N-methyl-D-aspartate channel and consciousness: from signal coincidence detection to quantum computing

Research on Blindsight, Neglect/Extinction and Phantom limb syndromes, as w ell as electrical measurements of mammalian brain activity, have suggested the dependence of vivid perception on both incoming sensory information at primary sensory cortex and reentrant information from associative cortex. C oherence between incoming and reentrant signals seems to be a necessary con dition for (conscious) perception. General reticular activating system and local electrical synchronization are some of the tools used by the brain to establish coarse coherence at the sensory cortex, upon which biochemical p rocesses are coordinated. Besides electrical synchrony and chemical modulat ion at the synapse, a central mechanism supporting such a coherence is the N-methyl-D-aspartate channel, working as a 'coincidence detector' for an in coming signal causing the depolarization necessary to remove Mg2+, and reen trant information releasing the glutamate that finally prompts Ca2+ entry. We propose that a signal transduction pathway activated by Ca2+ entry into cortical neurons is in charge of triggering a quantum computational process that accelerates inter-neuronal communication, thus solving systemic confl ict and supporting the unity of consciousness. (C) 2001 Elsevier Science Lt d. All rights reserved.