Effect of Cooperative and Non-Cooperative Social Interactions on Personal Space Regulation in Adults with Autism Spectrum Disorders: An fMRI Study

Background: Personal Space (PS) is the space immediately surrounding an individual and it can be regulated during social interactions. Intrusion into this space by others can generate feelings of discomfort. Developmental and psychiatric disorders influence the regulation of PS. Importantly, in the case of autism spectrum disorder (ASD), characterized by deficits in interpersonal interaction, the regulation of PS is often altered compared to typically developing (TD) children [1] and/or not modulated by changes in the quality of experienced social interactions [2].

Objectives: This study aimed at extending the previous findings to the ASD adult population and to investigate the behavioral and neurophysiological underpinning of PS and its modulation by different types of social interactions.

Methods: Fifteen ASD and fifteen TD matched participants underwent fMRI investigation while performing a modified version of the stop-distance paradigm for measuring PS preferences. In particular, participants were presented with several prerecorded videos from a first person perspective: an actor moving a predetermined number of steps towards them. They were asked to specify how comfortable they felt in regard to the observed distance. In order to see the effect of social interaction on PS perception, participants and confederates played a repeated trust game session, in which cooperative and non-cooperative interactions were experimentally manipulated. After the game, participants were confronted a second time with the distance task, in order to measure PS preference variation due to the type of social interaction (cooperative or not) previously experienced.

Results: We observed a significant modulation of the trust game on the PS, as TD participants showed increased comfort toward the cooperative player and increased discomfort towards the non-cooperative one (Fig.1), associated with modulation of emotional brain areas (bilateral insula). Notably, we observed the same effect in the ASD population on the behavioral level, but reduced insular activity on the neural level, suggesting that the perception of a cooperative (or not) interaction is processed differently in the ASD population (Fig.2A,B). Moreover, ASD participants showed a general reduction of activity in the intraparietal sulcus, a region involved during the observation of approaching stimuli (Fig. 2C). Notably, a stronger approaching-bias observed in this region has been recently associated to higher sociability in healthy participants [3].

Conclusions: The findings suggest differences between ASD and TD individuals in processing the emotional saliency of an approaching person, as result of the type of social interaction previously experienced. A better understanding of the behavioral and the neuronal mechanisms behind PS perception and its modulation will improve our knowledge of the social deficits observed in ASD.

[1] Gessaroli et al., PLoS One (2013).

[2] Candini et al., Autism Res. (2017).

[3] Holt et al., J.Neurosci (2014).