Cathodal tDCS stimulation of left anterior temporal lobe eliminates cross-category color discrimination response time advantage.

The linguistic category-advantage in color perception refers to better discrimination performance for stimuli that belong to different categories (e.g., green vs. blue) than equidistant stimuli from the same category (e.g., blue). Despite the robust nature of category-advantage in color perception, the related cognitive and neural mechanisms are not fully understood. Some views attribute this effect to early alteration of visual processing of color while others attribute it to post-perceptual conceptual processing. The current study investigated the causal role of the left anterior temporal lobe (ATL), as a post-perceptual semantic hub, in categorical color perception. We modulated the activity of the left ATL via cathodal tDCS or sham stimulation (within-subject) while participants were discriminating between successive presentations of color patches. Without stimulation, we found a category-advantage effect in both accuracy and response times. The inhibition of left ATL eliminated the category-advantage effect in terms of RTs but not accuracies. Our results point at the causal role of ATL in categorical color perception and provide indirect support for a post-perceptual processing account of this robust phenomenon.