The Need for a Non-computational Extension of Quantum Action in the Brain

Stuart R. Hameroff

Abstract In The Emperor’s New Mind and Shadows of the Mind, Roger Penrose followed a delicate thread to begin to unravel the problem of consciousness. He concluded that conscious thought is more than computation—our minds utilize some type of non-algorithmic processing unavailable in computers. Regarding the identity of the proposed processing, the intrepid sleuth also searched for a ‘subtle and largely unknown physical principle’ capable of performing the needed non-computational actions. That principle was deduced to be ‘objective reduction’ (OR) of quantum coherent superposition, Penrose’s quantum gravity solution for the problem of wave function collapse in quantum mechanics. The next piece of the puzzle then became: where and how could quantum coherent superposition and OR occur in the brain? To that end, Penrose began collaboration with this author, who suggested that the logical and most likely source of macroscopic quantum effects in the brain lies in neuronal microtubules in the cell cytoskeleton.

Christopher John Rourk

Integrated information theory (IIT) is a powerful tool that provides a framework for evaluating consciousness, whether in the human brain or in other systems. In Computing the Integrated Information of a Quantum Mechanism, the authors extend IIT from digital gates to a quantum CNOT logic gate, and while they explicitly distinguish the analysis from quantum theories of consciousness, they nonetheless provide an analytical road map for extending IIT not only to other quantum mechanisms but also to hybrid computing structures like the brain. This comment provides additional information relating to an adiabatic quantum mechanical energy routing mechanism that is part of a hybrid biological computer that provides an action selection mechanism, which has been hypothesized to exist in the human brain and for which predicted evidence has been subsequently observed, and it hopes to motivate the further evaluation and extension of IIT not only to that hypothesized mechanism but also to other hybrid biological computers.

Herbert S. Green, T. Triffet

Roger Penrose

Abstract Brain action, according to the conventional viewpoint, is to be understood in terms of essentially classical physics—or so it would seem. Nerve signals are normally taken to be ‘on or off’phenomena, just as are the currents in the electronic circuits of a computer, which either take place or do not take place—with none of the mysterious superpositions of alternatives that are characteristic of quantum actions. Whilst it would be admitted that, at underlying levels, quantum effects must have their roles to play, biologists seem to be generally of the opinion that there is no necessity to be forced out of a classical framework when discussing the large-scale implications of those primitive quantum ingredients.

Max Tegmark