Poster No:
738
Submission Type:
Abstract Submission
Authors:
Ryo Kitada1, Hiroaki Kawamichi2, Yuki Hamano3,4, Eri Nakagawa5, Sho Sugawara6, Norihiro Sadato7,8
Institutions:
1Graduate School of Intercultural Studies, Kobe University, Kobe, Hyogo, 2Gunma University, Maebashi, Japan, 3Waseda University, Tokyo, JAPAN, 4the Japan Society for the Promotion of Science, Tokyo, Japan, 5Shizuoka University, Hamamatsu, Japan, 6Tokyo Metropolitan Institute of Medical Sciences, Tokyo, Tokyo, 7Ritsumeikan University, Kyoto, Kyoto, 8National Institute for Physiological Sciences, Okazaki, Japan
First Author:
Ryo Kitada
Graduate School of Intercultural Studies, Kobe University
Kobe, Hyogo
Co-Author(s):
Yuki Hamano
Waseda University|the Japan Society for the Promotion of Science
Tokyo, JAPAN|Tokyo, Japan
Sho Sugawara
Tokyo Metropolitan Institute of Medical Sciences
Tokyo, Tokyo
Norihiro Sadato
Ritsumeikan University|National Institute for Physiological Sciences
Kyoto, Kyoto|Okazaki, Japan
Introduction:
Hand is the most touchable body part in social interaction and stationary hand contact between socially-close persons can alleviate distress. Neuroimaging studies have revealed the involvement of limbic structure and somatosensory cortices in affective processing of interpersonal touch. However, because these studies focused on the effect of stroking hairy skin, the brain network for interpersonal touch on the glabrous skin is scarcely understood. Here, we conducted an fMRI study to examine neural correlates of interpersonal touch by manipulating the touched body part and social closeness of the toucher.
Methods:
We used two 3-T whole-body MRI scanners (Verio; Siemens) with a multiband EPI sequence: gradient-echo EPI, TR = 1,000 ms, multiband factor = 6, echo time (TE) = 35 ms, flip angle = 65°, 60 axial slices of 2-mm thickness with a 25% slice gap, and in-plane resolution = 2.0 × 2.0 mm2.
Seventeen pairs of volunteers participated in the study (16 female friends and 18 male-female couples). We tested two types of stimuli: human hand and cosmetic brush. We manipulated the human hand stimulation with the two factors: the body area of the stimulation (hand and forearm) and the social closeness of the person who the subject believed touched their body (close person or stranger). Brush stimulation was used to serve as control of tactile input for interpersonal touch and to examine activity sensitive to slow brushing that is associated with peripheral C tactile fibers in the forearm. The brush stimulation was also manipulated with the two factors: the location of the stimulation (hand and forearm) and brushing speed (3 levels).
In each trial, the participant's right hand (palm side of the hand) and arm were stimulated by either brush or other's hand (finger pads). After 5-s stimulation, the participants used their left thumb to control the three buttons to answer their feelings using the visual-analogue scale (VAS).
We preprocessed fMRI data and conducted mass-univariate analyses using SPM12. In the mass-univariate analysis, the statistical threshold for the spatial extent test on the clusters was set at p < 0.05, family-wise error (FWE) corrected for multiple comparisons over the whole brain. The height (cluster-forming) threshold was set at p < 0.001 (uncorrected). We used CoSMoMVPA toolbox to perform the multi-voxel pattern analysis (MVPA).
Results:
Univariate analyses:
As compared to brush stimulation, the contact by other revealed regions of significant activation including the medial prefrontal cortex, posterior cingulate cortex, and temporal-parietal junction. We evaluated the effect of social closeness to the toucher on brain activity by comparing the close-person's touch with the stranger's touch. The close-person effect was found in the anterior cingulate cortex (ACC), bilateral ventromedial prefrontal cortex (vmPFC), middle occipital gyrus (MOG), and inferior temporal gyrus regardless of the body part. This close-person effect was stronger for hand than forearm in multiple brain regions such as ACC, anterior insula and nucleus accumbens (NAcc).
MVPA
Permutation tests on orbitofrontal cortex (OFC), ACC, NAcc, postcentral gyrus (PostCG) and parietal operculum (PO)/insula (with Bonferroni correction) showed significant results on all regions for interpersonal hand touch (p values < 0.05). The effect for other's contact to the arm was observed in all regions except for PO/insula (p values < 0.05). Paired t tests (with Bonferroni correction) showed that accuracy was greater for the hand than the forearm in the postCG, PO/Insula and ACC in the contact by others (p values < 0.001).
Conclusions:
These results suggest that ACC, vmPFC, and MOG constitute nodes of a network for the social-closeness effect, regardless of the body part. Furthermore, the anterior insula and NAcc may be additional nodes to cause the emotional effect unique to interpersonal hand touch.
Emotion, Motivation and Social Neuroscience:
Emotional Perception 1
Social Cognition
Social Interaction 2
Keywords:
FUNCTIONAL MRI
Perception
Social Interactions
Somatosensory
Touch
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