The title explains how the brain uses sensory information to develop and decide upon the appropriate action and how the brain determines the appropriate action to optimise the collection of new sensory information. Key questions answered include: How are percepts built up in the cortex and how are judgments of the percept made? In what way does information flow within and between cortical regions and what is accomplished by successive (and reverberating) stages of processing? How are decisions made about the percept subsequently acted upon, through their conversion to a response according to the learned criterion for action? How does the predicted or expected sensation interact with the actual incoming flow of sensory signals?