Noise reduction in the visual motion system: The connection between counter-phase motion and flicker noise

Motion opponency is a stage common to many motion processing models involving the combination of local motion vectors in space. Motion opponency functions as a mechanism for noise reduction during motion processing. Previous work has found evidence that human brains implement motion opponency, as locally-balanced and opposing motions (counter-phase stimuli) are known to elicit a weak response at human brain area MT+. This dissertation examines opponency, comparing counter-phase stimuli with novel flicker noise stimuli in psychophysical and neuroimaging experiments. Multivariate classification analyses found that the patterns of activation elicited by counter-phase stimuli were similar to that elicited by flicker stimuli. Furthermore, area V3A was strongly implicated as a participant in the brain’s motion opponency network. This work demonstrates the extent to which opponency selectively targets the locally-balanced motion signals common in flicker noise that suggests that brain’s implementation of noise reduction during motion processing is bigger than simply suppression of MT+ inputs originating from antagonistic V1 neurons