A study published in Nature has shown that psychedelics can reopen learning windows in the brain, known as “critical periods,” which typically occur during childhood. This discovery allows researchers to better understand how these substances can be used in the treatment of severe mental conditions such as depression and anxiety. Moreover, the study also suggests that psychedelics could benefit other conditions, such as certain types of blindness and deafness.
“During specific periods of brain development, the nervous system displays greater sensitivity to ethologically relevant stimuli, as well as increased malleability for synaptic, circuit, and behavioral modifications,” wrote the team of researchers led by neuroscientist Gül Dölen from Johns Hopkins University, explaining what critical periods are. “Neuroscientists have long been seeking methods to reopen them to find therapeutic benefits.”
It is common for these learning windows, which typically occur during childhood, to eventually close over time, making it more difficult for us to absorb new habits and knowledge.
In a previous 2019 article published in Nature, Dölen’s team had already demonstrated that MDMA is capable of reopening critical periods. In this new study, the researchers decided to test other substances.
Through tests on mice, they discovered that each psychedelic is capable of activating this learning window for a different period of time, with longer trips resulting in a greater opening. For example, an experience with ketamine, which lasts approximately 30 minutes in humans, opened a critical period of two days in mice. Sessions with MDMA, lasting up to five hours, maintained the opening for two weeks. LSD, with an effect lasting up to eight hours, achieved an opening of three weeks. Ibogaine, which can last up to 36 hours in humans, kept the mice in an open state for four weeks (the maximum measurement period).
These studies may also help understand the mechanisms of motor recovery. As Dölen explained in an article for Wired magazine, immediately after a stroke, for example, a critical period naturally opens and closes several months later. If the theory is correct, the reopening caused by psychedelics could help patients regain their motor skills. Understanding this issue, i.e., demonstrating that psychedelics can be used in various fronts, is the next step in Dölen’s research.
As psychiatrist Rachel Yehuda stated in Wired, the findings of the study help explain “how something as short-lived as the psychedelic experience can have lasting and transformative effects far beyond the period of time when the substance is present.”
Dölen reminds us, however, that this reopening also represents a period of vulnerability, highlighting the need for psychedelic therapies to be conducted in controlled environments with specialized teams. Although the discovery of the world can be enchanting for children, for example, they are also more impressionable. “We can really mess up kids more than adults,” the researcher told Wired, emphasizing the importance of protecting young individuals from exposure to potentially disturbing materials. “You want to teach new things to children, but you don’t want them to learn Japanese through Japanese pornography.”
That is why she refers to the reopening of a critical period as an “extremely agnostic” tool, as it may not be entirely good or bad.
“The results [of the study] suggest that psychedelics could serve as a ‘master key’ to unlock a wide range of critical periods,” wrote the researchers.
“In fact, recent evidence suggests that repeated administration of ketamine is capable of reopening the critical period for ocular dominance plasticity by targeting the extracellular matrix (ECM). This knowledge expands the scope of disorders that may benefit from psychedelic treatment (including autism, stroke, deafness, and blindness); exploring this possibility is an obvious priority for future studies.”