Characterizing the short-latency evoked response to intracortical microstimulation across a multi-electrode array.

Area of Science:

• Neuroscience
• Biomedical Engineering
• Rehabilitation Technology

Background:

• Brain-machine interfaces (BMIs) enable individuals with tetraplegia to control robotic arms for visually guided reaches.
• Lack of somatosensory feedback in BMIs leads to slow and imprecise movements, similar to proprioceptive deficits.
• Intracortical microstimulation (ICMS) offers potential for artificial somatosensory feedback, but requires understanding neural responses to stimulation patterns.

Purpose of the Study:

• To characterize the spatial and temporal responses of neurons to ICMS in non-human primates.
• To inform the development of biomimetic stimulation patterns for more effective afferent interfaces.
• To improve the informativeness and learnability of artificial sensory feedback for BMI users.

Main Methods:

• Recorded neural activity using a Utah multi-electrode array in two rhesus macaques during ICMS.
• Utilized a custom rapid-recovery amplifier to mitigate electrical artifacts from ICMS.
• Applied acausal high-pass filtering to time-reversed recordings to remove residual signal saturation.

Main Results:

• Transsynaptically-evoked neural activity was observed as early as ~0.7 ms after single ICMS pulses.
• Single pulses induced suppressed neural activity lasting 10-150 ms, while trains caused increased firing rates (~100 ms).
• Evoked responses on the stimulated electrode decayed rapidly during long trains, unlike responses on non-stimulated channels.

Conclusions:

• Detailed characterization of ICMS-evoked neural responses provides insights into cortical circuit connectivity and function.
• Findings contribute to designing more effective stimulation patterns for afferent interfaces.
• This research advances the development of sensory feedback for individuals using brain-machine interfaces.