Human perception of electrical stimulation on the surface of somatosensory cortex

TLDR

ECoG‑based brain‑computer interfaces have renewed interest in delivering somatosensory feedback via cortical surface electrodes. A 28‑day study implanted a high‑density ECoG grid over the somatosensory and motor cortices of a participant with brachial plexus‑induced arm paralysis to examine sensations evoked by cortical surface stimulation. Stimulation of the somatosensory cortex produced arm and hand sensations whose intensity rose with amplitude and frequency, whose type varied with pulse width, and whose location could be distinguished between electrodes 4.5 mm apart, demonstrating controllable, spatially resolved sensory feedback even in chronic paralysis.

Abstract

Recent advancement in electrocorticography (ECoG)-based brain-computer interface technology has sparked a new interest in providing somatosensory feedback using ECoG electrodes, i.e., cortical surface electrodes. We conducted a 28-day study of cortical surface stimulation in an individual with arm paralysis due to brachial plexus injury to examine the sensation produced by electrical stimulation of the somatosensory cortex. A high-density ECoG grid was implanted over the somatosensory and motor cortices. Stimulation through cortical surface electrodes over the somatosensory cortex successfully elicited arm and hand sensations in our participant with chronic paralysis. There were three key findings. First, the intensity of perceived sensation increased monotonically with both pulse amplitude and pulse frequency. Second, changing pulse width changed the type of sensation based on qualitative description provided by the human participant. Third, the participant could distinguish between stimulation applied to two neighboring cortical surface electrodes, 4.5 mm center-to-center distance, for three out of seven electrode pairs tested. Taken together, we found that it was possible to modulate sensation intensity, sensation type, and evoke sensations across a range of locations from the fingers to the upper arm using different stimulation electrodes even in an individual with chronic impairment of somatosensory function. These three features are essential to provide effective somatosensory feedback for neuroprosthetic applications.