AN INVESTIGATION OF MOTOR FUNCTION IN SCHIZOPHRENIA USING TRANSCRANIAL MAGNETIC STIMULATION OF THE MOTOR CORTEX

Background. In this first investigation of motor function in schizophr enia using transcranial magnetic stimulation (TMS) the general hypothe sis tested was that this methodology could be used to investigate the disruption of corticospinal inhibitory processes suggested by cognitiv e and psychophysiological paradigms. Method. Nine drug-free DSM-IV sch izophrenic patients were compared with nine age- and sex-matched norma l subjects. Electromyographic (EMG) recordings were made from the then ar muscles of the dominant hand during sustained, weak voluntary contr action. TMS over a particular threshold applied to the motor cortex wo uld elicit a compound motor evoked potential (cMEP) followed by a peri od of suppression of EMG. Results. The latency of cMEPs following TMS was significantly shorter in the schizophrenic patients. The two group s did not differ significantly with respect to mean latency of suppres sion of EMG activity, or stimulus thresholds for either cMEPs or EMG s uppression. Conclusion. These findings could be the result of a relati ve lack of corticospinal inhibition of motor responses; a change in th e site of TMS activation; or an abnormality of peripheral nervous func tion in schizophrenia. Drug effects were unlikely since seven of the p atients were drug-naive.