Altered reward network responses to social touch in major depression

The effects of different types of social interactions on the electrophysiology of neurons in the nucleus accumbens in rodents

BORLAND, J.M., The effects of different types of social interactions on the electrophysiology of neurons in the nucleus accumbens in rodents, NEUROSCI BIOBEH REV 21(1) XXX-XXX, 2024.-Sociality shapes an organisms' life. The nucleus accumbens is a critical brain region for mental health. In the following review, the effects of different types of social interactions on the physiology of neurons in the nucleus accumbens is synthesized. More specifically, the effects of sex behavior, aggression, social defeat, pair-bonding, play behavior, affiliative interactions, parental behaviors, the isolation from social interactions and maternal separation on measures of excitatory synaptic transmission, intracellular signaling and factors of transcription and translation in neurons in the nucleus accumbens in rodent models are reviewed. Similarities and differences in effects depending on the type of social interaction is then discussed. This review improves the understanding of the molecular and synaptic mechanisms of sociality.

Association between social withdrawal and suicidal ideation in patients with major depressive disorder: The mediational role of emotional symptoms

BACKGROUND

The study was designed to investigate the associations between social withdrawal, emotional symptoms, and suicide ideation in patients with major depressive disorder (MDD).

METHODS

This cross-sectional study included 2678 MDD patients from the National Survey on Symptomatology of Depression (NSSD). Differences in the sociodemographic factors, clinical characteristics, suicide ideation, and emotional symptoms were compared in patients with different frequencies of social withdrawal. Pearson correlation, multiple linear regression analysis, and mediation analysis were employed to assess the contribution of social withdrawal to suicide ideation.

RESULTS

MDD patients with a higher frequency of social withdrawal were prone to have a higher frequency of suicide ideation (p for trend <0.001) and history of suicide behavior (p for trend <0.001). Multiple linear regression analysis showed that there was a dose-response relationship between social withdrawal and suicide ideation in MDD patients, but this association became insignificant after adjusting for emotional symptoms. Mediation analysis suggested that all of the emotional symptoms had significant mediating effects on the association between social withdrawal and suicide ideation in MDD patients (p < 0.05). The magnitude of mediation varied between 4.3 % and 64.3 %, with the largest mediating effect in the feeling of despair (64.3 %), helplessness (41.2 %), and loneliness (40.0 %).

CONCLUSION

Our study provides evidence that social withdrawal was a common clinical presentation and it may increase the risk for suicide through emotional symptoms in MDD patients.

LIMITATIONS

Causal conclusions could not be drawn between social withdrawal, emotional symptoms, and suicide ideation because of the cross-sectional design of the study.

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

Interpersonal touch is an essential component of human non-verbal communication, facilitating social affiliation and bonding. With the widespread use of digital interfaces and online platforms in all realms of human interactions, there are fewer opportunities for communicating through touch. Popular online platforms that virtually simulate human interactions rely primarily on visual and auditory modalities, providing limited or no capacity for the exchange of tactile cues. Previous studies of virtual interactions have explored the simulation of social touch using haptic devices, but little is known about how the visual representation of interpersonal touch is perceived and integrated into a virtual social experience. In two studies we examined how the exchange of virtual touch mediated by simulated 3-dimensional human characters, or avatars, within an online virtual environment influenced affiliation towards an unfamiliar interaction partner. Surprisingly, the exchange of virtual touch negatively affected the perceived closeness and affiliation to the partner and the social evaluation of the interaction but did not affect the level of physiological arousal during the interaction. These results indicate that the visual representation of social touch is sufficient to virtually communicate touch-related cues that impact social affiliation, but the influence of touch may be dependent on the interaction context.