Touching the Void: Intracranial Stimulation for NeuroHaptic Feedback in Virtual Reality

Direct cortical stimulation of the somatosensory cortex (SI-DCS) has been shown to evoke distinct and localizable percepts, exploitable as neurohaptic feedback. In this study, we leveraged a novel virtual reality (VR) experimental platform to evaluate SI-DCS neurohaptic feedback during naturalistic object interaction. Two human subjects implanted with intracranial electrodes for seizure localization were asked to discriminate between visually identical virtual objects based on their distinct SI-DCS neurohaptic profiles. In a binary discrimination task, neurohaptic feedback was either present or absent while grasping a virtual object. In the ternary discrimination task, neurohaptic feedback was either present in one of two distinct neurohaptic sequences or absent. Both subjects performed significantly above chance in binary and ternary discrimination, demonstrating the efficacy of S1-DCS as neurohaptic feedback. Successful ternary discrimination also demonstrated that different sequences of amplitude-modulated SI-DCS at a single pair of electrodes can evoke discriminable neurohaptic percepts. Moreover, amplitude-modulated SI-DCS sequences were shown to elicit sensorimimetic percepts described as “bumpy” and “smooth” in Subject 1, and as a sensation of movement in the paralyzed hand of Subject 2. Our study demonstrates the reliability and discriminability of both simple and complex SI-DCS for neurohaptic feedback during immersive VR object interaction and supports the use of immersive VR for neurohaptic design towards the development of functional brain computer interface.