The Human Brain Network for Social Cognition: Connectome Topology, Individual Differences, and Vulnerability to Acquired Brain Injury

Social cognition encompasses the cognitive and affective processes that enable individuals to interpret social signals, infer others’ mental states, and regulate behaviour according to social norms. Although these functions have traditionally been associated with specific brain regions, current evidence suggests that they emerge from the coordinated activity of distributed neural systems. However, how the global topological organisation of the human connectome supports social-cognitive abilities, and how its disruption may contribute to deficits, remains incompletely understood, particularly in the context of acquired brain injury (ABI). This dissertation investigates the neural architecture of social cognition from a network neuroscience perspective, focusing on the role of connectome topology in both healthy individuals and clinical populations. The research is structured into three complementary studies. First, a systematic review synthesised evidence from lesion-based and neuroimaging studies in stroke and traumatic brain injury. The findings indicate that social cognition involves distributed and partially overlapping neural systems, suggesting that impairments cannot be readily attributed solely to damage to isolated brain regions. Second, an empirical study in healthy adults employed resting-state EEG and graph-theoretical analysis to examine whether individual differences in social cognition relate to intrinsic functional connectivity. The results showed that global network properties reflecting the balance between functional segregation and integration were selectively associated with social norm processing, indicating that variability in connectome topology relates to inter-individual differences in social-cognitive performance under normative conditions. Third, a clinical study investigated the relationship between Theory of Mind (ToM) and connectome topology in patients with severe ABI. The findings revealed significant ToM impairments alongside alterations in global network organisation. Furthermore, across the entire sample, greater global network integration was associated with better ToM performance independently of group membership. Taken together, these findings support the view that social cognition is a network-dependent function closely related to the global organisation of the connectome. By integrating systematic synthesis, normative evidence, and clinical investigation, this dissertation highlights the critical role of connectome topology in shaping social-cognitive functioning and provides new insights into mechanisms of vulnerability following brain injury.