The quantum-classical complexity of consciousness and orchestrated objective reduction
Alessandro Sergi, ANTONINO MESSINA, Gabriella Martino +5 more
The Complexity of Consciousness and Orch OR Orch OR states that phenomena such as the discrete perception of time unfolding, the subjective wholeness of perception, spatio-temporal binding, causal free will [28], mechanisms of anesthesia, and the so-called "hard problem" are explainable aspects of consciousness. It organizes these phenomena within a systematic framework capable of explaining possible underlying links and offering interpretations of related philosophical issues [29].We believe that, at present, the Orch OR model represents the most comprehensive and bold attempt to propose a framework for the hard problem of consciousness and other features that are connected to it. The foundations of the Orch OR model include Penrose's objective reduction conjecture [12,13,30,31,32] and the concept of orchestration in neural processes [16,23,22]. To our knowledge, there is one computational study that reports explicit theoretical calculations estimating decoherence times and gravitational collapse times in microtubules [25]. These coherence times were estimated to range from 10 -6 to 10 -4 seconds.Coherence times within this range have also been observed experimentally in microtubules [33], and are considered sufficient for Orch OR processes. We have not found theoretical or computational studies about how, e.g., textcolorvioletslower synaptic activity, membrane potentials, calcium ion flows orchestrate the quantum dynamics of the microtubules's lattice. Experimental studies have investigated electronic conduction, excitonic coupling, and electromagnetic resonances in microtubules [34,35,36,33,37].Additional research has explored the possibility of quantum effects in brain structures, including MRI observations of cardiac-evoked zero quantum coherence signals in the brain [38], and theoretical models describing coherent excitations in biological systems [39,40,41,42,43]. These elements are combined into a framework that is both intellectually engaging and ambitious in its aim to connect gravitation, quantum physics, neuroscience, consciousness, and anesthesia.We regard this narrative not as a finished structure, but as a foundation, an invitation to contribute with rigorous analysis and an open mind. In this paper, we identify key ideas of the Orch OR model and examine how their internal relations could be analyzed using physically grounded tools. Rather than offering a critique or a generalization, we want to integrate quantum-classical dynamics in the Orch OR framework to describe the evolution of brain structures before and after quantum state reduction. This perspective emphasizes the orchestration process and seeks to formulate it in rigorous physical and mathematical terms, by means of quantum-classical Hamiltonians [44,45,46,47] and the quasi-Lie algebra of quantum-classical brackets [48,49]. In doing so, we want to enlarge the possibilities of the model without altering its foundational premises. For clarity, our specific goal in this work is to propose that the framework of orchestration might find its natural formal expression within a quantum-classical theory [50,51,52,49,53,54,48,45,53,47]. Our paper contributes to the scientific debate on the unfolding of brain dynamics at the boundary between the quantum and classical realms, and aims to help develop Orch OR into a more predictive and testable framework. This paper is structured as follows. In Sec. 2, we discuss objective reduction. The second main idea of the Orch OR model, i.e., orchestration, is presented in Sec. 3. In Sec. 4, we outline a quantum-classical framework that could offer a dynamical description of the classical modulation of quantum events in Orch OR, with the aim of supporting its integration into a testable and predictive multiscale model. Section 5 addresses the quantum dynamics of microtubules. In Sec. 6, we describe how Professor Hameroff has skillfully used the Orch OR model, specifically the randomization of orchestrated quantum effects in microtubules, to develop a compelling narrative for explaining anesthesia. In Sec. 7, we discuss how the Orch OR model tackles big questions such as stimulus integration, free will, and the subjective sense of time's irreversibility associated with awareness. In Sec. 8 we discuss our thoughts about complexity and the meaning of quantum-classical complexity. Finally, in Sec. 9, we present our main conclusions and final remarks.The orthodox interpretation of quantum mechanics considers the quantum state ontologically real [9]. One of its main faults is that it fails to provide a unique and rigorous account of how the classical limit emerges [55,56,57]. Being a linear theory, it obeys the superposition principle, according to which a system can occupy two quantum states at the same time. If one assigns an ontological status to the quantum states, then the superposition principle does not obey the rule of reality. In the Copenhagen interpretation [9], only an act of measurement can destroy a superposition and, therefore, create reality as we know it, with systems only occupying a single state at a time. However, since in the Copenhagen interpretation [9], any act of measurements implies an observer and a measurement, the reality associated with it, is subjective.Typically, the collapse of the wave function is introduced in an ad hoc manner to force, although in a probabilistic way, the correspondence with the classical world. This has led to interpretations of quantum mechanics that border on metaphysics, such as the many-worlds interpretation [58,59,60,61,62].Penrose developed the idea that the probabilistic and observer-dependent nature of collapse could be dispensed with by using gravity as a constraint on the lifetime of generic superpositions. This is implemented by considering quantum superpositions not just as superpositions of physical states, but as superpositions of spacetime geometries. Drawing on Einstein's general relativity, where mass and energy curve spacetime, Penrose proposed that a quantum particle in a spatial superposition corresponds to a superposition of distinct spacetime curvatures, differing at the Planck scale. When the gravitational selfenergy of this superposition reaches a certain threshold, the state undergoes an objective reduction (OR), spontaneously collapsing to a definite geometry [30,31,32]. The timescale for quantum state reduction is determined by the gravitational self-energy E G of the difference between the mass distributions of the superposed states. This leads to the characteristic relation:τ ∼ E G ,(1)where τ is the mean lifetime of the superposition and is the reduced Planck's constant. According to Penrose [30,31,32,12,13], the exact time of the collapse cannot be predicted by any currently known physical law. Instead, it is hypothesized to follow a yet-to-be-formulated principle emerging from the unresolved conflict between general relativity and quantum mechanics [12,13,30,31,32]. The law proposed in Eq. ( 1) is said to be neither random nor algorithmically deterministic, but rather deterministic and non-computable.Objective reduction, with its threshold time given by Eq. ( 1), provides a physical solution to the quantumto-classical transition [55,56,57] which is neither derived from the currently known laws of physics nor computable by any algorithms using a finite number of steps. Reasoning about Gödel's theorem and free will, Penrose concluded that objective reduction could also be the root of what he called protoconsciousness [12,13]. In fact, the central assumption of Orch OR is that consciousness arises exclusively through objective reduction (OR). More precisely, Orch OR posits that the collapse of the quantum state of the microtubule lattice within the neuronal cytoplasm constitutes a proto-conscious event. Coherent quantum dynamics entangle the quantum states of individual microtubules, producing a unified quantum state for the entire lattice [13,16,23,22,28]. In summary, the OR model offers a compelling unification of quantum mechanics and gravity, and gives the Orch OR framework its unique character.The Orch OR framework posits that each objective reduction (OR) event corresponds to a discrete moment of subjective experience, or proto-conscious qualia, occurring when quantum superpositions self-collapse into definite classical states. In this view, OR events in isolated systems would give rise to random, disconnected moments, metaphorically described as proto-conscious noise, lacking continuity, memory, or context. These have been likened to the tones of musicians individually tuning their instruments. In contrast, Orch OR proposes that in the brain, OR events are orchestrated across entangled microtubule networks, forming temporally and spatially coherent patterns of reduction. This orchestration is proposed to underlie unified conscious states, resonating and interfering across multiple scales, much like chords and harmonies in a musical composition. The orchestration, realized in part by classical processes occurring in the brain, synchronizes all OR events within individual neurons [13,16,17,23,22]. The synchronization of multiple OR events gives rise to conscious experience.An analogy can be made with a classical system: consider many pendulum clocks, each initially out of phase, but all mounted on the same wall. Because the shared wall transmits vibrations among the clocks, constructive and destructive interference leads them to synchronize over time. Orchestration in Orch OR is a similar process, involving 'quantum clocks' inside neurons, with the classical processes of the brain acting as the shared 'wall.' This analogy aligns with more recent interpretations of microtubules as time crystals, structures that may exhibit intrinsic periodicity and support coordinated timing of OR events. [63,64,65,34,35,36,33] According to Orch OR [16,17,23], orchestration is caused by processes such as resonance, synaptic activity, membrane dynamics, cytoskeletal regulation (e.g., MAPs [66,67], microtubule-associated proteins, and CAMKII [68,69,70,71,72,73], biochemical activity (e.g., calcium waves, GTP hydrolysis), and, e.g., anesthesia. These are proposed to modulate or 'tune' the quantum superposition within microtubules, without collapsing it. Therefore, orchestration is the quantum coherent dynamics, embedded in the classical environment provided by brain structures, unfolding before an OR event occurs.If the interplay between the coherent dynamics of microtubules and the dynamics of synapses, membranes, cytoskeleton, MAPs [66,67], calcium waves, GTP et cetera invokes both quantum and classical phenomena, then the corresponding modeling requires an advanced formalism that treats quantum and classical degrees of freedom on the same footing [50,51,52,49,53,54,48,47]. At the same time, expecting that quantumclassical dynamics does generate quantum transitions, destroying quantum superpositions, is not consistent with what experiments and quantum-classical theory [50,51,52,49,54,48,45,53,47] tells us regarding nonadiabatic dynamics. 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( the quantum-classical in the of the quantum-classical The in the of Eq. ( the is the in the two in the of Eq. ( brackets in quantum-classical is a quasi-Lie that fails to the ( of of the quantum-classical algebra the of quantum features the system time with an initially ( when is Our is that, energy and is the quantum-classical of in irreversibility by the two quantum-classical formalism has also been derived as a of the for quantum for a offers a consistent framework to model systems where one is such as dynamics with classical and quantum or quantum in a classical gravitational In these are not their Eq. ( can be by a number of algorithms on the system and its is quantum-classical can be time are by the to Eq. ( believe that the quantum-classical formalism we in this and that has been in many of brain dynamics could be used to within the framework of are by the of one of the most in the brain and a of the neuronal of in a intrinsic to the from the and the where is more the by is the or within the neuronal In neurons, microtubules exhibit a distinct from that of other microtubules are and and the in The microtubules are in the and of 5 This unique neuronal that microtubules may classical to their in and synaptic microtubules have also been in mechanisms and of consciousness. to the Orch OR framework is the that microtubules support a range of and electromagnetic resonances computational models proposed that the of microtubules could to conscious this of the computational of cytoskeletal structures in the It has also been proposed that microtubules can support interference patterns from in their These interference effects could in the to this a possible between microtubule dynamics and neural to Orch OR, a coherent quantum state can within the of individual microtubules by and This state is proposed to dynamics of the and and of these synchronization may to a unified quantum state the across multiple microtubules with as a possible These are hypothesized to a from to and may contribute to the of conscious corresponding to characteristic neural and waves, are as of neuronal activity by classical electromagnetic and These that, Orch OR is in quantum mechanics its physical framework for a quantum-classical description also to exhibit coherent and resonances in patterns of from to and that function as capable of supporting Orch OR across effects involving the of are proposed to quantum processes. the mass of is to and their influence is the However, effects involving electromagnetic or in may For an undergoes a or superposition on the of one it through or coupling, a by about one the the Orch OR collapse time τ Eq. ( 1) is related to the gravitational self-energy E G involving more such as E G and the collapse were considered for estimating E G in a single spatial of of its spatial by the of a or 10 by the of a (e.g., a or the E G and the This then used to the number of to be in superposition to Eq. For to to a 10 10 would to be that a single estimated 10 coherence for is and decoherence may in only the time of from much in microtubules, from to This led to a Orch OR events 10 coherence to for only 10 a experimentally conscious phenomena such as potentials, and at in the range of of central of the Orch OR model is the of quantum in microtubules, in analogy with coherence were in the framework of microtubule dynamics Experimental work by has in isolated microtubules, single proteins, and neurons, including patterns across to These observations have been as of dynamics, coherence and ideas were in the work of although without explicit to time provides a perspective on consciousness, as it conscious other brain According to the with in to in neuronal In the Orch OR such are associated with in the of microtubules. 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( 1), provides a physically for the times of the quantum which to such a law cannot be implemented in quantum-classical it can be using a Quantum-classical models may also be to study how the classical environment can modulate the of superpositions. In this the dynamical to are the from the i.e., the of the to the is an multiple of from physical and biological to and comprehensive theory account for this nature without aspects such as subjective and It an open can of consciousness or all processes of conscious awareness. consciousness from to and from in to its in features that consciousness be as a system by and the of systems cannot be by a single mathematical a of models is to its many the models that study consciousness, the Orch OR framework a as it addresses the hard problem of consciousness the perspective of quantum-classical systems have two The is that integrate both quantum mechanics and classical mechanics through a quasi-Lie This that quantum-classical systems more than one theoretical model for their using the laws of can across scales, from the quantum of and to the of about phenomena reduction to a single model, on the problem of that not a and are or to be by a single This is developed in such as the and In that and have multiple and, therefore, cannot be through a single 2, If there is an in the natural where this principle is it is in the questions such as is or is reduction to a single concept or This of that only can model is an and theory a framework for the hard problem of consciousness. It is grounded in the that consciousness is deterministic, and to the objective reduction of quantum states, a that aims to the quantum measurement problem and the hard problem of consciousness within a single physical framework. Orch OR the of the microtubule lattice as the physical of quantum processes inside In it proposes orchestration, from the dynamics of classical neuronal networks, and other brain structures, these quantum processes. 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( 1) nonadiabatic transition in quantum-classical dynamics, to and of the other it may to model how classical brain structures modulate quantum states in microtubules and related a we to develop models for the of dynamics of and other systems These aim to quantum dynamics, or contribute to the of consciousness.
Frontiers in Human Neuroscience•Sep 5, 2025•1 citation