Magic Mushrooms and Brain Activity Revisited

By Bernardo Kastrup

Photo by Richard Büttner

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 isbrain activity (a totally inactive brain is, after all, a dead and unconscious brain under materialism). Not very long ago, 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?

graphic_Magic mushrooms and brain activity

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 substantiallyless 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.

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