The Effect of High Versus Low Cognitive Load on the Development of Nociceptive Hypersensitivity: The Roles of Sympathetic Arousal, Sex, and Pain-Related Fear

BACKGROUND: According to limited-capacity theories of attention, less attentional resources remain available when engaging in a high versus a low demanding cognitive task. This may reduce the perceived intensity and the evoked cortical responses of concomitant nociceptive stimuli. Whether and how the competition for limited attentional resources between a cognitive task and pain impacts the development of long-lasting hypersensitivity is unclear.

METHODS: Eighty-four healthy participants were randomized into a low or high cognitive load group. Low Frequency electrical Stimulation (LFS) of the skin was used to induce secondary hypersensitivity. We hypothesized that performing the high load task during LFS would reduce the development of hypersensitivity. We examined whether painfulness, non-pain-related sympathetic arousal, or sex related to hypersensitivity, by assessing intensity and unpleasantness of mechanical pinprick stimulation. During task execution, we recorded steady-state evoked potentials evoked by LFS, and skin conductance level for sympathetic arousal. Afterwards, participants reported task difficulty and LFS-related fear. For the primary outcomes, we used mixed ANOVAs.

RESULTS: The results confirmed the difference in cognitive load. Although LFS successfully induced hypersensitivity, the high load task did not reduce its development. Next, the steady-state evoked potentials did not differ between groups. Hypersensitivity correlated positively with pain-related fear and negatively with skin conductance level before LFS, despite the lack of group differences in skin conductance level. We did not find any sex differences in hypersensitivity.

CONCLUSIONS: These results do not confirm that high cognitive load or sex modulate hypersensitivity, but show associations with pain-related fear and non-pain-related sympathetic arousal.