Information Theory and Quantum Physics
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:
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.