Foveal masking impairs orientation discrimination of peripheral low-level stimuli

Feedback mechanisms are common in our visual system. However, the foveal feedback hypothesis proposes a new type of non-retinotopic feedback: shape and colour information from peripheral objects is fed back to the foveal cortex. We conducted three experiments to test if foveal feedback: a) occurs with low-level stimuli; b) is specific to shape discrimination; and c) is exclusive to the parvocellular system. In Experiment 1, participants performed a peripheral orientation discrimination task with Gabor patches, while a foveal mask was presented at various timings after peripheral stimuli onset (SOAs). We observed interference at a 182 ms SOA, confirming the feedback effect. In Experiment 2 we used stimuli designed to activate mainly either the magno- or parvocellular systems. We tested both orientation and contrast discrimination. Results showed that the foveal mask affected orientation discrimination in the same way for both systems, but had no clear effect on contrast discrimination. These results suggest that foveal feedback is not specific to the parvocellular system but is specific to shape analysis tasks. This suggests that we recruit foveal cortex for finer detailed shape analyses. This research contributes to a broader understanding of the interaction between central and peripheral vision.