THALAMIC CONTRIBUTIONS TO ATTENTION AND CONSCIOUSNESS

A tacit assumption since the 19th Century has been that the neocortex serves as the ''seat of consciousness.'' An unexpected challenge to th at assumption arose in 1949 with the discovery that high-frequency EEG activation associated with an alert state requires the intactness of the brainstem reticular formation. This discovery became the impetus f or nearly three decades of research on what came to be known as the re ticular activating system. By the 1970s, however, methodological and p hilosophical controversies led to the general abandonment of subcortic al theories of attention and consciousness, with a return to an almost exclusive focus upon the cortex. With recent advances in the neurosci ences the focus is shifting once more, this time to the unique contrib utions of cortical, thalamic, and brainstem structures in mediating se lective attention and perceptual awareness. This paper offers a nontec hnical review of the history of these developments up to contemporary interest in the putative role of oscillatory EEG patterns in the integ ration of perceptual features of experience. It puts forward the thesi s that a key to understanding attention and consciousness is an apprec iation of the contributions of the thalamus to these cognitive process es. (C) 1995 Academic Press, Inc.