Stuart Hameroff, Consciousness Researcher - Abstracts

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Alfredo Pereira Jr (group admin)

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25 August 2007

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1: Biosystems. 2002 Jan;64(1-3):149-68.

Conduction pathways in microtubules, biological quantum computation, and
consciousness.

Hameroff S, Nip A, Porter M, Tuszynski J.

Department of Anesthesiology and Psychology, Center for Consciousness Studies,
University of Arizona, Tucson, AZ 85721, USA. hameroff@u.arizona.edu

Technological computation is entering the quantum realm, focusing attention on
biomolecular information processing systems such as proteins, as presaged by the
work of Michael Conrad. Protein conformational dynamics and pharmacological
evidence suggest that protein conformational states-fundamental information units
(‘bits’) in biological systems-are governed by quantum events, and are thus
perhaps akin to quantum bits (‘qubits’) as utilized in quantum computation. ‘Real
time’ dynamic activities within cells are regulated by the cell cytoskeleton,
particularly microtubules (MTs) which are cylindrical lattice polymers of the
protein tubulin. Recent evidence shows signaling, communication and conductivity
in MTs, and theoretical models have predicted both classical and quantum
information processing in MTs. In this paper we show conduction pathways for
electron mobility and possible quantum tunneling and superconductivity among
aromatic amino acids in tubulins. The pathways within tubulin match helical
patterns in the microtubule lattice structure, which lend themselves to
topological quantum effects resistant to decoherence. The Penrose-Hameroff ‘Orch
OR’ model of consciousness is reviewed as an example of the possible utility of
quantum computation in MTs.

Publication Types: Historical Article Research Support, Non-U.S. Gov’t

PMID: 11755497 [PubMed – indexed for MEDLINE]

2: Trends Cogn Sci. 2001 Nov 1;5(11):472-478.

A quantum approach to visual consciousness.

Woolf NJ, Hameroff SR.

Dept of Psychology and Laboratory of Chemical Neuroanatomy, University of
California, 90095-1563, Los Angeles, CA, USA

A theoretical approach relying on quantum computation in microtubules within
neurons can potentially resolve the enigmatic features of visual consciousness,
but raises other questions. For example, how can delicate quantum states, which
in the technological realm demand extreme cold and isolation to avoid
environmental ‘decoherence’, manage to survive in the warm, wet brain? And if
such states could survive within neuronal cell interiors, how could quantum
states grow to encompass the whole brain? We present a physiological model for
visual consciousness that can accommodate brain-wide quantum computation
according to the Penrose-Hameroff ‘Orch OR’ model. In this view, visual
consciousness occurs as a series of several-hundred-millisecond epochs, each
comprising ‘crescendo sequences’ of quantum computations occurring at
approximately 40 Hz.

PMID: 11684479 [PubMed – as supplied by publisher]

3: Ann N Y Acad Sci. 2001 Apr;929:74-104.

Consciousness, the brain, and spacetime geometry.

Hameroff S.

Department of Anesthesiology and Psychology, Center for Consciousness Studies,
University of Arizona, Tucson, Arizona, USA. hameroff@u.arizona.edu,
hameroff@arizona.edu

What is consciousness? Conventional approaches see it as an emergent property of
complex interactions among individual neurons; however these approaches fail to
address enigmatic features of consciousness. Accordingly, some philosophers have
contended that “qualia,” or an experiential medium from which consciousness is
derived, exists as a fundamental component of reality. Whitehead, for example,
described the universe as being composed of “occasions of experience.” To examine
this possibility scientifically, the very nature of physical reality must be
re-examined. We must come to terms with the physics of spacetime—as described by
Einstein’s general theory of relativity, and its relation to the fundamental
theory of matter—as described by quantum theory. Roger Penrose has proposed a
new physics of objective reduction: “OR,” which appeals to a form of quantum
gravity to provide a useful description of fundamental processes at the
quantum/classical borderline. Within the OR scheme, we consider that
consciousness occurs if an appropriately organized system is able to develop and
maintain quantum coherent superposition until a specific “objective” criterion (a
threshold related to quantum gravity) is reached; the coherent system then
self-reduces (objective reduction: OR). We contend that this type of objective
self-collapse introduces non-computability, an essential feature of consciousness
which distinguishes our minds from classical computers. Each OR is taken as an
instantaneous event—the climax of a self-organizing process in fundamental
spacetime—and a candidate for a conscious Whitehead “occasion of experience.”
How could an OR process occur in the brain, be coupled to neural activities, and
account for other features of consciousness? We nominate a quantum computational
OR process with the requisite characteristics to be occurring in cytoskeletal
micro-tubules within the brain’s neurons. In this model, quantum-superposed
states develop in microtubule subunit proteins (“tubulins”) within certain brain
neurons, remain coherent, and recruit more superposed tubulins until a
mass-time-energy threshold (related to quantum gravity) is reached. At that
point, self-collapse, or objective reduction (OR), abruptly occurs. We equate the
pre-reduction, coherent superposition (“quantum computing”) phase with
pre-conscious processes, and each instantaneous (and non-computable) OR, or
self-collapse, with a discrete conscious event. Sequences of OR events give rise
to a “stream” of consciousness. Microtubule-associated proteins can “tune” the
quantum oscillations of the coherent superposed states; the OR is thus
self-organized, or “orchestrated” (“Orch OR”). Each Orch OR event selects
(non-computably) microtubule subunit states which regulate synaptic/neural
functions using classical signaling. The quantum gravity threshold for
self-collapse is relevant to consciousness, according to our arguments, because
macroscopic superposed quantum states each have their own spacetime geometries.
These geometries are also superposed, and in some way “separated,” but when
sufficiently separated, the superposition of spacetime geometries becomes
significantly unstable and reduces to a single universe state. Quantum gravity
determines the limits of the instability; we contend that the actual choice of
state made by Nature is non-computable. Thus each Orch OR event is a
self-selection of spacetime geometry, coupled to the brain through microtubules
and other biomolecules. If conscious experience is intimately connected with the
very physics underlying spacetime structure, then Orch OR in microtubules indeed
provides us with a completely new and uniquely promising perspective on the
difficult problems of consciousness.

Publication Types: Review

PMID: 11349432 [PubMed – indexed for MEDLINE]

4: Toxicol Lett. 1998 Nov 23;100-101:31-9.

Anesthesia, consciousness and hydrophobic pockets—a unitary quantum hypothesis
of anesthetic action.

Hameroff S.

Department of Anesthesiology, The University of Arizona, Tucson, USA.
hameroff@u.arizona.edu

1. A consensus view holds that anesthetics act by van der Waals forces in
hydrophobic pockets of select brain proteins to ablate consciousness. 2. What is
consciousness? Enigmatic features of consciousness (e.g. ‘qualia’, binding,
non-computability, pre-conscious—>conscious transition, nondeterministic free
will) may be explained by the occurrence of quantum coherent states in the brain.
3. Van der Waals electron pair couplings (London forces) in hydrophobic pockets
in non-anesthetic (conscious) conditions are a particular type of quantum capable
of supporting macroscopic quantum coherence. 4. The mechanism of anesthetics may
be to inhibit electron mobility and London forces necessary for quantum states
and consciousness in hydrophobic pockets of select brain proteins.

Publication Types: Review

PMID: 10049159 [PubMed – indexed for MEDLINE]

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