Control over spinal nociception as quantified by the nociceptive flexor reflex (RIII reflex) can be achieved under...

Descending pain modulatory systems control transmission of nociceptive information at the spinal level, and their activity can be modified by cognitive and emotional processes. Thus, it may be possible to learn using cognitive-emotional strategies to specifically target descending pathways in order to achieve pain reduction.

The present study used visual feedback of the nociceptive flexor reflex (RIII reflex) to train healthy subjects over three sessions to reduce their spinal nociception (RIII reflex size) by self-selected cognitive-emotional strategies. The study included two feedback groups (fixed vs. random stimulation intervals) and a control group without feedback (15 subjects each).

While all three groups successfully reduced their RIII reflexes (p < 0.01), reductions were larger in the feedback groups (p < 0.05). Success increased over training sessions in the feedback groups (p < 0.05). In the third session, RIII was reduced to 90 ± 15% of baseline in the control group, and to 72 ± 24 and 66 ± 22% in the feedback groups. Most subjects used mental imagery or relaxation to achieve RIII reduction. Pain reduction correlated with RIII reduction in the feedback groups, but was not significantly different between feedback and control groups.

The present results suggest that healthy subjects are able to learn using cognitive and emotional strategies to reduce their spinal nociception under feedback of their RIII reflex size. However, future studies will have to include a sham feedback group to differentiate true learning effects from expectancy effects induced by the feedback procedure.