Neuroplasticity
Your brain today isn't the same as yesterday. And what you do tomorrow will keep changing it.
That the adult brain changes with experience is very well established. What's still debated is to what extent new neurons are born in adulthood.
Sound familiar?
"I'm too old to learn this." It's one of the most common things people say… and one of the ideas neuroscience has most clearly debunked.
What it is
Neuroplasticity is the brain's ability to change its structure and function in response to experience, learning or injury. For a long time, the adult brain was thought to be practically fixed. We now know it isn't.
In 1949, Canadian psychologist Donald Hebb proposed a key idea: when two neurons repeatedly fire together, the connection between them gets stronger.1 It's the basis of how we learn: practising something strengthens the circuits involved.
The experiment
To get their licence, London taxi drivers have to memorise thousands of streets, an exam known as "The Knowledge". In 2000, Eleanor Maguire and her team scanned their brains and found that the back of the hippocampus, a key area for spatial memory, was larger than in other people. What's more, the longer they had been driving, the larger it was.2
Were they born that way, or was it the job? In 2011, the same team followed trainee taxi drivers for four years. Only those who passed the exam showed an increase in grey matter in that area; those who failed and the control group did not.3
What we know today
Changes can happen quickly. In a 2004 study, adults who learned to juggle over three months showed an increase in grey matter in visual areas related to motion, which shrank again after they stopped practising.4
An open debate is whether new neurons are born in the adult brain. In 2018, one study found no young neurons in the adult hippocampus.5 A year later, a research team in Madrid, using different tissue-preparation techniques, found thousands of them in healthy people in their eighties.6 The question still isn't fully settled.
Myth vs. reality
Myth "We only use 10% of our brain" or "after a certain age the brain stops changing".
Reality We use all of our brain, though not every area at once, and it keeps adapting throughout life. That said, plasticity is greatest in childhood.
In everyday life
- Practise regularly: short, frequent sessions work better than the occasional binge.
- Use it or lose it: connections that aren't used weaken, as the jugglers showed.
- It's never too late: learning something new as an adult changes your brain too.
Sources
- Hebb, D. O. (1949). The organization of behavior: A neuropsychological theory. Wiley.
- Maguire, E. A., Gadian, D. G., Johnsrude, I. S., et al. (2000). Navigation-related structural change in the hippocampi of taxi drivers. Proceedings of the National Academy of Sciences, 97(8), 4398–4403. doi.org/10.1073/pnas.070039597
- Woollett, K., & Maguire, E. A. (2011). Acquiring "the Knowledge" of London's layout drives structural brain changes. Current Biology, 21(24), 2109–2114. doi.org/10.1016/j.cub.2011.11.018
- Draganski, B., Gaser, C., Busch, V., Schuierer, G., Bogdahn, U., & May, A. (2004). Changes in grey matter induced by training. Nature, 427(6972), 311–312. doi.org/10.1038/427311a
- Sorrells, S. F., Paredes, M. F., Cebrian-Silla, A., et al. (2018). Human hippocampal neurogenesis drops sharply in children to undetectable levels in adults. Nature, 555(7696), 377–381. doi.org/10.1038/nature25975
- Moreno-Jiménez, E. P., Flor-García, M., Terreros-Roncal, J., et al. (2019). Adult hippocampal neurogenesis is abundant in neurologically healthy subjects and drops sharply in patients with Alzheimer's disease. Nature Medicine, 25(4), 554–560. doi.org/10.1038/s41591-019-0375-9