Affective modulation of eyeblink reactions to noxious sural nerve stimulation: a supraspinal measure of nociceptive reactivity?

Research suggests affective picture-viewing modulates subjective and physiological reactions to noxious stimulation (pain report, heart rate acceleration, skin conductance response, nociceptive flexion reflex). Because the nociceptive flexion reflex (a spinal reflex) is modulated by picture-viewing, this suggests affective processes are able to modulate afferent nociception at spinal levels. This highlights the importance of assessing nociceptive reactivity from physiological measures mediated at different levels of the neuraxis (spinal vs. supraspinal) to help elucidate the mechanisms associated with pain regulation. The present study examined whether affective pictures modulate eyeblink reactions (a supraspinal reflex) to noxious stimulation. Healthy men and women (N=23) were recruited from the psychology subject pool to participate. Pictures (attack, loss, neutral, food, erotica) that manipulated affective valence and arousal were presented and noxious electrodermal stimulations were delivered to the sural nerve. Picture duration (500-ms vs. 6-s) was also manipulated, balanced across picture content. Results suggested affective valence and arousal contributed to the modulation of eyeblinks. Eyeblinks were larger during highly arousing unpleasant pictures (attack) than highly arousing pleasant pictures (erotica), but low arousal pictures (loss, food) did not lead to significant modulation. Affective modulation was independent of picture duration or the perceived painfulness of noxious stimulation. This study suggests eyeblink reactions can serve as a supraspinal outcome in procedures used to study affective modulation of pain and nociception.