As we grow older, our brains undergo significant rewiring.

Recent studies indicate that this transformation takes place in various stages, or “epochs,” as our neural structures evolve, altering how we think and process information.

For the first time, scientists have pinpointed four key turning points in the typical aging brain: ages 9, 32, 66, and 83. During each of these phases, our brains display distinctly different structural characteristics.

The findings were Published Tuesday in Nature Communications, revealing that human cognitive ability does not merely peak and then decline with age. In reality, research suggests that the interval between 9 and 32 years old is the sole period in which our neural networks are increasingly efficient.

In adulthood, from 32 to 66 years, the structure of the average brain stabilizes without significant modifications, leading researchers to believe that intelligence and personality tend to plateau during this time.

Following another turning point, from age 83 and beyond, the brain increasingly relies on specific regions as connections between them slowly deteriorate.

“It’s not a linear progression,” comments lead author, Alexa Maudsley, a postdoctoral researcher at the University of Cambridge. “This marks an initial step in understanding how brain changes differ with age.”

These insights could shed light on why certain mental health and neurological issues emerge during specific rewiring phases.

Rick Betzel, a neuroscience professor at the University of Minnesota and not a part of the study, remarked that while the findings are intriguing, further data is necessary to substantiate the conclusions. He cautioned that the theory might face challenges over time.

“They undertook a very ambitious effort,” Betzel said about the study. “We shall see where things stand in a few years.”

For their research, Maudsley and colleagues examined MRI diffusion scans (images illustrating water molecule movement in the brain) of around 3,800 individuals, ranging from newborns to 90 years old. Their objective was to map neural connections at varying life stages.

In the brain, bundles of nerve fibers that convey signals are encased in fatty tissue called myelin—analogous to wiring or plumbing. Water molecules diffusing into the brain typically travel along these fibers, allowing researchers to identify neural pathways.”

“We can’t open up the skull…we depend on non-invasive techniques,” Betzel mentioned, discussing this form of neuroscience research. “We aim to determine the location of these fiber bundles.”

A groundbreaking study utilized MRI scans to chart the neural networks of an average individual across their lifetime, pinpointing where connections strengthen or weaken. The five “eras” discussed in the paper reflect the neural connections observed by the researchers.

They propose that the initial stage lasts until age nine, during which both gray and white matter rapidly increases. This phase involves the removal of redundant synapses and self-reconstruction.

Between ages 9 and 32, there is an extensive period of rewiring. The brain is characterized by swift communication across its regions and efficient connections.

Most mental health disorders are diagnosed during this interval, Maudsley pointed out. “Is there something about this second phase of life that might predispose individuals to mental health issues?”

From ages 32 to 66, the brain reaches a plateau. It continues to rewire, but this process occurs at a slower and less dramatic pace.

Subsequently, from ages 66 to 83, the brain undergoes “modularization,” where neural networks split into highly interconnected subnetworks with diminished central integration. By age 83, connectivity further declines.

Betzel expressed that the theory presented in this study is likely reflective of people’s experiences with aging and cognition.

“It’s something we naturally resonate with. I have two young kids, and I often think, ‘They’re transitioning out of toddlerhood,'” Betzel remarked. “Science may eventually uncover the truth. But are they precisely at the correct age? I’m not sure.”

Ideally, researchers would gather MRI diffusion data on a large cohort, scanning each individual across their lifespan, but that was unfeasible decades ago due to technological constraints.

Instead, the team amalgamated nine diverse datasets containing neuroimaging from prior studies, striving to harmonize them.

Betzel noted that these datasets vary in quality and methodology, and attempts to align them may obscure essential variations and introduce bias into the findings.

Nonetheless, he acknowledged that the paper’s authors are “thoughtful” and proficient scientists who did their utmost to mitigate that risk.

“Brain networks evolve throughout life, that’s undeniable. But are there five precise moments of transition? I hope you’ll take note of this intriguing notion.”