Clinical Scorecard: Exploring a New Circuit in the Primary Motor Cortex as a Potential Focus for Neuromodulation Therapy

At a Glance

Key Highlights

• Discovery of three inter-effector regions within M1 that interrupt the classical homunculus and connect to cognitive and motor planning areas.
• Plis de passage white matter structures anatomically link these inter-effector regions to the somato-cognitive action network.
• Neuromodulation therapies targeting M1 may need to consider differential effects on effector-specific versus inter-effector areas for improved motor recovery.

Guideline-Based Recommendations

Diagnosis

• Utilize functional neuroimaging and intraoperative electrical recordings to identify inter-effector regions within M1.
• Consider resting-state fMRI connectivity analyses focusing on plis de passage coordinates to map the somato-cognitive action network.

Management

• Apply non-invasive neuromodulation techniques (e.g., TMS, tDCS) targeting M1 with awareness of inter-effector and effector-specific regions.
• Incorporate knowledge of somato-cognitive action network connectivity to optimize brain stimulation protocols for motor recovery.

Monitoring & Follow-up

• Monitor motor evoked potentials (MEPs) elicited by stimulation of inter-effector regions to assess diffuse motor responses.
• Track changes in functional connectivity within M1 and related subcortical structures during neuromodulation therapy.

Risks

• Recognize interindividual variability in response to neuromodulation therapy post-stroke.
• Acknowledge the current unknowns regarding how stimulation of inter-effector areas influences motor system reorganization.

Patient & Prescribing Data

Patients with motor impairments due to stroke or Parkinson’s disease undergoing neuromodulation therapy

Neuromodulation targeting M1 shows moderate efficacy with variability; understanding inter-effector regions may enhance therapeutic outcomes.

Clinical Best Practices

• Integrate anatomical and functional mapping of M1 to distinguish effector-specific and inter-effector regions before neuromodulation.
• Tailor brain stimulation protocols to engage the somato-cognitive action network for improved sensorimotor integration and motor planning.
• Consider subcortical connectivity, especially with basal ganglia and thalamus, when designing neuromodulation strategies.
• Use multimodal assessment (histology, neuroimaging, intraoperative recordings) to guide individualized therapy.

References

• White matter connections within the central sulcus subserving the somato-cognitive action network by Skandalakis et al.