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NUM-SPACE RE-ORIENTATION: Visuo-spatial reorientation induced by numbers during a free visual scanning in healthy participants and hemineglect patients

Numbers induce shifts of spatial attention on the left or the right sides of external space as a function of their magnitude (e.g. de Hevia et al., 2006). However, the mechanisms underlying number-space associations are not yet fully understood. The present Post-Doc project, aims to examine how spatial reference frames affect spatio-numerical associations.

To this aim we will firstly present young healthy participants with a horizontally or vertically oriented numeral star cancellation task (Di Luca et al., 2013), to investigate the influence of numerical magnitude during a free visual scanning scene. Although very simple, this manipulation will provide unprecedented insights into the influence of spatial reference frames on number-space associations and inner representations, because all previous paradigms were constrained around one (predominantly the horizontal) axis used at a time. In addition to measuring how attention is freely oriented within a 2-dimensional display, the implementation of the cancellation task on a tablet pc also yields powerful and extremely precise possibilities for analyses based on positional, speed and acceleration of vector data, as well as the pressure of the marks. The development and use of this new analytic tool will be another important asset of the present project, that will be especially useful for the second study in which we will explore  whether and how numbers orient visuo-spatial attention in neglect patients. Patients with spatial neglect after right-sided brain lesions not only have a bias to orient and interact in physical space, but they can also suffer from a similar bias when processing numbers (Priftis et al., 2006). Here, we will present neglect patients with a series of numeral cancellation tasks under different instructions (i.e. cancel all digits vs. only small/large digits vs. only odd/even) to highlight those conditions in which numbers can reorient spatial attention, and show that numbers could also be used as therapeutic tool in neglect rehabilitation.

For further information, please do not hesitate to contact christine.schiltz@uni.lu.