Almost all of the messages that are received by the cerebral cortex from the environment or from the body's internal receptors come through the thalamus and much current thought about perceptual processing is based on sensory pathways that relay in the thalamus. This volume focuses on three major areas: the role of thalamocortical communication in cognition and attention; the role of the thalamus in communication between cortical areas; the hypothesis that much or all of the information relayed by thalamus, even to classical, pure "sensory" areas of cortex, represents a corollary message being sent simultaneously to motor centers. It presents a broad overview of important recent advances in these areas.