Hole superiority effect with 3D figures formed by binocular disparity.

The global-first theory of topological perception claims that topological perception is prior to the perception of local features (e.g., Chen, 1982, 2005). Our previous studies demonstrated a hole superiority effect (HSE): Figures with holes are more detectable than figures without holes. Such an HSE was shown with figures formed by either orientation-defined texture (Zhang, 2009) or a black-and-white contrast (Meng, Cui, Zhou, Chen, & Ma, 2012). The present study used binocular disparity as one more organizing factor for testing the abstract nature of the HSE, indicating holes, as a typical kind of topological invariance, are represented in vision independent of the features that were forming the holes. The disparity-forming figures were well controlled for luminance, spatial frequency, subjective contours, and other nontopological factors, which are commonly considered as counter explanations against the topological theory.

Separation effect of early visual cortex V1 under different crowding conditions: a transcranial magnetic stimulation study.

The visual crowding makes it difficult to identify the patterns in peripheral vision, but the neural mechanism for this phenomenon is still unclear because of different opinions. To study the separation effect of early visual cortex V1 under different crowding conditions, single-pulse transcranial magnetic stimulation (TMS) is applied within the right V1. The experimental design includes two factors: TMS intensity (10%, 65%, and 90% of the phosphene threshold) and crowding conditions (high and low). The accuracy results show that there is a strong interaction between crowding and TMS conditions. When the TMS intensity is 65% or 90% of the phosphene threshold, more crowding will be perceived under the high crowding condition, and less crowding under the low crowding condition. We concluded that the high and the low crowding conditions can be separated by TMS. These results support the assumption that the crowding is related to V1 and occurs in the visual coding phase.