#31: 🧠 The Science of Brain Plasticity and Lifelong Learning
Plus: A Brief History of Psychedelics
💬 In this note:
🧠 Key Milestones in Brain Development and Aging
🌈 The History of Psychedelics
📚 My Best Friend’s Exorcism
🧠 Key Milestones in Brain Development and Aging
Growth charts track metrics like height and weight through childhood, adolescence and into adulthood. These give a clearer picture of human physical development as we age. However, less is known about the key milestones of brain aging.
To find out more, an international team of researchers collected brain scan data from multiple studies representing 101,457 brains at all stages of life. The youngest scan in the study came from a 16-week-old fetus; the oldest was from someone 100 years old.
While the brain is largely set up by birth, with the creation of new neurons largely complete, how different parts of the brain communicate with one another changes over a person’s lifespan.
The good news is our brains are built to change, meeting the challenges set by every stage of life. While science cannot yet predict the exact ages of brain development, here’s a general guide to how the brain may change at various ages.
Infancy: Birth to 2 years
Infant brains have a huge number of synapses, which are the connections between neurons. This allows for a lot of excitatory connections, so there’s huge learning potential.
Childhood: 2 to 10 years
During childhood the brain shifts to learning, which involves strengthening important connections and decreasing ones that aren’t being used. To decrease connections, babies lose about half of the synapses they had in infancy in a process known as synaptic pruning. To strengthen connection, myelination, the process by which neuronal connections are wrapped and insulated with the fatty protein myelin, increases throughout childhood and beyond.
Because there is so much connection building and strengthening during childhood, the brain is particularly sensitive to interactions with caregivers and others in their environment. Stress stemming from trauma or neglect in this period can have deeply profound effects on the rest of a child’s brain development.
Adolescence: 10 to 19
At adolescence, there are dynamic changes in brain networks involved in learning how to process emotions and motivations around different experiences. This heightened sensitivity to our environment is reflected by widespread synaptic pruning and myelination in the circuits underlying emotion and reward processing. It’s why teens are incentivized to explore new experiences, no matter how risky or dangerous they can be.
Young Adulthood: 20 to 39
The 20s are often thought of as a “peak” of brain development or a stage at when the brain has “matured.” This myth stems in part due to the observation that white matter volume, a proxy for the speed of information processing, reaches a high level at these ages.
As the brain progresses into the 30s and 40s, it prioritizes, rather than diminishes, synaptic plasticity, or the ability for connections to strengthen or weaken in response to activity changes.
Age 40 - 65
Experiences such as engagement in a community, lifestyle choices or exposure to stress or toxins can drastically affect brain development and aging. A 50-year-old who is highly social and regularly exercising, traveling or volunteering might have a “younger” brain than a 50-year-old who is largely isolated from others and rarely engages in enriching activities.
Dr. Mark Harnett’s lab recently showed the presence of “silent synapses,” in adult mice. These are connections that are inactive until they’re recruited to help form new memories. These synapses had long been associated with early development, but Harnett and his lab have also confirmed their widespread presence in adult human brains across ages and different regions.
65 and older
In the latest stages of life, the brain does shrink in size and can begin to degenerate. Yet older individuals have the potential for greater wisdom built off a lifetime of experiences, though the brain circuitry tied to emotional processing and moral decision-making might be involved in different components of wisdom.
🌈 The History of Psychedelics
For thousands of years, indigenous societies in Mexico and Central America have used psychedelics for medicinal, spiritual, and cultural purposes. For instance, Native American tribes have used peyote in religious ceremonies, while indigenous people in the Amazon use ayahuasca for spiritual reasons.
In the 20th century, psychedelics became more widely known in Western society, thanks to the work of researchers like Swiss chemist Albert Hofmann, who synthesized lysergic acid diethylamide (LSD) in 1938 and accidentally discovered its psychedelic properties in 1943. This discovery led to a wave of research into the therapeutic potential of psychedelics in the 1950s and 60s.
In the 1950s, R. Gordon Wasson, an amateur mycologist and banker, and his wife Valentina Pavlovna traveled to Mexico to investigate the use of mushrooms in traditional Mexican religious ceremonies. There, Wasson participated in a Mazatec mushroom ceremony in Oaxaca, where he consumed psilocybin mushrooms and had a profound spiritual experience. His plant medicine guide was a woman named Maria Sabina, often referred to as the mother of mushrooms. She contributed to the popularization of the indigenous Mexican ritual use of entheogenic mushrooms with westerners.
Wasson later published an article about his experience in Life magazine, which introduced the use of magic mushrooms to a wider audience in the United States. Wasson's articles and subsequent research into the use of magic mushrooms by indigenous cultures helped spark interest in the psychedelic properties of psilocybin and other hallucinogenic substances in the US during the 1950s and 1960s.
The discovery of psilocybin mushrooms and LSD triggered a wave of research into the therapeutic potential of psychedelics in the 1950s and 1960s. During this time, researchers studied the therapeutic potential of psychedelics for conditions such as anxiety, depression, and addiction.
Interest in psychedelics eventually led to the counterculture movement of the late 1960s, which embraced the use of psychedelics as part of its rejection of mainstream culture and values.
However, with the rise of counterculture and the association of psychedelics with the hippie movement in the 1960s, the use of psychedelics became increasingly controversial and eventually led to their criminalization. The Controlled Substances Act of 1970 in the United States classified psychedelics as Schedule I drugs, which are deemed to have a high potential for abuse and no accepted medical use.
Despite the criminalization of psychedelics, there has been a recent resurgence of interest in their therapeutic potential. In recent years, research has shown promising results in the use of psychedelics such as psilocybin and MDMA for the treatment of conditions such as depression, anxiety, and PTSD.
Currently many regions of the world are embracing a resurgence of the psychedelic revolution. Some countries, such as the Netherlands, Australia, and Portugal have decriminalized or legalized the use of certain psychedelics for medicinal purposes, and several states in the US have followed suit.
📚 Book of the Week
My Best Friend’s Exorcism: A Novel by Grady Hendrix
Grady Hendrix does it again with a humorous yet thrilling page-turner which brings together the 80s, teenage angst and the supernatural. Hendrix is the author of another one of my favorite books, The Southern Book Club’s Guide To Slaying Vampires (5 / 5 stars on that one).
⚡️ Check This Out
Why are we so obsessed with creating a humanoid robot? Haven’t we seen enough apocalypse movies where robots revolt to know that this is a bad idea?
Here’s my favorite tweet about the company.