Functional properties of dorsolateral prefrontal cortex to primary motor cortex connectivity: a dual-site TMS study

Area of Science:

• Neuroscience
• Cognitive Motor Control
• Brain Injury Research

Background:

• The dorsolateral prefrontal cortex (DLPFC) is vital for cognitive-motor integration via top-down regulation of the primary motor cortex (M1).
• Functional lateralization of DLPFC and its regulation of M1, especially in brain-injured populations, are not well understood.

Purpose of the Study:

• To assess bilateral DLPFC regulation of M1.
• To compare ipsilateral vs. contralateral DLPFC effects on M1.
• To analyze DLPFC lateralization in M1 regulation.
• To investigate brain injury effects on the DLPFC-M1 pathway.

Main Methods:

• Dual-site paired-pulse transcranial magnetic stimulation (TMS) was used.
• 30 participants (20 stroke patients, 10 healthy) were tested.
• Conditioning stimuli targeted left/right DLPFC, with test stimuli on ipsilateral/contralateral M1.

Main Results:

• DLPFC significantly enhanced left M1 excitability in healthy and stroke groups.
• No significant difference was found between ipsilateral and contralateral DLPFC regulation of left M1.
• No significant DLPFC regulatory effect was observed on the right M1 across all groups.

Conclusions:

• Bilateral DLPFC exerts stable, non-specific facilitatory regulation on the left M1 at rest.
• This regulation persists in stroke patients' affected M1, indicating pathway plasticity.
• The lack of effect on right M1 highlights lateralization in DLPFC-M1 regulation, informing neurorehabilitation strategies.