The role of visuospatial working memory in numerical processing - an fMRI study

In the last decade, studies have indicated an association between Visual-Spatial Working Memory (VSWM) domain-general cognitive ability, and number processing. We aimed to further elaborate this relationship in adults behaviorally and neuro-cognitively via fMRI. Fifty one student were recruited from them forty students were included in the analysis (males, N = 23; females, N = 17). Based on an outside scanner VSWM task, the participants were divided into High and Low VSWM Groups. During an fMRI scan, participants performed a Number line estimation task. Data were analyzed at the individual-participant level and at the group level. Multiple comparisons between the groups were carried out on the whole brain level and at specific ROIs (Regions of Interest). Behavioral results showed that the Low VSWM Group exhibited longer reaction time as compared with the High VSWM Group, in symbolic numerical processing. Neuroanatomical comparisons revealed greater activation mainly in right fronto-parietal regions among the High VSWM Group during the Number line estimation task, while the Low VSWM group engaged the left hemisphere, in parietal, frontal and temporal regions. ROI analyses showed that the left IPS activation was positively correlated to the Number line Task, thus indicating its specific role in symbolic number processing. These results demonstrate hemispherical differences between the groups during number processing, suggesting that people with High VSWM recruit resources from a domain-general ability (VSWM) which enables them to process symbolic numbers more efficiently, while people with Low VSWM capacity rely more on verbal abilities to compensate for lower spatial abilities when processing symbolic numerals.