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

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<strong>number</strong>s within <strong>the</strong> triplets, processes <strong>of</strong> <strong>place</strong>-<strong>value</strong>, i.e., unit-decade, integration also<br />

deteriorated <strong>the</strong> fur<strong>the</strong>r left <strong>the</strong>y occurred in <strong>the</strong> neglected area upon <strong>the</strong> mental <strong>number</strong> line.<br />

This finding is <strong>of</strong> particular interest as <strong>the</strong> similar gradients <strong>of</strong> impaired magnitude as well as<br />

impaired <strong>place</strong>-<strong>value</strong> processing again suggested that <strong>place</strong>-<strong>value</strong> characteristics <strong>of</strong> <strong>number</strong>s<br />

may be inherent in <strong>the</strong> human <strong>number</strong> magnitude representation.<br />

Moreover, this evidence from neuropsychological patients was fur<strong>the</strong>r corroborated by<br />

a functional MRI study presenting a similar <strong>number</strong> bisection task to healthy adult<br />

participants to evaluate <strong>the</strong> neural correlates <strong>of</strong> processes <strong>of</strong> <strong>place</strong>-<strong>value</strong> integration such as<br />

<strong>the</strong> decade crossing effect. As previously observed for <strong>the</strong> case <strong>of</strong> <strong>number</strong> magnitude<br />

comparison and in particular <strong>the</strong> compatibility effect reflecting demands on <strong>place</strong>-<strong>value</strong><br />

processing (cf. Wood, Nuerk, & Willmes, 2006) increased activation <strong>of</strong> <strong>the</strong> intraparietal<br />

sulcus (IPS), bilaterally was associated with specific processing <strong>of</strong> decade crossings.<br />

Interestingly, <strong>the</strong> IPS is also generally agreed to be essentially involved in <strong>the</strong> representation<br />

<strong>of</strong> <strong>number</strong> magnitude in general (see Dehaene, Piazza, Pinel, & Cohen, 2003; Nieder &<br />

Dehaene, 2009, for reviews). And again, <strong>the</strong>se data suggest that <strong>the</strong> <strong>place</strong>-<strong>value</strong> structuring<br />

principle <strong>of</strong> <strong>the</strong> <strong>Arabic</strong> <strong>number</strong> system may be implemented into <strong>the</strong> human representation <strong>of</strong><br />

numerical magnitude. Never<strong>the</strong>less, triplets crossing into <strong>the</strong> next decade were also associated<br />

with increased neural activation in prefrontal cortex areas. Previously, increased activation <strong>of</strong><br />

prefrontal sites was observed in mental addition in general and for carry addition problems /<br />

borrowing subtraction problems, in particular (e.g., Kong et al, 2005; Imbo, Vandierendonck,<br />

& De Rammelaere, 2007). Both, <strong>the</strong> carry as well as <strong>the</strong> borrowing procedure in addition and<br />

subtraction, respectively, require processes <strong>of</strong> <strong>place</strong>-<strong>value</strong> integration (e.g., updating <strong>the</strong> sum<br />

<strong>of</strong> <strong>the</strong> decade digits <strong>of</strong> <strong>the</strong> summand by <strong>the</strong> carry). Generally, this increased prefrontal<br />

activation is interpreted to reflect increased demands <strong>of</strong> cognitive control / working memory /<br />

or attentional processes in carry addition / borrowing subtraction problems required for<br />

keeping intermediate results in mind, monitoring <strong>the</strong> columnwise solution process and finally<br />

317

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