A roadmap for implanting microelectrode arrays to evoke tactile sensations through intracortical microstimulation

medRxiv preprint, 2024 · DOI: https://doi.org/10.1101/2024.04.26.24306239 · Published: April 28, 2024

Simple Explanation

This study focuses on restoring the sense of touch to paralyzed individuals using a brain-computer interface (BCI) by implanting microelectrode arrays into the somatosensory cortex. The key is to precisely target the electrodes to specific areas of the brain that correspond to different parts of the hand, allowing for the creation of tactile sensations through intracortical microstimulation (ICMS). The researchers used detailed pre-surgical imaging techniques to map the hand area of the somatosensory cortex in participants with spinal cord injuries, ensuring successful placement of the stimulation electrodes.

Study Duration

Not specified

Participants

Five participants with cervical spinal cord injury

Evidence Level

Not specified

Key Findings

1
The imaging and planning procedures successfully enabled ICMS-evoked sensations localized to at least the first four digits of the hand in all five participants.
2
Functional maps closely matched between fMRI and MEG, with the center of gravity for each digit varying by between 3.1 and 6.8 mm.
3
Variability in the location of the sensory digit maps relative to the anatomical hand knob, highlights the importance of functional mapping in determining electrode placement.

Research Summary

This study presents a framework for reliably targeting the hand representation in somatosensory cortex using intracortical microstimulation (ICMS) to deliver tactile feedback for brain-computer interfaces (BCIs). The researchers used non-invasive neuroimaging (fMRI and MEG) to create individualized functional maps of somatosensation during attempted finger movements, followed by a structured surgical approach to ensure accurate electrode placement. The results demonstrated consistent evoked sensations that mapped to the desired digits, enabling closed-loop BCI systems with tactile feedback during grasping.

Practical Implications

Improved BCI Technology

The roadmap provides a pathway to broader use of BCIs that provide intuitive, somatotopically-matched sensory feedback, enhancing the embodiment and functionality of BCIs.

Clinical Translation

The rigorous planning and surgical workflow developed in this study can be adapted for other brain-computer interface studies, improving the success rate of electrode implantation and sensory restoration.

Personalized Treatment

The use of individualized functional maps created through neuroimaging allows for more precise targeting of electrodes, catering to the unique somatosensory cortex organization of each patient.

Study Limitations

1
While the mediolateral somatotopy was identifiable through imaging, we were unable to identify the anteroposterior somatotopy, which dictates the distal aspect of the finger sensation.
2
Functional neuroimaging may not be broadly available at medical centers, which could create challenges for translation of bidirectional BCI technology.
3
Our implants consisted of two 2.4x4mm arrays of electrodes wired in a checkerboard pattern

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