A schema for the fundamental components of spatial attention. Representations (blue) encode sensory information about the world (green) as well as information about motor plans, internal state, stored memories, etc (not shown). All components of attention are carried out in the forebrain network (right). All components except working memory are also carried out in the midbrain network (left, red box). Information from working memory in the forebrain network is conveyed to the midbrain network by top-down signals, and retinotopic spatial information from forebrain representations is conveyed to the midbrain network. Salience and priority information in the midbrain network influences the forebrain representations, and competitive selection of a location in the midbrain network biases, and sometimes dominates, competitive selection for the next locus of attention in the forebrain network. Modified from Knudsen, in press.