Magic mushrooms and brain activity revisited

(An improved and updated version of this essay has appeared in my book Brief Peeks Beyond. The version below is kept for legacy purposes.)

Unidentified wild mushrooms.
Photo by Selene's Art. Used with permission.

In Chapter 2 of Why Materialism Is Baloney, I illustrate a broad pattern associating procedures that reduce brain activity with expanded consciousness. These include hyperventilation, meditation, ordeals, gravity-induced loss of consciousness, strangulation, cardiac arrest, brain damage, and even psychedelics. Indeed, a 2012 paper by Carhart-Harris et al. has showed that psychedelics only reduce neural activity, with no increases anywhere in the brain. This is counter-intuitive from a materialist perspective since, according to materialism, consciousness is brain activity (a totally inactive brain is, after all, a dead and unconscious brain under materialism). Recently, however, an inaccurate and misleading media report on a more recent paper by the same team has claimed that the researchers have now "found increased activity in regions of the brain that are known to be activated during dreaming." This, if it were true, would contradict the conclusions of the earlier study. However, it is simply false. In this article, I want to clarify this.

Before I get to the essence of the issue, I want to insist on something I feel I cannot stop repeating. To quote my own words in the book (p. 50):
In both science and philosophy one must extract conclusions not from local and partial pieces of the data, but from a careful consideration of the data as a whole. One must look for broad patterns, because it is from these broad patterns that reliable conclusions can be extracted. While particular reports of transpersonal experiences could possibly be explained away, the broad pattern that associates peak transpersonal experiences with reductions of brain activity clearly points to a robust and consistent phenomenon.
Whether psychedelics only reduce neural activity (and they do) or not, is just one small element in the broader pattern. It would be unfortunate to focus one's attention exclusively on this small element, at the cost of losing sight of the whole pattern illustrated in the book.

OK, now on to the key point. I have taken the time to read through the actual scientific paper published recently, as opposed to the science media digest. And the paper is very clear. Here is a key passage (p. 2):
...the effects of psilocybin on the variance of brain activity parameters across time has been relatively understudied and this line of enquiry may be particularly informative ... Thus, the main objective of this article is to examine how psilocybin modulates the dynamics and temporal variability of resting state BOLD activity. (The italics are mine.)
"BOLD" stands for the Blood-Oxygen-Level-Dependent activity detected by a functional brain scanner (fMRI). It is a measure of the level of metabolism in the brain region being studied. This level of metabolism is what we call brain activity. Therefore, BOLD is a measure of brain activity. Clearly, unlike in the 2012 study mentioned above, the researchers this time aren't reporting on brain activity as measured by a time-averaged BOLD, but on the variability of that activity; that is, on how much the BOLD signal amplitude changes over time. Naturally, a brain displaying higher levels of activity variation can still have, overall, much lower levels of activity than normally. This is easily illustrated in the figure below. In both graphs, the activity level is represented by the area under the curve. Clearly, there is much more activity on the left side than the right side, even though the right side displays much higher variation of activity level. Do you see the critical difference?

The researchers go on to report on their findings (p. 11):
In summary, increased variance in the BOLD signal was observed in the bilateral hippocampi and ACC ... This change in variance is the expression of an increased amplitude of the BOLD signal fluctuations in these regions ... bursts of high amplitude activity have been seen in human rapid-eye movement (REM) sleep ... Given that phenomenological similarities have previously been noted between the psychedelic ... and dream states, it is intriguing to consider whether altered hippocampal activity may be an important common property of these states. (The italics are mine)
This excerpt probably makes it abundantly clear what the journalist who wrote the inaccurate IFL Science article got wrong, and what the correct interpretation is. If I were inclined to conspiracy theories, I would be feeling rather excited by now. However, I am of the personal opinion that this is merely a case of misunderstanding by a science journalist. It highlights the need to go to the actual scientific papers when one is seriously trying to derive conclusions from new research.

The new study in no way contradicts the earlier findings. As far as I can see from all this material, it stands that psilocybin only decreases neural activity. It doesn't increase it anywhere in the brain. The new study simply finds that the levels of activity, although either unchanged or reduced when compared to the baseline state, vary more over time in brain areas associated with dreaming. That's it.

Is the increase of variability relevant for understanding how psychedelics work? Of course. The study in question argues cogently for it. Do the new results make the original results more consistent with materialism? Certainly not. Materialism states that a fully-inactive brain is fully unconscious. Therefore, there is an undeniable dependency between brain activity and consciousness under materialism. Granted that this dependency is not as trivial as to say that the more activity there is, the more consciousness there should be. That would be an exceedingly simplistic and naive misinterpretation of materialism. For instance, a brain wherein all neurons were to fire together would be maximally active, yet the amount of information in this hypothetical brain state would be equal to that in a fully inactive brain: that is, precisely zero. I grant this with no discomfort. But results showing an increase in global variability in large brain areas, consisting of millions of neurons, do not mean that there is more information in these brain areas. For instance, the graph to the left, in the figure above, could easily represent much more information at the microscopic, neuronal level than the graph to the right, provided that it is different sets of neurons that are firing at each moment. In fact, short of exceedingly high levels of activity wherein more than half the available neurons are firing, the more active a certain brain region is, the higher the chance that more information will be present.

For the reasons I summarized in the 6-point argument in an earlier reply to Steven Novella, results showing a tight correlation between decreased overall brain activity and unfathomably expanded awareness and cognitive function remain, and will always remain, highly problematic for materialism. Whichever way a materialist twists the observations to try and fit them into his metaphysics (for instance, with convoluted, ambiguous, obscurantist arguments about the interplay between excitatory and inhibitory brain activity, which I discuss at length in my book), the bottom line is exceedingly simple: under materialism, consciousness is brain activity. When one finds substantially more consciousness correlating consistently with substantially less brain activity, one is forced to contemplate the possibility that the brain is somehow associated with filtering, constraining, or localizing consciousness, instead of generating it.


  1. Great points here Bernardo. It seems to me that the main issue with these journalists is the ambiguity of the word "activity" when used on its own without any further specificity. They see an increased variance in BOLD signals as illustrated in the paper and correctly interpret this is a sort of increased activity. But they then proceed to tout this fact without mentioning the narrow amplitude parameters that the increased activity applies to. It's like if someone were to measure the variance in amplitude of the waves in their backyard pool as people took turns doing cannonballs off the diving board and then claim that this activity exceeded that of the Atlantic Ocean on a calm day.

    Do you think that these science journalists are simply not reading the literature they're citing, or are they deliberately presenting a skewed/incomplete interpretation of the data in order to perpetuate the hype of the "mind equals brain" perspective?

    1. Personally, I think they simply don't quite understand what they are reading and/or do not have the intellectual rigor necessary to represent it accurately.

  2. A superb and lucid exposition of why we shouldn't automatically trust science journalism, especially in more controversial areas or where the implications of the research point away from the mainstream view.

  3. Those mushrooms look delicious! Do you have a recipe for Simm?

    1. :-) Not sure the shrooms are a good idea for everyone...

  4. Very nice illustration to show the difference in activity and variance.
    But one thing is not clear to me: The paper also says that the "BOLD total spectral power" was increased for ACC and Hippocampus (see tab 1, fig 1. Also meantioned in the discussion part ("[...] the high amplitude activity detected in the hippocampi and ACC [..]"))

    What is this "total spectral power" in your illustration? Sounds like something added up. I would have interpreted it as the blue area under the curve. (and maybe so did the journalist)

    1. Thanks for your reply. I studied the wikipedia article and I can't help but think this means they actually report an increase in signal power (and therefore brain activity)....?
      I mean: On whatever frequencies the signal is distributed - if you take the total of those contributing components, you get an increase power in ACC and hippocampus.
      Am I missing something?

    2. The word "power" is misleading here. It is used simply because the square of the BOLD signal is taken in the computation, which is analogous to "power" in electrical engineering applications (where this type of analysis is historically derived from). So BOLD is proportional to the activity in the neurons. When they do the spectral analysis, they take BOLD^2, and that is then the "power" in the spectrum. Physically it isn't power at all; it's just a mathematical analogy that got fixed in the jargon. Unfortunately, it becomes misleadingly suggestive in the context of what we are discussing.
      What you say above is strictly correct, provided that you interpret "power" in this proper manner. But even then you can't conclude from an increase in the total spectral "power" that there was also an increase in time-averaged BOLD (i.e. relevant brain activity). For instance, you can see in eq. (2) that only the amplitude of the Fourier Transform is taken into account when the spectral power is calculated, so phase information is ignored (!), which is critical when one wants to integrate the original BOLD signal over time to estimate actual brain activity. One can't recover the BOLD signal from this spectral power information. Do you see? One can't derive the conclusion you are trying to derive.
      Why did the researchers do it ambiguously like this? Were they being sloppy? Of course not. They simply were not interested in evaluating a time-averaged increase or decrease in brain activity. They wanted to look at variance and used both time- and frequency-domain methods to do it. Their approach fit their goals perfectly, so why should it be suitable for what we are trying to see into their results? As a matter of fact, "total spectral power" is mentioned only once, and even then within parentheses, in the main text of the paper. The authors don't even bother defining explicitly what they mean with it. The focus of their discussion is clearly on the observed increase in variance (sigma square) and decrease in spectral power at the lower frequencies (LFP).

    3. Let me elaborate more on a point I raised, Andy, to make sure it's clear. We lose phase information in the spectral power graph. Only amplitude is taken into account. We then know how much "power" each frequency component contributes to the original time-domain signal (BOLD). But without the phase info, we don't know whether this contribution is constructive or destructive. That is, we don't know whether these components interfere constructively or destructively with each other. So we may have a case where the total spectral power is huge, but the components interfere mostly destructively with each other, so the time-domain signal is puny. This is not only conceivable but ordinary. In contrast, we may have a case where low total spectral power corresponds to a significant time-domain signal because the component frequencies are in phase and interfere constructively, adding up their contributions. I hope this is clear.
      Your comments got me thinking. I suddenly became aware of how conducive to this specific form of misinterpretation this paper is. Sentences like "HIGHER total spectral POWER," "INCREASED AMPLITUDE variations," etc., are all suggestive of higher neuronal activity at first sight. I didn't notice this so much because I am very used to the jargon (I majored in electronics engineering in my bachelors, with emphasis on signal processing). But with your comments I suddenly realized how the specific choice of analysis made in this paper is incredibly conducive to misinterpretation if one isn't used to the nuances and specificities of the terms...
      Sobering... it gives me pause for thought...

  5. Hi Bernardo,

    Did you see this most recent story going around?

  6. In today's materialist science, you don't need "more brain activity" to have novel brain activity (or to have experience which seem more real than regular experience). These experiences could be explained, for example, by changing the connectivity of the brain. That is, exposing different regions of the brain to many signals that they do not normally receive by modification of information pathways by entheogens (for example DMT is quite similar to common neurotransmitters: ). This does not require more blood-flow to any part of the brain, but can still expose our insides to themselves in a way that is very novel and "psychedelic."

    1. Under materialism experience IS brain activity. Therefore, at some level, a broader and more intense experience has to correlate with more brain activity. It's disingenuous to deny this under materialism. A full elaboration of this point can be found in Chapter Two of my book Why Materialism Is Baloney. The complete argument cannot be captured in a blog comment.