Top-down attentional modulation of analgesia induced by heterotopic noxious counterstimulation.
Heterotopic noxious counterstimulation (HNCS) by the application of a sustained noxious stimulus has been shown to inhibit nociceptive processes and decrease pain induced by a competing noxious stimulus. However, it is still not clear how attentional processes contribute to these effects. The main objective of this study was to compare the analgesic effects of HNCS in 2 sessions during which top-down attention was manipulated. Acute shock pain and the nociceptive flexion reflex were evoked by transcutaneous electrical stimulations of the right sural nerve in 4 blocks (15 stimuli/block): baseline, heterotopic innocuous counterstimulation (HICS), HNCS, and recovery. Counterstimulation was applied on the left upper limb with a thermode (HICS) or a cold pack (HNCS). Attention was manipulated between sessions by instructing participants to focus their attention on shock pain or counterstimulation. Shock pain ratings decreased significantly during counterstimulation (P<.001) with stronger effects of HNCS vs HICS in both sessions (P<.01). Furthermore, shock pain inhibition during HNCS relative to baseline was stronger with attention focusing on counterstimulation compared to attention focusing on shocks (P = .015). However, the relative decrease in pain ratings during HNCS vs HICS was not significantly affected by the direction of attention (P = .7). As for spinal nociceptive processes, nociceptive flexion reflex amplitude was significantly decreased during counterstimulation (P<.001) with larger reductions during HNCS compared to HICS (P = .03). However, these effects were not altered by attention (P = .35). Together, these results demonstrate that top-down attention and HNCS produce additive analgesic effects. However, attentional modulation of HNCS analgesia seems to depend on supraspinal processes.
Department of Psychology, Université du Québec à Trois-Rivières, Trois-Rivières, QC, Canada G9A 5H7 Department of Chiropractic, Université du Québec à Trois-Rivières, Trois-Rivières, QC, Canada G9A 5H7 Groupe de recherche en Neuroscience, Université du Québec à Trois-Rivières, Trois-Rivières, QC, Canada G9A 5H7 Groupe de recherche sur les affections neuromusculosquelettiques, Université du Québec à Trois-Rivières, Trois-Rivières, QC, Canada G9A 5H7 Centre de recherche en neuropsychologie et cognition (CERNEC), Université de Montréal, Montréal, QC, Canada H3T 1J4 Centre de recherche, Institut universitaire de gériatrie de Montréal (CRIUGM), Université de Montréal, Montréal, QC, Canada H3T 1J4 Department of Stomatology, Université de Montréal, Montréal, QC, Canada H3T 1J4.
Alexandra
A
Ladouceur
Jessica
J
Tessier
Benjamin
B
Provencher
Pierre
P
Rainville
Mathieu
M
Piché
D000222:Adaptation, Physiological; D000328:Adult; D003214:Conditioning, Classical; D004554:Electric Countershock / Q000379:methods*; D004558:Electric Stimulation / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010146:Pain / Q000503:physiopathology* / Q000517:prevention & control*; D058748:Pain Perception / Q000502:physiology*; D017288:Pain Threshold; D012018:Reflex; D055815:Young Adult