Symmetric corticospinal excitability and representation of vastus lateralis muscle in right‐handed healthy subjects

Abstract

The purpose of this study was to determine the size and location of the representations of the anterior thigh muscles on the human motor cortex in the dominant and non-dominant hemispheres. Motor-evoked potentials (MEPs) induced by transcranial magnetic stimulation were recorded from the right and left vastus lateralis (rVL, lVL) muscles. A total of ten right-handed healthy volunteers participated in the study. In a single session experiment, we investigated VL muscle corticospinal excitability (motor threshold, MEP size, short interval intracortical inhibition, intracortical facilitation) and cortical representation (map area, volume, and location) in the dominant and non-dominant hemispheres. The motor threshold, MEPs, and intracortical excitability did not differ significantly between the hemispheres (P > 0.05). Furthermore, no difference between sides was found in the location of VL motor representation (mediolateral and anteroposterior axis) or in map area and volume (P > 0.05). Vastus lateralis muscle corticospinal excitability and cortical map were symmetrical in right-handed subjects. Future studies on patients with unilateral lower extremity injuries could examine side-to-side plastic reorganization in corticomotor output and map location in both hemispheres.

The use of transcranial magnetic stimulation to evaluate cortical excitability of lower limb musculature: Challenges and opportunities

“…Similar to findings in upper limb, corticospinal plasticity associated with LE rehabilitation may be accompanied by changes in the size or location of motor maps. Recent LE TMS mapping studies showed symmetrical maps between left and right hemispheres for the vastus lateralis (Al Sawah et al, 2014) and rectus femoris muscles (Ward et al, 2016) in able-bodied individuals. Another LE mapping study showed a more dispersed pattern of tiblialis anterior hotspot locations in individuals post-stroke compared to healthy individuals (Sivaramakrishnan, Tahara-Eckl, & Madhavan, 2016).…”

“…Furthermore, monosynaptic excitatory cortical projections, presumably common in upper limb muscles, may be fewer or weaker (have reduced synaptic strength) in LE muscles, such as the soleus (Bawa, Chalmers, Stewart, & Eisen, 2002; Brouwer & Ashby, 1990, 1992; Geertsen, Zuur, & Nielsen, 2010). Lower limb TMS studies have largely focused on the tibialis anterior (Beaulieu, Masse-Alarie, Ribot-Ciscar, & Schneider, 2017; Jayaram et al, 2012; Jayaram & Stinear, 2009; Sivaramakrishnan et al, 2016; Smith et al, 2017; Stinear & Hornby, 2005) and knee extensor muscles (Al Sawah et al, 2014; O’Leary, Morris, Collett, & Howells, 2015; Ward et al, 2016); with a few studies on the abductor hallucis muscle (Yen, Wang, Liao, Huang, & Yang, 2008). Variability in the strength of corticospinal connections across different lower limb muscles can markedly affect TMS-induced responses, and merits more systematic study.…”

Deficits in Quadriceps Force Control After Anterior Cruciate Ligament Injury: Potential Central Mechanisms

“…A custom-designed, form-fitting cap (EasyCap GmbH, Herrsching, Germany) with stimulus sites marked at 1-cm spacing in latitude and longitude was fitted to each participant's head. [27][28][29][30] The interaural and nasion-inion distances were measured for each participant, and the vertex was aligned with the center of the cap coordinates. 31 The belly of the rectus femoris was identified through palpation during manually resisted knee extension.…”

Assessing the feasibility of mapping the tibialis anterior muscle with navigated transcranial magnetic stimulation in neuro-oncologic patients

“…Investigating the feasibility of eliciting motor evoked potentials (MEPs) from different muscle groups, the anatomical constitutions need to be considered firstly. The area of the anatomic hand motor-hotspot can easily be recognized due to its omega-like shape 7 , 8 , whereas the anatomic leg motor-hotspot is located in the parasagittal cortical zone 7 , 9 – 12 . Previous studies found strong evidence for a very high correlation of nTMS data concerning the location of motor eloquent areas compared to intraoperative mapping so that we can assume a very high positive predictive value concerning the spatial location of nTMS positive sites 13 – 15 .…”