Neuromuscular Plasticity: Disentangling Stable and Variable Motor Maps in the Human Sensorimotor Cortex

Area of Science:

• Neuroscience
• Motor Control
• Biomarker Development

Background:

• Transcranial magnetic stimulation (TMS) motor mapping is crucial for assessing neurological conditions and treatment efficacy.
• High test-retest reliability over extended periods is essential for distinguishing stable neuroplasticity from short-term variability.
• Current methods require refinement to ensure robust long-term biomarker application.

Purpose of the Study:

• To evaluate the long-term test-retest reliability of TMS-derived motor maps.
• To assess the impact of a novel projection, interpolation, and coregistration technique on motor map stability.
• To identify reliable parameters for monitoring corticospinal connectivity changes over twelve weeks.

Main Methods:

• A novel gyral anatomy-informed projection, interpolation, and coregistration technique was applied.
• TMS motor maps were acquired biweekly over a twelve-week period in healthy subjects.
• Intraclass correlation coefficients and correlation analyses were used to assess reliability and stability.

Main Results:

• Motor maps exhibited significant long-term reliability, with notable interhemispheric differences.
• The dominant hemisphere's sensorimotor and nonprimary motor areas showed more stable and extended corticospinal connectivity.
• Resting motor threshold, center of gravity, and mean motor evoked potentials (MEPs) were identified as highly reliable parameters.

Conclusions:

• Refined analytical techniques significantly enhance the long-term reliability of TMS motor maps for monitoring corticospinal excitability.
• These reliable motor maps can serve as valuable biomarkers for tracking disease progression and guiding neurorehabilitation strategies.
• The findings support the use of TMS motor maps in interventions targeting dormant corticospinal pathways.