Stretch-evoked motor responses in the brainstem are modulated by task instructions

Area of Science:

• Neuroscience
• Motor Control Research
• Brainstem Imaging

Background:

• Noninvasive measurement of human brainstem activity during motor control is challenging.
• Understanding descending control pathways is essential for motor control research.
• Reticulospinal regions are key to rapid feedback control.

Purpose of the Study:

• To investigate task-dependent modulation of brainstem activation during motor control.
• To examine the role of reticulospinal regions in human feedback control.
• To correlate brainstem activity with stretch-evoked motor responses.

Main Methods:

• Brainstem-optimized whole-brain functional magnetic resonance imaging (fMRI) was employed.
• A behavioral experiment validated task-dependent modulation of long-latency responses (LLRs).
• Multi-echo fMRI with physiological noise compensation was used in a cohort of 26 participants.

Main Results:

• Task-dependent modulation of stretch-evoked motor responses was confirmed.
• Greater brainstem activation (pons and medulla) was observed during the 'Resist' task compared to 'Yield'.
• A rostrocaudal gradient in activation laterality was identified, shifting from ipsilateral to contralateral patterns.

Conclusions:

• Instruction-dependent modulation of motor responses is associated with measurable changes in human brainstem activation.
• Reticulospinal regions contribute to task-dependent feedback control.
• Brainstem-optimized fMRI is a viable tool for studying motor control mechanisms.