Figure 6. Architecture of spatial attention (Cavanagh et al, 2010).

A network of areas form a target map that subserves spatial attention as well as eye movements. Peaks of activity (in red) index the locations of targets and specify the retinotopic coordinates at which the target’s feature data are to be found in earlier visual cortices which are shown, highly simplified, as a stack of aligned areas divided into right and left hemifields with the fovea in the center. In object recognition areas, cells have very large receptive fields shown here as a heavy black outline for the receptive field of one cell that specializes in identifying pickup trucks. These cells must rely on attention to bias input in favor of the target and suppress surrounding distractors so that only a single item falls in the receptive field at any one time. The surround suppression has to be imposed in early retinotopic areas as the large fields in object recognition cannot have local modulation of sensitivity.