisms, independent of CRT-SD. These results suggest that slower CRT and increased intra-individual variability in CRT, while not fully independent of one another, may reflect separate aspects of symptomatic and cognitive dysfunction in schizophrenia.
Bibliographical noteFunding Information:
This work was supported in part by NIMH grant 52906-01A1 and by a Department of Veterans Affairs HSR&D Ancillary Funding Award to S.V.
- Intra-individual variability in reaction time
- Neuropsychological profile
- Reaction time