The development of number processing and its relation to other parietal functions in early childhood

The project has explored the developmental trajectories of several cognitive functions related to different brain regions: parietal cortex (quantity manipulation, finger gnosis, visuo-spatial memory and grasping abilities) and occipito-temporal cortex (face and object processing), in order to investigate their contributions to the acquisition of formal arithmetic in the first year of schooling. We tested preschooler, first grader and adult subjects, using correlational cross-sectional and longitudinal approaches. Results show that anatomical proximity is a strong predictor of behavioural correlations and of segregation between dorsal and ventral streams’ functions. This observation is particularly prominent in children: within parietal functions, there is a progressive separation across functions during development. During preschool age, presymbolic and symbolic number systems follow distinct developmental trajectories that converge during the first year of primary school. Indeed a possible cause of this phenomenon could be due to the refinement of the numerosity acuity during the acquisition of symbolic knowledge for numbers. Among the tested parietal functions, we observe a strong association between the numerical and the finger domain, especially in children. In preschoolers, finger gnosis is strongly associated with non-symbolic quantity processing, while in first graders it links up to symbolic mental arithmetic. This finding may reflect a pre-existing anatomical connection between the cortical regions supporting the quantity and finger-related functions in early childhood. In contrast, first graders exhibit a finger-arithmetic association more influenced by functional factors and cultural-based strategies (e.g. finger counting). Longitudinal data has allowed us to individuate which cognitive functions measured in kindergarteners predicts better the success in mental arithmetic in the first year of school. Results show that finger gnosis, as well as quantity and space–related abilities all concur at shaping the success in mental calculation in first graders. These results are important because, primarily, they are the first to observe a strong relation between visuo-spatial, finger and quantity related abilities in young children, and, secondly, because the longitudinal design provides strong evidence for a causal link between these functions and the success in formal arithmetic. These results suggest that educational programs should include training in each of these cognitive domains in mathematic classes. Finally, specific applications of these findings can be found within the domain of educational neuroscience and for the rehabilitation of children with numerical deficits (dyscalculia).