The anticipation of clinical benefit, a crucial component of placebo analgesia, has been suggested to be a special case of reward anticipation. Since reward processing is closely linked to the ventral striatum and the neurotransmitter dopamine, we examined the relationships between brain gray matter, placebo analgesic response, and personality traits associated with dopaminergic neurotransmission. We report that dopamine-related traits predict a substantial portion of the pain relief an individual gains from a sham treatment. Voxel-based morphometry of magnetic resonance images shows that the magnitude of placebo analgesia is related to gray matter density (GMD) in several brain regions, including the ventral striatum, insula, and prefrontal cortex. Similarly, GMD in ventral striatum and prefrontal cortex is related to dopamine-related personality traits. Our findings highlight the relationship between placebo and reward and potentially offer ways of identifying subjects who are likely to show large placebo analgesic responses.
Tuesday, April 21, 2009
Link between brain anatomy, personality, and the placebo analgesic response
As a companion to today's first post, on motivation, a note that Schweinhardt et al. provide some interesting correlations between personality traits related to dopaminergic neurotransmission (novelty seeking, harm avoidance (inversely related), behavioral drive, fun seeking, and reward responsiveness.), size of the mesolimbic reward system, and the effectiveness of the placebo effect: