Increased intra-subject reaction time variability in the volitional control of movement in schizophrenia.
Increased Reaction Time (RT) studies intra-subject variability is an emerging and consistent finding in RT studies of schizophrenia. A group of 23 patients suffering from DSM-IV schizophrenia and a group of 23 age-matched control subjects performed two RT tasks requiring basic sensorimotor processing and engaging two different motor systems: the Finger Lift Reaction Time task and the Voluntary Saccade Reaction Time task. The Ex-Gaussian model was applied to the RT distributions measuring the mean (mu), and standard deviation (sigma) of a Gaussian component thought to reflect sensorimotor processing and an exponential component (tau), thought to reflect an intermediate decision process. In both tasks, a significantly larger RT intra-subject variability effectively dissociated patients from controls. RT intra-subject variability in the two tasks was highly correlated only for patients. Both sigma and tau were significantly higher in the patient group with tau being the best predictor of schizophrenia. Furthermore, only in the patient group were sigma and tau highly correlated between the two tasks. The results reflect a deficit in information processing that may not be confined to decision processes related to the frontal cortex; rather, they may indicate dysfunction in distributed neural networks modulating adaptive regulation of performance.
Psychiatry Department, National and Kapodistrian University of Athens, Eginition Hospital, 72 V. Sofias Ave, Athens 11528, Greece.
Thomas
T
Karantinos
Neurology Department, National and Kapodistrian University of Athens, Eginition Hospital, Athens, Greece.
Evangelos
E
Tsoukas
Neurology Department, National and Kapodistrian University of Athens, Eginition Hospital, Athens, Greece.
Asimakis
A
Mantas
Psychiatry Department, National and Kapodistrian University of Athens, Eginition Hospital, 72 V. Sofias Ave, Athens 11528, Greece.
Emmanouil
E
Kattoulas
Psychiatry Department, National and Kapodistrian University of Athens, Eginition Hospital, 72 V. Sofias Ave, Athens 11528, Greece; School of Psychiatry and Clinical Neurosciences, University of Western Australia, Centre for Clinical Research in Neuropsychiatry(CCRN), Perth, Australia.
Nicholas C
NC
Stefanis
Neurology Department, National and Kapodistrian University of Athens, Eginition Hospital, Athens, Greece.
Ioannis
I
Evdokimidis
Psychiatry Department, National and Kapodistrian University of Athens, Eginition Hospital, 72 V. Sofias Ave, Athens 11528, Greece. Electronic address: smyrnis@med.uoa.gr.
Nikolaos
N
Smyrnis
D000328:Adult; D005625:Frontal Lobe / Q000503:physiopathology; D006801:Humans; D008297:Male; D009068:Movement / Q000502:physiology*; D010775:Photic Stimulation; D011597:Psychomotor Performance / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology*; D012438:Saccades / Q000502:physiology; D012559:Schizophrenia / Q000503:physiopathology*; D055815:Young Adult
Cognitive deficit; Decision; Ex-Gaussian; Manual response; Saccade; Sensorimotor