Feature-based attention enhances motion processing during dominance and suppression in binocular rivalry

摘要

Goal. Feature-based attention enhances the neuronal and perceptual representation of consciously perceived visual objects. But can feature-based attention also modulate responses to stimulus properties we are unaware of? Here we use binocular rivalry flash suppression to compare the effects of feature-based attention on perceptual and eye movement responses to visual motion in the presence and absence of visual awareness. Method. Stimuli were two orthogonally oriented, leftward or downward moving sine-wave gratings presented separately to each eye through a stereoscope. We used binocular rivalry flash suppression to manipulate stimulus visibility, rendering one stimulus dominant and the other suppressed. In each trial, the speed of either the dominant or suppressed stimulus briefly increased or decreased for 50 ms. Attention was directed to either leftward or downward motion by a 75%-valid arrow cue. In two judgments observers indicated (1) whether the speed change was an increment or decrement and (2) their perceived motion direction. Eye movements were recorded throughout each trial. Results. Feature-based attention affected (1) speed discrimination and (2) motion processing. (1) Performance in the speed change discrimination task was better for the dominant than suppressed stimulus. It was also better for attended than for unattended stimuli, regardless of whether the stimulus was dominant or suppressed. These findings indicate that observers successfully deployed attention to either leftward or downward motion. (2) When the suppressed stimulus was attended, perceptual and eye movement responses were shifted towards the motion direction of the suppressed stimulus. This study therefore shows that feature-based attention can affect motion processing as assessed by perception and eye movements, even when a stimulus is substantially weakened through binocular rivalry.