The "teenage" phase of the brain lasts much longer than we think – study

Scientists have identified five main "epochs" in the development of the human brain in a study that examined how the neural network changes from childhood to old age. This was reported by writes The Guardian.

The study, based on brain scans of nearly 4,000 people aged from under one year to 90, mapped out neural connections and how they evolve throughout life. This allowed for the identification of five broad phases, divided by four key "turning points" when the brain's organization shifts to a different trajectory – at approximately 9, 32, 66, and 83 years of age.

The childhood period of development lasts from birth to nine years of age, after which the adolescent phase begins – a stage that lasts on average until the age of 32. In the early 30s, the neural organization of the brain transitions into "adult mode" – the longest stage, lasting over three decades. The third turning point, at approximately 66 years of age, marks the beginning of the "early aging" phase of brain architecture. The "late aging" of the brain is formed at approximately 83 years of age.

Experts evaluated brain organization using 12 different metrics, including the efficiency of connections, the degree of their separation, and whether the brain relies heavily on central hubs or has a more branched network of connections.

From childhood to adolescence, the brain is defined by "network consolidation," where a vast number of synapses—connections between neurons—in a child's brain are reduced, and only the most active ones survive. During this period, the efficiency of connections in the brain decreases.

Meanwhile, gray and white matter rapidly increase in volume, so that the thickness of the cortex—the distance between the outer layer of gray matter and the inner layer of white matter—reaches its peak, and the cortical folds, the characteristic grooves on the surface of the brain, stabilize.

In the second "epoch" of brain development – adolescence – the volume of white matter continues to increase, so the organization of the brain's communication networks becomes increasingly sophisticated. This stage is characterized by a continuous increase in the efficiency of connections throughout the brain, which is associated with improved cognitive functions. The epochs were defined as sustained trends in brain development over a long period, rather than as fixed states.

"We are absolutely not saying that people in their 30s will behave like teenagers or that their brains will be like a teenager's brain," says Alexa Mouglis, who led the study. "It's more about the pattern of change itself." She added that the results could provide insight into risk factors for mental disorders that most often manifest in adolescence.

The most powerful overall trajectory shift occurs at around 32 years of age. Life events such as parenthood may play a role in some of the changes, though this study did not directly test for it. "We know that women's brains change after they have a baby," says Moseley. "It's a logical assumption that there might be a connection between these life milestones and what's happening in the brain."

From the age of 32, brain architecture is thought to stabilize compared to earlier phases, corresponding to a "plateau in intelligence and personality" as described in other studies. Brain regions also become more structurally divided.

The last two turning points were defined by a decrease in brain connectivity, which is likely related to aging and white matter degradation.