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

Developmental dyscalculia, a learning disorder marked by challenges in numerical cognition, has its cognitive and neural origins disputed. Two competing hypotheses suggest either domain-specific imprecise numerical representations or domain-general difficulties in maintaining and integrating numerical information. To examine both theories, researchers conducted an fMRI study on 33 adolescents and young adults with dyscalculia and 33 matched controls, aged 15-23, while they completed a sequential numerosity comparison task.

By merging computational modeling of choices and response times, the study isolated perceptual and memory noise from decision variables influencing the speed-accuracy tradeoff. Concurrent neuroimaging assessments delineated neural number representations and their network connections. The precision of parietal numerosity tuning was gauged using numerical population receptive field modeling, and personalized functional network maps of the parietal cortex were generated via community detection algorithms applied to connectivity patterns.

Dyscalculic participants exhibited increased perceptual and memory noise but a more conservative response criterion, balancing speed and accuracy to counteract representational imprecision. From a neural perspective, the numerosity model accounted for a smaller proportion of variance in parietal cortex activity, indicating less precise numerical representations.

Moreover, individualized network maps allocated less parietal cortex to the dorsal attention network and more to a visual network. These findings, rather than supporting a dichotomy between the two hypotheses, propose that dyscalculia results from both less precise numerical representations in parietal cortex and an altered distribution of this cortex across various functional systems.