p167fig04.43 (a) How bipole cells cause end cuts. (b) The Necker cube generates a bistable percept of two 3D parallelopipeds. (c) Focusing spatial attention on one of the disks makes it look both nearer and darker, as (Tse 1995) noted and (Grossbert, Yazdanbakhsh 1995) explained.<BR>|| T-junction sensitivity.  image -> bipole cells -> boundary.  (+) long-range cooperation, (-) short-range competition.