Intracellular and Quantum Aspects of Consciousness

Nancy J. Woolf, Jack Tuszynski, Stuart Hameroff

Paavo Pylkkanen is unable to arrive in time and has withdrawn. The program is rearranged as follows:

1) Why are quantum properties of intra-neuronal dendritic structures necessary to explain consciousness?

Stuart Hameroff

2) Information processing at a subneuronal level: is there a case for quantum effects?

Jack Tuszynski

 
3) The subcellular machinery of consicousness

Nancy J. Woolf

4) Anesthesia, consciousness and quantum mechanics: The case for a connection

Stuart R. Hameroff

5) Panel discussion, Q & A

1) Overview: Why are quantum properties of intra-neuronal dendritic structures necessary to explain consciousness? Stuart Hameroff M.D., Departments of Anesthesiology and Psychology, Center for Consciousness Studies, The University of Arizona, Tucson, Arizona

2) Information processing at a subneuronal level: is there a case for quantum effects?

Jack Tuszynski Ph.D., Department of Physics, University of Alberta, Edmonton, Canada

In this talk we discuss a recently proposed biophysical model representing the dendritic cytoskeleton as a computational device. This largely involves a molecular dynamical description of the functional role of cytoskeletal elements within the dendrites of a neuron. The working hypothesis is that the dendritic cytoskeleton, which includes both microtubules and actin filaments, plays an active role in computations affecting neuronal function. Critical to their model is the assumption that cytoskeletal elements are
affected by, and in turn regulate, a number of processes inside the neuron.Ion channel activity, MAPs and other cytoskeletal motors such as kinesin, for example, are viewed in terms of their interface with microtubules. We advance the novel and specific hypothesis that it is the C-termini protruding from the surface of a microtubule, existing in several
conformational states, which lead to collective dynamical properties of the neuronal cytoskeleton. From a physics point of view, these collective states of the C-termini on microtubules have a significant effect on the ionic condensation and ion cloud propagation. We provide an integrated view of this biophysical model using a bottom-up scheme with considerable evidence to support the model of ionic wave propagation along cytoskeletal structures impacting on channel function and computational capabilities of whole dendrites and entire neurons. The theoretical approach advanced here is
conceptually consistent with the experimental evidence put forth by Nancy
Woolf in her work. We will close this talk with a discussion about a possible involvement of quantum degrees of freedom in information processing at a molecular level.

3) The subcellular machinery of consciousness
Nancy J. Woolf

Behavioral Neuroscience, Department of Psychology,

University of California, Los Angeles, CA, U.S.A.

Dendrites are enriched with microtubules and associated proteins. The roles these ubiquitous proteins play in higher cognition have not been fully elaborated. Microtubule-associated protein-2 (MAP2) is a dendrite-specific cytoskeletal protein that acts as a signal transduction molecule under the control of synaptic release of glutamate and acetylcholine (Fig. 1A). The microtubule matrix is also a kind of storage site for memory, with MAP2 and tubulin being proteolyzed before a new subcellular architecture is formed (Woolf, Prog. Neurobiol. 55:59, 1998). Acetylcholine also controls the level of consciousness via muscarinic receptor activation of PI-PLC and stimulation of PKC and CaMKII, which are known to phosphorylate MAP2. Phosphorylation of MAP2 reduces its binding to microtubules, thereby affecting the protein conformation of tubulin subunits and altering the ability of microtubules to transport receptors, cytoskeletal proteins and mRNA to synapses. These two roles, taken together, enable microtubules to compute current synaptic inputs with previous synaptic activity, selecting particular synapses to further enhance via increased transport. We have previously proposed that acetylcholine enables quantum computations in microtubules by phosphorylating MAP2 (Woolf & Hameroff, Trends Cogn Sci. 5:472, 2001). In addition to actin filaments, MAP2 forms a gel surrounding microtubules and enabling isolation. Unlike actin, MAP2 is directly attached to the microtubule; moreover, the quasi-periodic MAP2 binding densities render a particular contour to this gel. This contour (Fig. 1B) is currently proposed to represent information stored by the learning mechanism and to provide a physical basis for realizing that stored information.

4) Anesthesia, consciousness and quantum mechanics: The case for a connection

Stuart Hameroff, Departments of Anesthesiology and Psychology, Center for Consciousness Studies, The University of Arizona

www.consciousness.arizona.edu/hameroff

Anesthetic gases reversibly and selectively erase consciousness while sparing other brain activities (EEG, control of autonomic functions, evoked potentials etc.). Anesthetic gases act in nonpolar, hydrophobic pockets of a set of dendritic brain proteins oscillating in gamma synchrony. The anesthetic effect occurs solely though quantum mechanical van der Waals London forces, with no chemical bonds. This implies that consciousness depends on London forces in hydrophobic pockets of a class of dendritic brain proteins, implying nonlocal entanglement and coherence among endogenous London forces.

Recent results on anesthetic gas effects and current status of the Orch OR model will be presented.