27.12.2013 Views

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

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

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

SHOW MORE
SHOW LESS

You also want an ePaper? Increase the reach of your titles

YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.

strategic <strong>value</strong> <strong>of</strong> retrieving this information, since multiplicative triplets formed only 12.5 %<br />

<strong>of</strong> all triplets instead <strong>of</strong> 25 % in <strong>the</strong> original study by Nuerk et al. (2002); and second, by<br />

reduced executive resources <strong>of</strong> both controls and patients. In <strong>the</strong> original study by Nuerk et al.<br />

(2002), 25 % <strong>of</strong> all triplets were part <strong>of</strong> a multiplication table. <strong>The</strong>refore, activating <strong>the</strong><br />

representation <strong>of</strong> multiplicativity was relevant for improving performance, as half <strong>of</strong> <strong>the</strong><br />

“Yes” responses could be determined by <strong>the</strong> recognition <strong>of</strong> multiplicatively related triplets. In<br />

<strong>the</strong> present study, only 12.5 % <strong>of</strong> all triplets were part <strong>of</strong> a multiplication table. This<br />

difference in <strong>the</strong> proportion <strong>of</strong> multiplicatively related triplets may have an impact on <strong>the</strong><br />

strategic relevance <strong>of</strong> multiplicativity. As it is strategically less relevant in <strong>the</strong> present study,<br />

<strong>the</strong> effect <strong>of</strong> multiplicativity may have disappeared.<br />

Moreover, automatically activating multiplication fact knowledge may have been<br />

hampered by general reductions in <strong>the</strong> capacity <strong>of</strong> neglect patients and control participants to<br />

monitor and integrate information from different sources in parallel due to age. In a recent<br />

fMRI study on <strong>the</strong> NBT, Wood et al. (submitted) showed that <strong>the</strong> left angular gyrus and in <strong>the</strong><br />

superior frontal gyrus were sensitive to multiplicativity. While <strong>the</strong> left angular gyrus may be<br />

associated with <strong>the</strong> retrieval <strong>of</strong> multiplication facts (cf. Dehaene et al., 2003; Delazer et al.,<br />

2003), <strong>the</strong> superior frontal gyrus was linked to <strong>the</strong> monitoring <strong>of</strong> potentially relevant<br />

information from different sources (e.g. Brass & von Cramon, 2005). Although <strong>the</strong>re is no<br />

reason to doubt that older patients as well as neglect patients can access <strong>the</strong> representation <strong>of</strong><br />

multiplicativity, <strong>the</strong>y may not have monitored for <strong>the</strong> multiplicativity in <strong>the</strong> present study due<br />

to limitations in executive resources and working memory (Doricchi, Guariglia, Gasparini,<br />

Tomaiuolo, 2005).<br />

CONCLUSIONS<br />

Neglect impairs <strong>number</strong> processing <strong>of</strong> two-digit <strong>number</strong>s in a specific way: neglect<br />

patients seem to neglect <strong>the</strong> left part <strong>of</strong> a given numerical interval activated on a spatially<br />

223

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!