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Go live Time : 19 June 2020, 09:49 PM

Penrose-Hameroff Orchestrated Objective Reduction (Orch OR) theory

Penrose-Hameroff 'Orch OR' is a theory of consciousness which grew from a confluence of two originally separate theories.

Beginning in 1982, Stuart Hameroff and colleagues had proposed that brain activities supporting consciousness were not limited to synaptic-level information processing in neuronal networks (as other theories suggest), but also extended downward to include computation in intra-neuronal cytoskeletal structures, specifically microtubules.

But while microtubule computation would increase capacity and speed of brain information processing (~10^15 operations per second per neuron), there was no accounting for consciousness per se, i.e. the nature of phenomenal experience, known now as the 'hard problem'.

In 1989 Sir Roger Penrose proposed that consciousness is a sequence of quantum computations, each terminated by a particular form of quantum state reduction occurring due to a specific objective threshold (hence 'objective reduction' – OR) related to quantum gravity. Quantum computing requires information (e.g. binary bits of either 1 or 0) to exist transiently as quantum superposition of both 1 and 0 (quantum bits, or 'qubits').

But while Penrose OR provided a mechanism for consciousness, it lacked a specific superpositioned qubit for OR-mediated quantum computing. Penrose conjectured that neurons could perhaps exist as superposition of both firing and not firing. But neurons are fairly macroscopic.

Hameroff suggested to Penrose that microtubules might be the quantum computers in the brain he was searching for, and that objective reduction might be the mechanism Hameroff was seeking. In 1994 Penrose and Hameroff met for several weeks in Denmark and began to hatch a theory of OR-mediated quantum computing in brain microtubules.

Penrose had proposed that OR occurred as E=h/t, where E is the gravitational self energy of the superposition, h is Planck's constant over 2 pi, and t is the time at which OR moments of consciousness occurred. So the larger the superposition E, the quicker the superposition would reach threshold for OR and consciousness at time t.

E=h/t is related to the quantum indeterminacy principle, and similar to the equation describing photons of the electromagnetic spectrum. If h is replaced by the speed of light c, E would be the energy of a photon, and t its wavelength. Penrose OR was describing a spectrum of conscious moments.

For consciousness in the brain, Penrose and Hameroff began by defining t in electrophysiological terms, e.g. related to the EEG (2 to 100 Hz; 10 to 500 milliseconds). They then calculated and found that superposition of microtubules in roughly hundreds of thousands, to millions of brain neurons was required for OR to occur in concert with EEG frequency bands correlating with consciousness (in particular, gamma synchrony at 30 to 90 Hz). OR quantum computations were 'orchestrated' by synaptic inputs, hence 'orchestrated objective reduction, Orch OR.

Questions abounded. How did the quantum computations in microtubules avoid decoherence in the warm, wet biological environment? How could quantum states isolated in one neuron extend throughout the brain? How could isolated quantum states receive inputs and provide outputs to the external, classical world? How could Orch OR solve the 'hard problem' of conscious experience?

Regarding the 'hard problem', P&H (1996) proposed that precursors of phenomenal experience were embedded in the fundamental level of the universe – spacetime geometry at the Planck scale, described through quantum gravity. Orch OR connected brain processes to the most basic level of the universe, and is thus consistent in a philosophical framework with neutral monism.

In 1998 Hameroff published 20 testable predictions of Orch OR, and reviewed their status in 2007. A number have been validated, and none refuted. To accommodate extension of quantum microtubule states throughout the brain, Orch OR predicted that gap junctions- windows between cells which allowed continuous internal cytoplasmic states – would be important for the neural correlate of consciousness. Indeed, gap junctions have been shown to be involved in gamma synchrony EEG, the best brain marker of consciousness.

Extensions of Orch OR include the 'Conscious pilot' model, developed by Hameroff to describe a gap junction-defined mobile zone of executive agency and Orch OR-mediated consciousness moving through the brain, and topological qubits in which winding pathways in microtubules (rather than individual microtubule subunits) function as qubits. Hameroff has further conjectured that consciousness as a process in fundamental spacetime geometry (in which Platonic values may be embedded, as suggested by Penrose) can account for various spiritual phenomena (interconnectedness, access to cosmic wisdom, and even after-life).

Orch OR has been criticized since its inception along several lines, especially the question of quantum states in the warm, wet biological environment. Recent demonstrations of quantum coherence in photosynthesis at ambient temperatures show that biology avoids decoherence.

To date, no facts or evidence have contradicted proposals supporting Orch OR. Testable and falsifiable, Orch OR remains the most complete, detailed and promising theory of consciousness ever put forward.

More Info: www.quantumconsciousness.org

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