Cerebral Hemispheres and Consciousness

This is the third of four online Companions to Velmans, M. (ed.) (2018) Consciousness (Critical Concepts in Psychology), a 4-volume collection of Major Works on Consciousness commissioned by Routledge, London. -/- The Companion to Volume 3 introduces major phases and findings in the search for the neural correlates of consciousness (NCC) starting with the time it takes for these to form and the wider research program that might lead to their discovery. This includes the search for mechanisms responsible for “neural (...) binding”—how widely dispersed neural activities support integrated conscious experiences, and the search for neural markers of consciousness that can serve to distinguish conscious from preconscious and unconscious activities in the brain. We then turn to global disorders of consciousness that indirectly reveal the conditions that support consciousness by establishing what abolishes it or impairs it, and conclude this section with reviews of the major challenges in the search for NCCs that still remain. This survey then continues with research on the divided brain with cerebral commissurotomy patients, which proved to be very useful in determining the respective functions of the left and right halves of the brain. It also raised philosophical questions. Could consciousness itself be divided by this operation? And, if so, would such patients have a distinct left-brain and right-brain consciousness? Philosophical issues also combine with methodological and experimental developments in the following sections on the reintroduction of first-person methods and how to combine these with complementary, third-person methods in neurophenomenology and experiential neuroscience—two well-developed research programs for both investigating consciousness and understanding its functions. This Companion (and associated Volume) then concludes with a survey of research on free will, covering both the major findings arising from neuropsychological research and a way to understand these that is consistent with a natural understanding of volition, ethics, and legal responsibility. -/- As with the other Companions to these Volumes there are many links to background resources (marked in pink) and to the selected readings themselves (marked in blue). -/- . (shrink)

The traditional verbal/nonverbal dichotomy is inadequate for completely describing cerebral lateralization. Musical functions are not necessarily mediated by the right hemisphere; evidence for a specialist left-hemisphere mechanism dedicated to the encoded speech signal is weakening, and the right hemisphere possesses considerable comprehensional powers. Right-hemisphere processing is often said to be characterized by holistic or gestalt apprehension, and face recognition may be mediated by this hemisphere partly because of these powers, partly because of the right hemisphere's involvement in emotional affect, and (...) possibly through the hypothesized existence of a specialist face processor or processors in the right. The latter hypothesis may, however, suffer the same fate as the one relating to a specialist encodedness processor for speech in the left. Verbal processing is largely the province of the left because of this hemisphere's possession of sequential, analytic, time-dependent mechanisms. Other distinctions are special cases of an analytic/holistic dichotomy. More fundamentally, however, the left hemisphere is characterized by its mediation of discriminations involving duration, temporal order, sequencing, and rhythm, at thesensory level, and especially at themotorlevel. Spatial aspects characterize the right, the mapping of exteroceptive body space, and the positions of fingers, limbs, and perhaps articulators, with respect to actual and target positions. Thus there is a continuum of function between the hemispheres, rather than a rigid dichotomy, the differences being quantitative rather than qualitative, of degree rather than of kind. (shrink)