Importance of quantum decoherence in brain processes

Phys. Rev. E 61, 4194 – Published 1 April 2000
Max Tegmark


Based on a calculation of neural decoherence rates, we argue that the degrees of freedom of the human brain that relate to cognitive processes should be thought of as a classical rather than quantum system, i.e., that there is nothing fundamentally wrong with the current classical approach to neural network simulations. We find that the decoherence time scales (10-1310-20 s) are typically much shorter than the relevant dynamical time scales (10-310-1 s), both for regular neuron firing and for kinklike polarization excitations in microtubules. This conclusion disagrees with suggestions by Penrose and others that the brain acts as a quantum computer, and that quantum coherence is related to consciousness in a fundamental way.


  • Received 6 July 1999
  • Published in the issue dated April 2000

© 2000 The American Physical Society

Authors & Affiliations

Max Tegmark*

  • Institute for Advanced Study, Olden Lane, Princeton, New Jersey 08540
  • Department of Physics, University of Pennsylvania, Philadelphia, Pennsylvania 19104

  • *Electronic address:

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