Li Zhaoping¹ (); ¹University of Tuebingen, Max Planck Institute for Biological Cybernetics

Consider a gray field comprising pairs of vertically aligned dots; in each pair, one dot is white the other black. When viewed in a peripheral visual field, these pairs appear horizontally aligned. This misperception of an orientation of such dot pairs by 90 degrees is called the flip tilt illusion (Zhaoping 2020). It arises because, according to the central-peripheral dichotomy (CPD) theory (Zhaoping 2019), top-down feedback from higher to lower visual cortical areas is too weak or absent in the periphery to veto confounded feedforward signals from the primary visual cortex (V1). The white and black dots in each pair activate, respectively, on and off subfields of V1 neural receptive fields. However, the sub-fields' orientations, and the preferred orientations, of the most activated neurons are orthogonal to the dot alignment. Hence, V1 reports the flip tilt to higher visual areas, assuming that an information bottleneck admits only information via these misleading V1 signals to feedforward to downstream brain areas along the visual pathway for perceptual outcome. Top-down feedback vetoes such misleading reports by querying for additional information from V1 (e.g., through activities of other V1 neurons), but only in the central visual field according to the CPD theory, making the illusion invisible in central vision. This work investigates whether this illusion can appear in the central visual field when the top-down feedback is compromised by backward masking. This study is ongoing and has so far preliminary findings, a fuller account will be reported at the annual conference.

Acknowledgements: partly supported by the Max Planck Society and the University of Tübingen