Apparent Motion Induces Activity Suppression in Early Visual Cortex and Impairs Visual Detection.

Apparent motion (AM) is induced when two stationary visual stimuli are presented in alternating sequence. Intriguingly, AM leads to an impaired detectability of stimuli along the AM path (i.e., AM-induced masking). It has been hypothesized that AM triggers an internal representation of a moving object in early visual cortex, which competes with stimulus-evoked representations of visual stimuli on the motion path in early visual cortex of 25 human adults (16 female). We tested this hypothesis by measuring BOLD responses in early visual cortex during the process of AM-induced masking, using fMRI and population receptive field methods. Surprisingly, and counter to our hypothesis, we showed that AM suppressed, rather than increased, BOLD responses along early visual (V1 and V2) representations of the AM path, including regions that were not directly activated by the AM inducer stimuli. This activity suppression of the visual response predicted the subsequent reduction in detectability of the target that appeared in the middle of the AM path. Our data thereby provide direct empirical evidence for suppressive neural mechanisms underlying AM and suggest that illusory motion can render us blind to objects on the motion path by suppressing neural activity at the earliest cortical stages of visual perception.