- Published1 Jul 2011
- Reviewed1 Jul 2011
- Source BrainFacts/SfN
For decades, scientists thought the adult human brain was static and unchanging, but in recent years have learned it is much more dynamic. Elizabeth and Neil Losin, University of California, Los Angeles, graduate students, explain how in their 2011 Brain Awareness Video Contest submission.
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Narrator: Our brain’s development is guided and shaped by experience during childhood and adolescence, but for most of the 20th Century, scientists thought that the brain’s malleability was lost by adulthood.
Liz Losin: If that’s true, the my brain now is the same as it was in that last picture, when I was in high school, despite the years that have past, and all the experiences I’ve had since then. In 1913, neuroanatomist Santiago Ramon y Cahal, wrote that “the nerve paths are fixed, ended, and immutable. Everything may die,” he wrote “nothing may be regenerated.” But we’ve learned a lot about the brain since then. And we are starting to realize that the adult brain is more dynamic than we ever imagined.
Narrator: Our earliest understanding of brain development came from experiments on animals. Blocking vision in one eye early in life dramatically reduced the representation of that eye in the brain, and could even cause blindness. But blocking an eye later in life had no such effect on the brain or vision.
Liz Losin: So the same treatment that caused change in the young brain did not cause change in the adult brain. Then neurologists began to realize that large scale alterations to the brain or body, such as traumatic injury, did cause changes in the adult brain. We’ll come back to our unfortunate amputee in a minute, but first, how does the brain rewire itself? The neuroscientist Paul Bach-y-Rita illustrated the process with a metaphor about getting from one place to another. I need to get from my office here in the Brain Mapping Center over to my seminar, here, in Haines Hall. But I’ve got a problem. My usual route is blocked by construction. So how and I going to get to my seminar? Well let’s find out.
Narrator: She begins by trying alternative routes. A similar rerouting process occurs in the brain after a traumatic injury. Just like a person finding a new path, the neurons affected by the injury rewire themselves. Some paths work better than others, and she gradually learns with route is the fastest. Once she does, this new route becomes her routine, and in a similar way, the brain’s neurons form new connections.
Liz Losin: This process by which the brain changes is called neuroplasticity.
Narrator: If a person has a limb amputated, the brain still expects to receive sensory input from the limb. Neighboring parts of the brain reroute input to the areas representing the missing limb, so when other parts of the body, like the face, are touched, it can feel like a touch on the missing limb, creating a so-called phantom limb.
Liz Losin: Ok, so major injuries can cause changes in the adult brain. But what about more benign, everyday activities? Juggling is a complex activity that requires a unique combination of visual and motor skills to perform. A skilled juggler can keep track of several objects at once, throwing and catching each object with precision, and constantly correcting small errors in the pattern. Could an activity like juggling change a person’s brain?
Narrator: Researchers in Germany taught adult subjects how to juggle and captured images of their brains in an MRI scanner as they became more proficient. Even after just seven days, the researchers found a measurable increase in gray matter in a brain region critical for visual motion recognition.
Liz Losin: So it turns out that a brain changing event does not have to be a life changing event. And a universal type of experience, a person’s culture, may shape the brain well into adulthood.
Researchers in Switzerland followed American exchange students as they learned to speak German and found that learning a new language caused gray matter growth in the left inferior frontal gyrus, an area that is active during language processing.
So what does this all mean? It means our brains are more dynamic than we ever imagined, even just a few decades ago. They have the potential for incredible recovery after injury and they can be shaped by our experiences even in adulthood. All as the result of an amazing process called neuroplasticity.