Penrose put forth OR as a mechanism for consciousness in physical science (the first, and still only specific proposal). For neurobiological implementation of OR, the Penrose–Hameroff model of “Orch OR” proposed quantum computations terminated by OR in microtubules within brain neurons, “orchestrated” by synaptic inputs, memory and other factors, hence “Orch OR” (Penrose and Hameroff, 1995
; Hameroff and Penrose, 1996a
; Hameroff, 1998
). Starting with classical microtubule automata (e.g., Rasmussen et al., 1990
) in which tubulins in microtubule lattices convey interactive bit states, e.g., of 1 or 0, and are thus capable of classical information processing (Figure ), Orch OR also proposed that quantum superpositioned tubulin bits, or “qubits,” e.g., of both 1 AND 0 compute via entanglement with tubulins in the same neuron, and also those in neighboring and distant neurons via gap junctions (Figure ). The quantum computations evolve by the Schrödinger equation in entangled microtubules in dendrites and cell bodies during integration phases of gap junction-connected integrate-and-fire neurons. Entangled superpositions contribute to increasing gravitational self-energy E. When threshold is met by E
, a conscious moment occurs as entangled tubulin qubits simultaneously undergo OR to classical tubulin states which then proceed to trigger (or not trigger) axonal firings, and adjust synapses. Microtubule quantum computations can thus be the “x-factor” in integration regulating axonal firing threshold. Compatible with known neurophysiology, Orch OR can account for conscious causal control of behavior.
Figure 12 Three toy neurons in an input/integration layer. Adjacent dendrites are connected by gap junction electrical synapses in “dendritic web,” showing internal cytoskeletal microtubules connected by microtubule-associated proteins. Insert: (more ...)
Entangled superpositions leading to OR and moments of consciousness by E = ħ/t are seen as sequential, only one “consciousness” occurring in the brain at any one time (except perhaps for “split-brain” patients, or those with other cognitive disorders). Superpositions outside the largest, most rapidly evolving gap junction-connected web may decohere randomly, or continue and participate in a subsequent moment of consciousness. The results of each Orch OR conscious moment set initial conditions for the next.
, superposition of about 2 × 1010
tubulins would reach threshold at t
= 25 ms, as in 40 Hz gamma synchrony, 40 conscious moments/s. Depending on the percentage of tubulins involved per neuron, this would entail thousands to hundreds of thousands of gap junction-connected neurons per conscious moment at 40 Hz as the NCC (Figure ). With specific neuronal distributions and brain regions defined by gap junction openings and closings, synchronized “dendritic webs” as the NCC can move and redistribute moment to moment. Within the NCC, consciousness by E
may occur on a spectrum of frequencies, at different fractal-like scales of brain activity (He et al., 2010
), with deeper order, finer scale entangled processes in microtubules correlating with high frequency, high intensity experience, and larger proportions of brain involvement.
Proteins can act as quantum levers, able to amplify quantum effects into particular classical states (Conrad, 1994
). Orch OR suggests that tubulin states and superpositions are initiated by electron cloud dipoles (van der Waals London forces) in clusters of aromatic resonance rings (e.g., in amino acids tryptophan, phenylalanine, tyrosine, Figures –). London force dipoles are inherently quantum mechanical, tending to superposition. They also mediate effects of general anesthetic gases which act in aromatic clusters (“hydrophobic pockets”) in neuronal proteins including tubulin to selectively erase consciousness (Hameroff, 2006
). This suggests a deeper order, finer scale component of the NCC.
Figure 13 (A) A microtubule, a cylindrical lattice of peanut-shaped tubulin proteins, with molecular model of enlarged single tubulin with C-termini tails (Craddock et al., 2012c). (B) Tubulin dimer, lower C terminus tail visible. Interior blowup shows aromatic (more ...)
Electron movements of one nanometer, e.g., in a London force dipole oscillation, displace atomic nuclei by one Fermi length, 10−15
m, the diameter of a carbon atom nucleus (Sataric et al., 1998
), and also the superposition separation distance required for gravitational self-energy E in Orch OR (Hameroff and Penrose, 1996a
). Thus London forces can induce superposition of an entire protein/tubulin mass, albeit by an extremely tiny separation distance. Nonetheless the protein-level (rather than electron only) superposition separation engenders significant gravitational self-energy E
, and thus by E
, usefully brief durations of time t
for conscious moments and actions.
Orch OR has been criticized on the basis of decoherence in the “warm, wet and noisy” brain, preventing superposition long enough to reach threshold (Tegmark, 2000
; cf. Hagan et al., 2001
). But subsequently plant proteins have been shown to routinely use electron superposition for chemical energy (Engel et al., 2007
). Further research has demonstrated warm quantum effects in bird brain navigation (Gauger et al., 2011
), ion channels (Bernroider and Roy, 2005
), sense of smell (Turin, 1996
), DNA (Rieper et al., 2011
), protein folding (Luo and Lu, 2011
), and biological water (Reiter et al., 2011
). Microtubules (Sahu et al., 2012
) appear to have kilohertz and megahertz resonance related to enhanced (?quantum) conductance through spiral pathways.
Conductance pathways through aromatic ring arrays in each tubulin aligned with neighbor tubulin arrays following spiral geometry in microtubule lattices (Figure ) allow helical macroscopic “quantum highways” through microtubules (Figure ) suitable for topological quantum computing (Kitaev, 1997
; Hameroff et al., 2002
; Penrose and Hameroff, 2011
). With particular spiral pathways as topological qubits (“braids”) rather than individual tubulins, overall microtubule information capacity is reduced, each topological bit/qubit pathway requiring many tubulins (Figure , Bottom). But topological qubits are robust, resist decoherence, and reduce to classical helical pathways (or combinations) which can, with each conscious moment, regulate synapses and trigger axonal firings.
Figure 14 (A) Alignment of aromatic ring structures in tubulins and through microtubule lattice suggests different helical pathways, possible macroscopic “quantum highways” e.g., following the Fibonacci sequence in the A lattice. (B) Top: superpositioned (more ...)
In Figure , two Orch OR conscious moments underlie gamma synchrony electrophysiology in an integrate-and-fire neuron. Quantum superposition E evolves during integration, increasing with time until threshold is met at E = ħ/t (t = 25 ms), at which instant an Orch OR conscious moment occurs (intensity proportional to E), and classical states of tubulin are selected which can trigger (or not trigger) axonal firings which control actions and behavior (as well as regulate synaptic strength and record memory).
Figure 15 Two Orch OR events (solid lines) underlie integrate-and-fire electrophysiology (dotted lines) in neurons. Orch OR and conscious moments occur here at t = 25 ms (gamma synchrony), with E then equivalent to superposition of approximately 2 × 10 (more ...)
Each Orch OR quantum state reduction also causes temporal non-locality, sending quantum information/quanglement (with gravitational self-energy E
) backward in what we perceive as classical time, integrating with forward-going E
to help reach E
, perhaps earlier than would otherwise occur (Figure ). As described previously, Orch OR temporal non-locality and backward time referral of quantum information can provide real-time conscious causal control of voluntary actions (Figure ; cf. Wolf, 1998
; Sarfatti, 2011
Do backward time effects risk causal paradox? In classical physics, the cause of an effect must precede it. But backward-going quanglement is acausal, only able to influence or correlate with information in a classical channel, e.g., as occurs in quantum entanglement, cryptography and teleportation. And according to some quantum interpretations, backward time effects can't violate causality if they only alter past events whose subsequent effects had not been consciously observed (“If a tree falls ….”). In the experimental studies cited here (Libet, pre-sentiment/Bem, delayed choice) backward referral itself is non-conscious (though Libet refers to it as “subjective experience”) until reduction occurs in the present. There is no causal paradox.
If conscious experience is indeed rooted in Orch OR, with OR relating the classical to the quantum world, then temporal non-locality and referral of acausal quantum information backward in time is to be expected (Penrose and Hameroff, 2011
). Temporal non-locality and backward time referral can rescue causal agency and conscious free will.