Psilocybin Study Reveals Disordered Brain Networks

Research has repeatedly indicated that psilocybin, the psychoactive compound in magic mushrooms, could help treat several mental health conditions.

Yet little is known about what happens within “functional brain networks” – the communication routes linking different areas of the brain.

To explore this more closely, scientists at Washington University School of Medicine in St. Louis scanned the brains of seven healthy participants on numerous occasions before, during and after they took psilocybin. Their results were recently published in Nature.

On average, each person underwent 18 brain scans. The fMRI scans, which track changes in cerebral blood flow, showed that links within recognised brain networks became disrupted, whereas communication across separate networks increased.

Put differently, psilocybin makes the brain’s usual information processing less predictable. Under the psychedelic, the brain becomes more disorganised.

Psilocybin brain-network study: strengths and findings

There is a great deal to appreciate in this new research. Its especially distinctive feature is the rigour and quality of the methods used.

Anyone who has run an fMRI experiment will understand how costly and time-consuming it can be, even before accounting for the added challenge of managing participants while they are tripping. The researchers also deserve credit for using an “active control” – a stimulant medication.

In the days and weeks following the psychedelic session, the team identified lasting alterations in the connections between the hippocampus, an area involved in short-term memory, and the default mode network, a collection of brain regions active when someone is resting rather than attending to their surroundings.

These temporary shifts may be responsible for psilocybin’s neuroplastic – meaning the brain’s malleability – and therapeutic effects. In this respect, the study aligns with renewed interest in psychedelic-assisted therapy for anxiety, depression and addiction.

Limits of psilocybin research in healthy volunteers

Because the research involved healthy volunteers alone, however, it remains uncertain whether its results apply to patients – the people who might benefit from psilocybin-assisted psychotherapy.

Furthermore, most results came from repeated measurements in only six people, after one participant withdrew. The paper gives no details about these individuals’ previous experience with psychedelics. This creates a possible risk of “selection bias”, further restricting how far the findings can be generalised to the wider population.

Other issues also limit the conclusions that can be made. Although the researchers used an active placebo, rather than an inactive sugar pill, they did not say whether participants or researchers could identify whether psilocybin or placebo had been given once the experiment was under way.

That is highly likely, and represents a common difficulty in psychedelic research: psilocybin’s psychoactive effects mean that the double-blind approach, in which neither the researchers nor participants know who has received the drug or placebo, simply fails.

This matters because previous studies show that placebo effects can themselves produce mystical-type experiences.

It is therefore uncertain whether the recorded differences in brain activity arose only from the drug, or were also shaped by the participants’ beliefs and expectations about psilocybin’s effects.

Several authors disclose conflicts of interest. This is not inherently a warning sign, but certain disclosures are directly connected to commercialising the neurotechnologies, including precision fMRI for therapeutic use, employed in the study. The paper also does not make clear how the risk of potential bias was reduced.

There also seem to be departures from the study protocol – its planned methods, primary goals and the material ultimately reported. One secondary aim, for example, was to assess enduring changes in participants’ wellbeing using the persisting effects questionnaire.

Had these results been reported, they might have offered insight into the clinical significance of receiving psilocybin. Unfortunately, the paper contains no data from this questionnaire.

Questions remain

The altered brain patterns initially look striking, yet the precise meaning of these impressive brain images is not immediately obvious. Subjective, self-reported information is absent from the picture. Such evidence is needed to establish what the changes in neural connectivity actually represent.

Key unresolved questions include: what does it mean for someone’s brain to become more disorganised? And how do the observed changes in brain activity relate to the way people feel and thrive in their everyday lives?

Answering them requires opening neuroscience’s black box, perhaps by introducing methods that bridge the divide between “objective” brain measurements and “subjective” human experience.

Only by returning the strangeness of the subjective psychedelic experience to the brain picture can we decide whether it was truly worthwhile to scan the hell out of all those participants.

Until then, we should take care not to create high expectations among desperate patients simply because colourful images appear compelling.

Michiel van Elk, Associate Professor, Cognitive Psychology, Leiden University

This article is republished from The Conversation under a Creative Commons licence. Read the original article.