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

Inferior parietal cortex, the angular gyrus and fact knowledge
The fMRI signal in the angular gyrus was stronger (i) when numerical range was
small, (ii) when problem size was small, (iii) when numbers were part of a multiplication
table, (iv) when no decade crossing occurred, and (v) when the distance to the mean
increased. Two main reasons for the activation of the angular gyrus shall be discussed: First,
the unspecific familiarity with relatively smaller numbers, and second, the capacity to monitor
procedural and rule-based information from different sources.
Familiarity with arithmetic problems
Small and more frequently encountered arithmetic problems establish stronger
representations. Therefore, they are solved more efficiently than larger and less frequent
problems (Domahs, Delazer and Nuerk, 2006). In the present study, stronger fMRI signal was
found in the anterior cingulate gyrus and retrosplenial cortex when range was small (Figure
1A). Additionally, when problem size was small (i.e. a triplet consisting of relatively small
numbers, e.g. 3_5_8), increased activation was observed in the left angular gyrus and in the
right angular gyrus to a smaller extent (Figure 1C). Generally, increased activation in the
anterior cingulate gyrus and the retrosplenial cortex is associated with processing more
familiar information (Sugiura, Shah, Zilles, & Fink, 2005; Shah et al., 2001). For the case of
the NBT this means that activation in the retrosplenial cortex and angular gyrus is associated
with the processing of smaller and/or easier triplets. Specifically, these are triplets with a
small problem size and spanning a small range. Thus, the higher familiarity with the numbers
constituting such triplets can be interpreted as a corollary of the higher exposure to them.
Additionally, activation in the angular gyrus was often accompanied by a small portion of the
superior prefrontal cortex being activated (e.g. Figure 3, multiplicative>non multiplicative
triplets contrast). Activation in this region may reflect the involvement of executive
mechanisms responsible for monitoring different cognitive features of the triplet (Brass and
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