14 DAY TRIAL // The human brain generally loses its ability to learn new tricks and process new experiences with age, experts say. Now, scientists finally shed some light on the mechanism that leads to this phenomenon.
In a new study, conducted on lab rat animal models, investigators revealed that the process of learning from new experiences is enabled by a host of tiny brain-cell structures. The latter become rigid with old age, and the brain therefore loses this essential ability.
Even if the study was not conducted on humans, the rat brain is a good analog for our own in such studies, so the finding hold for our species too. The new research was carried out by experts at the Mount Sinai School of Medicine (MSSM).
In order to figure out which area of the brain played the most significant part in this process, the research team decided to focus its attention on the prefrontal cortex. Past researches demonstrated that this area of the brain is essential for higher learning.
In addition, it controls a host of other cognitive processes, and this made it an appealing place to start.
One of the things that experts kept in mind throughout the research was that neurons in this brain region are usually very flexible and plastic in young animals, including humans. As such, neural circuitry in the prefrontal cortex are often remodeled.
Life experiences are primarily responsible for these changes. Stress is also a critical factor, as it was shown to play a role in reducing the number of synapses nerve cells make with each other.
But the studies also showed that the stress-affected neural circuits regain their capabilities after the harmful stimuli are gone. This does not appear to happen in the aging brain, LiveScience reports.
Nerve cell structures called spines “are modified when you learn something. In a sense, that's where learning occurs,” explains MSSM neuroscience professor and study researcher John Morrison.
When young rats were subjected to stress in the lab, many of their neural spines disappeared, but grew back after a stress-free period. A shortening of neural projections called dendrites was also noted.
In young rats, dendrites recovered after the stress was discontinued, but the same recovery process was not seen in older rats. “The way we interpret that is that with aging you lose a lot of the capacity to have experience-induced plasticity,” Morrison explains.
“So we think this gives us a really good working model for why with age you have these cognitive declines and impaired learning,” the expert goes on to say.
Details of the new research appear in the May 25 issue of the esteemed Journal of Neuroscience.