Neural stimulation and recording performance in human sensorimotor cortex over 1500 days

Area of Science:

• Neuroscience
• Biomedical Engineering
• Rehabilitation Medicine

Background:

• Intracortical microstimulation (ICMS) offers potential for restoring sensation in individuals with spinal cord injury.
• Long-term stability of implanted electrodes and stimulation effectiveness are critical for clinical translation.
• Previous research highlights potential degradation of recording quality and stimulation longevity as barriers.

Purpose of the Study:

• To evaluate the long-term recording stability of intracortical electrodes in the somatosensory cortex (SIROF-sensory) and motor cortex (platinum-motor) in a human participant.
• To assess the stability of ICMS-evoked sensations over time using detection thresholds.
• To compare the performance of stimulated SIROF electrodes against non-stimulated platinum electrodes.

Main Methods:

• Implantation of microelectrode arrays with SIROF tips in the somatosensory cortex and platinum tips in the motor cortex of a human participant with spinal cord injury.
• Regular stimulation of SIROF electrodes to evoke tactile sensations.
• Quantification of electrode signal quality (waveforms, voltage, noise, SNR) and impedances over 1500 days.
• Measurement of ICMS detection thresholds over time.

Main Results:

• Recording quality (high-amplitude waveforms, SNR) declined over time for both SIROF-sensory and platinum-motor electrodes.
• SIROF-sensory electrodes demonstrated superior ability to maintain high-amplitude signals compared to platinum-motor electrodes.
• Detection thresholds for ICMS-evoked sensations decreased significantly over 1500 days, indicating improved sensitivity to stimulation.

Conclusions:

• ICMS in the human somatosensory cortex can be delivered effectively for extended durations without compromising recording or stimulation functions.
• Sputtered iridium oxide film electrodes show promise for long-term use in neuroprosthetic applications.
• The study suggests that sensitivity to ICMS may improve over time, potentially enhancing functional outcomes for individuals with spinal cord injury.