Altered Effective Connectivity of the Numerical Brain in Children With Developmental Dyscalculia.

Numerical-order ability, a strong predictor of arithmetic, is often impaired in children with developmental dyscalculia (DD). While previous research has shown altered brain responses in number-processing regions in DD compared to typically developing children (TD), little is known about how these regions interact during number processing. This exploratory study examined the effective connectivity between six regions in the right parietal, frontal, and insular cortex as well as the vermis, using dynamic causal modeling (DCM). We investigated how number-order and number-identification tasks modulate connectivity within this network and the group differences related to DD. The number-order task led primarily to increased excitatory connectivity from the pre-supplementary motor area (preSMA) to all other regions, indicating an orchestrating role of the preSMA. DD, who exhibited deficits in number-order performance, demonstrated aberrant modulation of incoming connectivity to the ventral premotor cortex (vPMC) from the anterior intraparietal sulcus (aIPS), the preSMA, and the dorsal anterior insula (d-aINS). In TD, number-identification led to inhibitory modulation from the vPMC to the aIPS and the vermis. While behavioral performance in number-identification was unimpaired in DD, they showed increased excitatory connectivity from dorsal and ventral PMC to the d-aINS and from vPMC to the aIPS. Our results imply that, for both impaired and unimpaired number-related behavioral performance, neuronal number processing differs between DD and TD. This conclusion is further supported by the high predictive validity of the modulating connectivity group-effect parameters. We suggest the underlying explanation for this pattern may be related to decreased acuity of neuronal number representation in DD.