Progress in executive-function research: From tasks to functions to regions to networks

It has long been observed that damage to the frontal cortex affects a person's ability to control thought, behavior, and emotion while sometimes leaving fundamental processes such as vision, hearing, and long-term memory intact. Such observations have led theoreticians to suppose that a set of executive control functions exists, at the top of the hierarchy of mental processes. To study these executive functions and their relation to the frontal cortex and its subregions, researchers have long employed several now-classic cognitive tests in patients with brain damage. Yet until recently it has proved difficult to reliably localize the putative executive functions to discrete regions. This article illustrates how recent progress in executive-functions research has been driven by the coupling of sophisticated neuroscience techniques with advances in experimental psychology. Taking examples from recent studies, it shows how experimental tasks may be decomposed into cognitive components that can be localized to discrete-but structurally connected-brain regions. What emerges is a new ontology for executive function in terms of which cognitive components exist and of how, and when, they are recruited during task performance.