Stuart Hameroff—Microtubules, Quantum Mechanics, and Consciousness

Stuart Hameroff, as an anæsthesiologist, brings a different spin to the study of consciousness than many of the people investigating that somewhat woolly topic. He says, “I’m in the business of turning consciousness off and on again, which makes me curious about the mechanisms involved.” Why do so many simple chemicals, including the “noble gas” xenon, switch human consciousness off and on without major effects upon the functioning of the other aspects of the brain and body?

He suspects the site of consciousness is the microtubules in the brain’s neurons, where he believes quantum effects allow consciousness to transcend “mere computation” and, with Nobel Prize winning physicist Roger Penrose, has developed a theory for how quantum effects could be manifest in a system as “warm and wet” as the brain. If this theory is correct, computer-simulation of neurons as simple switches and emulation of neural networks by deterministic computers will never achieve consciousness., and the complexity of the biological brain may be many orders of magnitude greater than these simple models suggest.


Ham(m)eroff is a great name for an anesthesiologist! Patients used to ask about the hammer we use to “knock them out “. I would tell them it was velvet. Another good name for an anesthesiologist was one of my former chairmen- Dr. Torpey, sadly gone from us for several years now. He was a gentleman.


My variation on the Hameroff-Penrose theory is described in Section 7 of Paavo Pylkkänen, Is the Brain Analogous to a Quantum Measuring Apparatus? - PhilPapers


Experiencing “precognition” predisposes suspicion that the arrow of time, while strongly biased from the past to the future, is not unidirectional. Such experiences are quite weird but whether they require “quantum” weirdness or not is another question. Classical mechanics are time symmetric as well – which my late colleague, Tom Etter allows as one interpretation of psychic phenomena. Since Tom arrived with Ray Solomonoff early at the 1956 Dartmouth Summer, and Solomonoff’s scientific induction proof was based on unidirectional time (ie: forward time only computation as classical Turing machine) I suspect they had some “woolly” conversations about the nature of “consciousness” leading up to that seminal artificial intelligence conference.

PS: My defense of Solomonoff’s perspective as the revolution in the natural sciences we must come to terms with to get past the threat of a rhyme with The Thirty Years War is not to disparage Tom’s alternate revolution. These men were both seminal thinkers in their own right. But Solomonoff’s revolution is something I’ve taken up because the machinery of state denies human agency at the individual level by centralizing sovereignty in the Federal government (or even global government). The pretense that all is “determined”, which is increasingly adopted by the wealthy and powerful, must be addressed on its own terms so long as discourse with it obtains.

PPS: Shortly after Marcus Hutter took up my 2005 suggestion for a prize to compress Wikpedia as the path forward in langauge modeling, Solomonoff came out with a very strange blog post that I’ve not been able to locate in the archives, basically saying that the choice of Turing machine permitted by his theory of induction was a feature, not a bug. Hutter disagreed and called the notion that one can gut objectivity by the simple expedient of positing a Turing machine that included a data-determined instruction to output the observations being modeled was a “philosophical nuisance”. Recently, it appears that someone managed to send John Carmack, and his new AGI company, off the rails by convincing him that Solomonoff’s late-in-life brain fart was actually Hutter denying his own model of AGI. Sheesh.


This is consistent with the view that the observed arrow of time is a phenomenon of statistical mechanics which we observe because the universe started in a state of extraordinarily low entropy. If the universe started in a state of equilibrium, there would be no observable change in the macrostate and thus no apparent arrow of time.

This, in turn, suggests that violations of causality may be, like local violations of the second law of thermodynamics, extremely improbable but not forbidden by the (time-symmetric) laws of physics. Further, the smaller the system, the more likely such a violation will be observed, just as in a box with only ten gas molecules in it, observing them all on one side of the box at once isn’t at all improbable.


Dr Hameroff suspects that loss of coherence in neural microtubules (MT) may be implicated in Alzheimer’s disease. He recommends:


Here is a paper on “Transcranial Pulse Stimulation with Ultrasound in Alzheimer’s Disease—A New Navigated Focal Brain Therapy” (full text at link). This is the abstract.

Ultrasound-based brain stimulation techniques may become a powerful new technique to modulate the human brain in a focal and targeted manner. However, for clinical brain stimulation no certified systems exist and the current techniques have to be further developed. Here, a clinical sonication technique is introduced, based on single ultrashort ultrasound pulses (transcranial pulse stimulation, TPS) which markedly differs from existing focused ultrasound techniques. In addition, a first clinical study using ultrasound brain stimulation and first observations of long term effects are presented. Comprehensive feasibility, safety, and efficacy data are provided. They consist of simulation data, laboratory measurements with rat and human skulls and brains, in vivo modulations of somatosensory evoked potentials (SEP) in healthy subjects (sham controlled) and clinical pilot data in 35 patients with Alzheimer’s disease acquired in a multicenter setting (including neuropsychological scores and functional magnetic resonance imaging (fMRI)). Preclinical results show large safety margins and dose dependent neuromodulation. Patient investigations reveal high treatment tolerability and no major side effects. Neuropsychological scores improve significantly after TPS treatment and improvement lasts up to three months and correlates with an upregulation of the memory network (fMRI data). The results encourage broad neuroscientific application and translation of the method to clinical therapy and randomized sham-controlled clinical studies.

Here is a more recent paper, “Transcranial ultrasound pulse stimulation reduces cortical atrophy in Alzheimer’s patients: A follow‐up study” (full text at link). Abstract:


Ultrasound for the brain is a revolutionary therapeutic concept. The first clinical data indicate that 2–4 weeks of therapy with transcranial pulse stimulation (TPS) improve functional networks and cognitive performance of Alzheimer’s disease (AD) patients for up to 3 months. No data currently exist on possible benefits concerning brain morphology, namely the cortical atrophy characteristic of AD.


We performed a pre‐/post‐therapy analysis of cortical thickness in a group of N = 17 AD patients.


We found a significant correlation between neuropsychological improvement and cortical thickness increase in AD‐critical brain areas.


AD patients who benefit from TPS appear to manifest reduced cortical atrophy within the default mode network in particular, whose memory‐related subsystems are believed to be disrupted in AD. TPS may therefore hold promise as a new add‐on therapy for AD.

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