Overview of the Contributions

We begin this volume with several experimental chapters. In the first chapter, Dick Bierman and Stephen Whitmarsh describe several recent experiments testing the subjective reduction interpretation of the measurement problem in quantum physics. These experiments investigate the proposition that consciousness acts as the ultimate measurement device, where a measurement is defined as the collapse of the statevector describing the external physical system, due to interaction with a conscious observer. To briefly summarize earlier work, auditory evoked potentials (AEPs) of subjects observing (previously unobserved) radioactive decay were recorded. The timing and peak amplitudes of these AEPs were compared with AEPs from events that were already observed and thus supposedly already collapsed into a singular state. In these earlier studies, significant differences in brain signals of the observer were found. In this chapter the authors report a further replication, which is improved upon the previous experiments by adding a nonquantum event as a control. Unfortunately, only marginal differences were found between the quantum and classical conditions. Possible explanations for the inability to replicate the previous findings are given in this chapter as well as suggestions for further research.

Nancy Woolf discusses the role that microtubules may play in neurocog-nition, in particular, how neurotransmitter receptors influence microtubules and how restructured microtubule/MAP networks could provide permanent memory storage in the subsynaptic zone underlying the synapse. She reviews her experimental work demonstrating that microtubules and microtubule-associated protein-2 (MAP2) are proteolyzed with learning, as exemplified in hippocampal neurons of rats with contextual fear conditioning. Corroborating data are discussed, including results indicating the critical involvement of MAP2 in contextual fear conditioning with knockout mice deficient for the N-terminus of MAP2 [33] and results that overexpression of the MAP, tau, disrupts memory in Drosophila ( [40]; also see Mershin et al., this volume). The role of MAP2 and microtubules in kinesin-mediated transport is also reviewed and the participation of this motility in cognition in noted. Related to the issue of transport, local storage of mRNA within neuronal dendrites raises the possibility of rapid dispatch to synapses. Microtubules and actin filaments provide the needed tracks for protein cargo to reach synapses in response to increased synaptic activation. A number of researchers have proposed that the parameters of this transport result from microtubule-based computations, as opposed to the cytoskeleton acting as a system of passive cables. A model is presented in which microtubules compute on the basis of their protein conformational states determined by the binding of MAPs and motor proteins, such as kinesin. These computations are responsible for the mobilization of specific receptors to specific sites. Rather than synapses or spines being the locus of permanent memory storage, the microtubules that carry cargo to the synapse or spine are proposed as the storage site. The overall pattern is stored at multiple neural locations, such that it can be reconstructed as the proteins involved turnover. Finally, it is argued that microtubules possess the capability of self-organization, and that through this capacity; microtubules initiate mobilization of receptors and postsynap-tic density proteins to synapses on spine heads. Thus, the model is able to account for the fact that ideas can occur spontaneously and can exist independently from sensory inputs. Other chapters in this volume elaborate on the key physical properties of microtubules mentioned above; in particular, the chapter by Priel et al. is devoted to microtubule computations.

Andreas Mershin et al. in their chapter entitled "Towards Experimental Tests of Quantum Effects in Cytoskeletal Proteins" emphasize the absolute need for properly controlled and replicable experimental work if one is to take seriously any proposed quantum phenomena in biological matter, let alone consciousness. These authors detail the critical kinds of experiments that one must devise to test hypotheses that quantum effects have a fundamental place in the phenomenon of consciousness. These authors astutely identify that the three different scale ranges to address are: (1) tissue-to-cell, (2) cell-to-protein and (3) protein-to-atom. The authors exclude experiments that aim to detect quantum effects at larger levels arguing negative results and inconsistencies. Mershin and coauthors pay particular attention to those consciousness experiments belonging to the tissue-to-cell scale frequently utilizing techniques such as electroencephalography (EEG) or magnetic resonance imaging (MRI) to track the activity of living, conscious human brains. They point to experiments by Christoff Koch's group, for example, designed to elucidate the multi-and single-cellular substrate of visual consciousness and likely to lead to profound insights into the working human brain. Nonetheless, because of the large spatial and long temporal resolution of these methods, Mershin et al. argue it is unclear whether they can reveal possible underlying quantum behavior (unless of course classical physics is obviously violated in some manner such as with nonlocality of neural firing). Mershin and co-authors argue that the second size scale that is explored for evidence of quantum behavior related to aspects of consciousness (memory in particular) is that between a single cell and a protein. They point to experimental work done by Nancy Woolf on dendritic expression of MAP2 in rats followed by significant experiments from their own laboratory on MAP-tau overexpression on the learning and memory of transgenic Drosophila. They argue the merits of such approaches, while specifying that it is still hard to see how experiments involving tracking the memory phenotypes and intracellular redistribution of proteins can show a direct quantum connection. These authors conclude that experimentation at the cell-to-protein size scale can at best provide evidence that is consistent with quantum consciousness. Lastly, these authors spend a great deal of time discussing the protein-to-atom scale, where quantum effects are likely to play a significant role in whole-protein function, It is at this level that the authors give an overview of their theoretical quantum electrodynamics (QED) model of microtubules and the extensive experimental work undertaken.

Alwyn Scott in his chapter entitled: "Physicalism, Chaos and Reduction-ism" strongly argues against the need for quantum basis of consciousness using a number of examples such as the decoherence issue. Instead, he puts forward an argument that the concept of emergence is sufficient to explain the onset of consciousness as an evolutionary development.

Stuart Hameroff, on the other hand, equally vigorously stresses the presence of connections between consciousness, neurobiology and quantum mechanics. This chapter enumerates and discusses the crucial unresolved problems in consciousness research ranging from those related to the neural correlates of conscious perception to the binding problem, to the electrophys-iological correlates and their properties to the distinction between conscious and unconscious behavior and finally, to the hard problem. The author then states that prevalent approaches assume that consciousness arises from in formation processing in the brain, with the level of relevant detail varying among philosophical stances. Hameroff strongly disagrees that all-or-none firings of axonal action potentials (spikes) could alone account for higher brain functions. Moreover, these simple binary states are comparable to unitary information states and switches in classical computers, which may not suffice in recapitulating consciousness given that consciousness presumably emerges from nonlinear dynamics of neuronal networks. Hameroff further argues that conscious states are sculpted by the modulation of electrochemical synapses and form metastable patterns identified with conscious experience (e.g. [16, 55]). Hameroff applies his analogy to a nonliving robot, and argues that if a robot were precisely constructed to mimic the brain activities, which modern neuroscience assumes to be relevant to consciousness, then the robot would be conscious regardless of its material basis. Lastly, Hameroff presents an overview of the elegant Orch OR model he and coauthor Roger Penrose have been working on over the last decade. Hameroff provides support for his own model, which has had a major impact on current thinking in consciousness studies, and goes on to further define the need for quantum approaches to consciousness studies.

Christopher Davia in his chapter entitled: "Life, Catalysis and Excitable Media: A Dynamic Systems Approach to Metabolism and Cognition" examines how life maintains its organization and describes an entirely novel principle that unites all living processes, from protein folding to macropro-cesses. Davia's hypothesis is that the same excitable media principle applies at every scale: living processes involve catalysis, biological processes mediate transitions in their environments, and enzymatic reactions act accordingly. By pinpointing enzyme catalysis as a prototypical process, Davia identifies energy dissipation as playing a major role in biology. Possible mechanisms contributing to excitable media are identified, including solitons and traveling waves, nondissipative and robust waves, all of which maintain their energy and structure in their biologically relevant environments. Particular emphasis is placed upon the relationship between microscopic instances of catalysis and traveling waves in excitable media. Pertinently to the topic of this volume, it is suggested that the brain is an excitable medium, and that cognition and possibly consciousness correlate with the spatiotemporal pattern of traveling waves in the brain. Davia offers this theory as an alternative to the functionalist perspective that underlies much of current theoretical biology. A key strength of his theory is that the same principle applies at multiple scales, potentially explaining how many biological processes that comprise an organism work and cooperate.

Avner Priel, Jack Tuszynski and Horacio Cantiello, discuss the biophysical model representing the dendritic cytoskeleton as a computational device. This chapter presents a molecular dynamical description of the functional role of cytoskeletal elements within the dendrites of a neuron. These authors present the working hypothesis 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. Priel and coauthors go on to 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. This is similar to what has been found recently for actin filaments. The authors provide an integrated view of their model using a bottom-up scheme. They marshal considerable evidence to support their 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 in this chapter is conceptually consistent with the experimental evidence put forth by Nancy Woolf in her chapter.

Laxmidhar Behera and colleagues develop a theoretical brain model using a nonlinear Schrodinger equation. In the general scope, their model proposes the existence of a quantum process that mediates the collective response of a neural lattice representing the classical brain. The specific example used in their model is eye movements when tracking moving targets. By using a recurrent quantum neural network while simulating the quantum brain model, the authors find two novel phenomena. The first is that eyesensor data are processed in the classical brain, while a wave packet is triggered in the quantum brain. The second is that when the eye tracks a fixed target, the wave packet moves in a discrete mode, with jumps and rest periods reproducing experimental observations very accurately. These authors have accomplished a great deal and offer a very interesting theoretical development that combines the robustness of classical approaches with the quirkiness of quantum theories.

Elizabeth Behrman and her collaborators present a mathematical model of microtubules as a quantum Hopfield neural network. The motivation behind this work is the suggested existence of quantum computation in mi-crotubule protein assemblies inside living cells as proposed by Hameroff and Penrose. The authors set up their equations within the constraints of a quantum Hopfield network with qubits representing tubulins interacting electrostatically by Coulomb forces. Simulations presented in this work focus on the existence of stable states, such as local minima, of the network. The authors report quantum information processing in microtubules is feasible, though at temperatures much lower than physiological temperatures. They conclude that microtubules can be used as information storage devices but not as quantum information devices at physiological temperatures.

Gordon Globus, in his chapter entitled "Consciousness and Quantum Brain Dynamics" argues that the opposition to quantum brain theory is deconstructed. The author refers back to quantum brain theory originated by Umezawa and coworkers, reiterating the differences between unimode quantum brain dynamics (QBD), a Hermitean-dual mode QBD and a non-Hermitean dual-mode QBD. Globus argues that unlike the non-Hermitean version, the Riemann hypothesis offers a unique approach. This chapter is rich in philosophical discussion and traces interesting connections to advanced mathematics.

Johnjoe McFadden outlines conscious electromagnetic field theory (CEMI) revealing seven clues to the nature of consciousness. The author argues that if consciousness is an epiphenomenon then, as scientists, we must turn aside and leave the topic to the philosophers and theologians to make sense of. However, consciousness does generate observable phenomena and thus belongs to the realm of empirical science. One undeniable example is that consciousness has had a major impact on the lives of philosophers, scientists and theologians who have studied the subject. In his chapter, McFadden examines the seven clues to the nature of consciousness and discusses how the conscious electromagnetic field theory (CEMI field theory) makes sense of them. As McFadden cogently argues, any successful theory of consciousness needs to include a physical mechanism enabling our conscious mind to interact with the matter of our brain.

Chris King, through the use of quantum cosmology addresses the hard problem of the conscious brain. The author explores a model resolving many aspects of the hard problem in consciousness research through cosmic subject-object complementarity. King's model combines a number of mathematical topics, including: transactional quantum theory, chaos, and fractal dynamics. These serve as a basis for a direct relationship between phase coherence in global brain states and anticipatory boundary conditions in quantum systems, which complement conscious perception and intentional will. King's aim is to describe unusual physical properties of excitable cells, which may form a basis for the evolutionary selection of subjective consciousness.

Paola Zizzi ambitiously deals with the issue of consciousness and logic in a model of a quantum-computing universe. The universe is described at various stages. The early inflationary universe is seen as a superposed state of quantum registers. In the end, at the close of the inflationary period, one universe is selected out of a superposition of many by a self-reduction mechanism. This kind of reduction is similar to Penrose's objective reduction (OR) model; moreover, it depends on gravity and can be numerically specified in terms of quantum registers (109 quantum registers). Zizzi then draws an analogy between the very early quantum-computing universe and our mind. Zizzi argues that events at the end of inflation of the universe (the so-called "Big Wow") acted to indelibly imprint on future minds to come, dictating future modes of computation, consciousness and logic. From this point on, the uni verse organized itself according to two computational modes: quantum and classical, like the two conformations assumed by the cellular automaton of tubulins in our brain, as in Hameroff's model. Zizzi speculates that the universe uses, as subroutines, black holes - quantum computers and quantum minds, which operate in parallel. He further suggests that the outcomes of the overall quantum computation are universal attributes endowed with subjective meaning. In other words, qualia are related to Planckian black holes. The author then considers two aspects of the quantum mind that are not algorithmic in the usual sense: the self and mathematical intuition. Zizzi argues the self corresponds to a self-measurement of a quantum state of superposed tubulins and that mathematical intuition is due to the consistent pattern of logic of the internal observer in a quantum-computing universe.

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