How quantum brain biology can rescue conscious free will
Stuart Hameroff, 2012
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Conscious “free will” is problematic because (1) brain mechanisms causing consciousness are unknown, (2) measurable brain activity correlating with conscious perception apparently occurs too late for real-time conscious response, consciousness thus being considered “epiphenomenal illusion,” and (3) determinism, i.e., our actions and the world around us seem algorithmic and inevitable. The Penrose–Hameroff theory of “orchestrated objective reduction (Orch OR)” identifies discrete conscious moments with quantum computations in microtubules inside brain neurons, e.g., 40/s in concert with gamma synchrony EEG. Microtubules organize neuronal interiors and regulate synapses. In Orch OR, microtubule quantum computations occur in integration phases in dendrites and cell bodies of integrate-and-fire brain neurons connected and synchronized by gap junctions, allowing entanglement of microtubules among many neurons. Quantum computations in entangled microtubules terminate by Penrose “objective reduction (OR),” a proposal for quantum state reduction and conscious moments linked to fundamental spacetime geometry. Each OR reduction selects microtubule states which can trigger axonal firings, and control behavior. The quantum computations are “orchestrated” by synaptic inputs and memory (thus “Orch OR”). If correct, Orch OR can account for conscious causal agency, resolving problem 1. Regarding problem 2, Orch OR can cause temporal non-locality, sending quantum information backward in classical time, enabling conscious control of behavior. Three lines of evidence for brain backward time effects are presented. Regarding problem 3, Penrose OR (and Orch OR) invokes non-computable influences from information embedded in spacetime geometry, potentially avoiding algorithmic determinism. In summary, Orch OR can account for real-time conscious causal agency, avoiding the need for consciousness to be seen as epiphenomenal illusion. Orch OR can rescue conscious free will.
Introduction: Three Problems with Free Will
We have the sense of conscious control of our voluntary behaviors, of free will, of our mental processes exerting causal actions in the physical world. But such control is difficult to scientifically explain for three reasons:
Consciousness and Causal Agency
What is meant, exactly, by “we” (or “I”) exerting conscious control? The scientific basis for consciousness, and “self,” are unknown, and so a mechanism by which conscious agency may act in the brain to exert causal effects in the world is also unknown.
Does Consciousness Come Too Late?
Brain electrical activity correlating with conscious perception of a stimulus apparently can occur after we respond to that stimulus, seemingly consciously. Accordingly, science and philosophy generally conclude that we act non-consciously, and have subsequent false memories of conscious action, and thus cast consciousness as epiphenomenal and illusory (e.g., Dennett, 1991; Wegner, 2002).
Even if consciousness and a mechanism by which it exerts real-time causal action came to be understood, those specific actions could be construed as entirely algorithmic and inevitably pre-ordained by our deterministic surroundings, genetics and previous experience.
We do know that causal behavioral action and other cognitive functions derive from brain neurons, and networks of brain neurons, which integrate inputs to thresholds for outputs as axonal firings, which then collectively control behavior. Such actions may be either (seemingly, at least) conscious/voluntary, or non-conscious (i.e., reflexive, involuntary, or “auto-pilot”). The distinction between conscious and non-conscious activity [the “neural correlate of consciousness (NCC)”] is unknown, but often viewed as higher order emergence in computational networks of integrate-and-fire neurons in cortex and other brain regions (Scott, 1995). Cortical-cortical, cortical-thalamic, brainstem and limbic networks of neurons connected by chemical synapses are generally seen as neurocomputational frameworks for conscious activity, (e.g., Baars, 1988; Crick and Koch, 1990; Edelman and Tononi, 2000; Dehaene and Naccache, 2001), with pre-frontal and pre-motor cortex considered to host executive functions, planning and decision making.
But even if specific networks, neurons, membrane, and synaptic activities involved in consciousness were completely known, questions would remain. Aside from seemingly occurring too late for conscious control, neurocomputational activity fails to: (1) distinguish between conscious and non-conscious (“auto-pilot”) cognition, (2) account for long-range gamma synchrony electro-encephalography (“EEG”), the best measurable NCC (Singer and Gray, 1995), for which gap junction electrical synapses are required, (3) account for “binding” of disparate activities into unified percepts, (4) consider scale-invariant (“fractal-like,” “1/f”) brain dynamics and structure, and (5) explain the “hard problem” of subjective experience (e.g., Chalmers, 1996). A modified type of neuronal network can resolve some of these issues, but to fully address consciousness and free will, something else is needed. Here I propose the missing ingredient is finer scale, deeper order, molecular-level quantum effects in cytoskeletal microtubules inside brain neurons.
In particular, the Penrose–Hameroff “Orch OR” model suggests that quantum computations in microtubules inside brain neurons process information and regulate membrane and synaptic activities. Microtubules are lattice polymers of subunit proteins called “tubulin.” Orch OR proposes tubulin states in microtubules act as interactive information “bits,” and also as quantum superpositions of multiple possible tubulin states (e.g., quantum bits or qubits). During integration phases, tubulin qubits interact by entanglement, evolve and compute by the Schrödinger equation, and then reduce, or collapse to definite states, e.g., after 25 ms in gamma synchrony. The quantum state reduction is due to an objective threshold [“objective reduction (OR)”] proposed by Penrose, accompanied by a moment of conscious awareness. Synaptic inputs and other factors “orchestrate” the microtubule quantum computations, hence “orchestrated objective reduction (Orch OR).”
Orch OR directly addresses conscious causal agency. Each reduction/conscious moment selects particular microtubule states which regulate neuronal firings, and thus control conscious behavior. Regarding consciousness occurring “too late,” quantum state reductions seem to involve temporal non-locality, able to refer quantum information both forward and backward in what we perceive as time, enabling real-time conscious causal action. Quantum brain biology and Orch OR can thus rescue free will.
Consciousness, Brain, and Causality
Consciousness involves awareness, phenomenal experience (composed of what philosophers term “qualia”), sense of self, feelings, apparent choice and control of actions, memory, a model of the world, thought, language, and, e.g., when we close our eyes, or meditate, internally-generated images and geometric patterns. But what consciousness actually isremains unknown.
Most scientists and philosophers view consciousness as an emergent property of complex computation among networks of the brain’s 100 billion “integrate-and-fire” neurons. In digital computers, discrete voltage levels represent information units (e.g., “bits”) in silicon logic gates. McCulloch and Pitts (1943) arranged logic gates as integrate-and-fire silicon neurons, leading to “perceptrons” (Rosenblatt, 1962; Figure 1) and self-organizing “artificial neural networks” capable of learning and self-organized behavior. Similarly, according to the standard “Hodgkin and Huxley” (1952) model, biological neurons are “integrate-and-fire” threshold logic device in which multiple branched dendrites and a cell body (soma) receive and integrate synaptic inputs as membrane potentials. The integrated potential is then compared to a threshold potential at the axon hillock, or axon initiation segment (AIS). When AIS threshold is reached by the integrated potential, an all-or-none action potential “firing,” or “spike” is triggered as output, conveyed along the axon to the next synapse. Axonal firings can manifest will and behavior, e.g., causing other neurons to move muscles or speak words.