The study of neurobiology has long involved the actions and interactions among neurons and their synapses. Changes in concentrations of various ions carry impulses to and from the central nervous system and are responsible for all the information processed by the nervous system as a whole. This has been the prominent theory for many years, but, now, there is a new one to be reckoned with; the Quantum Brain Theory (QBT). Like many new theories, the QBT has merits and flaws. Many people are wholeheartedly sold on it; however, this vigor might be uncalled for. Nevertheless, this could prove to be a valid and surprisingly accurate theory of brain function.
One of the most convincing arguments of the QBT is its explanation of how reality is conceived by the brain. Classically, reality should always be changing, even by the slightest notion, and the brain should be aware of these changes as they occur. According to quantum mechanics, this would be impossible; there is no time during which something is changing. Therefore, the brain cannot be in a state of change, it must be in one state or another, there is no in between. The QBT states that our brain takes in reality one moment at a time, it is never in a state where it is observing something change. It observes reality before the change and then after the change and then fuses these two images together in order to make sense of them.
One question about the QBT comes when reality itself is considered; "why can't reality be a quantum system?" Well, there are a few explanations. One is that quantum systems are usually very small. Quantum mechanics cannot be used to explain the universe as a whole in all venues, however, can explain the movements of an electron, or the actions of a black hole. Another reason why reality cannot be explained by quantum mechanics is that quantum mechanics call for a holistic interpretation of the system. Reality, then, is much too large for all of it to be encompassed in one interpretation. Non-locality, another feature of quantum mechanics, prevents reality from being explained by quantum mechanics. Non-locality means that distance is not an issue in the effects of one part of a system on another. For example, curtains might not be blowing because your window is open and there is a wind, they might be blowing because somewhere in Russia, a woman is beating her rugs. This is impossible. Therefore, reality must be classically interpreted.
The features of holism and non-locality of quantum physics do strengthen the QBT. Through holism, the entire nervous system must be involved in every action. This doesn't mean that every part of the nervous system is active during one particular action, but that its state is taken into account by the central nervous system. Non-locality comes into the picture when the state of the brain is related to the actions of the hand, even though they are comparatively far away.
Many scientists, who support the QBT, also say that microtubules are the most influential part of the nervous system. Microtubules, they say, make up the neurons do what the synapses and concentration gradients do in "classical neurobiology." There are two schools of thought on these microtubules, however. The other states that the microtubules take the job of the concentration gradients and that the synapses do what they have always done. The latter seems to be the best, and will be discussed here. While in the cell, a message is carried through the microtubules by a quantum wave function, not by concentration changes. When these waves reach the synapses, they become neurotransmitters and then move onto another neuron where the process is repeated. These quantum waves can move extraordinarily fast and with little energy. Because of the immensely short period of time it takes for a signal to travel throughout the nervous system, this seems a much better theory than changing concentrations. Memory is another area where the QBT is helpful. Humans have an extraordinarily large number of neurons, in the order of trillions. Most of these neurons, though, are not contained in the memory centers of the nervous system. Even if all of these were donated to memory, there still would not be enough to explain the memory capacity of a human. The QBT, however, shows a different story. Using quantum states, there are infinite possible arrangements of the neurons, even if there is a finite number of them. For instance, if every neuron is used up in one state, instead of having to erase all of the memories, the neurons just start to "remember" in a different state.
Even though there are much merit to the QBT, it is not the last word in neurobiology. Much of this information is speculative; it is just a new explanation that hasn't been proven yet. There are also reasons to disagree with many of its advocates. One scientist insisted that the collapsing of the wave function when observed, one of the basic tenets of quantum mechanics was totally wrong and that he didn't believe it. Then proceeded to use it as proof of the QBT. There are also those who use the QBT so vehemently, that even proven theories are disregarded.
(1) The Brain Project
(2) The Enchanted Mind:The Quantum Mechanical Brain and Creativity
(3) HARC Astroparticle Physics Group
(4) Quantum Physics Research
(6) PSYCHE An Interdisciplinary Journal of Research on Consciousness
(7) A Quantum Theory of Consciousness
(8) Quantum Gravity
(9) Kvantfysikens Dolda Variabler
(11) Microtubules on the Web
(13) John S. Bell
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This paper reflects the research and thoughts of a student at the time the paper was written for a course at Bryn Mawr College. Like other materials on Serendip, it is not intended to be "authoritative" but rather to help others further develop their own explorations. Web links were active as of the time the paper was posted but are not updated.