Thalamocortical Pathways and Consciousness

Abstract

The relatively orderly series of discoveries of the functional organization of the cerebral cortex, in which anatomy and physiology often shared a certain simultaneity of discovery (as in the production of movement when precentral gyri are stimulated), did not characterize the exploration of structures beneath the cortex. On the contrary, the subcortical regions of the brain were dissected and anatomic structures described and named in profusion before any correct function was assigned to them. The major reason for the discrepancy between the rapid advance of anatomical knowledge and the slow elucidation of its related physiology was, paradoxically, the lack of a methodology to precisely locate structures deep in the living brain. Even though electrophysiologic techniques applied to peripheral nerves were advancing, their utility for investigation of the central nervous system depended on reliable localization. A second hurdle was the confused nomenclature that muddled any new information about the thalamus. In this and subsequent chapters, the history of the discoveries of some prominent sub-cortical structures and their functions is explored with emphasis on the novel developments in methodology that were essential for further progress.

O’what a world of unseen visions and heard silences, this insubstantial country of the mind!”

(Jaynes, 1976, p. 1)