Domain-specific and domain-general signatures of dyscalculia in computational models of behavior and parietal cortex

Developmental dyscalculia is a learning disorder characterized by marked difficulties in numerical cognition, yet its cognitive and neural underpinnings remain debated. Competing accounts attribute dyscalculia either to domain-specific imprecise representations of number or to domain-general deficits in the maintenance and integration of numerical information. Here, we test both accounts in 33 adolescents and young adults with dyscalculia and 33 age- and gender-matched controls (15-23 years) who performed a sequential numerosity comparison task during fMRI. Joint computational modeling of choices and response times allowed us to dissociate perceptual and memory noise from decision variables governing the speed-accuracy tradeoff, while complementary neuroimaging analyses characterized neural number representations and their network embedding. Specifically, we quantified the precision of parietal numerosity tuning with numerical population receptive field (nPRF) modeling and derived individualized functional network maps of the same region using community detection algorithms applied to connectivity patterns. Dyscalculic participants showed greater perceptual and memory noise but also a more cautious response criterion, trading speed for accuracy to compensate for representational imprecision. Neurally, the numerosity model explained less variance in parietal cortex, suggesting less precise numerical representations, and individualized network maps assigned less of this cortex to the dorsal attention network and more to a visual network. Rather than supporting a dichotomy between the two accounts, our findings suggest that dyscalculia reflects both less precise numerical representations in parietal cortex and an altered allocation of this cortex to distributed functional systems.