MRI-based visualization of rTMS-induced cortical plasticity in the primary motor cortex

Area of Science:

• Neuroscience
• Neuroimaging
• Motor Cortex Research

Background:

• Repetitive transcranial magnetic stimulation (rTMS) is known to alter cortical excitability.
• The spatial extent of rTMS-induced cortical plasticity remains incompletely understood.
• Previous research indicates rTMS affects interhemispheric functional connectivity.

Purpose of the Study:

• To precisely determine the spatial extent of cortical plasticity induced by rTMS.
• To investigate changes in interhemispheric functional connectivity following quadripulse stimulation (QPS) in the primary motor cortex (M1).
• To assess the relationship between stimulated regions and functional activation maps.

Main Methods:

• Quadripulse stimulation (QPS) applied to the index finger representation in the left primary motor cortex (M1) using an online navigation system.
• Resting-state functional magnetic resonance imaging (rs-fMRI) acquired before and after QPS.
• Analysis of interhemispheric functional connectivity changes and spatial overlap with functional localizer scans.

Main Results:

• A spatially restricted cluster of altered interhemispheric functional connectivity was observed in the central sulcus.
• The connectivity changes extended approximately 10 mm laterally and 20 mm in depth from the stimulation center.
• This cluster significantly overlapped with the cortical representation of index finger motion.

Conclusions:

• Cortical plasticity induced by rTMS in M1 is spatially confined.
• rTMS can induce neural plasticity in restricted cortical regions, potentially revealing functional dissociation between adjacent areas.
• These findings contribute to understanding the precise spatial effects of non-invasive brain stimulation.