[ExI] quantum brains

[Damien Broderick]

On 1/23/2010 7:07 PM, The Avantguardian wrote:

> Then there is the way that excitory post-synaptic potentials (EPSP) and inhibitory post-synaptic potentials (IPSP) can sum over time and space to trigger neuronal depolarization that is very reminiscent of constructive and destructive interference. Although by my cursory swim through the literature, reports are all over the board with the quantitative measurements of these things, the mean voltages of these signals are approximately 5 millivolts and the mean current is about 25 picoamps. The average duration of these signals are about 20 milliseconds. Multiply all these rough figures together and you get approximately 2.5 femtojoules or about 15,600 eV which is admittedly too much energy for quantum effects.
>
> However there are EPSP that fire spontaneously at a much smaller voltage called miniature EPSPs or mEPSPs that are in range of about 400 microvolts, 10 picoamps, and last about 1 millisecond. These are thought to be caused by single vessicles of neurotransmitters being randomly being released into the synaptic cleft. These things have an energy of about 25 eV which for comparison is not much higher than the ground state of the hydrogen atom at -13.6 eV. Moreover these things happen quite frequently.
>
> http://jp.physoc.org/content/494/Pt_1/171.full.pdf+html
>
> Now it seems to me that these mEPSPs in the brain are very similar to the quantum fluctuations in normal matter. Like the fluctuations in a nebula of hydrogen gas that could trigger the condensation of the gas into a protostar. Since EPSP are additive, one or more of these things could push a subthreshold normal EPSP over the threshold causing a recipient neuron to depolarize and initiate an action potential. So this is a potential mechanism for leaps of intuition, hunches, imagination, and creativity. And it seems a much more testable hypothesis than quantum microgravity yanking on microtubules ala Penrose and Hammeroff. Now the interesting question is are these things capable of the more bizzare quantum behavior like uncertainty, entanglement, and wave-particle duality? e.g. could mEPSPs interfere with themselves? Or might they exhibit particle properties and be called "psions"?

Are you familiar with the analyses by physicist Evan Harris Walker, 
somewhat along these lines? (I happen to think he was full of shit, and 
said so to his e-face, but I might be wrong.) And of course Eccles and 
Popper, back in the day.

Damien Broderick