In your article, the possibility is mentioned that patients with Parkinson’s disease might have improved in the study because of the placebo effect rather than the administration of the protein glial-cell-line-derived neurotrophic factor. The article then says, “However, brain scans of these patients . . . showed that dopamine supplies in the putamen improved over that time,” seemingly suggesting that such an increase in dopamine would not be likely to occur if the improvement were due to the placebo effect.