Examining The Structure Of Symbolic Number Representations In The Parietal Cortex: An RSA Study
Abstract
Previous studies using fMRI adaptation to investigate the neural substrate of symbolic number processing have found ratio-dependent responses in regions of the parietal cortex, suggesting that number symbols are coded by overlapping neuronal populations: the larger the ratio between two numerals, the more their representation overlap. The current study analyzed the distributed patterns of activation associated with numerals presented during this task. I could not find substantial evidence supporting the ratio-dependent structure of the similarity space predicted by the univariate adaptation analyses. I also failed to find evidence in favor of the alternative model that similarities were driven by lexical frequency. These null results were confirmed by Bayesian analysis showing substantial support for the null. These findings do not align with the theory of ratio-dependent overlapping representation of number symbols and challenge previous interpretations of the adaptation literature.