Authors
M C Hall, M Zoghi, L Perraton, S Jaberzadeh
Published in
Physiological reports. Volume 14. Issue 20. Pages e71144.
Abstract
Transcranial magnetic stimulation (TMS) studies in upper limb muscles have shown that stimulus direction can influence corticospinal and intracortical excitability; however, limited evidence exists for lower limb muscles. This study investigated the effect of TMS stimulus direction on corticospinal and intracortical excitability of the tibialis anterior (TA) muscle using paired-pulse TMS. Nineteen healthy adults (10 males, 9 females; mean age 41.8 ± 23 years) participated. Single- and paired-pulse TMS was delivered using a figure-of-eight coil oriented to induce anterior-to-posterior (AP) or posterior-to-anterior (PA) current flow in the left motor cortex while recording motor evoked potentials (MEPs) from the right TA. Resting motor threshold (RMT), short-interval intracortical inhibition (SICI), long-interval intracortical inhibition (LICI), and intracortical facilitation (ICF) were assessed under both stimulus directions in a single session. No significant differences were identified between AP and PA stimulation for RMT, SICI, or LICI (p > 0.05). However, AP stimulation produced significantly greater ICF responses compared with PA stimulation (p = 0.027). AP and PA stimulus directions produced comparable RMT, SICI, and LICI measures in the TA muscle, although AP stimulation elicited greater ICF. These findings suggest facilitatory intracortical circuits may be more sensitive to stimulus direction than inhibitory pathways.
PMID:
42885435
Bibliographic data and abstract were imported from PubMed on 16 Oct 2026.
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