A major aim of Jon Driver's research was to identify principles by which the brain selects behaviorally relevant stimuli or thoughts for in-depth processing. His insights have shaped neurobiological models of selective attention that highlight top-down modulations of sensory cortex as a neural substrate of adaptive behavioral control. In this paper, I review research on the characteristics and neural origins of such top-down modulations. The studies reviewed show that neural processing in sensory cortical areas can be biased toward behaviorally relevant stimuli and thoughts by feedback projections from frontal and parietal brain areas. Such modulatory influences are similarly present for judgments about external sensory information (during attention) or internal representations (during imagery and short-term memory), potentially reflecting common neural mechanisms that enhance sensory processing of relevant neural signals. How such top-down control processes may ultimately be guided by motivational brain systems is a topic of current debate, for which Jon Driver's work will continue to provide important inspiration.