Space by the numbers

Numerical and spatial abilities have been correlated on many occasions. People who tend to be more proficient at spatial tasks also tend to be more proficient at mathematical operations and understanding of numbers. The current work takes several approaches to describe this relationship in further detail by investigating the role of attentional systems and executive control with regards to the processing of numbers and quantities. In a first attempt to do so we provide two studies whose goal it was to replicate the classical association between Arabic digits and response modality (SNARC-effect) and the association between Arabic digits and attentional shifts (Attentional SNARC-effect).
In two further studies, we investigated the role of the Attentional SNARC-effect with regards to visual processing and consciousness. In the first of these studies, we made use of a backwards-mask to obscure a single Arabic digit from conscious processing, resulting in the loss of its spatial association in a line-bisection task.
Secondly, we used a novel binocular rivalry paradigm to suppress two lateral stimuli from conscious perception and found that the duration of suppression was influenced by the numerical magnitude of a single presented Arabic digit. Specifically, we found that a stimulus on the left side of space would return faster when the Arabic digit was lower than five and that the right side of space would exhibit the same effect when the Arabic digit was higher than five.
A crucial manipulation in these last two experiments was an adaptation to the original paradigm for measuring the attentional SNARC-effect. By adding a control-question on the magnitude or parity at the end of each trial, we ensured that the spatial effects would occur during these experiments. Furthermore, this effectively turned the experiments into working-memory tasks.
Finally, we tested the influence of a visuo-spatial working-memory task and an addition-task on fronto-parietal network associated with mathematical operations in an event-related fMRI-experiment. This experiment included members of three populations with different levels of mathematical proficiency (Children with Developmental Dyscalculia, Typically developing children and Typical Adults). We found that brain-areas associated with executive control and basic visual processing were affected differently for children with developmental dyscalculia, hinting at a deficiency in visuo-spatial processing in this particular group.