Investigating the influence of contextual information on the processing of degraded feedforward visual information (v1)

The influence of top-down predictions on visual processing is broadly accepted. However, the mechanism by which predictions exert an effect at the neuronal level is still debated. Some accounts postulate that the representation of predictable sensory information is enhanced, whereas others suggest that unpredictable sensory information drives greater cortical responses, as an error response. Using human fMRI in visual cortex, we tested whether top-down predicted information amplifies low contrast feedforward input. We used a partial visual occlusion paradigm in which we presented a series of natural scenes with the lower right image quadrant shown at low contrast, thus degrading the feedforward input to a region of early visual cortex. The content of the occluded region either matched or did not match the rest of the scene, manipulating the consistency (and therefore predictability) of the contextual information. Using 3T fMRI, we investigated the cortical BOLD response to this contextual modulation in early visual cortex. We report two experiments in which the contrast of the occluded region was either shown at 50% threshold-level or at 75% threshold-contrast.