[jkingsman]

This concerns Functional Connectivity[0], which is basically a measure of how temporally correlated regions are; those that fire in sync or in a strongly correlated pattern are functionally connected.

Essentially, the TL;DR of this study is that psilocybin's 5-HT2A agonism seems to reduce synchronized FC activity not just in neurons but the whole brain: psilocybin makes parts of the brain overall that otherwise work together (in a time-correlated sense) stop displaying time-correlation. These results were seen most in the Default Mode[1] network, which is more or less the brain system in operation when you are inside your head — daydreaming, thinking, remembering, etc. — as opposed to processing visual cues or observing the physical world.

[0]: https://en.wikipedia.org/wiki/Dynamic_functional_connectivit...

[1]: https://en.wikipedia.org/wiki/Default_mode_network — this article is one of those that just blows my mind clean out my ears (heh); the brain is such a wonder.

[jppittma]

I think the fact that nobody knows how to deal with negative correlations in functional connectivity takes away from the validity of the whole concept. People literally throw out negatively correlated voxels/ROI's. This, on top of the fact that functional connectivity is only related to physical connectivity in the abstract. (it's about the correlated time series activity in pixels over time, and isn't bound by any cellular connectivity). I just struggle to discern any meaning from the concept.

[robwwilliams]

I second the question below. The phase, magnitude, and polarity are all used. Yes, sure, you can focus on sub-systems with positive correlation under the presumption that joint increases in signal signify joint increases in O2 use and neuronal activity. Functional connectivity is functional more relevant than mere axonal connectivity. Only a small fraction of an axonal arbor — its collection of presynaptic terminals—-is functionally and reliably coupled to postsynaptic targets.

[free_energy_min]

any source that mentions throwing away negative correlations?

[parpfish]

It’s commonly done in fMRI studies and I always got the impression it was less about not being able to understand negative relationships (e.g., it’s well understood that things like the default mode network is inversely related to active processing) and it’s more about not being clear how to use negative values as edge weights in graph theoretic analysis of networks

[nikkwong]

Yeah, this is super interesting. The obvious follow up for me is what implication this desynchronization has on cognition. People who have done a lot of psilocybin tend to be quite a bit 'different' at least in my experience—they tend to be more reserved, maybe a bit more thoughtful, slower, introspective, etc.

But what causes this change in personality? People who have done a lot of psilocybin seem to be a lot less worried, a lot less neurotic, and a lot less wrapped up in the ego than those who haven't. After all, who wants to be wrapped up and ruminating based on the content of their thoughts? I've always thought of this behavior by those who have used psilocybin to be a feature, not a bug—as if they're enlightened.

But if, say, this newfound personality is the result of a loss in functional connectivity—what does that tell us about how other markers of cognitive function have changed? Is strong FC a prerequisite for strong executive function or other measures of intelligence? The paper seems to suggest that the changes in FC are associated with the default mode network and maybe not other states of brain focus.

But will a macro dose of psilocybin, say—make someone better at their job? Maybe we don't know yet, and maybe there won't be a clear answer; there is a lot of heterogeneity in the way people think, and how they exploit their own cognitive abilities to provide value in the world—so maybe a loss in FC will mean different things to different individauls. But given the suggestion from this paper that the effects of psilocybin may be somewhat permanent, the answer to this question will be a very useful for those looking to benefit from this therapeutic.

[robwwilliams]

The study uses cool methods but they are still at very crude global level and the temporal resolution is poor. Functional synchrony (or para-synchrony) is more of an initial pointer to the much faster synaptic processing we really would love to understand better. the ither limit is that fMRI studies focus on relatively large chunks of cortex, but lots of critical changes are sub-cortical. I’d love to see a focus on thalamo-cortico and cortico-thalamic modulation. I suspect these connections are just as important as cortico-cortical and cortico-hippocampal connections.

Finally, there will be a great deal of individual differences. One story will not fit all of us.

[chiefalchemist]

Suggested reading:

"How to Change Your Mind" by Michael Pollan

https://michaelpollan.com/books/how-to-change-your-mind/

There's also a multi-part Netflix series based on the book.

https://www.netflix.com/title/80229847?preventIntent=true

[bongodongobob]

I completely disagree with your anecdotal premise.

[gorlilla]

Why? I only ask because I didn't find your anecdotal disagreement as having added to the conversation in any constructive manner.