Priming for motion direction with first- and second-order stimuli

Priming for first-order motion has been shown to rely on the functional integrity of area V5/MT (Campana et al, 2002 Cerebral Cortex 12 663 - 669). The retinotopicity of this area would predict a reliance of direction priming on spatial position. In order to test this hypothesis, and to see whether a similar priming exists with second-order motion, we tested motion direction priming and its interaction with spatial position with both first- and second-order motion. Indeed, mechanisms and neural substrates mediating implicit memory for these two types of motion perception are still unknown. Our results indicate that motion-direction priming occurs not only with first-order, but also with second-order motion. Priming for motion direction is position-sensitive with both types of motion, suggesting for both a locus of representation within the V5/MT complex, where retinotopicity is still maintained. Finally, cross-order motion priming also exists, but is not sensitive to spatial position, suggesting a neural locus where processings of first- and second-order motion converge in MST or beyond.