time and indexing visual objects helps to ground visual concepts. Feature integration theory Summary of problem The visual feature binding problem refers to the question of why we do not confuse a red circle and a blue square with a blue circle and a red square. The understanding of the circuits in the brain stimulated for visual feature binding is increasing. A binding process is required for us to accurately encode various visual features in separate cortical areas. In her feature integration theory, Treisman suggested that one of the first stages of binding between features is mediated by the features' links to a common location. The second stage is combining individual features of an object that requires attention, and selecting that object occurs within a "master map" of locations. Psychophysical demonstrations of binding failures under conditions of full attention provide support for the idea that binding is accomplished through common location tags. An implication of these approaches is that sensory data such as color or motion may not normally exist in "unallocated" form. For Merker: "The 'red' of a red ball does not float disembodied in an abstract color space in V4." If color information allocated to a point in the visual field is converted directly, via the instantiation of some form of propositional logic (analogous to that used in computer design) into color information allocated to an "object identity" postulated by a top-down signal as suggested by Purves and Lotto (e.g. There is blue here + Object 1 is here = Object 1 is blue) no special computational task of "binding together" by means such as synchrony may exist. (Although Von der Malsburg poses the problem in terms of binding "propositions" such as "triangle" and "top", these, in isolation, are not propositional.) How signals in the brain come to have propositional content, or meaning, is a much larger issue. However, both Marr and Barlow suggested, on the basis of what was known about neural connectivity in the 1970s that the final integration of features into a percept would be expected to resemble the way words operate in sentences. The role of synchrony in segregational binding remains controversial. Merker has recently suggested that synchrony may be a feature of areas of activation in the brain that relates to an "infrastructural" feature of the computational system analogous to increased oxygen demand indicated via BOLD signal contrast imaging. Apparent specific correlations with