Fronto-temporal structural alterations in congenital aphantasia

Abstract

Congenital aphantasia is characterized by a lifelong self-reported absence of voluntary visual imagery despite preserved visual knowledge, offering a natural model for dissociating sensory representation from conscious imagery. Functional imaging evidence suggests that this dissociation may arise from altered top-down interactions between higher-order control systems and high-level visual cortex, but its structural correlates remain unknown. Here, using diffusion and structural MRI in 18 individuals with congenital aphantasia and 18 matched visualisers, we tested two competing accounts of aphantasia: one predicting structural differences in visual pathways, the other predicting differences in higher-order associative networks. Across multimodal analyses of white-matter tract microstructure, functional-ROI tractography, graph-theoretic network organization, and cortical morphometry, aphantasia was associated with structural differences in frontotemporal and cingulate white-matter tracts, including the uncinate fasciculus, posterior interparietal callosal fibres, and dorsal cingulum, and in frontotemporal cortical regions, including the anterior insula, anterior prefrontal cortex, and medial temporal cortex, together forming a candidate neuroanatomical signature for the broad cognitive-affective profile of aphantasia. By contrast, we found no reliable group differences in early visual cortex, major visual tracts, or the direct structural connections of the core imagery network. Congenital aphantasia therefore exhibits a pattern of structural alterations centered on frontotemporal and cingulate systems, sparing the principal visual pathways. Given the modest sample size, these findings are exploratory and hypothesis-generating and require replication in larger cohorts; they nonetheless suggest that higher-order systems supporting integration and conscious access, rather than visual representations themselves, may contribute to the absence of conscious imagery in congenital aphantasia.