Visual awareness is constrained by the functional organization of the higher-level visual system
Cohen, Nakayama, Konkle, & Alvarez
The limits of visual awareness are often attributed to a fi nite supply of visual
attention (Chun & Wolfe, 2001) and processing constraints of the prefronto-parietal
network (Dehaene & Changeux, 2011). Here, we investigate the
extent to which the limits of visual awareness are related to representational
constraints within the higher-level visual system. To measure the limits of
visual awareness, we used two different behavioral paradigms that render
stimuli invisible. In Experiment 1, we used visual masking to measure how
well items from different categories mask one other (e.g., buildings masking
cars). In Experiment 2, we used continuous fl ash suppression to measure
how long it takes an item from one category (e.g., a face) to break through
suppression by items from another category (e.g., bodies). We then used
fMRI to measure the similarity of the neural responses elicited by those
categories across the visual hierarchy and used representational similarity
analysis (Kriegeskorte & Kievit, 2013) to compare the behavioral and neural
results. In both experiments, we found that pairs of categories that strongly
mask and suppress each other in behavior also elicit more similar neural
response patterns. Brain/behavior correlations were strong within ventral
occipital cortex (Exp. 1: r=0.84*; Exp. 2: r=0.64*) and lateral occipital cortex
(Exp. 1: r=0.70*; Exp. 2: r=0.73*), weaker within occipitoparietal cortex (Exp.
1: r=0.52*; Exp. 2: r=0.44), and not signifi cant within V1-V3 (Exp. 1: r=0.05;
Exp. 2: r=-0.39). Together, these results show that the organization of higher-level
visual cortex predicts the degree to which different stimuli will
compete for visual awareness. We suggest that this organization imposes
a limit on the capacity of visual awareness. Under this view, the extent to
which items activate overlapping, capacity-limited neural channels constrains
the amount of information that can be accessed by visual awareness.
Cohen, M., Nakayama, K., Konkle, T., Alvarez, G. (2015).
Visual awareness is constrained by the functional organization of the higher-level visual system.
Poster presented at the annual meeting of the Vision Sciences Society, May 15-20, St. Pete Beach, FL.