The Four Ages When Your Brain Completely Reorganizes Itself

The brain, like all our organs, ages: the information is not a scoop. Although it would be tempting to believe that it declines in a homogeneous manner towards the inevitable loss of its abilities, this is a false idea, which neuroscience today contradicts. A team of researchers from the prestigious University of Cambridge has just demonstrated that brain decline does not follow a linear curve.

Published on November 25 in the journal Nature Communicationstheir study demonstrates that upon reaching four different ages, our brain sees its internal organization undergo significant changes. In total, it will go through five major “ brain eras », which occur precisely at nine, 32, 66 and 83 years.

The long transition from childhood to neuronal maturity

To determine these four stages, researchers analyzed diffusion MRI scans from people aged 0 to 90 years old. These brain examinations make it possible to track the movements of water molecules in our brain. In the white matter (the connecting fibers of the brain), water tends to propagate in the direction of the neuronal fibers (anisotropy phenomenon). It was by measuring anisotropy that researchers were able to map the wiring and evolution of brain connections over time.

By observing these data, the researchers found that, from birth to the age of 9, the brain makes a large number of connections (synapses)while eliminating those he does not use. An essential sorting phase for the child, which allows him to strengthen the brain circuits heavily used by learning and the environment. Those who resist this process of elimination will form the basis of its fury great cognitive networks.

During this period, white matter and gray matter are also experiencing very rapid expansion in their volumebecause the brain optimizes its transmission speed and processing capacity.

It was also during this period that the brain is the most vulnerablethe researchers explaining that it corresponds to “ a time when cognitive abilities are progressing strongly, but when the risk of neurodevelopmental disorders is also more marked “. To image the phenomenon, imagine the ultra-rapid assembly of a high scaffolding: as long as its bars are not solidly fixed (the neural networks), the slightest pitching can prove very dangerous.

Then comes a tipping point around age 32; it is according to the team, the period when brain architecture is most optimized. Alexa Mousley, neuroscientist and co-author of the study, explains that this is when “ largest directional changes in wiring and largest trajectory inflection (Editor’s note: evolution of the structure and organization of brain networks over time). The brain here completes its maturity and finally emerges from the structural changes typical of adolescence, beginning the longest and stable period of its existence: its connections are perfectly defined.

From there, for almost 30 years, the brain changes very littleits internal organization is in the plateau phase, coinciding, according to the team, with “ stability of intelligence and personality “. This is when we are at our zenith, from a cerebral point of view, of course.

The last decades of the brain: the end of the cerebral routine

Around age 66, the brain enters its third major period. Nothing catastrophic or any sudden change according to the researchers, but it is at this age that we see the first slowdowns appear : connections become less vivid and their reorganization is slower; neuronal plasticity attenuates. White matter deteriorates slightly, causing areas of the brain to communicate more slowly with each other. According to Mousley, this transition also corresponds to “ and age when people are at greater risk for a range of health problems that can affect the brain, such as hypertension ».

Then comes the ultimate transformation, which occurs around age 83. Not that the brain can no longer function, but its large neural networks are used differently. Instead of making its larger areas (such as the frontal, parietal and temporal areas) work in coordination, it uses more to areas that are still efficient and have lost less robustness (especially primary sensory and motor regions).

The latter generally keep better connectivity and are more resistant to aging. According to the conclusions of the study, the brain moves from a global mode of operation (large areas of the brain work together) to a local mode (only a few well-preserved regions take over).

Our brain therefore remains surprisingly active and plastic, even in the twilight of its lifewhich completely contradicts false theories who rocked neurobiology throughout the 20th century^th century. Those who postulated that our brain froze once childhood passeda dogma that was taught until the 1990s. A reasoning that has aged horribly poorly, unlike some of our neurons, which, on the contrary, strive to keep the machine in working order.