This article examines the anatomy and circuitry of skills that, like reading, calculating, recognizing, or remembering, are common abilities of humans. While the anatomical areas active are unique to each skill there are features common to all tasks. For example, all skills produce activation of a small number of widely separated neural areas that appear necessary to perform the task. These neural areas relate to internal codes that may not be observed by any external behavior nor be reportable by the (...) performer. There is considerable plasticity to the performance of skills. Task components can be given priority through attention, which serves to increase activation of the relevant brain areas. Attention can also cause reactivation of sensory areas driven by input, but usually only after a delay. The threshold for activation for any area may be temporarily reduced by prior activation . Skill components requiring attention tend to cause interference resulting in the dual tasks effects and unified focus of attention described in many cognitive studies. Practice may change the size or number of brain areas involved and alter the pathways used by the skill. By combining cognitive and anatomical analyses, a more general picture of the nature of skill emerges. (shrink)

Norman's aim to reconcile two longstanding and seemingly opposed philosophies of perception, the constructivist and the ecological, by casting them as approaches to complementary subsystems within the visual brain is laudable. Unfortunately, Norman overreaches in attempting to equate direct perception with dorsal/unconscious visual processing and indirect perception with ventral/conscious visual processing. Even a cursory review suggests that the functional and neural segregation of direct and indirect perception is not as clear as the target article would suggest.

ERP studies have shown modulation of activation in left frontal and posterior cortical language areas, as well as recruitment of right hemisphere homologues, based on task demands. Furthermore, blood-flow studies have demonstrated changes in the neural circuitry of word processing based on experience. The neural areas and time course of language processing are plastic depending on task demands and experience.