Altered reward network responses to social touch in major depression

Abstract

Background Social touch is an integral part of social relationships and has been associated with reward. Major depressive disorder (MDD) is characterized by severe impairments in reward processing, but the neural effects of social touch in MDD are still elusive. In this study, we aimed to determine whether the neural processing of social touch is altered in MDD and to assess the impact of antidepressant therapy. Methods Before and after antidepressant treatment, 53 MDD patients and 41 healthy controls underwent functional magnetic resonance imaging (fMRI) while receiving social touch. We compared neural responses to social touch in the reward network, behavioral ratings of touch comfort and general aversion to interpersonal touch in patients to controls. Additionally, we examined the effect of treatment response on those measures. Results Clinical symptoms decreased after treatment and 43.4% of patients were classified as responders. Patients reported higher aversion to interpersonal touch and lower comfort ratings during the fMRI paradigm than controls. Patients showed reduced responses to social touch in the nucleus accumbens, caudate nucleus and putamen than controls, both before and after treatment. Contrary to our hypotheses, these effects were independent of touch velocity. Non-responders exhibited blunted response in the caudate nucleus and the insula compared to responders, again irrespective of time. Conclusions These findings suggest altered striatal processing of social touch in MDD. Persistent dysfunctional processing of social touch despite clinical improvements may constitute a latent risk factor for social withdrawal and isolation.

Virtually simulated interpersonal touch negatively affects perceived closeness and social affiliation to an avatar partner

“…Comfort with interpersonal distance and social touch are also associated 79 , and both are influenced by adverse life experience and linked by underlying neural processing 80 . Furthermore, mental disorders that are characterized by increased social distancing, such as depression 81 , can affect neural processing of social touch stimuli 82 . This body of evidence indicates that the role of social distance cues in the visual representation of social touch, as well as individual preferences regarding social proximity and comfort with touch 83 , are important to consider in future investigations of virtual touch interactions.…”

Autonomic modulations to cardiac dynamics in response to affective touch: Differences between social touch and self-touch

“…So far, evidence indicates that affective touch can increase HRV, suggesting a parasympathetic modulation to cardiac dynamics and a sympathetic inhibition [9], [10], whereas sympathetic activations rather occur under the conditions of thermoception and nociception [11], [12]. Pathological conditions can cause disruptions in autonomic balance, such as major depression [13] or depersonalization disorder [14], which could potentially explain the physiological underpinnings of the impairment in the processing of affective touch in those conditions [15], [16].…”