Fractionating the neural correlates of individual working memory components underlying arithmetic problem solving skills in children

Abstract

Baddeley and Hitch's multi-component working memory (WM) model has played an enduring and influential role in our understanding of cognitive abilities. Very little is known, however, about the neural basis of this multi-component WM model and the differential role each component plays in mediating arithmetic problem solving abilities in children. Here, we investigate the neural basis of the central executive (CE), phonological (PL) and visuo-spatial (VS) components of WM during a demanding mental arithmetic task in 7-9 year old children (N=74). The VS component was the strongest predictor of math ability in children and was associated with increased arithmetic complexity-related responses in left dorsolateral and right ventrolateral prefrontal cortices as well as bilateral intra-parietal sulcus and supramarginal gyrus in posterior parietal cortex. Critically, VS, CE and PL abilities were associated with largely distinct patterns of brain response. Overlap between VS and CE components was observed in left supramarginal gyrus and no overlap was observed between VS and PL components. Our findings point to a central role of visuo-spatial WM during arithmetic problem-solving in young grade-school children and highlight the usefulness of the multi-component Baddeley and Hitch WM model in fractionating the neural correlates of arithmetic problem solving during development.

Keywords: Arithmetic cognition; Central executive; Development; Individual differences; Visuo-spatial; Working memory; fMRI.

Graphical abstract

Fig. 1

Arithmetic complexity-related brain activation. Significant group-level activations for the contrast of Complex–Control were detected in bilateral anterior insula, right inferior frontal gyrus, left premotor cortex, right posterior hippocampus, bilateral lingual and fusiform gyri, and left intra-parietal sulcus. Deactivation was detected only in the ventromedial prefrontal cortex. Complex addition problems were of the form x + y = z with one operand from 2 to 9 and the other from 2 to 5; the Control problems had the same format except that x or y was set to 1. PMC, premotor cortex; Ins, insula; IPS, intra-parietal sulcus; LG, lingual gyrus; FG, fusiform gyrus; IFG, inferior frontal gyrus; SFG, superior frontal gyrus; CG, cingulate gyrus; LG, lingual gyrus; Hipp, hippocampus (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.).

Fig. 2

Brain areas associated with visuo-spatial component of working memory. Individual differences in visuo-spatial ability emerged as the strongest and most consistent predictor of behavior and brain response during arithmetic problem solving. Increased arithmetic complexity-related brain responses were located in left dorsolateral and right ventrolateral prefrontal cortex, as well as bilateral posterior parietal cortex including intra-parietal sulcus. MFG, middle frontal gyrus; IPS, intra-parietal sulcus; SMG, supramarginal gyrus; SFG, superior frontal gyrus; IFG, inferior frontal gyrus. Bottom panel: regions of interest depicted as orange open circles (radius: 6 mm). Scatter plots are based on functional clusters identified using whole-brain regression analysis, and are provided for the purpose of visualization. L, left; R, right. Behavioral Performance: for comparison, plots of cognitive assessments of math and visuo-spatial ability. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

Fig. 3

Brain areas associated with the central executive component of working memory. Central executive ability was correlated with distributed brain areas including dorsolateral prefrontal cortex, posterior parietal cortex, and hippocampus during arithmetic problem solving. SPL, superior parietal lobule; SMG, supramarginal gyrus; IPS, intra-parietal sulcus; MFG, middle frontal gyrus; AG, angular gyrus; FG, fusiform gyrus; OC, occipital cortex. Bottom panel: regions of interest depicted as orange open circles (radius: 6 mm). Scatter plots are based on functional clusters identified using whole-brain regression analysis, and are provided for the purpose of visualization. L, left; R, right. Behavioral Performance: for comparison, plots of cognitive assessments of math and visuo-spatial ability. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

Fig. 4

Brain areas associated with the phonological component of working memory. Negative correlations were observed in the frontal pole (FP). Positive correlates were detected in left anterior intra-parietal sulcus (IPS) and lingual gyrus (LG). Regions of interest depicted as open orange circles (radius: 6 mm). Scatter plots are based on functional clusters identified using whole-brain regression analysis, and are provided for the purpose of visualization.

Fig. 5

Functional dissociations and overlap between brain areas associated with each of the three components of working memory. Overlap between central executive (CE) and visuo-spatial (VS) components was observed only in left supramarginal gyrus (SMG), overlap between CE and phonological (PL) components was observed only in the left intra-parietal sulcus (IPS) and no overlap was observed between VS and PL components. Negative correlation between activity and PL ability is not depicted (see Fig. 4). No overlap for VS and PL (magenta) was observed. Bottom panel: coronal slices depict regions of interest selected as overlap in correlations of activity and individual working memory components. Scatter plots are based on functional clusters identified using whole-brain regression analysis, and are provided for the purpose of visualization. L, left.