Testing the exteroceptive function of nociception: The role of visual experience in shaping the spatial representations of nociceptive inputs

Abstract

Adequately localizing pain is crucial to protect the body against physical damage and react to the stimulus in external space having caused such damage. Accordingly, it is hypothesized that nociceptive inputs are remapped from a somatotopic reference frame, representing the skin surface, towards a spatiotopic frame, representing the body parts in external space. This ability is thought to be developed and shaped by early visual experience. To test this hypothesis, normally sighted and early blind participants performed temporal order judgment tasks during which they judged which of two nociceptive stimuli applied on each hand's dorsum was perceived as first delivered. Crucially, tasks were performed with the hands either in an uncrossed posture or crossed over body midline. While early blinds were not affected by the posture, performances of the normally sighted participants decreased in the crossed condition relative to the uncrossed condition. This indicates that nociceptive stimuli were automatically remapped into a spatiotopic representation that interfered with somatotopy in normally sighted individuals, whereas early blinds seemed to mostly rely on a somatotopic representation to localize nociceptive inputs. Accordingly, the plasticity of the nociceptive system would not purely depend on bodily experiences but also on crossmodal interactions between nociception and vision during early sensory experience.

No Evidence for an Effect of the Distance Between the Hands on Tactile Temporal Order Judgments

“…However, this seems unlikely as, on the contrary, one of the main advantages of psychophysics adaptive methods over constant stimuli methods is to allow more reliable estimation of the parameters of the psychometric function even when a limited number of stimuli is used (Filbrich, Alamia, Burns, et al., 2017; Kontsevich & Tyler, 1999). Accordingly, using the same adaptive method as the one used in the present experiment, previous studies succeeded to reliably estimate both the threshold (Filbrich, Alamia, Blandiaux, et al., 2017; Filbrich, Alamia, Burns, et al., 2017; Filbrich, Alamia, Verfaille, et al., 2017; Filbrich et al., 2018; Legrain et al., 2018; Manfron et al., 2019; Torta et al., 2018; Vanderclausen et al., 2017) and the slope parameters (Vanderclausen, Bourgois, et al., 2020; Vanderclausen et al., in press; Vanderclausen, Manfron, et al., 2020) of the TOJ-fitting psychometric function and to significantly measure changes in participants’ judgments according to experimental manipulations such as the posture of the stimulated limbs. For instance, Vanderclausen and colleagues (Vanderclausen, Bourgois, et al., 2020; Vanderclausen et al., in press; Vanderclausen, Manfron, et al., 2020) have shown significant and reliable crossing hands effects during TOJ tasks with somatosensory (vibrotactile or radiant heat) stimuli delivered using the adaptive psi procedure.…”

“…For each pair of stimuli, the two vibrotactile stimuli were separated by 1 out of 22 possible time intervals (SOAs for stimulus onset asynchronies): ±5, ±10, ±15, ±30, ±45, ±60, ±75, ±90, ±145, ±200, and ±400ms (negative values indicate that the vibrotactile stimulus on the left hand was applied first; positive values that the right hand stimulus was applied first). At each trial, the presented SOA was selected using the adaptive psi method (Kingdom & Prins, 2010) based on the participant’s responses in all the previous trials (see Filbrich, Alamia, Verfaille, et al., 2017; Vanderclausen, Bourgois, et al., 2020; Vanderclausen, Manfron, et al., 2020 for details regarding the use of the psi method for TOJ tasks). More specifically, the algorithm adopts a Bayesian framework with the ultimate goal of estimating the posterior probability of the parameters of interest (i.e., the α (point of subjective simultaneity [PSS]) and the β (slope)) without probing extensively all the SOAs.…”

“…A third nonstandard parameter was derived a posteriori to further characterize participants’ performances. Based on all trials presented for each condition, we computed the mode of the presented SOA to index which of the time interval values was the most often presented to a given participant (see Vanderclausen, Bourgois, et al., 2020; Vanderclausen, Manfron, et al., 2020).…”

“…The ability to code somatosensory (tactile or nociceptive) information according to spatiotopic reference has been assessed, among others, using temporal order judgment (TOJ) tasks (Badde et al., 2014, 2015; Crollen, Albouy, et al., 2017; Crollen, Lazzouni, et al., 2017; Crollen et al., 2019; De Paepe et al., 2015; Heed & Azañón, 2014; Röder et al., 2004; Sambo et al., 2013; Shore et al., 2002; Vanderclausen, Bourgois, et al., 2020; Vanderclausen, Manfron, et al., 2020; Yamamoto & Kitazawa, 2001). In these tasks, participants judge the temporal order of two successive somatosensory stimuli, one applied to each hand, separated by different temporal delays.…”

Letter on the pain of blind people for the use of those who can see their pain

“…However, without disregarding the possibility of the 2 former mechanisms presented here above, recent data, presented in the following paragraphs, attempt to corroborate the latter hypothesis, notably by studying the importance of the visual system in the ability to detect and locate noxious events. 70,73…”