BACKGROUND Neurological soft signs (NSS) such as a disturbed finger-to-thumb opposition are frequently found in schizophrenia. To identify the underlying cerebral changes we investigated sensorimotor cortex and supplementary motor area (SMA) activation during finger-to-thumb opposition using functional magnetic resonance imaging (fMRI).
METHOD Ten DSM-III-R schizophrenics and seven healthy controls were included. All subjects were right-handed. fMRI was carried out in a resting condition followed by an activation state (finger-to-thumb opposition) and the activities in the sensorimotor cortices and SMA recorded.
RESULTS All subjects showed a significant activation of the SMA and both ipsilateral and contralateral sensorimotor cortices. In the controls, ipsilateral finger-to-thumb opposition was associated with a greater left than right hemispheric sensorimotor cortex coactivation. When compared with the healthy controls, the schizophrenic patients showed a decreased activation of both sensorimotor cortices and SMA, as well as a reversed lateralisation effect.
CONCLUSION Sensorimotor cortex and SMA dysfunction are associated with motor disturbances in schizophrenia.