Changes of somatosensory function by low frequency transcranial magnetic stimulation over the motor cortex

2005 Fiscal Year Final Research Report Summary

• Project/Area Number: 15500388
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Rehabilitation science/Welfare engineering
• Research Institution: Tokai University
• Principal Investigator: ISHIDA Akira Tokai University, School of medicine, Professor, 医学部, 教授 (50118907)
• Co-Investigator(Kenkyū-buntansha): FURUKAWA Toshiaki Tokai University, School of medicine, Assistant Researcher, 医学部, 助手 (30276852) ; TOYOKURA Minoru Tokai University, School of medicine, Associate Professor, 医学部, 助教授 (20217566) ; HANAYAMA Kozo Tokai University, School of medicine, Associate Professor, 医学部, 助教授 (80189589) ; KODAMA Mitsuhiko Tokai University, School of medicine, Assistant Researcher, 医学部, 助手 (90317777)
• Project Period (FY): 2003 – 2005
• Keywords: transcranial magnetic stimulation / current perception threshold / somatosensory function

Research Abstract

Objective : To study changes of current perception threshold (CPT) by repetitive transcranial magnetic stimulation (rTMS) over the motor cortex in humans.
Experiment 1
1. Subjects and Methods : 0.9Hz rTMS over the right motor cortex, sensory cortex and sham stimulation were given to ten healthy subjects (five men and five women ; mean age ± SD, 35.8 ± 5.7). The intensity of rTMS was fixed at 90% of the resting motor threshold at the hand area of motor cortex. 500 stimuli were given in each subject. CPTs (2k, 250, 5 Hz) of the left index finger were determined by using Neurometer^<TM> (Neurotoron, Baltimore, MD), before and after rTMS.
2. Results : The CPTs of 2k and 5 Hz were significantly increased after rTMS over the motor cortex, but the changes were within normal limits. Sham stimulation or rTMS over the sensory cortex had no effect on CPTs.
Experiment 2
1. Subjects and Methods : 56-year-old woman with a brain contusion of left fronto- parietal lobe at the age of 51 was the subject. She had right hemiparesis without hypesthesia and hypalgesia. rTMS was given over the left motor cortex in the same condition as the healthy subjects. CPTs (2k and 5 Hz) of the right index finger were determined before and after rTMS.
2. Results : CPTs of 2k Hz as well as 5 Hz were decreased.
Conclusions
2kHz CPT is related to the threshold of Aβ-fiber, and 5Hz CPT is C fiber, and they are involved in tactile sensation and a slow pain respectively. Experiment 1 suggests that rTMS increased the threshold of tactile sensation and a slow pain in a healthy volunteer at the same time. But it remains a within normal limits, and this result suggests to that of the safety of rTMS.
At experiment 2, because of limited case, it is unclear whether the result indicates the tendency all patients with brain damage at this moment.