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
