The brain that changes itself is now mainstream science. Neuroplasticity, the nervous system’s ability to reshape itself over time, was widely dismissed about 30 years ago, according to an essay published by the AAAS. Today it counts as a basic feature of the nervous system and a subject of rigorous study. Norman Doidge’s book The Brain That Changes Itself tells of the pioneers who fought to prove the idea, and of stroke patients who made remarkable recoveries.
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How a brain rewires
Much of the change happens at the synapse, the junction where one neuron passes a signal to the next. A review in the Nature journal Neuropsychopharmacology describes plasticity as the nervous system changing the strength of its connections through experience or injury. That reweighting is what lets the brain lay down lasting memories.
Timing drives much of it. If one neuron fires just before the neuron it feeds, the link between them grows stronger. If it fires just after, the link weakens. The window for this runs to tens of milliseconds, and the review calls it the physical basis of learning and memory. Slower processes act over hours, days or weeks. They turn connections down when activity runs high and up when it drops.
The idea was once limited to the young. The BBC’s science writer notes that researchers now see it as a constant force through adult life.
Why flexibility needs a limit
More change is not always better. Andrea Gomez, a cell biologist at the University of California, Berkeley, told Science News that the brain works on “a knife’s edge” between flexibility and rigid structure. With too much plasticity, she said, no memory would ever form.
Her own work shows how small the switches can be. In 2016, she and colleagues reported that when mice lacked one spliced version of a protein, some synapses responded weakly, and the mice began avoiding new objects instead of exploring them. She is now studying psychedelics, which are thought to open windows of plasticity. In early work, one dose of psilocybin set off thousands of splicing events in mouse brains.
What it means for health
Plasticity going wrong sits behind a wide range of conditions, including depression, schizophrenia, addiction and post-traumatic stress disorder, the Nature review says. It also notes that the best ways to trigger helpful change for therapy remain open questions.
Some of the tools are ordinary. Thorsten Barnhofer, who teaches clinical psychology at the University of Surrey, told the BBC that stress can directly hold back plasticity. Managing stress helps the brain stay adaptable, he said. For a six-week trial, he set the BBC’s reporter 30 minutes a day of guided mindfulness, with one coached session a week over Zoom.
The AAAS essay raises the next question. If plasticity can repair a brain after a stroke, it could also be pushed to lift ordinary thinking, and that brings ethical choices with it.
