Book Review

Information Theory and Quantum Physics
Physical Foundations for Understanding the Conscious Process

H.S. Green
Springer Verlag, 2000, 244 pp


The prediction of quantum theory that a conscious observer is required to collapse the wave equation of a coherent system and produce a unique outcome, has led many physicists to speculate about the role of quantum phenomena in consciousness. Penrose, for example, proposed in Shadows of the Mind that microtubules were somehow capable of acting as quantum transducers that could detect quantum fields and produce consciousness and indeterminate behavior in the brain. In Information Theory and Quantum Physics , H.S. Green follows the same line of reasoning and concludes that, not microtubules, but ion channels, are the seat of consciousness.

The exposition in this book is far more technical than Penrose's book. In simplest terms, Green's theory is that qubits, which are the quantum mechanical analogue of ordinary bits used in information theory, represent information about which a conscious being is aware, and the difference in information content between qubits and ordinary bits indicates consciousness.

The first seven chapters are devoted to a summary of results from almost every branch of mathematical physics, from relativity and gravitational field equations, the Bohr atom, string theory, and quantum electrodynamics, to the Debye-Huckel equation and the theory of electrolytes. These results are presented at a moderately high level, with little preparation for the reader, and this makes the book tough reading for anyone not thoroughly acquainted with modern physics.

Many of the topics, such as gravitation, gauge groups, space-time curvature, and Lorentz transformations, have little relevance to any theory of consciousness, but relate the qubit results to other branches of physics. The actual theory of consciousness, in chapter 8, is fairly brief, and is preceded by a description of Purkinje cell and pyramidal cell electrophysiology and neuroanatomy. The author's goal in this chapter is to express cellular membrane electrical potential in terms of qubits, and he relates this in a roundabout manner to the Shannon entropy to create an interesting and novel theory. However, the description of various ion channels having characteristic frequencies, and the attempt to relate these to EEG frequencies, betrays some common misunderstandings among physicists of the nature of ion channels.

Perhaps my expectations about the subject matter in the book were inaccurate, but after struggling through this book, it seemed that, although the theory was interesting, the more fundamental question about whether the brain really could be a type of quantum computer had not been addressed. In particular, the author does not discuss what seem to me to be several critical issues:

  1. The author, like Penrose, says that indeterminate behavior is a benefit of their theory. But why would indeterminacy be desirable to an organism? Any behavior caused by random phenomena would itself be random and therefore useless.
  2. Prof. Green should have explained more about how detection of quantum phenomena by ion channels translates into consciousness or behavior. In other words, although the benefits to the phenomenon generating the wave equation are obvious, what is gained by the organism by using its ion channels to detect quantum fields, and how does resolving the wave function produce consciousness in any way that is different from detecting an ordinary photon or any other event in the environment?
  3. Finally, there is no biochemical reason to suppose that ion channels or (in Penrose's theory) microtubules, have any of the unique properties needed for detecting quantum phenomena if such phenomena should indeed occur in the brain. It would have been nice to have some reasoning, and maybe even evidence, on a biochemical level, why this should be the case.

H.S. Green's theory is one of the most innovative approaches from a physicist's standpoint thus far to the theory of consciousness. He also wrote Sources of Consciousness with T. Triffet. Sadly, there will be no more books from this highly innovative and knowledgeable author, who died in 1999.