I’m totally novice in neuronal physiologic, but see an analogy in data transmission both in the brain and an electrical computer. As computer technology evolves, data transfer rate higher than some threshold turned to favor serial ways rather than good old parallel ways.
Serial transmission is slower than parallel transmission given the same signal frequency. With a parallel transmission you can transfer one word per cycle (e.g. 1 byte = 8 bits) but with a serial transmission only a fraction of it (e.g. 1 bit).
The reason modern devices use serial transmission is the following:
You cannot increase the signal frequency for a parallel transmission without limit, because, by design, all signals from the transmitter need to arrive at the receiver at the same time. This cannot be guaranteed for high frequencies, as you cannot guarantee that the signal transit time is equal for all signal lines (think of different paths on the mainboard). The higher the frequency, the more tiny differences matter. Hence the receiver has to wait until all signal lines are settled – obviously, waiting lowers the transfer rate.
Another good point (from this post) is that one needs to consider crosstalk with parallel signal lines. The higher the frequency, the more pronounced crosstalk gets and with it the higher the probability of a corrupted word and the need to retransmit it.1
So, even if you transfer less data per cycle with a serial transmission, you can go to much higher frequencies which results in a higher net transfer rate.
1 This also explains why UDMA-Cables (Parallel ATA with increased transfer speed) had twice as many wires as pins. Every second wire was grounded to reduce crosstalk.
Then I wonder if spiking signals transferred via axons can reach an enough high frequency that the induced electromagnetic wave/resonance could establish crosstalk among axons (esp. in white matters where they are dense)?
And maybe we should more/equally view brain information in serial ways as in parallel ways? I see SDR has a rather parallel flavor.
if I remember correctly, axons can send ion pulses at around 100m/s max, and neurons frequency top at around 300hz, I don’t think its fast enough to worry about electromagnetic effects.
The wavelength of a 300 Hz EM signal would be on the order of 1000 km. You typically don’t need to worry about cross talk until the wavelength starts getting close to the size of the wiring.
Actually, in rare circumstances axons can have significant cross-talk
The Myelin Sheath Maintains the Spatiotemporal Fidelity of Action Potentials by Eliminating the Effect of Quantum Tunneling of Potassium Ions through the Closed Channels of the Neuronal Membrane
Abstract: The myelin sheath facilitates action potential conduction along the axons, however, the mechanism by which myelin maintains the spatiotemporal fidelity and limits the hyperexcitability among myelinated neurons requires further investigation. Therefore, in this study, the model of quantum tunneling of potassium ions through the closed channels is used to explore this function of myelin. According to the present calculations, when an unmyelinated neuron fires, there is a probability of [one in one thousand] that it will induce an action potential in other unmyelinated neurons, and this probability varies according to the type of channels involved, the channels density in the axonal membrane, and the surface area available for tunneling. The myelin sheath forms a thick barrier that covers the potassium channels and prevents ions from tunneling through them to induce action potential. Hence, it confines the action potentials spatiotemporally and limits the hyperexcitability. On the other hand, lack of myelin, as in unmyelinated neurons or demyelinating diseases, exposes potassium channels to tunneling by potassium ions and induces the action potential. This approach gives different perspectives to look at the interaction between neurons and explains how quantum physics might play a role in the actions occurring in the nervous system.
This phenomenon can be observed in healthy humans:
… the low spatial fidelity of the unmyelinated neurons of the anterolateral tract, which transmit slow
pain, thermal sensation, crude touch, itching and sexual sensation. This is manifested as poor
localization of the sensation and is extended to distant sites away from the original or local site, such
as in referred pain and referred itching [1,19]. This might be explained as form of hyperexcitability
due to lack of myelin in these neurons giving the opportunity for potassium ions to tunnel through
the exposed potassium channels and generate a depolarization effect on adjacent neurons, and
consequently action potentials occur. Thus, the brain cannot exactly identify the precise location of
the stimulus.
