Objective Mechanical pinprick stimuli delivered via robotic systems have been applied using parameters derived from studies using handheld stimulators. This work evaluates the effects of stimulus force and duration on neurophysiological responses and subjective perception.

Methods Twenty-seven healthy volunteers received pinprick stimuli on the right volar forearm using different combinations of force and duration that configured three stimulus intensities: low, medium and high impulse. The robotic system recorded stimulus force and duration in real-time, and participants rated the perceived intensity after each stimulus on a numerical rating scale (NRS). The peak amplitudes and latencies of the pinprick evoked potentials (PEPs) were compared for the stimulation impulse intensities. The NRS ratings were analysed using linear mixed models, and the PEP features were evaluated through spatio-temporal cluster permutation tests.

Results The NRS ratings were 2.5 [7.0] for low, 16.4 [18.0] for medium, and 28.5 [31.1] for high impulse stimuli. Differences in brain activity were found when comparing all impulse intensities. Peak N2 latency was longer for high compared to low and for medium compared to low. P2 latency showed no differences across impulse intensities. N2 was more negative for high vs. low and for medium vs. low, with no significant difference between high and medium impulses.

Conclusions Both cortical and subjective responses depend on the applied impulse intensity. Stimulation parameters should be selected based on the specific effect under investigation, as a range of peripheral afferents may be activated by mechanical stimuli.

The authors have declared no competing interest.

NCT06183593

This research was supported by Biennial Research Projects (PIBAA), Scientific and Technological Research Projects (PICT), the Argentinian National Scientific and Technical Research Council (CONICET), and the German Academic Exchange Service (DAAD)

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Ethics committee of comite central de bioetica de Entre Rios gave ethical approval for this work

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Clinical trial registration: ClinicalTrials.gov (identifier: NCT06183593)

Funding sources: National Scientific and Technical Research Council (CONICET, Argentina) – German Academic Exchange Service (DAAD, Germany)

Conflict of interest: All authors have no conflict of interest to report.