EEG cortical responses after HiPi: High-speed robot-controlled pinprick stimulation

Objective: This study presents HiPi, a high-speed robot-controlled pinprick stimulation system designed to estimate tissue stiffness and evaluate neurophysiological and subjective responses to mechanical impulses. Methods: The system was validated in an experimental study, in which twenty-seven healthy volunteers received pinprick stimuli on the right forearm at three levels of mechanical impulse (low, medium, high), with real-time recording of stimulus force and duration. Participants rated perceived intensity on a numerical scale. Pinprick evoked potentials (PEPs) were recorded, and N2\/P2 peak amplitudes and latencies were compared. Intensity ratings were analyzed using linear mixed models and PEPs with spatiotemporal cluster permutation tests. Results: Median [IQR] perceived intensity ratings were 2.5 [1.14-8.15] (low), 16.4 [8.86-26.9] (medium), and 28.5 [10.2-41.4] (high). N2 peak latency was longer for high and medium impulses versus low, while P2 latency did not differ. N2 amplitude increased for high and medium versus low impulses, with no difference between high and medium. Conclusion: HiPi reliably elicited PEPs at varying impulse levels and enabled estimation of tissue stiffness, highlighting differences in neurophysiological responses based on stimulation force and duration. Significance: Robot-controlled systems like HiPi may standardize the assessment of mechanical nociception.