“Ancient Greeks had differing views on the function of the brain. Hippocrates believed the brain to be the seat of intelligence. Aristotle believed that the brain was a cooling mechanism for the blood while the heart was the seat of intelligence.”
We are interested in modeling Brain function as a Fermionic Quantum Neural Network, with its quantum elements1 subject to local magnetic ﬁeld, hovering near the critical point. Let us motivate the need of the previous features:
- Fermionic, given that we believe that conscious behaviour emerges due to the choice between two vacua.
- Quantum, given that we believe that we are dealing with superpositions of states, in the sense described in the previous sections.
- (Quantum) Neural Networks, given that not only they mimic the structure of neurons but they probably exhibit learning and memory properties (This has been shown for the classical ones).
- Local Magnetic Field, because it is needed for coherence in high temperatures and also exhibits the reduced symmetry that can mimic classical behaviour: We believe that the way that the symmetry breaking occurs is the following: Phase transitions gives rise to a fermionic quantum condensate. This is described by a spinor which has a SU(2) symmetry3 associated with it. The presence of classical magnetic ﬁeld gives rise to a preferred axis (which coincides with that of the microtubules’) and reduces explicitly the SU(2) symmetry of the spinor to a discrete Z2 symmetry, which corresponds to the time reversal symmetry. The direction (”up” OR ”down” ) of the magnetic ﬁeld (which we believe that can be variable) of the system breaks further explicitly the Z2 to nothing giving rise to a preferred direction.
- Near the critical point, given that consciousness (or more accurately in this case, the “one bit” process) in our description is a phase transition.
1 – The fundamental unit being a spin 1/2 quantum condensate.
2 – Microtubules are hollow cylinders -polymers of tubulin- where quantum coherence is expected to be taking place.
3 – The magnetic field and the quantum condensate should not be considered independent. The SU(2) is itself emergent, hence never exact. The very existence of the quantum condensate is due to the magnetic field. The picture of the exact SU(2) symmetry broken by the classical magnetic field is adopted in order to make contact with the traditional formulation of quantum theory.
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