Figure 10.

T-junctions and end gaps in figure-ground perception. (A) T-Junction Sensitivity: (left panel) T-junction in an image. (middle panel) Bipole cells activate long-range recurrent excitatory horizontal connections (cooperation, +) and also short-range inhibitory interneurons (competition, −); (right panel). An end gap in the vertical boundary arises because, for cells near where the horizontal top and vertical stem of the T come together, the top of the T activates bipole cells along the top of the T much more than bipole cells are activated along the T stem. As a result the stem boundary gets inhibited by the short-range inhibitory signals from the horizontal bipole cells, whereas the top boundary does not receive comparable inhibition from the vertical bipole cells (Reprinted with permission from Grossberg, 1997). (B) Necker cube. This 2D picture can be perceived as either of two 3D parallelopipeds whose shapes flip bistably through time. (C) When attention switches from one circle to another, that circle pops forward as a figure and its brightness changes. See text and Grossberg and Yazdanbakhsh (2005) for an explanation. Reprinted with permission from Tse (2005).