Performance depends on both stages, often leaving unclear the relative participation of each stage of processing. The standard model of global form processing involves two stages: a first stage of orientation filtering of dot pairs and a second stage of integration of locally derived orientations (Dakin & Bex, 2002 Wilson & Wilkinson, 1996 Wilson et al., 1997). When contrast effects (thought to be at stage 1) are factored out, there is little or no eccentricity or velocity dependence, suggesting that the efficiency of the stage 2 integration does not change with velocity or eccentricity (Hess & Aaen-Stockdale, 2008).Ĭertainly, the use of dots in glass patterns have provided evidence for a global processing stage that some (Wilson et al., 1997) have argued preferentially feeds into global detectors interested in rotational shapes (also see Dakin & Bex, 2002). Our ability to detect global motion is limited by two stages of processing (Morrone, Burr, & Vaina, 1995): the initial stage of local motion transduction, thought to be in striate cortex, and a later stage of global integration of these local motions, thought to be in extrastriate cortex. The ability of the visual system to detect the motion direction of the signal elements in the presence of noise is thought to reflect the integrative and segregative properties of neurons in the dorsal pathway and, in particular, area MT/MST (Newsome & Pare, 1988). Global motion stimuli consist of an array of moving elements where some are moving in a coherent direction (termed signal) and the rest are moving in a random direction (termed noise). This latter ability is often referred to as global processing and has been studied more extensively in terms of motion processing (Hess & Aaen-Stockdale, 2008 Morgan & Ward, 1980 Newsome & Pare, 1988 Williams & Brannan, 1994 Williams & Sekuler, 1984). Our visual abilities involve not only the detection of localized low contrast static or moving stimuli, but also the integration of form and motion information that extends across space.
0 Comments
Leave a Reply. |