Interhemispheric transfer and laterality effects in simple visual reaction time in schizophrenics.
BACKGROUND
There is evidence that schizophrenics have an abnormal corpus callosum and an abnormal pattern of cerebral asymmetries. We investigated whether there are corresponding functional abnormalities in interhemispheric transfer (IT) and laterality effects.


METHODS
Medicated schizophrenic patients and matched controls were tested in the Poffenberger paradigm, that is, a simple manual reaction time (RT) paradigm with laterally presented visual stimuli designed to provide a behavioural estimate of IT. By subtracting RT averaged across the uncrossed hand-hemifield conditions, from RT averaged across the crossed hand-hemifield conditions, one can obtain an estimate of IT time.


RESULTS
In schizophrenic patients the difference between crossed and uncrossed conditions was 0 because of an unusually prolonged RT in the uncrossed condition right hand/ right field. A broadly similar result has been obtained previously in the tactile modality (Ditchfield & Hemsley, 1990) and is consistent with a left hemisphere impairment. This effect was still present when the patients were retested about 2 years later.


CONCLUSIONS
These results demonstrate the existence in schizophrenic patients of a consistent slowing down of simple visuomotor responses subserved by the left hemisphere.
Florio
Vincenzo
V
University of Verona, Italy.
Fossella
Sabrina
S
Maravita
Angelo
A
Miniussi
Carlo
C
Marzi
Carlo Alberto
CA