A sense of touch
Touch is essential for hand use. Yet, brain-controlled prosthetic limbs have not been endowed with this critical sense. In a new study by Flesher et al., microelectrode arrays were implanted into the primary somatosensory cortex of a person with spinal cord injury and, by delivering current through the electrodes, generated sensations of touch that were perceived as coming from his own paralyzed hand. These sensations often felt like pressure, could be graded in intensity, and were stable for months. The authors suggest that this approach could be used to convey information about contact location and pressure necessary for prosthetic hands to interact with objects.
Intracortical microstimulation of the somatosensory cortex offers the potential for creating a sensory neuroprosthesis to restore tactile sensation. Whereas animal studies have suggested that both cutaneous and proprioceptive percepts can be evoked using this approach, the perceptual quality of the stimuli cannot be measured in these experiments. We show that microstimulation within the hand area of the somatosensory cortex of a person with long-term spinal cord injury evokes tactile sensations perceived as originating from locations on the hand and that cortical stimulation sites are organized according to expected somatotopic principles. Many of these percepts exhibit naturalistic characteristics (including feelings of pressure), can be evoked at low stimulation amplitudes, and remain stable for months. Further, modulating the stimulus amplitude grades the perceptual intensity of the stimuli, suggesting that intracortical microstimulation could be used to convey information about the contact location and pressure necessary to perform dexterous hand movements associated with object manipulation.
The original publication can be found here.