This monograph is based on two symposia organized by the Neurosciences Institute at The Rockefeller University. Presents current knowledge on the thalamus and views the thalamus as a whole rather than as a collection of unrelated nuclear masses. Chapters are organized in four sections--history, morphology, electrophysiology, and state-related cellular modes. Topics addressed include the structure and function of intrinsic thalamic circuitry, thalamic modulation by cortical and brain-stem projections, and the feedback onto the brain stem of thalamocortical and paleocortical transactions.