Modulation of Spinal Nociceptive Excitability by Nociceptive-Visual Interaction.

BACKGROUND

The existence of multisensory interactions between nociception and vision has recently been highlighted by showing that near visual stimuli can influence nociceptive perception. However, although such interactions have been hypothesized to serve a motor function, their effects on nociception-related motor responses have not been empirically demonstrated. The present study tested whether spinal nociceptive excitability, measured with the nociceptive withdrawal reflex (NWR), can be modulated by the presence of dynamic visual stimuli, and whether this would be specifically the case for visual stimuli presented near the stimulated lower limb.

METHODS

NWRs were elicited by applying transcutaneous electrical stimuli at the sole of the foot of healthy participants (N = 21). The electrical stimulus was either preceded by a visual stimulus rapidly approaching a location near the stimulated foot, a visual stimulus approaching a location further away from the foot, or applied without any visual stimulus (baseline). Measures of interest were NWR amplitude, latency, and perceived intensity of the electrical stimuli.

RESULTS

Results show that NWR amplitude was significantly increased (change from baseline ~30%) by the presence of a visual stimulus (p = 0.013, η p 2 = 0.196 $$ {\eta}_{\mathrm{p}}^2=0.196 $$ ), but no significant difference between near and far visual stimuli. There were furthermore no significant effects on latency and perceived intensity.

CONCLUSIONS

This suggests that spinal nociceptive excitability can be modulated by the presence of external visual stimuli that have no explicit emotional or task-related valence. Whether the proximity of the visual stimuli might play a role in such interactions needs to be further investigated.

SIGNIFICANCE STATEMENT: Multisensory interactions between vision and nociception have been shown to affect nociceptive perception, but whether such interactions can also shape nociception-related motor processes is currently unknown. We investigated the potential influence of dynamic visual stimulation on the NWR in healthy participants. Results show that the presence of dynamic visual stimuli without any explicit task-related attentional or emotional valence can modulate the amplitude of the NWR without affecting the perceived intensity of the electrical stimulus eliciting the reflex.