Restoring Touch through Intracortical Microstimulation of Human Somatosensory Cortex

Intracortical microstimulation (ICMS) in the primary somatosensory cortex (S1) offers a potential method to restore somatosensory perception in people that have lost this capacity through injury or disease. Under an Investigation Device Exemption, a twenty-eight year old participant with a long-term cervical spinal cord injury was implanted with two microelectrode arrays in primary motor cortex and two microelectrode arrays in area 1 of S1. Detection thresholds had a median value of less than 30 μA and have been essentially stable over two years. We also found that increasing the stimulation amplitude did not systematically change the size of the projected field that the participant reported feeling, but that it did reliably increase the intensity of the evoked sensations. Increasing the stimulation amplitude on some electrodes did cause increases in the projected field size, but on other others, decreased the projected field size. Overall, we found that percepts were evoked at somatotopically relevant locations and that the perceived intensity of stimuli scaled linearly over a wide range. Restoring these two streams of somatosensory information could have a major impact on neuroprosthetic hand dexterity and embodiment.