The brain ages in the same way as all structures and other systems in our body. However, it seems that the weather affects some people more than others, not only physically, but also in terms of their abilities. Why does this happen? What can we do about it? Are some people more apt to age, or do we have tools that can help us delay the effects of the passing of years?
At first glance, the answers that can solve the mystery of brain aging lie in certain genes. A group of researchers from the Babraham Institute in Cambridge (UK) and Sapienza University in Rome (Italy) have found answers by digging deeper into the generic gears that influence the complex mechanism of age-related cognitive deterioration. .
What is certain is that much of what happens when the brain ages is already known. For example, we know that neurons deteriorate and die, only to be replaced by others. This process is facilitated by a type of parent cell called neural stem cells (NSC). These are cells in the brain system that can self-regenerate and give rise to progenitor cells.
However, over time, these cells become less functional, and as a result, our brains become less functional as well. Now, what causes the aging of these cells? What exactly are the molecular changes that are responsible for their deterioration? These are the questions the researchers found answers to.
What happens when the brain ages?
Before we discover together why the brain ages, let’s first see what brain aging consists of. The latter is inevitable to some extent, although not uniform. In fact, it affects all brains, but in different ways. Decreasing the aging of the brain or stopping it altogether would be the best elixir for successfully attaining eternal youth.
The human brain is made up of approximately 100,000 million neurons interconnected through billions of synapses. Over the course of our lives, our brains change more than any other part of our body. From the moment the brain begins to develop in the third week of pregnancy until old age, its complex structures and functions are constantly changing.
In the first years of life, a child’s brain makes more than a million new neural connections per second. The size of the brain increases four times during the preschool period and up to 6 years it reaches approximately 90% of adult volume.
The frontal lobes, which are the areas of the brain responsible for executive functions (such as planning, operative memory, and impulse control), are among the last areas of the brain to mature. In fact, they may not even be fully developed until the age of 35.
But at a certain point, we start to age. As we age, all of our body’s systems gradually decrease their ability to perform, including the brain. Thus, certain changes in memory are associated with normal aging.
Common memory changes that are associated with normal aging include:
- Difficulty learning something new: memorizing new information may take longer.
- Difficulty remembering names and numbers: Strategic memory that helps remember names and numbers begins to decline at age 20.
- Difficulty remembering appointments.
While some studies show that one-third of older people have difficulty with declarative memory (remembering facts or events that have been accumulated and can be retrieved), other studies indicate that one-fifth of people at least 70 years old perform cognitive tests as well as those who are 20 years old.
General changes identified during brain aging would include:
- Brain mass: contraction in the frontal lobe and the hippocampus (areas involved in higher cognitive function and the coding of new memories). The changes start around the age of 60 to 70.
- Cortical density: narrowing of the outer surface of the sulcus due to the decrease in synaptic connections. Fewer connections, so this results in a slower cognitive process.
- White matter: White matter consists of myelinated nerve fibers that group together in rows and transmit nerve signals among brain cells. It is believed that myelin is reduced with age, and as a result, this delays the process and decreases cognitive function.
- Neurotransmitter systems: Researchers suggest that the brain generates fewer chemical messages as it ages, and it is this decrease in the activity of dopamine,
The role of genes as the brain ages
Now that we know what happens as the brain ages, let’s go back to the study we mentioned at the start of this article to see what the role of genes is in this process. At first glance, according to what the researchers indicate, the Dbx2 gene may explain brain aging.
The researchers compared the genetic changes and the stem cells / progenitor cells (NSPC) of old mice (18 months old) and young mice (3 months old). They were therefore able to identify more than 250 genes that changed their behavior over time, which means that it is likely that these genes are causing the cells indicated to malfunction.
Subsequently, the scientists noted that the increased activity of the gene called Dbx2 seemed to change the old NSPCs. They performed in vivo and in vitro tests which found that the increased activity of this gene in young NSPCs causes them to behave more like old stem cells. The increased activity of Dbx2 prevented NSPCs from growing or proliferating as young cells do.
Additionally, in older NSPCs, researchers have identified changes in epigenetic markings that may explain why stem cells can deteriorate over time. If we think of our DNA as an alphabet, epigenetic marks would be like accents and punctuation marks, since they tell our cells whether or not they should read genes, and if so, how they should do it. In this study, scientists discovered how these marks fit in the genome differently, by “telling” NSPCs to grow more slowly.
With this study, researchers have shown that these changes can contribute to the aging of the brain by slowing the process of brain renovation. Researchers are hopeful that these findings will one day lead to the reversal of the aging process. By understanding how aging affects the brain, at least in mice, researchers hope to identify ways to detect neural stem cell decline.