Strategy over operation: Neural activation in subtraction and multiplication during fact retrieval and procedural strategy use in children

Strategy or operation? Neural activity in subtraction and multiplication during retrieval and procedural strategies in children. Over the last years, accumulating evidence is suggesting that a fronto-parietal network is consistently activated during arithmetic in adults (Menon, 2015). Furthermore, fMRI studies have indicated that activation in this arithmetic brain network is modulated by strategy use. In children, studies have also suggested such alternate activation by, for example, manipulating the problem size or format of the presented problems (e.g., De Smedt et al., 2011; Prado et al., 2014), yet such an approach only enabled these studies to make implicit assumptions on children’s strategy use; a trial-by-trial testing to check the children’s actual strategy use (Siegler, 1988) was yet to be done, leaving it unclear how brain activity alters as different strategies are used. The current study is the first to investigate neural activation while taking individual differences in children’s arithmetic strategy use into account, which is crucial when considering the large developmental changes in strategies. Furthermore, such data are important to understand mathematical learning disabilities or dyscalculia, as difficulties in arithmetic strategy use are the hallmark of this disorder (Geary, 2011). Participants were 26 typically developing 4th graders (9- to 10-year-olds). In a behavioral session, all children were asked to, on a trial-by-trial basis, verbally report how they had solved 100 subtraction and multiplication items. The majority of these items (80 of the 100 items, divided over 4 runs with 20 items each) were subsequently presented during functional magnetic resonance imaging (fMRI). A schematic overview of a trial is presented in Figure 1. Data were analyzed with the SPM12 software (ref.). By implementing an event-related design, we were able to analyze the brain responses during retrieval and procedural strategy use trials, based on the children’s verbal reports. The data were analyzed by means of a full factorial 2 x 2 ANOVA with strategy (retrieval vs. procedure) and operation (subtraction vs. multiplication) as within-subject factors. This allowed us to examine the main effects of strategy use and of operation as well as the strategy by operation interaction. The main effect of strategy use on brain activity is presented in Figure 2. During retrieval, we observed increased activity in the bilateral angular and supramarginal gyri, left middle to inferior temporal gyrus, right superior temporal gyrus, and superior medial frontal gyrus. For procedural strategies, activation increases were observed in the inferior and superior parietal lobes (intraparietal sulci), inferior to superior frontal gyri, bilateral areas in the occipital lobe, and insular cortex. Consequently, these results provide evidence for alternate neural activation when children use different arithmetic strategies. We also found no effect of operation, as no differences were found between subtraction and multiplication, nor did we observe an interaction between strategy use and operation, which suggests that the differences between retrieval and procedure use were not different between both operations. The current study is thus the first in children that identified the brain networks underlying specific arithmetic strategies and to reveal that previously found operation differences in brain activity in children are explained by their arithmetic strategy use.status: publishe