Effective intracortical microstimulation parameters applied to primary motor cortex for evoking forelimb movements to...

Area of Science:

• Neuroscience
• Motor Control
• Computational Neuroscience

Background:

• High-frequency, long-duration intracortical microstimulation (HFLD-ICMS) is a key technique for mapping the motor cortex.
• Evoked movements exhibit stable spatial end points regardless of initial limb position, crucial for reliable mapping.

Purpose of the Study:

• To determine effective stimulus parameters for HFLD-ICMS to elicit forelimb movements to stable spatial end points from the primary motor cortex (M1) in awake monkeys.
• To establish safe and consistent stimulation protocols for corticomotor mapping.

Main Methods:

• Investigated HFLD-ICMS parameters (frequency, amplitude, duration) applied to M1 in awake monkeys.
• Recorded electromyographic (EMG) activity from 24 forelimb muscles and movement kinematics using a motion capture system.

Main Results:

• Identified effective parameters: 80-140 Hz frequency, 80-140 μA amplitude, and 1,000 ms train duration for stable forelimb translocation and endpoint stabilization.
• Mean time to elicit successful movement was 475.8 ± 170.9 ms; median successful frequency and amplitude were 110 Hz and 110 μA.
• Suboptimal parameters led to inconsistent movements, while excessive parameters caused physiological spread and adverse effects.

Conclusions:

• Established optimal HFLD-ICMS parameters for consistent forelimb movements to stable spatial end points, forming a basis for systematic M1 mapping.
• Findings contribute to understanding how the central nervous system encodes movement and refine corticomotor mapping techniques.