F-3-07-02
A NEW MEASUREMENT OF MAGNETIC EVOKED POTENTIAL IN HEMIPLEGIC PATIENTS
M. Arita (Tokyo Metropolitan Rehabilitation Hospital, Tokyo, Japan*l), S. Izumi (Tokai University), E. Saito (Fujita Health University), Y. Tomita (Keio University*2), S. Sonoda(*l), Y. Igarashi(*2), O. Takahashi(*l), T. Ota(*l), F. Hotta(*l), N. Takahashi(*l), N. Chino(*2)
The change of motor evoked potentials (MEPs) with facilitation has been investigated in 10 healthy volunteers and 20 hemiplegic patients. The target muscles were the wrist flexor and extensor. We used a Neuropack8 electomyograph (EMG) machine, a biofeedback machine, a Magstim200 magnetic stimulator and a pair of active electrodes. The pre-stimulus condition was composed of rest with open eyes, intention of movement, and voluntary movement maintained at 10%, 20%, 30%, and 40% of maximum contraction. The stimulus was triggered by the maximum negative peak of the EMG at each voluntary contraction. In the control subjects as the facilitation increased from rest to 30% contraction, the area and amplitude of MEPs significantly increased. However, no significant difference was found between the amplitude at 30% and that at 40% contraction. The effect of facilitation by 30% voluntary contraction seemed to reach maximum. In the patients the individual largest MEPs has been evoked at either 10% or 20% of maximum contraction. This would suggest the disturbance of facilitation due to the damage of the pyramidal tract. Thus we conclude that it is possible to evaluate the hemiplegia of upper extremities in patients with a method to measure MEPs maintaining voluntary contraction using a biofeedback machine.
F-3-07-03
EFFECT OF FOCAL TRANSCRANIAL MAGNETIC STIMULATION ON REACTION TIME AND CHRONOMETRIC CORRELATION OF MOTOR CONTROL
Lumy Sawaki, Tsunetaka Okita, Makoto Fujiwara (Hyogo College of Medicine, Department of Rehabilitation, Japan)
Kosaku Mizuno (Kobe University, Orthopaedic Department, Japan)
Earlier studies have demonstrated that focal Transcranial Magnetic Stimulation (TMS) delivered in appropriate time, intensity and scalp position can shorten or prolong the latency of simple reaction time. The present work evaluates the effect of focal TMS on go/no go and choice reaction time tasks in 7 normal right-handed subjects. And also correlates the time course of motor control and the time for the best effect of TMS.
Subthreshold TMS was randomly delivered over the motor cortex at variable delays to the go signal while subjects were performing different tasks. In a separate session cortical potential preceding movement was recorded for different tasks.
Prolongation of reaction time was attained progressively in go/no-go and choice paradigm. Regardless of the presented task TMS was more effective 100 ms before the movement onset, when much steeper negative slope was observed in the contralateral cortical potential.
The present results of RT and cortical potential finding support earlier reports that subthreshold TMS shows best effects when applied just before the onset of the movement, corresponding to the time of motor program transfer from supplementary motor area to the primary motor area.
