Perceived Timing of Cutaneous Vibration and Intracortical Microstimulation of Human Somatosensory Cortex

Abstract

AbstractBackgroundElectrically stimulating the somatosensory cortex can partially restore the sense of touch. Though this technique bypasses much of the neuroaxis, prior studies with non-human primates have found that conscious detection of touch elicited by intracortical microstimulation (ICMS) lags behind the detection of vibration applied to the skin. These findings may have been influenced by a mismatch in stimulus intensity; typically, vibration is perceived as more intense than ICMS, which can significantly impact temporal perception.ObjectiveThe goal of this study was to evaluate the relative latency at which intensity-matched vibration and ICMS are perceived in a human subject.MethodsA human participant implanted with microelectrode arrays in somatosensory cortex performed a reaction time task and a temporal order judgment (TOJ) task. In the reaction time task, the participant was presented with vibration or ICMS and verbal response times were obtained. In the TOJ task, the participant was sequentially presented with a pair of stimuli – vibration followed by ICMS or vice versa – and reported which stimulus occurred first.ResultsWhen vibration and ICMS were matched in intensity at a “high” stimulus level, the reaction time to vibration was 48 ms faster than ICMS. When both stimuli were perceived as lower in intensity, the difference in reaction time was even larger: vibration was perceived 90 ms before ICMS. However, in the TOJ task, vibratory and ICMS sensations arose at comparable latencies, with points of subjective simultaneity that were not significantly different from zero.ConclusionsBecause the perception of ICMS is slower than that of intensity-matched vibration, it may be necessary to stimulate at stronger ICMS intensities (thus decreasing reaction time) when incorporating ICMS sensory feedback into neural prostheses.