Altered patterns of dynamic functional connectivity underpin reduced expressions of social-emotional reciprocity in autistic adults.

To identify the neurocognitive mechanisms underpinning the social difficulties that characterise autism, it is necessary to emulate the conditions of real-world social interactions under which they manifest. To achieve this, the present study performed functional magnetic resonance imaging on pairs of autistic and non-autistic adults simultaneously (dual-fMRI) whilst they interacted with one another on the iterated Ultimatum Game (iUG) – an economic game that emulates the reciprocal characteristic of naturalistic interpersonal exchanges. Two age-matched sets of male-male dyads were investigated: 16 comprised pairs of an autistic adult Responder and a non-autistic Proposer, and 19 comprised non-autistic pairs of Responder and Proposer that served as a comparison group. Players’ round-by-round behaviour was modelled as reciprocal choices, and dynamic functional connectivity (dFC) among seven intrinsic functional brain networks was measured to identify the neural mechanisms underpinning altered expressions of reciprocity during these interpersonal exchanges. Behavioural expressions of reciprocity were significantly reduced in autistic compared with non-autistic Responders, yet no such differences were observed between the non-autistic Proposers in either set of dyads. Furthermore, we identified four states of dFC with temporal properties (less dynamism) associated with these altered expressions of reciprocity. This was true especially for states characterised by co-ordinated patterns of integration and segregation among the Default Mode Network and cognitive control networks. Autistic interactants spend less time in brain states characterised by dynamic inter-network integration and segregation, suggesting that their characteristic difficulties in social-emotional reciprocity reflect less efficient reconfigurations among brain networks supporting flexible cognition and behaviour. These findings advance our mechanistic understanding of the social difficulties characterising autism.