The neural origin of the priming distance effect: distance-dependent recovery of parietal activation using symbolic magnitudes.

Numerical magnitudes are known to be processed in areas around the intraparietal sulci of the brain. We used an fMRI-adaptation paradigm to investigate how they are actually coded at the neural level. In a number identification task, we manipulated the numerical distance between prime and target numbers (same, close, and far pairs) and their symbolic notation (Arabic and verbal numerals). We show that bilateral parietal activations present a distance-dependent recovery of activation positively correlated with the distance between primes and targets: the larger the prime-target distance, the higher the recovery of activation. Importantly, this effect is only present for trials where an Arabic numeral precedes a verbal numeral and not the reverse. Together, these findings reveal the neural origin of the behavioral priming distance effect and demonstrate that the relative importance of the semantic and nonsemantic pathways in a dual-route model of number processing is modulated by symbolic notation.