Over the last decade or so, much work has focussed on the interactions within and between the filtering modules performing local analyses. For example, contrast interactions have been found between neighboring regions on the retina in psychophysics (Ejima & Takahashi,
1985; Ishikawa, Shimegi, & Sato,
2006; Meese & Hess,
2004; Olzak & Laurinen,
1999; Petrov, Carandini, & McKee,
2005; Xing & Heeger,
2000), single-cell physiology (Born & Tootell,
1991; Cavanaugh, Bair, & Movshon,
2002a; Jones, Grieve, Wang, & Sillito,
2001; Levitt & Lund,
1997; Webb, Tinsley, Barraclough, Parker, & Derrington,
2003), and functional imaging (Ohtani, Okamura, Yoshida, Toyama, & Ejima,
2002; Williams, Singh, & Smith,
2003; Zenger-Landolt & Heeger,
2003). Interactions between different spatial frequency and orientation bands at the same location on the retina are also well known (Bonds,
1989; Burr & Morrone,
1987; DeAngelis, Robson, Ohzawa, & Freeman,
1992; Foley,
1994; Meese,
2004; Morrone, Burr, & Maffei,
1982; Ross & Speed,
1991). These studies of contextual modulation are valuable because they open the door to architectural and functional details of the early visual system. In particular, they have implications for contrast gain control (Carandini & Heeger,
1994; Foley,
1994; Levitt & Lund,
1997; Meese,
2004; Tolhurst & Heeger,
1997), image coding strategies (Felsen, Touryan, & Dan,
2005; Guo, Robertson, Mahmoodi, & Young,
2005; Olshausen & Field,
2005; Schwartz & Simoncelli,
2001), contour integration (Field, Hess, & Hayes,
1993; Hess, Dakin, & Field,
1998; Huang, Hess, & Dakin,
2006; Kapadia, Ito, Gilbert, & Westheimer,
1995; Polat & Sagi,
1993; Sillito, Grieve, Jones, Cudeiro, & Davis,
1995), border ownership (Sakai & Nishimura,
2006), and image segmentation (Born & Tootell,
1991; Grigorescu, Petkov, & Westenberg,
2004; Olzak & Laurinen,
2005), although probably not a pop-out phenomena in general (Hegdé & Felleman,
2003; Levitt & Lund,
1997).