Placebo effects on analgesia related to testosterone and premotor activation.

Using functional magnetic resonance imaging, we tested whether graded placebo conditions could modulate the degree of placebo effect and brain activation patterns in study participants and whether the placebo effect could be influenced by hormones. Each participant was investigated under three conditions: the control (no placebo) condition, the low-placebo condition, and the high-placebo condition (HPC). Activations of the premotor areas, anterior cingulate cortex, and prefrontal cortex were stronger in the HPC compared with those in the control and low placebo conditions. The premotor areas were activated by increased testosterone levels under the HPC. These results suggest that testosterone may affect the brain activation and response to pain during a high-placebo response, with the data supported by brain imaging.