How are grammatical and arithmetic processing related in the brain? An ALE meta-analysis.

Grammatical and arithmetic skills are consistently associated, but the nature of this relationship remains debated. On the one hand, it may be due to shared linguistic processes. On the other hand, it may also come from domain-general abilities involved in extracting and applying abstract structured rules. To address this question, we investigated the neural basis of the relation between grammatical and arithmetic processing by conducting an activation likelihood estimation (ALE) meta-analysis of whole-brain fMRI studies of grammatical (n=48) and arithmetic (n=66) processing in healthy children and adults. Left perisylvian language regions were more consistently recruited for grammatical than arithmetic processing, whereas bilateral parietal regions were more consistently recruited for arithmetic than grammatical processing. The conjunction analysis revealed overlapping activation in four left-lateralized regions: the junction between the Inferior and Middle Frontal Gyrus, the Supplementary Motor Area, the Parietal Lobule, and the Anterior Insula. Together, these findings indicate that grammatical and arithmetic processing recruit both shared and domain-specific neural systems. The overlapping regions largely correspond to areas associated with the multiple-demand network, suggesting that both domains engage domain-general cognitive mechanisms involved in complex rule-based processing. In contrast, classical perisylvian language regions were selectively recruited during grammatical processing, whereas bilateral parietal regions were more consistently associated with arithmetic processing. These findings therefore suggest that the relationship between grammar and arithmetic is better explained by the coexistence of shared domain-general mechanisms and domain-specific neural systems than by shared linguistic processes alone.