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Orchestrated objective reduction
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<h2 id="background">Background</h2> <p class="note">Further information: <a href="/facts/Penrose%E2%80%93Lucas_argument/Ap05EwRw">Penrose–Lucas argument</a></p> <p>In 1931, mathematician and logician <a href="/facts/Kurt_G%C3%B6del/P14DqKqK">Kurt Gödel</a> proved that any <a href="/facts/Effective_procedure/4kC9c5hE">effectively generated</a> theory capable of proving basic arithmetic cannot be both <a href="/facts/Consistency/IHkdnA9M">consistent</a> and <a href="/facts/Completeness_(logic)/GzK9zLnu">complete</a>. In other words, a mathematically sound theory lacks the means to prove itself.<a class="footnote-ref" id="fnref:18" href="#fn:18"><sup>18</sup></a> In his first book concerning consciousness, <i><a href="/facts/The_Emperor%27s_New_Mind/eYAE87Yl">The Emperor's New Mind</a></i> (1989), <a href="/facts/Roger_Penrose/r4mlrFUH">Roger Penrose</a> argued that equivalent statements to "Gödel-type propositions" had recently been put forward.<a class="footnote-ref" id="fnref:19" href="#fn:19"><sup>19</sup></a> </p><p>Partially in response to Gödel's argument, the <a href="/facts/Penrose%E2%80%93Lucas_argument/Ap05EwRw">Penrose–Lucas argument</a> leaves the question of the physical basis of non-<a href="/facts/Computable_function/dzwBlLGn">computable</a> behaviour open. Most physical laws are computable, and thus algorithmic. However, Penrose determined that <a href="/facts/Wave_function_collapse/f7KvbBHK">wave function collapse</a> was a prime candidate for a non-computable process. In <a href="/facts/Quantum_mechanics/BRc3Mzgr">quantum mechanics</a>, particles are treated differently from the objects of <a href="/facts/Classical_mechanics/ykG8upsN">classical mechanics</a>. Particles are described by <a href="/facts/Wave_function/KgM5ykjY">wave functions</a> that evolve according to the <a href="/facts/Schr%C3%B6dinger_equation/3csgSIWF">Schrödinger equation</a>. Non-stationary wave functions are <a href="/facts/Linear_combination/CVjL6kuN">linear combinations</a> of the <a href="/facts/Eigenstate/7jbxd7Dx">eigenstates</a> of the system, a phenomenon described by the <a href="/facts/Superposition_principle/GKGs9C92">superposition principle</a>. When a quantum system interacts with a classical system—i.e. when an <a href="/facts/Observable/fcBAsBjm">observable</a> is measured—the system appears to <a href="/facts/Wave_function_collapse/f7KvbBHK">collapse</a> to a random eigenstate of that observable from a classical vantage point. </p><p>If collapse is truly random, then no process or algorithm can deterministically predict its outcome. This provided Penrose with a candidate for the physical basis of the non-computable process that he hypothesized to exist in the brain. However, he disliked the random nature of environmentally induced collapse, as randomness was not a promising basis for mathematical understanding. Penrose proposed that isolated systems may still undergo a new form of wave function collapse, which he called objective reduction (OR).<a class="footnote-ref" id="fnref:20" href="#fn:20"><sup>20</sup></a> </p><p>Penrose sought to reconcile <a href="/facts/General_relativity/jVsoIg8X">general relativity</a> and quantum theory using his own ideas about the possible structure of <a href="/facts/Spacetime/uRIN1x4b">spacetime</a>.<a class="footnote-ref" id="fnref:21" href="#fn:21"><sup>21</sup></a><a class="footnote-ref" id="fnref:22" href="#fn:22"><sup>22</sup></a> He suggested that at the <a href="/facts/Planck_scale/xDU6KlDM">Planck scale</a> curved spacetime is not continuous, but discrete. He further postulated that each separated <a href="/facts/Quantum_superposition/4z1UJg9o">quantum superposition</a> has its own piece of <a href="/facts/Spacetime_curvature/jVsoIg8X">spacetime curvature</a>, a blister in spacetime. Penrose suggests that gravity exerts a force on these spacetime blisters, which become unstable above the Planck scale of 10 − 35 m {\displaystyle 10^{-35}{\text{m}}} and collapse to just one of the possible states. The rough threshold for OR is given by Penrose's indeterminacy principle: </p> τ ≈ ℏ / E G {\displaystyle \tau \approx \hbar /E_{G}} where: <ul><li> τ {\displaystyle \tau } is the time until OR occurs,</li> <li> E G {\displaystyle E_{G}} is the gravitational self-energy or the degree of spacetime separation given by the superpositioned mass, and</li> <li> ℏ {\displaystyle \hbar } is the <a href="/facts/Reduced_Planck_constant/qGHAe3qq">reduced Planck constant</a>.</li></ul> <p>Thus, the greater the mass–energy of the object, the faster it will undergo OR and vice versa. <a href="/facts/Mesoscopic_physics/QKWer6fG">Mesoscopic</a> objects could collapse on a timescale relevant to neural processing.<a class="footnote-ref" id="fnref:23" href="#fn:23"><sup>23</sup></a>[<i>additional citation(s) needed</i>] </p><p>An essential feature of Penrose's theory is that the choice of states when objective reduction occurs is selected neither randomly (as are choices following wave function collapse) nor algorithmically. Rather, states are selected by a "non-computable" influence embedded in the <a href="/facts/Planck/KKk0698y">Planck</a> scale of spacetime geometry. Penrose claimed that such information is <a href="/facts/Platonism/0mvr2x2p">Platonic</a>, representing pure mathematical truths, which relates to Penrose's ideas concerning the three worlds: the physical, the mental, and the Platonic mathematical world. In <i><a href="/facts/Shadows_of_the_Mind/1XFKGFdD">Shadows of the Mind</a></i> (1994), Penrose briefly indicates that this Platonic world could also include aesthetic and ethical values, but he does not commit to this further hypothesis.<a class="footnote-ref" id="fnref:24" href="#fn:24"><sup>24</sup></a> </p><p>The Penrose–Lucas argument was criticized by mathematicians,<a class="footnote-ref" id="fnref:25" href="#fn:25"><sup>25</sup></a><a class="footnote-ref" id="fnref:26" href="#fn:26"><sup>26</sup></a><a class="footnote-ref" id="fnref:27" href="#fn:27"><sup>27</sup></a> computer scientists,<a class="footnote-ref" id="fnref:28" href="#fn:28"><sup>28</sup></a> and philosophers,<a class="footnote-ref" id="fnref:29" href="#fn:29"><sup>29</sup></a><a class="footnote-ref" id="fnref:30" href="#fn:30"><sup>30</sup></a><a class="footnote-ref" id="fnref:31" href="#fn:31"><sup>31</sup></a><a class="footnote-ref" id="fnref:32" href="#fn:32"><sup>32</sup></a><a class="footnote-ref" id="fnref:33" href="#fn:33"><sup>33</sup></a> and the consensus among experts in these fields is that the argument fails,<a class="footnote-ref" id="fnref:34" href="#fn:34"><sup>34</sup></a><a class="footnote-ref" id="fnref:35" href="#fn:35"><sup>35</sup></a><a class="footnote-ref" id="fnref:36" href="#fn:36"><sup>36</sup></a> with different authors attacking different aspects of the argument.<a class="footnote-ref" id="fnref:37" href="#fn:37"><sup>37</sup></a><a class="footnote-ref" id="fnref:38" href="#fn:38"><sup>38</sup></a> <a href="/facts/Marvin_Minsky/HTU5MYLL">Minsky</a> argued that because humans can believe false ideas to be true, human mathematical understanding need not be consistent and consciousness may easily have a deterministic basis.<a class="footnote-ref" id="fnref:39" href="#fn:39"><sup>39</sup></a> <a href="/facts/Solomon_Feferman/Bt6DRjuk">Feferman</a> argued that mathematicians do not progress by mechanistic search through proofs, but by trial-and-error reasoning, insight and inspiration, and that machines do not share this approach with humans.<a class="footnote-ref" id="fnref:40" href="#fn:40"><sup>40</sup></a> </p> <h2 id="orch-or">Orch OR</h2> <p>Penrose outlined a predecessor to Orch OR in <i>The Emperor's New Mind</i>, coming to the problem from a mathematical viewpoint and in particular Gödel's theorem, but lacked a detailed proposal for how quantum processes could be implemented in the brain. <a href="/facts/Stuart_Hameroff/YX1mr9GP">Stuart Hameroff</a> separately worked in cancer research and <a href="/facts/Anesthesia/b3MKVn8E">anesthesia</a>, which gave him an interest in brain processes. Hameroff read Penrose's book and suggested to him that <a href="/facts/Microtubule/ENL1TxSe">microtubules</a> within neurons were suitable candidate sites for quantum processing, and ultimately for consciousness.<a class="footnote-ref" id="fnref:41" href="#fn:41"><sup>41</sup></a><a class="footnote-ref" id="fnref:42" href="#fn:42"><sup>42</sup></a> Throughout the 1990s, the two collaborated on the Orch OR theory, which Penrose published in <i><a href="/facts/Shadows_of_the_Mind/1XFKGFdD">Shadows of the Mind</a></i> (1994).<a class="footnote-ref" id="fnref:43" href="#fn:43"><sup>43</sup></a> </p><p>Hameroff's contribution to the theory derived from his study of the neural <a href="/facts/Cytoskeleton/1sWlJRX9">cytoskeleton</a>, and particularly on microtubules.<a class="footnote-ref" id="fnref:44" href="#fn:44"><sup>44</sup></a> As neuroscience has progressed, the role of the cytoskeleton and microtubules has assumed greater importance. In addition to providing structural support, microtubule functions include <a href="/facts/Axoplasmic_transport/NVMbGmgk">axoplasmic transport</a> and control of the cell's movement, growth and shape.<a class="footnote-ref" id="fnref:45" href="#fn:45"><sup>45</sup></a> </p><p>Orch OR combines the Penrose–Lucas argument with Hameroff's hypothesis on quantum processing in microtubules. It proposes that when condensates in the brain undergo an objective wave function reduction, their collapse connects noncomputational decision-making to experiences embedded in spacetime's fundamental geometry. The theory further proposes that the microtubules both influence and are influenced by the conventional activity at the synapses between neurons. </p> <h3>Microtubule computation</h3> <p>Hameroff proposed that microtubules were suitable candidates for quantum processing.<a class="footnote-ref" id="fnref:46" href="#fn:46"><sup>46</sup></a> Microtubules are made up of <a href="/facts/Tubulin/j4Bk2wcL">tubulin</a> <a href="/facts/Protein/Jxmagu3E">protein</a> subunits. The tubulin protein <a href="/facts/Dimer_(biochemistry)/c8LwFJPG">dimers</a> of the microtubules have <a href="/facts/Hydrophobic/Ifya0CXQ">hydrophobic</a> pockets that may contain delocalized <a href="/facts/%CE%A0_electron/3Q6LAGYK">π electrons</a>. Tubulin has other, smaller non-polar regions, for example 8 <a href="/facts/Tryptophan/JcUxlxAh">tryptophans</a> per tubulin, which contain π electron-rich <a href="/facts/Indole/HT72P6e6">indole</a> rings distributed throughout tubulin with separations of roughly 2 nm. Hameroff claims that this is close enough for the tubulin π electrons to become <a href="/facts/Quantum_entanglement/afzslwN0">quantum entangled</a>.<a class="footnote-ref" id="fnref:47" href="#fn:47"><sup>47</sup></a> During entanglement, particle states become inseparably correlated. </p><p>Hameroff originally suggested in the fringe <i><a href="/facts/Journal_of_Cosmology/BHP22WzN">Journal of Cosmology</a></i> that the tubulin-subunit electrons would form a <a href="/facts/Bose%E2%80%93Einstein_condensate/76peCwfW">Bose–Einstein condensate</a>.<a class="footnote-ref" id="fnref:48" href="#fn:48"><sup>48</sup></a> He then proposed a <a href="/facts/Frohlich_condensate/vvMvUKNU">Frohlich condensate</a>, a hypothetical coherent oscillation of dipolar molecules. However, this too was rejected by Reimers's group.<a class="footnote-ref" id="fnref:49" href="#fn:49"><sup>49</sup></a> Hameroff and Penrose contested the conclusion, considering that Reimers's microtubule model was oversimplified.<a class="footnote-ref" id="fnref:50" href="#fn:50"><sup>50</sup></a> </p><p>Hameroff then proposed that condensates in microtubules in one <a href="/facts/Neuron/G7CyTVdH">neuron</a> can link with microtubule condensates in other neurons and <a href="/facts/Glial_cell/F8BhPmaA">glial cells</a> via the <a href="/facts/Gap_junctions/nhAEWww4">gap junctions</a> of <a href="/facts/Electrical_synapse/3IuCLs3v">electrical synapses</a>.<a class="footnote-ref" id="fnref:51" href="#fn:51"><sup>51</sup></a><a class="footnote-ref" id="fnref:52" href="#fn:52"><sup>52</sup></a> Hameroff proposed that the gap between the cells is sufficiently small that quantum objects can <a href="/facts/Quantum_tunneling/WU4NMrKx">tunnel</a> across it, allowing them to extend across a large area of the brain. He further postulated that the action of this large-scale quantum activity is the source of 40 Hz <a href="/facts/Gamma_wave/1jXxu2HK">gamma waves</a>, building upon the much less controversial theory that gap junctions are related to the gamma oscillation.<a class="footnote-ref" id="fnref:53" href="#fn:53"><sup>53</sup></a> </p> <h3>Related experimental results</h3> <h4>Superradiance</h4> <p>In a study Hameroff was part of, <a href="/facts/Jack_Tuszy%C5%84ski/RDgvP3tq">Jack Tuszyński</a> of the <a href="/facts/University_of_Alberta/08ERvE5c">University of Alberta</a> demonstrated that anesthetics hasten the duration of a process called delayed luminescence, in which microtubules and tubulins re-emit trapped light. Tuszyński suspects that the phenomenon has a quantum origin, with <a href="/facts/Superradiance/p0Mr8vEv">superradiance</a> being investigated as one possibility (in a 2024 study, superradiance was confirmed to occur in networks of <a href="/facts/Tryptophan/JcUxlxAh">tryptophans</a>, which are found in microtubules).<a class="footnote-ref" id="fnref:54" href="#fn:54"><sup>54</sup></a><a class="footnote-ref" id="fnref:55" href="#fn:55"><sup>55</sup></a> Tuszyński told <i>New Scientist</i> that "We're not at the level of interpreting this physiologically, saying 'Yeah, this is where consciousness begins,' but it may."<a class="footnote-ref" id="fnref:56" href="#fn:56"><sup>56</sup></a> </p><p>The 2024 study, called Ultraviolet Superradiance from Mega-Networks of Tryptophan in Biological Architectures and published in <i><a href="/facts/The_Journal_of_Physical_Chemistry/v9He6WJ8">The Journal of Physical Chemistry</a></i>, confirmed superradiance in networks of tryptophans.<a class="footnote-ref" id="fnref:57" href="#fn:57"><sup>57</sup></a><a class="footnote-ref" id="fnref:58" href="#fn:58"><sup>58</sup></a> Large networks of tryptophans are a warm and noisy environment, in which quantum effects typically are not expected to take place.<a class="footnote-ref" id="fnref:59" href="#fn:59"><sup>59</sup></a> The results of the study were theoretically predicted and then experimentally confirmed by the researchers.<a class="footnote-ref" id="fnref:60" href="#fn:60"><sup>60</sup></a><a class="footnote-ref" id="fnref:61" href="#fn:61"><sup>61</sup></a> <a href="/facts/Majed_Chergui/XKjlcuAK">Majed Chergui</a>, who led the experimental team, stated that "It's a beautiful result. It took very precise and careful application of standard protein spectroscopy methods, but guided by the theoretical predictions of our collaborators, we were able to confirm a stunning signature of superradiance in a micron-scale biological system."<a class="footnote-ref" id="fnref:62" href="#fn:62"><sup>62</sup></a> <a href="/facts/Marlan_Scully/qvna0Twq">Marlan Scully</a>, a physicist well-known for his work in the field of theoretical quantum optics, said "We will certainly be examining closely the implications for quantum effects in living systems for years to come."<a class="footnote-ref" id="fnref:63" href="#fn:63"><sup>63</sup></a> The study states that "by analyzing the coupling with the electromagnetic field of mega-networks of tryptophans present in these biologically relevant architectures, we find the emergence of collective quantum optical effects, namely, superradiant and subradiant eigenmodes. ... our work demonstrates that collective and cooperative UV excitations in mega-networks of tryptophans support robust quantum states in protein aggregates, with observed consequences even under thermal equilibrium conditions."<a class="footnote-ref" id="fnref:64" href="#fn:64"><sup>64</sup></a> </p> <h4>Microtubule quantum vibration theory of anesthetic action</h4> <p>In an experiment, <a href="/facts/Gregory_D._Scholes/741WMwII">Gregory D. Scholes</a> and Aarat Kalra of <a href="/facts/Princeton_University/n3EPGHBM">Princeton University</a> used lasers to excite molecules within tubulins, causing a prolonged excitation to diffuse through microtubules farther than expected, which did not occur when repeated under anesthesia.<a class="footnote-ref" id="fnref:65" href="#fn:65"><sup>65</sup></a> However, diffusion results have to be interpreted carefully, since even classical diffusion can be very complex due to the wide range of length scales in the fluid filled extracellular space.<a class="footnote-ref" id="fnref:66" href="#fn:66"><sup>66</sup></a> </p><p>At high concentrations (~5 <a href="/facts/Minimum_alveolar_concentration/7JCn3K0b">MAC</a>) the anesthetic gas <a href="/facts/Halothane/PQ58E6ah">halothane</a> causes reversible depolymerization of microtubules.<a class="footnote-ref" id="fnref:67" href="#fn:67"><sup>67</sup></a> This cannot be the mechanism of anesthetic action, however, because human anesthesia is performed at 1 <a href="/facts/Minimum_alveolar_concentration/7JCn3K0b">MAC</a>. (Neither Penrose or Hameroff claim that depolymerization is the mechanism of action for Orch OR.)<a class="footnote-ref" id="fnref:68" href="#fn:68"><sup>68</sup></a><a class="footnote-ref" id="fnref:69" href="#fn:69"><sup>69</sup></a> At ~1 MAC halothane, reported minor changes in tubulin protein expression (~1.3-fold) in primary cortical neurons after exposure to halothane and isoflurane are not evidence that tubulin directly interacts with general anesthetics, but rather shows that the proteins controlling tubulin production are possible anesthetic targets.<a class="footnote-ref" id="fnref:70" href="#fn:70"><sup>70</sup></a> Further proteomic study reports 0.5 mM [14C]halothane binding to tubulin monomers alongside three dozens of other proteins.<a class="footnote-ref" id="fnref:71" href="#fn:71"><sup>71</sup></a> In addition, modulation of microtubule stability has been reported during anthracene general anesthesia of tadpoles.<a class="footnote-ref" id="fnref:72" href="#fn:72"><sup>72</sup></a> The study called Direct Modulation of Microtubule Stability Contributes to Anthracene General Anesthesia claims to provide "strong evidence that destabilization of neuronal microtubules provides a path to achieving general anesthesia".<a class="footnote-ref" id="fnref:73" href="#fn:73"><sup>73</sup></a> </p><p>A highly disputed theory put forth in the mid-1990s by Hameroff and Penrose posits that consciousness is based on quantum vibrations in tubulin/microtubules inside brain neurons. Computer modeling of tubulin's atomic structure<a class="footnote-ref" id="fnref:74" href="#fn:74"><sup>74</sup></a> found that anesthetic gas molecules bind adjacent to amino acid aromatic rings of non-polar <a href="/facts/Pi_electron/3Q6LAGYK">π-electrons</a> and that collective quantum dipole oscillations among all π-electron resonance rings in each tubulin showed a spectrum with a common mode peak at 613 <a href="/facts/Tera-/qWTDFAI1">T</a><a href="/facts/Hz/6Wshj5qm">Hz</a>.<a class="footnote-ref" id="fnref:75" href="#fn:75"><sup>75</sup></a> Simulated presence of 8 different anesthetic gases abolished the 613 THz peak, whereas the presence of 2 different nonanesthetic gases did not affect the 613 THz peak, from which it was speculated that this 613 THz peak in microtubules could be related to consciousness and anesthetic action.<a class="footnote-ref" id="fnref:76" href="#fn:76"><sup>76</sup></a> </p><p>Another study that Hameroff was a part of claims to show "anesthetic molecules can impair π-resonance energy transfer and exciton hopping in 'quantum channels' of tryptophan rings in tubulin, and thus account for selective action of anesthetics on consciousness and memory".<a class="footnote-ref" id="fnref:77" href="#fn:77"><sup>77</sup></a> </p><p>In a study published in August 2024, an undergraduate group led by a <a href="/facts/Wellesley_College/Vnaa2b3I">Wellesley College</a> professor found that rats given <a href="/facts/Epothilone/xLKGJy9D">epothilone B</a>, a drug that binds to microtubules, took over a minute longer to fall unconscious when exposed to an anesthetic gas.<a class="footnote-ref" id="fnref:78" href="#fn:78"><sup>78</sup></a> </p> <h2 id="criticism">Criticism</h2> <p>Orch OR has been criticized both by physicists<a class="footnote-ref" id="fnref:79" href="#fn:79"><sup>79</sup></a><a class="footnote-ref" id="fnref:80" href="#fn:80"><sup>80</sup></a><a class="footnote-ref" id="fnref:81" href="#fn:81"><sup>81</sup></a><a class="footnote-ref" id="fnref:82" href="#fn:82"><sup>82</sup></a><a class="footnote-ref" id="fnref:83" href="#fn:83"><sup>83</sup></a> and <a href="/facts/Neuroscientist/DvcNRpyM">neuroscientists</a><a class="footnote-ref" id="fnref:84" href="#fn:84"><sup>84</sup></a><a class="footnote-ref" id="fnref:85" href="#fn:85"><sup>85</sup></a><a class="footnote-ref" id="fnref:86" href="#fn:86"><sup>86</sup></a> who consider it to be a poor model of brain <a href="/facts/Physiology/fh25y2pQ">physiology</a>. Orch OR has also been criticized for lacking <a href="/facts/Explanatory_power/fV2TfhPo">explanatory power</a>; the philosopher <a href="/facts/Patricia_Churchland/1LQEtwpB">Patricia Churchland</a> wrote, "Pixie dust in the synapses is about as explanatorily powerful as quantum coherence in the microtubules."<a class="footnote-ref" id="fnref:87" href="#fn:87"><sup>87</sup></a> </p><p><a href="/facts/David_Chalmers/poKbqEWc">David Chalmers</a> argues against quantum consciousness. He instead discusses how quantum mechanics may relate to <a href="/facts/Mind%E2%80%93body_dualism/IbrW6R7C">dualistic consciousness</a>.<a class="footnote-ref" id="fnref:88" href="#fn:88"><sup>88</sup></a> Chalmers is skeptical that any new physics can resolve the <a href="/facts/Hard_problem_of_consciousness/Um6k4wz6">hard problem of consciousness</a>.<a class="footnote-ref" id="fnref:89" href="#fn:89"><sup>89</sup></a><a class="footnote-ref" id="fnref:90" href="#fn:90"><sup>90</sup></a><a class="footnote-ref" id="fnref:91" href="#fn:91"><sup>91</sup></a> He argues that quantum theories of consciousness suffer from the same weakness as more conventional theories. Just as he argues that there is no particular reason why particular macroscopic physical features in the brain should give rise to consciousness, he also thinks that there is no particular reason why a particular quantum feature, such as the EM field in the brain, should give rise to consciousness either.<a class="footnote-ref" id="fnref:92" href="#fn:92"><sup>92</sup></a> </p> <h3>Decoherence in living organisms</h3> <p>In 2000 <a href="/facts/Max_Tegmark/4Y3DefCk">Max Tegmark</a> claimed that any quantum coherent system in the brain would undergo effective <a href="/facts/Wave_function_collapse/f7KvbBHK">wave function collapse</a> due to environmental interaction long before it could influence neural processes (the "warm, wet and noisy" argument, as it later came to be known).<a class="footnote-ref" id="fnref:93" href="#fn:93"><sup>93</sup></a> He determined the decoherence timescale of microtubule entanglement at brain temperatures to be on the order of <a href="/facts/Femtosecond/vaVXTVyR">femtoseconds</a>, far too brief for neural processing. <a href="/facts/Christof_Koch/XvABx1QX">Christof Koch</a> and <a href="/facts/Klaus_Hepp/PStuo6Xm">Klaus Hepp</a> also agreed that <a href="/facts/Coherence_(physics)/NF1Rgdoa">quantum coherence</a> does not play, or does not need to play any major role in <a href="/facts/Neurophysiology/XLkEyW8c">neurophysiology</a>.<a class="footnote-ref" id="fnref:94" href="#fn:94"><sup>94</sup></a><a class="footnote-ref" id="fnref:95" href="#fn:95"><sup>95</sup></a> Koch and Hepp concluded that "The empirical demonstration of slowly decoherent and controllable quantum bits in neurons connected by electrical or chemical synapses, or the discovery of an efficient quantum algorithm for computations performed by the brain, would do much to bring these speculations from the 'far-out' to the mere 'very unlikely'."<a class="footnote-ref" id="fnref:96" href="#fn:96"><sup>96</sup></a> </p><p>In response to Tegmark's claims, Hagan, Tuszynski and Hameroff claimed that Tegmark did not address the Orch OR model, but instead a model of his own construction. This involved superpositions of quanta separated by 24 nm rather than the much smaller separations stipulated for Orch OR. As a result, Hameroff's group claimed a decoherence time seven orders of magnitude greater than Tegmark's, although still far below 25 ms. Hameroff's group also suggested that the <a href="/facts/Debye_force/xIcFMvL7">Debye</a> layer of <a href="/facts/Counterion/RNwGeM3l">counterions</a> could screen thermal fluctuations, and that the surrounding <a href="/facts/Actin/Hu3qIUL9">actin</a> <a href="/facts/Gel/gBFE0s9G">gel</a> might enhance the ordering of water, further screening noise. They also suggested that incoherent metabolic energy could further order water, and finally that the configuration of the microtubule lattice might be suitable for <a href="/facts/Quantum_error_correction/lrUNMuob">quantum error correction</a>, a means of resisting quantum decoherence.<a class="footnote-ref" id="fnref:97" href="#fn:97"><sup>97</sup></a><a class="footnote-ref" id="fnref:98" href="#fn:98"><sup>98</sup></a> </p><p>In 2009, Reimers <i>et al.</i> and McKemmish <i>et al.,</i> published critical assessments. Earlier versions of the theory had required tubulin-electrons to form either <a href="/facts/Bose%E2%80%93Einstein_condensate/76peCwfW">Bose–Einsteins</a> or <a href="/facts/Herbert_Fr%C3%B6hlich/vvMvUKNU">Frohlich</a> condensates, and the Reimers group noted the lack of empirical evidence that such could occur. Additionally they calculated that microtubules could only support weak 8 MHz coherence. McKemmish <i>et al.</i> argued that <a href="/facts/Aromaticity/wK0DzRY6">aromatic molecules</a> cannot switch states because they are delocalised; and that changes in tubulin protein-conformation driven by <a href="/facts/Guanosine_triphosphate/NAwoHjTW">GTP</a> conversion would result in a prohibitive energy requirement.<a class="footnote-ref" id="fnref:99" href="#fn:99"><sup>99</sup></a><a class="footnote-ref" id="fnref:100" href="#fn:100"><sup>100</sup></a><a class="footnote-ref" id="fnref:101" href="#fn:101"><sup>101</sup></a> </p><p>In 2022, a group of Italian physicists conducted several experiments that failed to provide evidence in support of a gravity-related quantum collapse model of consciousness, weakening the possibility of a quantum explanation for consciousness.<a class="footnote-ref" id="fnref:102" href="#fn:102"><sup>102</sup></a><a class="footnote-ref" id="fnref:103" href="#fn:103"><sup>103</sup></a> </p> <h3>Neuroscience</h3> <p class="note">Further information: <a href="/facts/Neuroscience/o5RV8Cas">Neuroscience</a></p> <p>Biology-based criticisms have been offered, including a lack of explanation for the probabilistic release of <a href="/facts/Neurotransmitter/LlpYFSU3">neurotransmitter</a> from presynaptic <a href="/facts/Axon_terminal/QhUJg8SH">axon terminals</a><a class="footnote-ref" id="fnref:104" href="#fn:104"><sup>104</sup></a><a class="footnote-ref" id="fnref:105" href="#fn:105"><sup>105</sup></a><a class="footnote-ref" id="fnref:106" href="#fn:106"><sup>106</sup></a> and an error in the calculated number of the tubulin dimers per cortical neuron.<a class="footnote-ref" id="fnref:107" href="#fn:107"><sup>107</sup></a> </p><p>In 2014, Penrose and Hameroff published responses to some criticisms and revisions to many of the theory's peripheral assumptions, while retaining the core hypothesis.<a class="footnote-ref" id="fnref:108" href="#fn:108"><sup>108</sup></a><a class="footnote-ref" id="fnref:109" href="#fn:109"><sup>109</sup></a> </p> <h2 id="see-also">See also</h2> <ul><li><a href="/facts/Copenhagen_interpretation/DvMFrYJa">Copenhagen interpretation</a></li> <li><a href="/facts/Electromagnetic_theories_of_consciousness/IP4fltKV">Electromagnetic theories of consciousness</a></li> <li><a href="/facts/Holonomic_brain_theory/b3nPqRLV">Holonomic brain theory</a></li> <li><a href="/facts/Many-minds_interpretation/3ynRS4RQ">Many-minds interpretation</a></li> <li><a href="/facts/Penrose_interpretation_of_Quantum_Theory/aeA9zPqP">Penrose interpretation</a></li> <li><a href="/facts/Quantum_Aspects_of_Life/WLMwC8Lv"><i>Quantum Aspects of Life</i> (book)</a></li> <li><a href="/facts/Quantum_mind/C5SWprNI">Quantum mind</a></li> <li><a href="/facts/Quantum_cognition/FpKj2QY6">Quantum cognition</a></li></ul> <h2 id="sources">Sources</h2> <ul><li><a href="/facts/Douglas_Hofstadter/LxUaf01J">Hofstadter, Douglas</a> (1979), <a href="/facts/G%C3%B6del,_Escher,_Bach/5VCxjXvk"><i>Gödel, Escher, Bach: an Eternal Golden Braid</i></a></li> <li><a href="/facts/Stuart_J._Russell/f6EbRvSV">Russell, Stuart J.</a>; <a href="/facts/Peter_Norvig/GkCUHH4H">Norvig, Peter</a> (2003), <a href="http://aima.cs.berkeley.edu/"><i>Artificial Intelligence: A Modern Approach</i></a> (2nd ed.), Upper Saddle River, New Jersey: Prentice Hall, <a href="/facts/ISBN_(identifier)/15AdSPa9">ISBN</a> 0-13-790395-2</li> <li><a href="/facts/Alan_Turing/klov9b6g">Turing, Alan</a> (October 1950). <a href="https://academic.oup.com/mind/article/LIX/236/433/986238">"Computing Machinery and Intelligence"</a>. <i><a href="/facts/Mind_(journal)/GAjKJqwo">Mind</a></i>. 59 (236): 433–460. <a href="/facts/Doi_(identifier)/muM9Etpq">doi</a>:<a href="https://doi.org/10.1093%2Fmind%2FLIX.236.433">10.1093/mind/LIX.236.433</a>. <a href="/facts/ISSN_(identifier)/DPAflDvU">ISSN</a> <a href="https://search.worldcat.org/issn/1460-2113">1460-2113</a>. <a href="/facts/JSTOR_(identifier)/YTeVmaJ7">JSTOR</a> <a href="https://www.jstor.org/stable/2251299">2251299</a>. <a href="/facts/S2CID_(identifier)/ldJsHa2Y">S2CID</a> <a href="https://api.semanticscholar.org/CorpusID:14636783">14636783</a>.</li></ul> <h2 id="external-links">External links</h2> <ul><li><a href="http://consciousness.arizona.edu/">Center for Consciousness Studies</a></li> <li><a href="http://www.quantumconsciousness.org/">Hameroff's "Quantum Consciousness" site</a></li> <li>Hameroff, Stuart; Bandyopadhyay, Anirban; <a href="/facts/Dante_Lauretta/C2k8VNNJ">Lauretta, Dante</a> (8 May 2024). <a href="https://iai.tv/articles/life-and-consciousness-what-are-they-auid-2836">"Consciousness came before life"</a>. <i><a href="/facts/Institute_of_Art_and_Ideas/blMsgIDw">Institute of Art and Ideas</a></i>.</li> <li><a href="https://web.archive.org/web/20160514103339/http://online.kitp.ucsb.edu/plecture/penrose/">Penrose, Roger (1999). "Science and the Mind". Kavli Institute for Theoretical Physics Public Lectures.</a></li></ul> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>Hameroff, Stuart (2012). "How quantum brain biology can rescue conscious free will". Frontiers in Integrative Neuroscience. 6: 93. doi:10.3389/fnint.2012.00093. PMC 3470100. PMID 23091452. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3470100" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3470100</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>Hameroff, Stuart; Penrose, Roger (2014). "Reply to seven commentaries on "Consciousness in the universe: Review of the 'Orch OR' theory"". Physics of Life Reviews. 11 (1): 94–100. Bibcode:2014PhLRv..11...94H. doi:10.1016/j.plrev.2013.11.013. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>Penrose, Roger (2014). "On the Gravitization of Quantum Mechanics 1: Quantum State Reduction". Foundations of Physics. 44 (5): 557–575. Bibcode:2014FoPh...44..557P. doi:10.1007/s10701-013-9770-0. S2CID 123379100. <a href="https://doi.org/10.1007%2Fs10701-013-9770-0" target="_blank">https://doi.org/10.1007%2Fs10701-013-9770-0</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> <li id="fn:4"><p>McCulloch, Warren S.; Pitts, Walter (1943). "A logical calculus of the ideas immanent in nervous activity". Bulletin of Mathematical Biophysics. 5 (4): 115–133. doi:10.1007/bf02478259. <a href="/wiki/Warren_Sturgis_McCulloch" target="_blank">/wiki/Warren_Sturgis_McCulloch</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li> <li id="fn:5"><p>Hodgkin, Alan L.; Huxley, Andrew F. (1952). "A quantitative description of membrane current and its application to conduction and excitation in nerve". Journal of Physiology. 117 (4): 500–544. doi:10.1113/jphysiol.1952.sp004764. PMC 1392413. 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S2CID 5085015. <a href="https://doi.org/10.1038%2F440611a" target="_blank">https://doi.org/10.1038%2F440611a</a> <a href="#fnref:16" class="footnote-back-ref">↩</a></p></li> <li id="fn:17"><p>Hepp, K. (September 2012). "Coherence and decoherence in the brain". Journal of Mathematical Physics. 53 (9): 095222. Bibcode:2012JMP....53i5222H. doi:10.1063/1.4752474. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:17" class="footnote-back-ref">↩</a></p></li> <li id="fn:18"><p>Hofstadter 1979, pp. 476–477, Russell & Norvig 2003, p. 950, Turing 1950 under "The Argument from Mathematics" where he writes "although it is established that there are limitations to the powers of any particular machine, it has only been stated, without sort of proof, that no such limitations apply to the human intellect." - Hofstadter, Douglas (1979), Gödel, Escher, Bach: an Eternal Golden Braid <a href="#fnref:18" class="footnote-back-ref">↩</a></p></li> <li id="fn:19"><p>Penrose, Roger (1989). The Emperor's New Mind: Concerning Computers, Minds and The Laws of Physics. Oxford University Press. pp. 108–109. ISBN 978-0-19-851973-7. <a href="978-0-19-851973-7" target="_blank">978-0-19-851973-7</a> <a href="#fnref:19" class="footnote-back-ref">↩</a></p></li> <li id="fn:20"><p>Hameroff, Stuart; Penrose, Roger (2014). "Consciousness in the universe". Physics of Life Reviews. 11 (1): 39–78. Bibcode:2014PhLRv..11...39H. doi:10.1016/j.plrev.2013.08.002. PMID 24070914. <a href="https://doi.org/10.1016%2Fj.plrev.2013.08.002" target="_blank">https://doi.org/10.1016%2Fj.plrev.2013.08.002</a> <a href="#fnref:20" class="footnote-back-ref">↩</a></p></li> <li id="fn:21"><p>Penrose, Roger (1989). The Emperor's New Mind: Concerning Computers, Minds and The Laws of Physics. Oxford University Press. pp. 108–109. ISBN 978-0-19-851973-7. <a href="978-0-19-851973-7" target="_blank">978-0-19-851973-7</a> <a href="#fnref:21" class="footnote-back-ref">↩</a></p></li> <li id="fn:22"><p>Penrose, Roger (1989). Shadows of the Mind: A Search for the Missing Science of Consciousness. Oxford University Press. pp. 416–7, 457. ISBN 978-0-19-853978-0. <a href="978-0-19-853978-0" target="_blank">978-0-19-853978-0</a> <a href="#fnref:22" class="footnote-back-ref">↩</a></p></li> <li id="fn:23"><p>Hameroff, Stuart; Penrose, Roger (2014). "Consciousness in the universe". Physics of Life Reviews. 11 (1): 39–78. Bibcode:2014PhLRv..11...39H. doi:10.1016/j.plrev.2013.08.002. PMID 24070914. <a href="https://doi.org/10.1016%2Fj.plrev.2013.08.002" target="_blank">https://doi.org/10.1016%2Fj.plrev.2013.08.002</a> <a href="#fnref:23" class="footnote-back-ref">↩</a></p></li> <li id="fn:24"><p>Penrose, Roger (1989). Shadows of the Mind: A Search for the Missing Science of Consciousness. Oxford University Press. pp. 416–7, 457. ISBN 978-0-19-853978-0. <a href="978-0-19-853978-0" target="_blank">978-0-19-853978-0</a> <a href="#fnref:24" class="footnote-back-ref">↩</a></p></li> <li id="fn:25"><p>LaForte, Geoffrey, Patrick J. Hayes, and Kenneth M. Ford 1998.Why Gödel's Theorem Cannot Refute Computationalism. Artificial Intelligence, 104:265–286. <a href="https://web.archive.org/web/20060901233518/http://www.cs.uwf.edu/~glaforte/papers/whyGodel.ps" target="_blank">https://web.archive.org/web/20060901233518/http://www.cs.uwf.edu/~glaforte/papers/whyGodel.ps</a> <a href="#fnref:25" class="footnote-back-ref">↩</a></p></li> <li id="fn:26"><p>Feferman, Solomon (1996). "Penrose's Gödelian argument". Psyche. 2: 21–32. CiteSeerX 10.1.1.130.7027. <a href="/wiki/Solomon_Feferman" target="_blank">/wiki/Solomon_Feferman</a> <a href="#fnref:26" class="footnote-back-ref">↩</a></p></li> <li id="fn:27"><p>Krajewski, Stanisław (2007). "On Gödel's Theorem and Mechanism: Inconsistency or Unsoundness is Unavoidable in any Attempt to 'Out-Gö del' the Mechanist". Fundamenta Informaticae. 81 (1–3): 173–181. <a href="https://content.iospress.com/articles/fundamenta-informaticae/fi81-1-3-11" target="_blank">https://content.iospress.com/articles/fundamenta-informaticae/fi81-1-3-11</a> <a href="#fnref:27" class="footnote-back-ref">↩</a></p></li> <li id="fn:28"><p>Putnam, Hilary (1 July 1995). "Book Review: Shadows of the mind". Bulletin of the American Mathematical Society. 32 (3): 370–374. doi:10.1090/S0273-0979-1995-00606-3. <a href="https://doi.org/10.1090%2FS0273-0979-1995-00606-3" target="_blank">https://doi.org/10.1090%2FS0273-0979-1995-00606-3</a> <a href="#fnref:28" class="footnote-back-ref">↩</a></p></li> <li id="fn:29"><p>"MindPapers: 6.1b. Godelian arguments". Consc.net. Retrieved 28 July 2014. <a href="http://consc.net/mindpapers/6.1b" target="_blank">http://consc.net/mindpapers/6.1b</a> <a href="#fnref:29" class="footnote-back-ref">↩</a></p></li> <li id="fn:30"><p>"References for Criticisms of the Gödelian Argument". Users.ox.ac.uk. 10 July 1999. Retrieved 28 July 2014. <a href="http://users.ox.ac.uk/~jrlucas/Godel/referenc.html" target="_blank">http://users.ox.ac.uk/~jrlucas/Godel/referenc.html</a> <a href="#fnref:30" class="footnote-back-ref">↩</a></p></li> <li id="fn:31"><p>Boolos, George; et al. (1990). "An Open Peer Commentary on The Emperor's New Mind". Behavioral and Brain Sciences. 13 (4): 655. doi:10.1017/s0140525x00080687. S2CID 144905437. <a href="/wiki/George_Boolos" target="_blank">/wiki/George_Boolos</a> <a href="#fnref:31" class="footnote-back-ref">↩</a></p></li> <li id="fn:32"><p>Davis, Martin (September 1993). "How subtle is Gödel's theorem? More on Roger Penrose". Behavioral and Brain Sciences. 16 (3): 611–612. doi:10.1017/S0140525X00031915. S2CID 144018337. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:32" class="footnote-back-ref">↩</a></p></li> <li id="fn:33"><p>Lewis, David (July 1969). "Lucas against Mechanism". Philosophy. 44 (169): 231–233. doi:10.1017/s0031819100024591. S2CID 170411423. <a href="https://doi.org/10.1017%2Fs0031819100024591" target="_blank">https://doi.org/10.1017%2Fs0031819100024591</a> <a href="#fnref:33" class="footnote-back-ref">↩</a></p></li> <li id="fn:34"><p>Bringsjord, Selmer; Xiao, Hong (July 2000). "A refutation of Penrose's Gödelian case against artificial intelligence" (PDF). Journal of Experimental & Theoretical Artificial Intelligence. 12 (3): 307–329. doi:10.1080/09528130050111455. S2CID 5540500. <a href="http://cogprints.org/553/3/pen.sel8.pdf" target="_blank">http://cogprints.org/553/3/pen.sel8.pdf</a> <a href="#fnref:34" class="footnote-back-ref">↩</a></p></li> <li id="fn:35"><p>In an article at "King's College London - Department of Mathematics". Archived from the original on 25 January 2001. Retrieved 22 October 2010. L.J. Landau at the Mathematics Department of King's College London writes that "Penrose's argument, its basis and implications, is rejected by experts in the fields which it touches." <a href="https://web.archive.org/web/20010125011300/http://www.mth.kcl.ac.uk/~llandau/Homepage/Math/penrose.html" target="_blank">https://web.archive.org/web/20010125011300/http://www.mth.kcl.ac.uk/~llandau/Homepage/Math/penrose.html</a> <a href="#fnref:35" class="footnote-back-ref">↩</a></p></li> <li id="fn:36"><p>Princeton Philosophy professor John Burgess writes in On the Outside Looking In: A Caution about Conservativeness (published in Kurt Gödel: Essays for his Centennial, with the following comments found on pp. 131–132) that "the consensus view of logicians today seems to be that the Lucas–Penrose argument is fallacious, though as I have said elsewhere, there is at least this much to be said for Lucas and Penrose, that logicians are not unanimously agreed as to where precisely the fallacy in their argument lies. There are at least three points at which the argument may be attacked." <a href="http://www.princeton.edu/~jburgess/Montreal.doc" target="_blank">http://www.princeton.edu/~jburgess/Montreal.doc</a> <a href="#fnref:36" class="footnote-back-ref">↩</a></p></li> <li id="fn:37"><p>Princeton Philosophy professor John Burgess writes in On the Outside Looking In: A Caution about Conservativeness (published in Kurt Gödel: Essays for his Centennial, with the following comments found on pp. 131–132) that "the consensus view of logicians today seems to be that the Lucas–Penrose argument is fallacious, though as I have said elsewhere, there is at least this much to be said for Lucas and Penrose, that logicians are not unanimously agreed as to where precisely the fallacy in their argument lies. 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