News concerning Artificial Intelligence (AI) abounds again. The progress with Deep Learning techniques are quite remarkable with such demonstrations of self-driving cars, Watson on Jeopardy, and beating human Go players. This rate of progress has led some notable scientists and business people to warn about the potential dangers of AI as it approaches a human level. Exascale computers are being considered that would approach what many believe is this level.
However, there are many questions yet unanswered on how the human brain works, and specifically the hard problem of consciousness with its integrated subjective experiences. In addition, there are many questions concerning the smaller cellular scale, such as why some single-celled organisms can navigate out of mazes, remember, and learn without any neurons.
In this blog, I look at a recent review that suggests brain computations being done at a scale finer than the neuron might mean we are far from the computational, power both quantitatively and qualitatively. The review is by Roger Penrose (Oxford) and Stuart Hameroff (University of Arizona) on their journey through almost three decades of investigating the role of potential quantum aspects in neurons’ microtubules. As a graduate student in 1989, I was intrigued when Penrose, a well-known mathematical physicist, published the book, “The Emperor’s New Mind”, outlining a hypothesis that consciousness derived from quantum physics effects during the transition from a superposition and entanglement of quantum states into a more classical configuration (the collapse or reduction of the wavefunction). He further suggested that this process, which has baffled generations of scientists, might occur only when a condition, based on the differences of gravitational energies of the possible outcomes, is met (i.e., Objective Reduction or OR). He then went another step in suggesting that the brain takes advantage of the this process to perform computations in parallel, with some intrinsic indeterminacy (non-computability), and over a larger integrated range by maintaining the quantum mix of microtubule configurations separated from the noisy warm environment until this reduction condition was met (i.e., Orchestrated Objective Reduction or Orch OR).
As an anesthesiologist, Stuart Hameroff questioned how relatively simple molecules could cause unconsciousness. He explored the potential classical computational power of microtubules. The microtubules had been recognized as an important component of neurons, especially in the post synaptic dendrites and cell body, where the cylinders lined up parallel to the dendrite, stabilized, and formed connecting bridges between cylinders (MAPs). Not only are there connections between microtubules within dendrites but there are also interneuron junctions allowing cellular material to tunnel between neuron cells. One estimate of the potential computing power of a neuron’s microtubules (a billion binary state microtubule building blocks , tubulins, operating at 10 megahertz) is the equivalent computing power of the assumed neuron net of the brain (100 billion neurons each with 1000 synapses operating at about 100 Hz). That is, the brain’s computing power might be the square of the standard estimate (10 “petaflops”) based on relatively simple neuron responses.
Soon after this beginning, Stuart Hameroff and Roger Penrose, found each other’s complementary approach and started forming a more detailed set of hypotheses. Much criticism was leveled about this view. Their responses included modifying the theory, calling for more experimental work, and defending against general attacks. Many experiments await to be done, including whether objective reduction occurs but this experiment cannot be done yet with the current resolution of laboratory instruments. Other experiments on electronic properties of microtubules were done in Japan in 2009 which discovered high conductance at certain frequencies from kilohertz to gigahertz frequencies. These measurements, which also show conductance increasing with microtubule length, are consistent with conduction pathways through aligned aromatic rings in the helical and linear patterns of the microtubule. Other indications of quantum phenomena in biology include the recent discoveries quantum effects in photosynthesis, bird navigation, and protein folding
There are many subtopics to explore. Often the review discusses potential options without committing (or claiming) a specific resolution. These subtopics include interaction of microtubule with associated protein and transport mechanisms, the relationship of microtubules to diseases such as Alzheimer’s, the frequency of the collapse from the range of megahertz to hertz, memory formation and processing with molecules that bind to microtubules, the temporal aspect of brain activity and conscious decisions, whether the quantum states are spin (electron or nuclear) or electrical dipoles, the helical pattern of the microtubule (A or B), the fraction of microtubules involved with entanglement, the mechanism for environmental isolation, and the way that such a process might be advantageous in evolution. The review ends not with a conclusion concerning the validity of the hypothesis but instead lays a roadmap for the further tests that could rule out or support their hypothesis.
As I stated at the beginning, the progress in AI has been remarkable. However, the understanding of the brain is still very limited and the mainstream expectation that computers are getting close to equaling computing potential may be far off both qualitatively and quantitatively. While in the end it is unclear how much of this hypothesis will survive the test of experiments, it is very interesting to consider and follow the argumentative scientific process.
Stuart Hameroff’s Web Site: http://www.quantumconsciousness.org/
Review Paper site: http://smc-quantum-physics.com/pdf/PenroseConsciouness.pdf