Characterization of perceptual and electrophysiological responses to high-speed robot controlled pinprick stimulation

ObjectiveThis work utilises a novel high-speed robot-controlled stimulator to evaluate the effects of different levels of mechanical impulse (force and duration) of pinprick stimuli on neurophysiological responses and subjective perception. MethodsTwenty-seven healthy volunteers received pinprick stimuli on the right volar forearm using different combinations of force and duration that configured three distinct levels: low, medium and high mechanical impulse stimuli. The robotic system recorded stimulus force and duration in real time, and participants rated the pinprick perceived intensity on a numerical rating scale (NRS). The peak amplitudes and latencies of the pinprick evoked potentials (PEPs) were compared across stimulation levels. Perceived intensity ratings were analysed using linear mixed models, and the PEP features were evaluated through spatio-temporal cluster permutation tests. ResultsPerceived intensity ratings, expressed as median [IQR], were 2.5 [1.14 - 8.15] for low, 16.4 [ 8.86 - 26.9] for medium and 28.5 [10.2 - 41.4] for high impulse stimuli. Differences in brain activity were found when comparing across stimulation levels: the N2 Peak latency was longer for high impulse compared to low impulse and for medium impulse compared to low impulse. The P2 peak latency showed no differences across levels. The N2 amplitude was larger for high vs. low impulse and for medium vs. low impulse, with no significant difference observed between high and medium impulse stimulation. ConclusionsHigh speed robot-controlled pinprick stimulation successfully elicited pinprick-evoked potentials (PEPs) across different mechanical impulse levels. The use of robot-controlled systems may help standardize the assessment of mechanical nociception.