Citation

Leisman G, Koch P. Rev. Neurosci. 2009; 20(3-4): 151-176.

Affiliation

F. R. Carrick Institute for Clinical Ergonomics, Rehabilitation, and Applied Neuroscience, Leeds Metropolitan University, Leeds, UK. g.Leisman@leedsmet.ac.uk

Copyright

(Copyright © 2009, Freund Publishing)

DOI

unavailable

PMID

20157986

Abstract

We demonstrate brain locations appearing to correlate with consciousness, but not being directly responsible for it. Technology reveals that brain activity is associated with consciousness but is not equivalent to it. We examine how consciousness occurs at critical levels of complexity. Conventional explanations portray consciousness as an emergent property of classical computer-like activities in the brain's neural networks. Prevailing views in this camp are that patterns of neural network activities correlate with mental states, that synchronous network oscillations in the thalamus and cerebral cortex temporally bind information, and that consciousness emerges as a novel property of computational complexity among neurons. A hard-wired theory is enigmatic for explaining consciousness because the nature of subjective experience, or 'qualia'- 'inner life' - is a "hard problem" to understand; binding spatially distributed brain activity into unitary objects, and a coherent sense of self, or 'oneness' is difficult to explain as is the transition from pre- to conscious states. Consciousness is non-computable and involves factors that are neither random nor algorithmic - consciousness cannot be simulated; explanations are also needed for free will and for subjective time flow. Convention argues that neurons and their chemical synapses are the fundamental units of information in the brain, and that conscious experience emerges when a critical level of complexity is reached in the brain's neural networks. The basic idea is that the mind is a computer functioning in the brain. In fitting the brain to a computational view, such explanations omit incompatible neurophysiological details, including widespread apparent randomness at all levels of neural processes (is it really noise, or underlying levels of complexity?); glial cells (which account for some 80% of the brain); dendritic-dendritic processing; electrotonic gap junctions; cytoplasmic/cytoskeletal activities; living state (the brain is alive!); and absence of testable hypotheses in emergence theory. There is no threshold or rationale specified; rather, consciousness 'just happens'. Consciousness then involves an awareness of what we are sensing or experiencing and some ability to control or coordinate voluntary actions. These issues of life, death, and consciousness are discussed in the context of Mike, the headless chicken, who survived for 18 months, and in the context of consciousness with high degrees of intellectual and cognitive function in a congenitally anencephalic brain; additionally, in the reanimation work of Soviet scientists in the 1920-30s, and in auditory sentence processing in patients in comatose, vegetative, and minimally conscious states.

Language: en