A Developmental Functional MRI Study of the Approximate Number System: Age and Math Achievement Associations to Parietal Lobe Activity

摘要

Humans and other species are able to understand and accurately compare quantities from a very early age. This "number sense" is hypothesized to depend on an "Approximate Number System" (ANS) linked to activity in intraparietal sulcus. Recent findings suggest that the ANS possibly does not mature until adolescence, with ANS accuracy predictive of math academic achievement. However, the neural development of the ANS is not well understood. Here, we present findings from a developmental event-related FMRI study using a variant of the Panamath numerosity task (http://panamath.org) testing 46 children (6-12 years), teens (13-16 years), and adults (18-34 years). Participants were shown collections of blue and yellow dots on the left and right sides of the screen, respectively, and had to indicate which side had the greater number of dots via a button response. Task difficulty was manipulated by using four different ranges of blue:yellow dot ratios, or bins (lowest ratios more difficult). We also collected IQ, math achievement, and verbal achievement scores. All groups were less accurate at numerosity judgments in the two most difficult bins and achieved near perfect performance on the easiest two bins. Overall, children were less accurate and responded more slowly than teens and adults, and teens performed similarly to adults. We evaluated age and math achievement correlations to whole-brain FMRI BOLD activity in the hardest bin using linear regression. Age was positively correlated to increased activation in the supramarginal and angular gyrus, particularly in the left hemisphere. The Woodcock Johnson III Math Fluency test was positively correlated with activity in the right supramarginal and angular gyrus after accounting for age. These findings provide important new information about the neural development of the ANS and suggest that math achievement and age may be associated with activity in different hemispheres of the parietal lobe.