Repetitive transcranial magnetic stimulation reveals abnormal plastic response to premotor cortex stimulation in schizophrenia.
BACKGROUND
Schizophrenia may be characterized by abnormal plastic modulation in cortical neuronal circuits. Activation of premotor cortex using repetitive transcranial magnetic stimulation (rTMS) produces suppression of cortical excitability in primary motor cortex. We hypothesized that premotor rTMS would cause less suppression of motor cortical excitability in patients with schizophrenia than in control subjects.


METHODS
Twelve patients diagnosed with schizophrenia and twelve healthy control subjects underwent subthreshold rTMS to the premotor area in a 15-min conditioning train. Measurements of primary motor cortical excitability (motor evoked potential; MEP), the resting motor threshold (RMT), and cortical inhibition (CI) were taken before and after the rTMS.


RESULTS
There was no difference in RMT between groups at baseline, although the patient group had less CI than the control group at baseline. Following rTMS, the change in both MEP size and RMT between groups was significant. After rTMS, MEP size was suppressed in the control group and increased in the patient group, whereas RMT increased in the normal control group and decreased in the patient group.


CONCLUSIONS
Patients with schizophrenia demonstrate abnormal brain responses to rTMS applied to the premotor cortex that appear to relate to reduced motor cortical inhibition.
Oxley
Tom
T
Alfred Psychiatry Research Centre, Department of Psychological Medicine, The Alfred and Monash University, Melbourne, Victoria, Australia 3004.
Fitzgerald
Paul B
PB
Brown
Timothy L
TL
de Castella
Anthony
A
Daskalakis
Z Jeff
ZJ
Kulkarni
J
J
D000328:Adult; D000704:Analysis of Variance; D001931:Brain Mapping; D016022:Case-Control Studies; D004558:Electric Stimulation; D004576:Electromyography / Q000379:methods; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D009044:Motor Cortex / Q000473:pathology / Q000528:radiation effects*; D009433:Neural Inhibition / Q000528:radiation effects; D009473:Neuronal Plasticity / Q000528:radiation effects*; D011569:Psychiatric Status Rating Scales; D012559:Schizophrenia / Q000503:physiopathology* / Q000601:surgery; D013997:Time Factors; D050781:Transcranial Magnetic Stimulation