Conveying tactile object characteristics through customized intracortical microstimulation of the human somatosensory cortex

Microstimulation of the somatosensory cortex can evoke tactile percepts in people with spinal cord injury, providing a means to restore touch. While location and intensity can be reliably conveyed, two issues that prevent creating more complex naturalistic sensations are a lack of methods to effectively scan the large stimulus parameter space and difficulties with assessing percept quality. Here, we addressed both challenges with an experimental paradigm that enabled three individuals with tetraplegia to control their stimulation parameters in a blinded fashion to create sensations for different virtual objects. Participants felt they could reliably create object-specific sensations and reported vivid object-appropriate characteristics. Despite substantial overlap in stimulus parameter selections across objects, both linear classifiers and participants could match stimulus profiles with their respective objects significantly above chance without any visual cues. We conclude that while visual information contributes to the experience of artificial touch, microstimulation in the somatosensory cortex itself can evoke intuitive percepts with a variety of tactile properties. This novel self-guided stimulation approach may be used to effectively characterize percepts from future stimulation paradigms.