1. National Center for Complementary and Integrative Health, National Institutes of Health, Bethesda, Maryland 20892, USA;
2. Center for Social and Affective Neuroscience, Department of Clinical and Experimental Medicine, Linköping University, 583 30 Linköping, Sweden
3. NIH–Brown University Graduate Program in Neuroscience, Providence, Rhode Island 02912, USA
4. National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892, USA