Exercising helps erase bad memories, according to science.
“Hit the gym hard and don't give it another thought.” That phrase, half meme, half well-intentioned advice, has more scientific backing than exercise seems. Behind protein shakes and mirror selfies, there's a surprisingly solid scientific basis: working out can help us forget bad memories . And no, this isn't broscience (something like the science of gym-goers), this is real neuroscience.
Deep within our brain, in the hippocampus—a brain structure key to memory—is the subgranular zone of the dentate gyrus, where new neurons are continuously generated. This process, called adult neurogenesis, is one of the few examples of nerve cell development that continues throughout our lives.
The "newborn" neurons will integrate into existing brain circuits, forming new synaptic connections. And this is where the interesting part comes in: these new neurons and the new "wiring" added to our brain, in addition to helping us learn, destabilize memories we no longer need. In other words, the brain is continually renewing its connections, and this rewiring allows us to forget certain things.
A group of scientists has demonstrated in mice that increasing neurogenesis in this area of the hippocampus after a traumatic experience reduces the memory of that experience and the symptoms of post-traumatic stress associated with it. The laboratory animals stop overreacting to situations to which they shouldn't react, show fewer symptoms of anxiety, and are better at extinguishing fear-associated memories . The more new neurons, the fewer traumatic memories and fewer stress-related behaviors.
And how can we increase neurogenesis? With exercise. With cardio, weight training, or simply by moving and staying active. Several studies already indicate that physical activity promotes the formation of new neurons in adults. Moderate aerobic exercise (such as brisk walking, running, or cycling) appears to be especially effective, although strength training can also provide benefits.
This effect is produced by several molecules released during physical activity, such as BDNF (brain-derived neurotrophic factor), which acts as a "fertilizer" for neurons, promoting their growth and connection. Other substances, such as irisin, IGF-1, and beta-endorphins, are also involved in this regenerative process. In addition to creating new neurons, exercise improves brain plasticity, that is, the brain's ability to adapt and change.
To learn more about how this process works, a research team simulated neurogenesis events in a neural network trained to recognize objects. By introducing new neurons (i.e., renewing some connections), the network performed better and was able to generalize knowledge to new images . It's possible that our brains use neurogenesis in the same way: preventing cognitive overload, breaking up old patterns, and making room for new ones.
But don't wait too long! Another study found that this healthy form of forgetting, promoted by neurogenesis, only works while memories still depend on the hippocampus. If we wait too long and that traumatic memory becomes "distributed" throughout the brain, it will be less susceptible to changes in hippocampal plasticity, and no matter how much exercise we do, it will still hurt.
In short: exercise doesn't just make us feel better; it can help us reset our brains. Not just by burying old memories, but by helping us forget them from a biological perspective. Everything seems to indicate that the brain needs that neurogenesis to help us forget, adapt, and move forward. So, at least this time, your friend at the gym, that gymbro, was right.
In 2019, researcher Lauretta El Hayek found that experimental animals improved their memory performance when they exercised. This improvement resulted from the release of lactate, a waste product of anaerobic metabolism produced by physical activity that we now know is very useful for various tissues.
In particular, lactate has the ability to cross the blood-brain barrier (whose function is to prevent all substances circulating in the blood from reaching the nervous system) and reach the brain. Once there, it is absorbed by neurons and stimulates the production of brain-derived neurotrophic factor (BDNF), a protein essential for the memory encoding mechanism.
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