Using single cases to understand visual processing: The magnocellular pathway

Abstract

Vannuscorps et al. (2021b) report on an individual (Davida) with a developmental deficit who consistently perceived stimuli as rotated around and/or mirrored across the object’s primary axes. Interestingly, Davida was unimpaired under a variety of conditions. Her ability to judge stimulus orientation was excellent when using touch without vision, for three-dimensional objects, and for two-dimensional objects that were blurred, low contrast, moving, or flickered. Her errors instead occurred for two-dimensional stimuli that were sharp, high contrast, stationary and sustained. This pattern is consistent with proposals suggesting a distinction between two visual pathways, a magnocellular pathway (M-pathway or transient system) specialized for brief, moving, low contrast stimuli, and a parvocellular pathway (P-pathway or sustained system) specialized for stationary, high spatial frequency stimuli.