title: Social touch modulates endogenous μ-opioid system activity in humans.
abstract: In non-human primates, opioid-receptor blockade increases social grooming, and the endogenous opioid system has therefore been hypothesized to support maintenance of long-term relationships in humans as well. Here we tested whether social touch modulates opioidergic activation in humans using in vivo positron emission tomography (PET). Eighteen male participants underwent two PET scans with [11C]carfentanil, a ligand specific to μ-opioid receptors (MOR). During the social touch scan, the participants lay in the scanner while their partners caressed their bodies in a non-sexual fashion. In the baseline scan, participants lay alone in the scanner. Social touch triggered pleasurable sensations and increased MOR availability in the thalamus, striatum, and frontal, cingulate, and insular cortices. Modulation of activity of the opioid system by social touching might provide a neurochemical mechanism reinforcing social bonds between humans.
authors.affiliation: Department of Neuroscience and Biomedical Engineering, School of Science, Aalto University, 00076 AALTO, Finland; Turku PET Centre, University of Turku, 20520 Turku, Finland. Electronic address: lauri.nummenmaa@aalto.fi.
authors.forename: Lauri
authors.initials: L
authors.lastname: Nummenmaa
authors.affiliation: Turku PET Centre, University of Turku, 20520 Turku, Finland.
authors.forename: Lauri
authors.initials: L
authors.lastname: Tuominen
authors.affiliation: Department of Neuroscience and Biomedical Engineering, School of Science, Aalto University, 00076 AALTO, Finland; Department of Experimental Psychology, University of Oxford, OX1 3UD Oxford, UK.
authors.forename: Robin
authors.initials: R
authors.lastname: Dunbar
authors.affiliation: Turku PET Centre, University of Turku, 20520 Turku, Finland.
authors.forename: Jussi
authors.initials: J
authors.lastname: Hirvonen
authors.affiliation: Department of Neuroscience and Biomedical Engineering, School of Science, Aalto University, 00076 AALTO, Finland.
authors.forename: Sandra
authors.initials: S
authors.lastname: Manninen
authors.affiliation: Turku PET Centre, University of Turku, 20520 Turku, Finland.
authors.forename: Eveliina
authors.initials: E
authors.lastname: Arponen
authors.affiliation: Department of Experimental Psychology, University of Oxford, OX1 3UD Oxford, UK.
authors.forename: Anna
authors.initials: A
authors.lastname: Machin
authors.affiliation: Department of Art, School of Arts, Design and Architecture, Aalto University, 00076 AALTO, Finland.
authors.forename: Riitta
authors.initials: R
authors.lastname: Hari
authors.affiliation: Department of Neuroscience and Biomedical Engineering, School of Science, Aalto University, 00076 AALTO, Finland.
authors.forename: Iiro P
authors.initials: IP
authors.lastname: Jääskeläinen
authors.affiliation: Department of Neuroscience and Biomedical Engineering, School of Science, Aalto University, 00076 AALTO, Finland.
authors.forename: Mikko
authors.initials: M
authors.lastname: Sams
mesh_terms: D000328:Adult; D001921:Brain / Q000378:metabolism*; D005260:Female; D006801:Humans; D008297:Male; D057054:Molecular Imaging / Q000379:methods; D009769:Object Attachment; D057181:Pleasure / Q000502:physiology*; D049268:Positron-Emission Tomography / Q000379:methods; D017450:Receptors, Opioid, mu / Q000378:metabolism*; D012919:Social Behavior; D014110:Touch / Q000502:physiology*; D055698:Touch Perception / Q000502:physiology*
chemical_list: D017450:Receptors, Opioid, mu
keywords: Bonding; Opioids; PET; Somatosensory; Touching