0
$\begingroup$

I'm trying to understand neuronal synchronization/desynchronization and oscillation, as well as the psychedelic state. The following sentence confused me a bit.

Psilocybin reduced spontaneous cortical oscillatory power from 1 to 50 Hz in posterior association cortices, and from 8 to 100 Hz in frontal association cortices.

It is taken from this article on how Broadband Cortical Desynchronization Underlies the Human Psychedelic State, featured in the Abstract section.

Now, as far as I've understood, the "power" of an oscillation is the square of its amplitude. In the quoted sentence, they say that the oscillatory "power" decreased with the increase of Hertz. Judging by that sentence, it would seem that an increase in the amplitude of a neuronal oscillation means a decrease in the oscillation's frequency. Is this correct, incorrect or perhaps imprecise?

$\endgroup$
1
$\begingroup$

This is sort of sloppy writing about their results, and statistical significance.

In the paper, they're analyzing data in bands 1-4Hz, 4-8Hz, 8-13Hz, 13-30Hz, 30-50Hz, and 50-100Hz.

Psilocybin reduced spontaneous cortical oscillatory power from 1 to 50 Hz in posterior association cortices

means "we saw significant reductions in all of the bands except 50-100Hz".

and from 8 to 100 Hz in frontal association cortices

means "we saw significant reductions in all of the bands except 1-4Hz and 4-8Hz".

They're not saying anything in those sentences about the magnitude of the changes, only about the locations in space and in the frequency domain where they saw changes. And it doesn't really mean they don't see changes in the other bands, just that any changes there did not meet their criteria for significance. They're also sort of mixing a quantitative and qualitative assessment of the data. The sentence in the abstract refers to Figure 3 of the paper, where you can see that the magnitude and extent of the changes is far more frequency dependent than that short sentence conveys.

$\endgroup$
8
  • $\begingroup$ So, if I get you right, there was a significant decrease in the oscillatory power of the beta and alpha brain waves, whereas there wasn't a significant decrease in the oscillatory power of the delta, theta and gamma brain waves? Also, is is true that the "oscillatory power" refers to the square of the amplitude? $\endgroup$ – A. Kvåle Feb 1 at 20:00
  • 1
    $\begingroup$ @A.Kvåle Power in neuroscience usually refers to en.wikipedia.org/wiki/Spectral_density - the term is used a bit sloppily so it isn't necessarily in units of amplitude squared. The first statement is equivalent to saying there were decreases in all frequencies except high gamma, the second is equivalent to saying there were decreases everywhere except delta and theta. I don't know where you're getting the other bands from. $\endgroup$ – Bryan Krause Feb 1 at 20:25
  • 1
    $\begingroup$ I think it's also important to realize that these bands aren't "real". They're just ranges imposed on a continuous spectrum, where certain phenomena have been noticed in those ranges. Broadband changes are probably not changes in "each of" the bands, they are broadband shifts in the power-frequency relationship. $\endgroup$ – Bryan Krause Feb 1 at 20:32
  • 1
    $\begingroup$ @A.Kvåle Yeah, it's ambiguous whether 'broadband' refers to 'all frequencies' or just 'a broader range than typically considered within one band'. $\endgroup$ – Bryan Krause Feb 1 at 20:49
  • 1
    $\begingroup$ Given your interests lately I thought you may be interested in an answer I wrote just now on someone else's question: psychology.stackexchange.com/questions/26610/… $\endgroup$ – Bryan Krause Feb 5 at 16:30

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.