Motor cortical excitability in dominant and non-dominant limbs: a transcranial magnetic stimulation study

Abstract

Abstract Background Threshold tracking transcranial magnetic stimulation (TT-TMS) is increasingly recognized as a promising diagnostic tool for estimating motor cortical excitability, and previous studies have shown hyperexcitability in patients with amyotrophic lateral sclerosis (ALS) compared with healthy subjects. However, whether limb dominance affects cortical excitability has rarely been examined. This study aimed to investigate physiological motor cortical function differences in the dominant and non-dominant upper and lower limbs in healthy subjects, and to establish basic cortical excitability data in healthy subjects. Methods In 28 healthy subjects (mean age 35), motor cortical functions were examined using single pulse TMS and paired-pulse TT-TMS in the bilateral (dominant and non-dominant) abductor pollicis brevis (APB) and tibialis anterior (TA) muscles. TT-TMS was performed using the novel parallel tracking method, incorporating short-interval intracortical inhibition (SICI) with interstimulus intervals of 1–7 ms and intracortical facilitation with interstimulus intervals of 10–30 ms. Results No significant differences were found between the dominant and non-dominant limbs in any of the single-pulse TMS and paired-pulse TT-TMS parameters. In contrast, a significant difference in recorded excitability indices was observed between the upper (APB) and lower (TA) limbs. Furthermore, SICI variability was greater in the lower limbs than in the upper limbs. The resting motor threshold was correlated with SICI and intracortical facilitation in both the upper and lower limbs. Conclusions Our findings show that motor cortical excitability is similar in the dominant and non-dominant sides when assessed using TT-TMS with the parallel tracking method. These findings provide basic physiological reference data for cortical excitability measurements in healthy individuals.

The authors' abstract, as published at the source. BMC Neurology, 2026 · DOI ↗