The project yielded the following three main scientific results. First, to clarify the development of number-related brain functions that may influence MLD, the researcher collected fMRI data from 5- and 8-year-old children and examined age-related changes in children’s number representations based on these cross-sectional data. Brain activity was measured while children passively perceived nonsymbolic and symbolic number stimuli. Cross-format decoding analysis revealed a format-independent neural representation of quantity in the right parietal cortex for 5-year-olds, but not for 8-year-olds. This indicates that, after three years of formal education, brain representations of symbolic numbers are likely to become more independent from nonsymbolic quantity. This work has been published in PLOS Biology (Nakai et al., PLOS Biol 2023).
Second, the researcher performed model-based machine learning analysis using voxel-wise encoding models, based on fMRI data from eight participants solving math word and expression problems. Mathematical problems with different formats had similar cortical organization in the intraparietal sulcus, indicating that mathematical problems are represented in the brain in a format-invariant manner. Moreover, based on the same dataset, the researcher further constructed encoding models using artificial neural networks (ANNs) and found shared representations between ANN and brain activity patterns for mathematical problem solving. These results demonstrate that it is possible to perform model-based machine learning analysis using ANN features of mathematics. This work has been published in European Journal of Neuroscience (Nakai and Nishimoto, Eur J Neurosci 2023) and NeuroImage (Nakai and Nishimoto, NeuroImage 2023).
Third, the researcher performed a systematic review of brain-based machine learning applications on mathematical ability and other cognitive functions. The researcher reviewed articles with the cross-sectional and longitudinal designs in the literacy and numeracy domains, and described how they can be coupled with regression and classification approaches. The researcher argued that the field needs a standardization of methods, as well as a greater use of accessible and portable neuroimaging methods that have more applicability potential than lab-based neuroimaging techniques. This work has been published in Imaging Neuroscience (Nakai et al., Imag Neurosci 2024).
Overall, the project produced eight peer-reviewed articles and two preprints currently under-review, as well as participation in four international conferences, three workshops, one press release, and two articles in a general magazine. These results indicate that the project has reached beyond its initial objectives and has led to international and interdisciplinary collaborations, generating further research in related areas.