Thus, we expect the VEP latency to attended stimuli to be shorter than that to stimuli in the unattended portion of the visual field. In addition, we tested the hypothesis that such a priority mechanism relies on the fast-transmission magnocellular system. Luminance or colour contrast gratings were used to maximize the activation of magnocellular or parvocellular pathways. For luminance stimuli, both latency and amplitude of VEPs were modified by attention. On the other hand, for colour gratings, attention affected only the amplitude, not the latency.
Spatial attention uses different mechanisms when magno or parvo systems are preferentially involved.