Given that brain waves are characterised as such by virtue of the wave-like properties of 'electrical activity' in the brain, what is the speed of such waves; and how does it differ from neural conduction rates in peripheral nerves ordinarily in the range ~50 cm/sec. (Oddly I have had difficulty locating an answer to this question elsewhere).


Unfortunately the term "wave" is ambiguous in neuroscience. What you are referring to, alpha waves, only means that neuronal activity tends to oscillate at about 10Hz. Neural oscillations are a widespread phenomena occurring in all brain areas. But it doesn't necessarily mean these waves travels. There are examples of traveling waves, whose speed can vary a lot (from $10^{-1}$ to $10^{-5}\ m.s^{-1}$ depending on the studies). Oscillations across brain areas tends to be synchronized during a task (so one could argue, infinite speed), and within area activity tends to hold a specific phase relationship which varies spatially (as if a wave was "frozen", in which case its speed would be 0). Traveling waves and neural synchrony/coherence might be different phenomena implementing different functions. It is still unclear what brain oscillations are for, or even if they have any purpose at all. Below are some reviews on these topics.

Ermentrout, G.B. and Kleinfeld, D. (2001) Traveling electrical waves in cortex: insights from phase dynamics and speculation on a computational role. Neuron 29, 33–44

Sato, T. K., Nauhaus, I., & Carandini, M. (2012). Traveling waves in visual cortex. Neuron, 75(2), 218-229.

Engel, A. K., Fries, P., & Singer, W. (2001). Dynamic predictions: oscillations and synchrony in top–down processing. Nature Reviews Neuroscience, 2(10), 704-716.

Fries, P. (2005). A mechanism for cognitive dynamics: neuronal communication through neuronal coherence. Trends in cognitive sciences, 9(10), 474-480.


It of course quite depends on which waves you are studying. One cool recent example from the Sejnowski group at the Salk Institute show these circular brain waves occurring during sleep, which complete within ~70msec travelling a loop of ~30cm... http://www.salk.edu/news-release/princess-leia-brainwaves-help-sleeping-brain-store-memories/ (Original paper: https://elifesciences.org/articles/17267)

  • $\begingroup$ Consider the simple case of 'alpha waves', with a frequency ~8-12 Hz. What is the speed of propagation within the brain and presumably in its 'white matter'?. $\endgroup$ – jeremiah Nov 7 '17 at 5:43
  • $\begingroup$ @jeremiah See the answer by baca - when people refer to "brain waves" they are talking about oscillations in a recording, they are wave-like in time, not necessarily space. If they travel in space, too, that's a separate property. $\endgroup$ – Bryan Krause Nov 7 '17 at 17:08
  • $\begingroup$ @jeremiah That's right, as baca and Bryan have explained, these 'alpha waves' to which you refer are activities within a frequency band recorded from collective ensembles of neurons (e.g via EEG) where these oscillations might indicate a degree of coherence in a population. The circular brain wave I mentioned above I thought was one of the better examples of a wave I could find (in a more normal sense of the word) where excitation spreads through space and a speed could theoretically be calculated. $\endgroup$ – Louis Leung Nov 7 '17 at 20:57
  • $\begingroup$ Excellent and very helpful answers. My interest is more in the spatial aspect, or I suppose, the co-ordinated relation in sequential activity between or within areas of the cerebrum--but is at this stage still ill-informed. The implication of pyramidal cells seems interesting. $\endgroup$ – jeremiah Nov 8 '17 at 6:00
  • $\begingroup$ @jeremiah Yes, the coordination of waves throughout the brain is fascinating. You asked a good question and I wish I could have provided you with more well-studied examples. $\endgroup$ – Louis Leung Nov 8 '17 at 7:42

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