The Neural Mechanism of Number Line Bisection: A fMRI study.

The neural networks involved in number line bisection are poorly understood. We used functional magnetic resonance imaging (fMRI) to investigate these. fMRI was analyzed from 28 healthy volunteers who performed number and physical line bisection tasks (and their respective baselines). Whole brain analyses showed that these two bisection tasks shared common neural correlates in bilateral parietal-frontal networks; furthermore, bilateral parietal-frontal areas, right cerebellum, left insula and supplementary motor area (SMA) showed higher activity when contrasting the number line with a physical line bisection task. Importantly, psychophysiological interaction (PPI) analyses further indicated that left SMA and right cerebellum were connected to parietal-frontal areas for implementing the number line bisection task. Our findings suggested that a visuospatial attention control system was recruited, and mental imagery of a number line was used to find the midpoint of a numerical interval without calculations.