Understanding the mechanisms through which spatial attention acts on nociception

Abstract

showing that spatial attention is further able to modify the chronometry of nociceptive processing by modulating the latency and temporal jitter of the recorded responses. The mechanisms through which attention could possibly modulate nociceptive processing are discussed here, with a particular focus on novel findings and future perspectives.laser-evoked potentials; spatial attention; nociception PAIN IS A COMPLEX EXPERIENCE that emerges, in normal conditions, in response to the activation of peripheral nociceptors. Pain has to be distinguished from the related notion of nociception: although the two concepts are clearly related, they are not the same. This distinction between the activation of a sensory stream (nociception) and the conscious experience of the stimulus (pain) has rendered the study of pain and its cognitive modulations particularly challenging (Wiech et al. 2008). Several studies have shown that attention is able to modulate behavioral and brain responses to noxious inputs (see Legrain et al. 2012 for a review on event-related potentials, ERPs). However, attention is not a unitary construct; indeed, different attentional processes have been identified, and a systematic investigation of the physiological mechanisms through which these different processes can shape nociception remains elusive.In their recent article, Franz et al. (2015) provide an interesting perspective on the mechanisms through which spatial attention (i.e., attention allocated to a specific spatial location) exerts its modulation on brain responses to nociceptive laser stimuli (i.e., laser-evoked potentials, LEPs). The authors aimed to investigate not only the effects of attention on the magnitude of the response but also the effects on the latency of the response, with a particular focus on the trial-to-trial variability. By examining the possible effects of attention on the singletrial basis, the authors sought to explore whether differences in the magnitude of the response can be influenced by latency jitters of the response. Importantly, these latency jitters become irrelevant when the analysis is performed at a single-trial level.The authors applied laser stimuli onto the left hand and electrical stimuli onto the right hand. Interspersed with these noxious stimuli, the authors delivered nonnoxious air puffs to both hands. In the "attend left hand condition," the authors maximized the effects of spatial attention on the processing of nociceptive stimuli by asking participants to count the number of targets (laser stimuli and air puffs) applied on the left hand. Importantly, attending to the left hand inevitably implied also attending to laser stimuli ("attend laser stimuli," ALS), considering that laser stimuli were always applied on the same hand. While receiving laser stimuli on the left hand, participants also received electrical painful shocks (and nonnoxious air puffs) on the right hand. Electrical stimuli were matched for intensity with laser stimuli, thereby constituting a control for salient stimuli. Therefore, in t...

Intense pain influences the cortical processing of visual stimuli projected onto the sensitized skin

“…Furthermore, previous studies have also shown that spatial attention can increase the magnitude of the negative vertex component elicited by stimuli belonging to several modalities (e.g. [9,10,20,41], see [3,12,21,34] for reviews and commentary). Therefore, a possible explanation to the "crossmodal sensitization" observed in the present study could be that HFS-related sensations induce cross-modal links in endogenous or exogenous spatial attention.…”

“…Twenty-six participants took part in the experiment (18 women, 8 men, median age 23, range [19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37]. Participants were recruited among students and staff of the university and were naïve to the aims of the study.…”