Processing Pathways in Mental Arithmetic—Evidence from Probabilistic Fiber Tracking

TLDR

Numerical cognition involves distributed, multi‑modular brain processing, yet the anatomical and functional connections between involved cortical areas and their alignment with dorsal‑ventral processing streams remain undefined. The study sought to distinguish neural correlates and connectivity patterns for easy versus difficult addition tasks, linking them to fact‑retrieval or magnitude‑manipulation strategies. The authors re‑analyzed existing fMRI data and integrated probabilistic fiber‑tracking from a separate cohort to map connectivity. Results indicate that magnitude‑ and fact‑retrieval processes are supported by two largely distinct dorsal‑ventral networks that differ in activation localization and inter‑regional connections, yet functionally integrate during mental calculation.

Abstract

Numerical cognition is a case of multi-modular and distributed cerebral processing. So far neither the anatomo-functional connections between the cortex areas involved nor their integration into established frameworks such as the differentiation between dorsal and ventral processing streams have been specified. The current study addressed this issue combining a re-analysis of previously published fMRI data with probabilistic fiber tracking data from an independent sample. We aimed at differentiating neural correlates and connectivity for relatively easy and more difficult addition problems in healthy adults and their association with either rather verbally mediated fact retrieval or magnitude manipulations, respectively. The present data suggest that magnitude- and fact retrieval-related processing seem to be subserved by two largely separate networks, both of them comprising dorsal and ventral connections. Importantly, these networks not only differ in localization of activation but also in the connections between the cortical areas involved. However, it has to be noted that even though seemingly distinct anatomically, these networks operate as a functionally integrated circuit for mental calculation as revealed by a parametric analysis of brain activation.