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morrowasted
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Serotonergic psychedelics LSD & psilocybin increase the fractal dimension of cortical brain activity in spatiotemporal domains 1
#26981518 - 10/12/20 01:15 PM (3 years, 6 months ago) |
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https://www.sciencedirect.com/science/article/pii/S1053811920305358
Quote:
Psychedelic drugs, such as psilocybin and LSD, represent unique tools for researchers investigating the neural origins of consciousness. Currently, the most compelling theories of how psychedelics exert their effects is by increasing the complexity of brain activity and moving the system towards a critical point between order and disorder, creating more dynamic and complex patterns of neural activity. While the concept of criticality is of central importance to this theory, few of the published studies on psychedelics investigate it directly, testing instead related measures such as algorithmic complexity or Shannon entropy. We propose using the fractal dimension of functional activity in the brain as a measure of complexity since findings from physics suggest that as a system organizes towards criticality, it tends to take on a fractal structure. We tested two different measures of fractal dimension, one spatial and one temporal, using fMRI data from volunteers under the influence of both LSD and psilocybin. The first was the fractal dimension of cortical functional connectivity networks and the second was the fractal dimension of BOLD time-series. In addition to the fractal measures, we used a well-established, non-fractal measure of signal complexity and show that they behave similarly. We were able to show that both psychedelic drugs significantly increased the fractal dimension of functional connectivity networks, and that LSD significantly increased the fractal dimension of BOLD signals, with psilocybin showing a non-significant trend in the same direction. With both LSD and psilocybin, we were able to localize changes in the fractal dimension of BOLD signals to brain areas assigned to the dorsal-attenion network. These results show that psychedelic drugs increase the fractal dimension of activity in the brain and we see this as an indicator that the changes in consciousness triggered by psychedelics are associated with evolution towards a critical zone.
Can anyone with a neuroscience background break this down a bit?
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Sugabearcrisp
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Re: Serotonergic psychedelics LSD & psilocybin increase the fractal dimension of cortical brain activity in spatiotemporal do... [Re: morrowasted] 1
#26982001 - 10/12/20 05:42 PM (3 years, 6 months ago) |
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Really interesting.
Mathematically fractals are end result of naturally repeating sequences that represent algorithimic growth that happens to describe how life organizes. For the purposes of this article they are using the level of fractilness as a measure of complexity within the otherwise randomness of a brain's neurons.
From wikipedia
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One way that fractals are different from finite geometric figures is the way in which they scale. Doubling the edge lengths of a polygon multiplies its area by four, which is two (the ratio of the new to the old side length) raised to the power of two (the dimension of the space the polygon resides in). Likewise, if the radius of a sphere is doubled, its volume scales by eight, which is two (the ratio of the new to the old radius) to the power of three (the dimension that the sphere resides in). However, if a fractal's one-dimensional lengths are all doubled, the spatial content of the fractal scales by a power that is not necessarily an integer.[1] This power is called the fractal dimension of the fractal, and it usually
key quote from the study
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Studies with psilocybin have found that the patterns of functional connectivity in the brain undergo dramatic reorganization, characterized primarily by the rapid emergence and dissolution of unstable communities of interacting brain regions that do not occur in normal waking consciousness...
They describe the brain as a system in which higher levels of activity are increases in entropy, but the real critical piece is the application of fractal measurement to the entropy to separate meaningful increases in activity from just random neuron firing.
Quote:
We stress that entropy is not identical to randomness in all circumstances (it is entirely possible to have a highly structured system with higher entropy), but rather in this context, many of the measures, such as LZC monotonically increase with randomness. This is a useful, but limited understanding of “complexity”, particularly in the context of critical systems, prompting our proposal of fractal dimension as an additional measure that can be related to critical processes
They also discuss criticality as a transition from our normal non plastic hard wired brain to a state of increased plasicity (flexibility) of neurons to connect in novel (new) ways.
The underlying implication is the pyschedelics create increases in brain activity that are analagous to a higher state of function in which new pathways are built and old ones potentially overwritten.
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sonoramo
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Re: Serotonergic psychedelics LSD & psilocybin increase the fractal dimension of cortical brain activity in spatiotemporal do... [Re: Sugabearcrisp] 5
#26983273 - 10/13/20 12:07 PM (3 years, 6 months ago) |
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Interesting article. I carried out research developing MRI systems and fMRI sequences. I also carried out (ahem, unsanctioned...) experiments with mushrooms, but not while getting scanned. So it's interesting to imagine what these experiments would be like.
MRI time is expensive, and that probably explains the rather small number of volunteers who got to participate. 20 for the LSD comparison and 14 for the psilocybin comparison. That's a really small group. Presumably these were all experienced psychonauts.
The dosages are moderate, 75ug LSD and 2mg of psilocybin. I have no experience with LSD, but 2mg psilocybin is comparable to 0.4g dried mushrooms if you believe your mushrooms are 0.5 percent actives by dry weight. It didn't say if the volunteers had previous experience with either substance. If I were inexperienced with mushrooms or MRI, even that low dose coming on while inside an MRI system running 15-minute fMRI sequences could be scary. It might also be difficult to remain still for 15 minutes at a time, as is required to get the best MRI data. Since I'm very experienced with both, I'd probably find it interesting. Hell, if I still had access to an MRI machines and a tech to run it for me, I'd do the experiment on the sly. Presumably the volunteers didn't have any claustrophobia issues or fears of being pushed into a machine that makes very loud brrrup-brrrup-brrrup noises for 15 minutes at a time.
I think these are interesting results, especially given the low-ish doses given. It supports the idea that low-dose effects have some physiological reality. Fractal dimensionality corresponds pretty well to what my brain seems to do under the influence of mushrooms. They came up with a creative way to compare spatial fractal dimension with other chaos measures in MRI and MEG data. The tools they used (Python/Numpy/PyEEG and MATLAB) are familiar to me, and I'd love to have at their data, given the chance.
On the other hand, the experiment leaves a lot of questions unanswered. No criticism of the researchers, just a note about how limited their budget was for this experiment. It would have been nice if they could run diffusion-tensor sequences as well as BOLD sequences (which measure localized activity). I bet they would have done this if they had the $$ for it. Diffusion tensor mapping shows the actual connectivity within the brain, and it would be really interesting to see if "subjecting" someone to regular high doses of psychedelics modifies the structural connectivity in the brain. I'd also want to know if how long structural and physiological changes persist. They tested probably over a few hours before and after infusion. But what happens as the volunteer comes back down, and what happens in the days following?
Since these guys are injecting materials anyway, I think it would be really interesting to see if they could assess differences in brain and even retinal response by infusing selectively, for example, with intracarotid or intraocular injection. Maybe that's something for animal "volunteers" rather than humans,...
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Holybullshit
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Re: Serotonergic psychedelics LSD & psilocybin increase the fractal dimension of cortical brain activity in spatiotemporal do... [Re: sonoramo]
#26986579 - 10/15/20 07:55 AM (3 years, 5 months ago) |
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So eating mushrooms takes you to the "fractal dimension", lol.
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Mrwiggletree
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Re: Serotonergic psychedelics LSD & psilocybin increase the fractal dimension of cortical brain activity in spatiotemporal do... [Re: sonoramo]
#27008389 - 10/28/20 01:22 PM (3 years, 5 months ago) |
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I was curious about your comment on the amount of dose on psilocybin. I can explain more later, but I recently had a 2g dried dose, and well.... I can explain more later. But it seems to me that you know what you are talking about.
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sonoramo
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Re: Serotonergic psychedelics LSD & psilocybin increase the fractal dimension of cortical brain activity in spatiotemporal do... [Re: Mrwiggletree]
#27008510 - 10/28/20 02:12 PM (3 years, 5 months ago) |
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Quote:
Mrwiggletree said: I was curious about your comment on the amount of dose on psilocybin. I can explain more later, but I recently had a 2g dried dose, and well.... I can explain more later. But it seems to me that you know what you are talking about.
I'm not sure which comment you had in mind. For me, 2g dried, consumed in a tea, typically produces a "level 3" experience that lasts 2-2.5 hours after 1-hour come-up period. The dose is probably equivalent to 10mg psilocybin. But I have no way of knowing that, since I don't have any objective way to measure psilocybin content in the mushrooms. So, your mileage may vary. And so will mine.
My only point is that, if the subjects were given 2mg psilocybin doses, they probably weren't having any kind of "big" experience. And yet, the researchers were able to measure effects.
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Mrwiggletree
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Re: Serotonergic psychedelics LSD & psilocybin increase the fractal dimension of cortical brain activity in spatiotemporal do... [Re: sonoramo]
#27009903 - 10/29/20 08:59 AM (3 years, 5 months ago) |
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Yes thank you immensely, I was referring to your astute observation of the power of 2g dried. I had frightening/awesome experience on 2 mg truly dried, and at the time I thought I had Level 5 experience but really it was 3-4 combined with panic attacks resulting in ER visit and all the regret and embarrassment that goes along with that. Your background in imaging is wonderfully useful. I have clinical background. Very curious what was happening in my brain during this experience, 5HT-2A saturation and what is it about these receptors that uncork the rest of the brain? I understand that the thalamus is sort of slowed and leaves the cortical activity to run free but I’m so curious why visuals have that mesmerizing effect. And why consciousness sort of vanishes briefly during the higher doses. The feeling of disorientation and feeling as though I could get lost physically in the park I was at.
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ShabbyRabbit
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Re: Serotonergic psychedelics LSD & psilocybin increase the fractal dimension of cortical brain activity in spatiotemporal do... [Re: sonoramo]
#27011025 - 10/29/20 07:21 PM (3 years, 5 months ago) |
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Soo lets crowed source a MRI machine. I can think of a dozen experiments off-hand that are low hanging fruit... due to legislation. I'll put up $10k. Can we get a Funding Platform @ythan?
-------------------- Trade List
Edited by ShabbyRabbit (10/29/20 07:25 PM)
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nooneman
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Re: Serotonergic psychedelics LSD & psilocybin increase the fractal dimension of cortical brain activity in spatiotemporal do... [Re: morrowasted] 1
#27011315 - 10/30/20 12:05 AM (3 years, 5 months ago) |
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So, I looked into this after you posted it, and it's a little complex. I'm not really qualified to explain this so I'll probably do a shitty job, but here's what I understand about it:
Not all things in math are purely 1 dimensional or 2 dimensional, some things are in-between. Fractals are things that have an "inbetween" number of dimensions. For example, a fractal "line" is more than 1 dimensional, but less than 2 dimensional. It fills space like a 2 dimensional thing, but less than a 2 dimensional thing, but also more than a 1 dimensional thing. The Koch Snowflake is a thing like that.
If you want to measure a 1 dimensional fractal like the Koch Snowflake, you can't measure it's length like you can with an ordinary line because it's length is infinite. Instead, you have to measure it's "fractal dimension" which is a measurement of self-similarity. What that really means is exactly where does the given fractal fall between 1 or 2 dimensions: is it closer to 1 dimensional (in that it fills less space) or is it closer to 2 dimensional (in that it fills more space). This is related to how complex the fractal is, which is related to self similarity.
The fractal dimension tells you how much complexity there is as you zoom in. You can zoom into a fractal forever, right? But how complex and detailed is it as you zoom in? If it's very complex and very detailed the more you zoom in, that has a higher fractal dimension than something that is less complex and less detailed.
You can calculate this "fractal dimension" for lots of complex things, like coastlines. What you do for a coastline is, say that you have a ruler that is a mile long, and you find out how many of these mile long rulers it would take to represent the coastline. Then, you take a ruler that is half a mile long, and you find out how many half mile rulers it would take to represent the coastline. In fractal things, the smaller the ruler you use, the longer the coastline gets. The fractal dimension is a representation of how much longer the coastline gets as the ruler gets smaller, and it tells you about the complexity of the thing.
So they took some scans of the human brain, and did something similar, and calculated the fractal dimension of the brain, and they found a (very, very slight) increase in the fractal dimension of certain specific parts of the brain under the effects of certain psychedelics. The exact effect or interpretation of this is not very clear. They propose that it means that the brain is moving closer to some critical point between organization and disorder, but the reality is just that they've shown that the mathematical fractal dimension of brain activity very slightly increases under the effects of psychedelics.
If I understand this correctly, it really means that brain activity becomes slightly more complex and less predictable under the effects of psychedelics. But who knows, you might even interpret this as a result (or cause) of the fractal visuals seen under the influence.
Anyway, here's more about the fractal dimension: https://en.wikipedia.org/wiki/Fractal_dimension
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morrowasted
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Re: Serotonergic psychedelics LSD & psilocybin increase the fractal dimension of cortical brain activity in spatiotemporal do... [Re: nooneman]
#27011429 - 10/30/20 03:37 AM (3 years, 5 months ago) |
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Thanks a bunch that was helpful
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sonoramo
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Re: Serotonergic psychedelics LSD & psilocybin increase the fractal dimension of cortical brain activity in spatiotemporal do... [Re: nooneman]
#27012085 - 10/30/20 12:58 PM (3 years, 5 months ago) |
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Quote:
nooneman said: So, I looked into this after you posted it, and it's a little complex. I'm not really qualified to explain this so I'll probably do a shitty job, but here's what I understand about it...
I thought yuors was a great explanation, nothing shitty about it at all!
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Pu-Erh
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Re: Serotonergic psychedelics LSD & psilocybin increase the fractal dimension of cortical brain activity in spatiotemporal do... [Re: sonoramo] 1
#27023265 - 11/05/20 01:08 PM (3 years, 5 months ago) |
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* introduction That was a fun read. I am the kind of nerd that enjoys reading mathy papers for fun. So, nooneman did a great job of explaining what they did, but since he said he's not really qualified, and I am somewhat qualified, I will try to do an deeper layman-terms summary. If you are interested in that, READ ON.
But first a DISCLAIMER. I have nada / zero / no clue about brain stuff. But I took an MSc in Applied Math, specialized in Time Series, and when I started working Graphs where all the rage, so I have done a couple of graph projects. So ANYTHING BRAIN RELATED THAT I SAY IS PROBABLY WRONG, but I HAVE A GRASP ON THE MATH. I will do my best to summarize the article and clearly state if anything is my opinion, interpretation or invention. * what are they trying to prove? Some literature on how the brain works sustains the HYPOTHESIS that the brain has two different states, if you have seen any Stamets' talk were he brings a picture neuron connections when sober and high, keep it in mind, it will be extremely helpful: - regular waking brain - this is your brain on drugs (and REM sleep, maybe?) these two brain states are defined by NEURON CONNECTIVITY and they are not far away from each other in those terms. As neuron connectivity increases cause your are high, your brain becomes more flexible, disorganized and more entropic. Now, I think everyone knows what flexible means, but disorganized and entropic are may need comment. More entropic means that amount of information the system is able hold. This does not relate to memory. This means that if you have 2 coins and toss them, you can get 4 different outcomes, that is more entropic that tossing 1 coin which has 2 outcomes. If you are sober, your brain has whatever number configurations possible, if you are high, the range of configurations increases. Configurations is a term I am using and probably wrong, I just hope is illustrative.
About disorganized, if you have been high, you have noticed that your mind runs and some tasks are hard. I BELIEVE they are not talking about that. What they mean is, whatever hierarchy or specialization in the brain is reduced.
What I have written above is a HYPOTHESIS, some people think that is how the brain works, but we do not have COLD.HARD.FACTS to prove it. They are trying to solve that. * what did they do? Again, shutout to nooneman here, he did a great job explaining the gist of things. Fractals live in dimensions and a half. Or a quarter, whatever. Why do we care about fractals? We don't really. They are a tool. If a system is going from one state to another, say brain going from sober to high under our hypothesis, it might happen that any fractal dimensions in the brain might be more noticeable. That would be an indicator that the HYPOTHESIS is not totally bunk. It does not prove the hypothesis tho.
** Time to do the sciences! They took fMRI images and BOLD scans of peoples' brains on drugs. I don't know what ANY of that means, and some people posting here seem to know, so maybe they want to comment further, I don't. From those images they built Time Series and Graphs. Time Series is a set of numbers of what happened at each time, like this one: https://finance.yahoo.com/quote/BTC-USD?p=BTC-USD&.tsrc=fin-srch here you have the price of bitcoin at each day (maybe hour, who cares). You can also have multiple numbers at each time, like price of bitcoin and price of oil. But you can also have brain measurements over time, like levels of excitement of a given sets of neurons in different brain areas. Again, no idea about brain. Graph is a set of nodes (say cities or neurons) connected by edges (say roads or dendrites, middle school biology at is finest, I know a brain word). This means they have measures of the brains in 2 dimensions, temporal and spatial. Thus they can measure how "whatever-gets-measured-with-fMRI" changes in space and time when you are high.
Now we are ready to look for increases in fractal dimensions on those two brain representations, the question now is: HOW?
** MATH!! You can ignore this part if you want, just know they did math.
*** GRAPHS Bear in mind that we are looking for dimensions and a bit, say 2.453 dimensions. How do we know how many dimensions in a graph? Well you count. It's a rather involved count, and you do it with log-logs and regressions. But the gist of it is: - you tile/parcel the network with boxes of equal size. This means you overlay, say 4, boxes over the graph, and each node is then on one of those 4 boxes. - if you make the boxes smaller, then you need more boxes to tile your graph. - this means that we have a function that tells us how many boxes we need, given the size of the box. AND this number is somehow proportional the size of the box to the power of minus DIMENSIONS. Which means with some algebra, you get the dimensions. *** TIME SERIES This is a bit more abstract, but a lot simpler algorithm. what they did was: - create a bunch different time series form the original. Like taking every other number in the series, then every other second, third, fourth number, and so on and so forth. - measure the length of the different series created. This again is proportional to something to the power of minus DIMENSIONS. Which again means algebra and you get dimensions. * RESULTS!! So in general, they found the number of dimensions to increased, which is consistent with their hypothesis. The change was more pronounced in the Graph / Spatial dimension (going from about 3 to about 3.5, don't get caught on the numbers) than on the Temporal (going from 0.9 to 1, see what I mean). They also looked at specific brain regions, and found changes with different levels of significance.
So, really cool read, great piece of science, but the results were weak at best, not enough to prove their hypothesis, but definitely not a debunked idea. This happens with science, their language is kinda grand, but at the end of the day, results are weak. Nothing wrong, but it can be misleading.
Hope you enjoy the read, and if you have any comments, or something is not clear, let me know! Thanks for reading!
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InnerWisdom
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Re: Serotonergic psychedelics LSD & psilocybin increase the fractal dimension of cortical brain activity in spatiotemporal do... [Re: Pu-Erh]
#27023270 - 11/05/20 01:13 PM (3 years, 5 months ago) |
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Psychedelics increase the fractal dimension alright.. Might even take you in it
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morrowasted
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Re: Serotonergic psychedelics LSD & psilocybin increase the fractal dimension of cortical brain activity in spatiotemporal do... [Re: InnerWisdom]
#27023392 - 11/05/20 02:36 PM (3 years, 5 months ago) |
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Quote:
More entropic means that amount of information the system is able hold. This does not relate to memory. This means that if you have 2 coins and toss them, you can get 4 different outcomes, that is more entropic that tossing 1 coin which has 2 outcomes. If you are sober, your brain has whatever number configurations possible, if you are high, the range of configurations increases. Configurations is a term I am using and probably wrong, I just hope is illustrative.
this is excellent, thanks
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