Visuo-nociceptive interactions and their effect on the motor system

Abstract

Pain, besides its contribution to body homeostasis, has also the function of providing information on external stimuli that can potentially harm the body. Such exteroceptive function relies on an optimally integrated multisensory representation of the body and its surrounding space, which is based on interactions between somatic and extra-somatic stimuli occurring near the body. While such interactions between nociceptive and near visual stimuli have recently been demonstrated, showing that visual stimuli can impact the perception of nociceptive stimuli and vice versa, their functional role is not clear yet. It is indeed hypothesized that one of the functions of such multisensory representations would be to optimize defensive reactions against threatening stimuli. However, the idea of this potential defensive purpose has, to date, mainly been based on studies conducted in non-human primates. I will present two studies investigating whether interactions between nociceptive and near visual stimuli can shape motor reactions of the stimulated limb. More precisely, we tested whether visual stimuli approaching the body part on which nociceptive stimuli are applied can modulate spinal, as well as cortico-spinal, excitability (measured with the spinal nociceptive withdrawal reflex and single-pulse transcranial magnetic stimulation, respectively). Spinal nociceptive excitability was shown to be modulated by the presence of the visual stimuli, but neither spinal, nor cortico-spinal excitability, were modulated differently by approaching vs. receding visual stimuli, suggesting that our experimental set-up did not allow to highlight specific visual-nociceptive interaction effects, which might depend on a more complex, time-dependent, interplay between the nociceptive and the visual stimulation