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

J Neural Eng., 2021 · DOI: 10.1088/1741-2552/ac18ad · Published: August 13, 2021

Simple Explanation

Brain-computer interfaces (BCIs) can restore functional motor control by connecting the brain to assistive devices, bypassing the spinal cord. Electrical microstimulation in somatosensory cortex can also generate tactile sensations. This study investigates how well microelectrode arrays function in the human brain over long periods, specifically focusing on electrodes used for intracortical microstimulation (ICMS) in somatosensory cortex compared to non-stimulated electrodes in motor cortex. The research examines the stability of these electrodes over 1500 days by measuring recorded signal quality, electrode impedances, and the ability to evoke sensations using ICMS, providing insights into the long-term effectiveness and safety of brain implants.

Study Duration

1500 days

Participants

A single subject with a C5/C6 spinal cord injury

Evidence Level

Not specified

Key Findings

1
Recording quality decreased over time on both stimulated SIROF and non-stimulated platinum electrodes, but stimulated SIROF electrodes were more likely to continue recording high-amplitude signals.
2
Detection thresholds for stimulus-evoked tactile sensations decreased over time, indicating increased sensitivity to stimulation.
3
There was no significant relationship between injected charge and median peak-to-peak voltage or the number of high amplitude waveforms recorded.

Research Summary

This study evaluated the long-term stability of intracortical microstimulation (ICMS) and neural recording in a human participant over 1500 days, comparing stimulated SIROF electrodes in somatosensory cortex with non-stimulated platinum electrodes in motor cortex. The results showed that while recording quality decreased over time for both types of electrodes, the stimulated SIROF electrodes maintained a higher signal-to-noise ratio and were more likely to record high-amplitude signals. Importantly, the detection thresholds for ICMS-evoked tactile sensations decreased over time, indicating improved sensitivity to stimulation, which supports the long-term utility of microstimulation in somatosensory cortex.

Practical Implications

Long-Term Feasibility

ICMS in human somatosensory cortex can be provided over long periods without harming recording or stimulation abilities.

Improved Sensory Restoration

The increased sensitivity to stimulation over time suggests enhanced potential for sensory restoration through brain-computer interfaces.

Clinical Translation Support

The findings support the continued development of neural prostheses and sensory restoration systems for clinical applications.

Study Limitations

1
The study was conducted on only one participant.
2
The amount of stimulation delivered may be less than what would be provided in a deployable BCI system.
3
The stimulation electrodes in somatosensory cortex were coated in SIROF, while the recording electrodes in motor cortex were coated with platinum.

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