The influence of the place-value structure of the Arabic number ...

ABSTRACT
Mental arithmetic and calculation rely on a complex network of multiple numerical
representations. Usually the components of this network are examined in a between-task
approach, which presents the disadvantage of relying upon different instructions, tasks and
inhomogeneous stimulus sets across experimental conditions. A within-task approach may
avoid these disadvantages and may access the numerical representations more specifically. In
the present study we employed a within-task approach to investigate the numerical
representations activated in the number bisection task (NBT) in a parametric rapid eventrelated
fMRI study. The only required instruction was to judge whether the middle number of
a triplet was also their arithmetic mean (23_26_29) or not (23_25_29). Activity in the left
inferior parietal cortex was associated with the deployment of verbal number (fact)
representations, while activation of the intraparietal cortex was associated with deeper
magnitude processing, instrumental aspects of calculation and activation of the base-10
structure of two-digit numbers. These results replicate strong evidence from the literature.
Furthermore, activation in the dorsolateral and ventrolateral prefrontal cortex reveals
mechanisms of feature monitoring and inhibition and allocation of cognitive resources in
order to solve a specific triplet. We conclude that the network of numerical representations
should be studied in a within-task approach and not only with between-task approaches.
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