The Quantum-Like Brain

Andrei Khrennikov

University of Växjö

Journal of Consciousness Studies, 15, No. 7, 2008, pp. 39-77

The author regards quantum mechanics as a general mathematical formalism for describing incomplete information about events. He suggests that quantum-like (QL) processing occurs in the brain. He is at pains to stress that he does not see this as related to actual quantum states in the brain, as is the case with most other theories of quantum consciousness. QL processing is suggested to arise from the brain as described by conventional neuroscience with neurons/synapses as the basic units. It is suggested that the unconscious mind uses classical processing, while only the conscious mind runs on QL.

Unconscious information is projected into consciousness, where it is subject to QL processing. In the manner of quantum mechanics, complex-number probability amplitudes constitute a wave function, in this case a mental wave function, related to probability by the algorithms of quantum mechanics. Consciousness is here claimed to operate with quantum algorithms that are essentially different from those used by existing (classical) computers. In the case of the brain, this theory suggests that the quantum algorithms can be used without involving actual quantum states, but instead spring from the already known biological processes that are themselves described by classical physics. The system is seen as being based on and created by the parallel workings of billions of neurons, with a QL facility much faster than any classical computer(1-6). Khrennikov also thinks the neural processing depends on two distinct timescales, a fine grained timescale for classical processing, and a less exact timescale of possibly about 100 ms produced by quantum averaging. He discusses some recent studies that he considers supportive of this suggestion.(7-11).

The author argues that there is nothing surprising about algorithms derived from quantum mechanics being implemented on biological processes that can themselves be understood in a strictly classical way. He points out that differential calculus was developed to serve Newtonian mechanics, but proved useful for other areas of physics. I am not sure that this argument is completely convincing. The common feature of the theories for which calculus was useful is that they described the movement of matter and energy in space and time, without the acausal disjuncture involved in the randomness of the quantum wave function collapse. In the case of Khrennikov’s theory, we are asked to accept the application of a system which does involve an acausal disjuncture to resolve the processing of a biological system that is deemed to be classical. The two systems, at first sight, appear much more dissimilar than the various classical theories for which calculus is useful.

Khrennikov argues that his QL scheme does not suffer from the difficulty of explaining how quantum states could persist in the brain for a length of time likely to be relevant to neural processing. This has long been the most cogent argument against theories of quantum consciousness. However, in common with more conventional researchers, Krennikov’s discussion of quantum theories of consciousness appears skimpy. He mentions in passing the problem of likely rapid quantum decoherence in the conditions of the brain, without discussing the possibility of quantum features being shielded, which is an important aspect of some quantum consciousness theories. He says that it is hard not to view the neurons as the basic units of neural processing, and suggests that quantum consciousness more-or-less ignores the processing of neurons. However, this is not always the case. The Penrose/Hameroff theory involves an interactive exchange between microtubular processing and synapses, while with Bernroider’s ion channel theory the quantum processes drive the ion channels, which in turn constitute a fundamental element within the conventional neuron theory.

Khrennikov is more convincing when he discusses the advantages of QL. If an organism does not have access to complete information, or does not have time to classically process the information that it possesses, QL can create a model based on partial information. He argues that in classical processing the brain would need to perform integration over space having the dimension of a few billions. From this, he argues that in an advanced brain simple acts of cognition would take an impossibly long time. Similar arguments have been advanced by other researchers on perception, who argue that while bottom up calculations do not yield a unique solution, bottom down calculations take an impractically long time(12-27).

The real problem with this theory, as with all classical approaches and quite a few quantum approaches to consciousness, is that while it is insightful, at the end of the day it seems to lack explanatory power as regards the essential subjective experience of consciousness. If quantum algorithms did arise from a classical biological strata, in order to deal with the perception problems of the brain, there is no apparent reason why such quantum processing should not be achieved unconsciously, as is quantum processing in physics outside the brain. Quantum consciousness theories appear to have no special advantage over classical theories, unless they can appeal to some special function at the fundamental level of energy or possibly spacetime that is possibly capable of acting as the source of consciousness.

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