Related Experiment Video
Updated: Dec 1, 2025
Assessing Primary Motor Cortex Excitability and Excitability Modulation by Pairing Transcranial Magnetic Stimulation with Electromyography
Published on: October 7, 2025
Effect of primary motor cortex excitability changes after quadripulse transcranial magnetic stimulation on
Megumi Okawada1, Fuminari Kaneko2, Eriko Shibata3
1First Division of Physical Therapy, School of Health Sciences, Sapporo Medical University, S1 W17 Chuo, Sapporo, Hokkaido, Japan; Department of Rehabilitation Medicine, Keio University School of Medicine, 35 Shinanomachi, Shjinjuku-ku, Tokyo, Japan; Department of Rehabilitation, Hokuto Hospital, Hokuto Social Medical Corporation, 7-5 Kisen, Inada-cho, Obihiro-shi, Hokkaido, Japan.
Abstract:
Muscle spindles provide the greatest contribution to kinesthetic perception. Primary motor cortex (M1) excitability changes in parallel with the intensity of kinesthetic perception inputs from muscle spindles; M1 is therefore involved in kinesthetic perception. However, the causal relationship between changes in kinesthetic sensitivity and M1 excitability is unclear. The purpose of this study was to test whether artificially and sustainably modulated M1 excitability causes changes in kinesthetic sensitivity in healthy individuals. We evaluated motor evoked potentials (MEP) in Experiment 1 and joint motion detection thresholds (JMDT) in Experiment 2 before and after quadripulse transcranial magnetic stimulation (QPS). Nine healthy right-handed male volunteers were recruited. In each experiment, participants received QPS or sham stimulation (Sham) on separate days. MEP amplitude and JMDT were recorded before and at 0, 15, 30, 45, and 60 min after QPS and Sham. Our results showed that M1 excitability and kinesthetic sensitivity increased after QPS, whereas neither changed after Sham. In the five subjects who participated in both experiments, there was a significant moderate correlation between M1 excitability and kinesthetic sensitivity. Thus, the long-lasting change in kinesthetic sensitivity may be due to changes in M1 excitability. In addition, M1 may play a gain adjustment role in the neural pathways of muscle spindle input.
