The human brain goes through five 'non-linear' stages of development, according to new study

The human brain goes through five major stages of development in its lifetime, each bringing "distinctive age-related changes", scientists have identified.

Data shows there is a "non-linear change across development" in the brain, highlighting it does not continue on one steady progression throughout your life.

The study "identified four major topological turning points across the life span" which occur at the ages of nine, 32, 66, and 83 years old.

Nearly 4,000 people aged from under one up to 90 had their brains scanned for the study conducted by the University of Cambridge.

Dr Alexa Moseley is from the university's Cognition and Brain Sciences Unit and led the study. She said the brain goes through "major turning points" in its rewiring.

"What we were able to find is that around these turning points, the manner in which the brain is reorganising shifts and begins a new trajectory," she said.

"Each turning point is characterised by slightly different changes."

The stages were identified as childhood — from birth to age nine, adolescence — from nine to 32, adulthood — from 32 to 66, early aging — from 66 to 83, and late aging — from 83 onwards.

"Many neurodevelopmental, mental health and neurological conditions are linked to the way the brain is wired," Duncan Astle, a professor of neuroinformatics who was part of the team responsible for the research said.

"Differences in brain wiring predict difficulties with attention, language, memory, and a whole host of different behaviours."

Adolescence goes beyond teenage years

The study referred to each period of brain growth as "epochs" and highlighted key "topological developments" within each age bracket.

The first epoch indicates that the "childhood topological trajectory ends around nine years old" the report states.

In that period, topological efficiency actually decreases in line with synaptic elimination.

"From infancy until about nine years old, the brain is actually becoming less efficient," Dr Moseley said.

"But after nine years old, this changes and the brain starts becoming more efficient all the way up until around 32 years old."

The second epoch is between nine and 32. In that time the brain transitions from childhood to adolescence.

This period is the only one where the brain's neuron network gets more efficient, the study showed.

Different to what most people may think, this study showed that adolescence continues later in your life.

"What we're showing here is essentially that the path or the pattern of rewiring in the brain is continuous all the way up until 32 years old," Dr Moseley added.

Adult life and aging

Adulthood is the longest epoch of the five, lasting three decades from 32 to 66, and its length offers a period of stability for the brain.

During this period, the brain efficiency decreases but it is here where our brains reach its height of intelligence and personality.

Early aging begins at 66, the study shows, and it is here where a decline in brain connections begins.

The brain starts to become separated into areas that work together, rather than as one whole brain.

That change is called "increasing modularity", Dr Moseley said.

And then at the age of 83, the brain enters its final stage of development. It is here that there are more pronounced signs of aging.

"What's happening in the late aging phase is something that we call an increase in centrality," Dr Moseley said.

That is a technical term to say "some regions become more important for connectivity than others", she added.

Professor Astle added the research shows the brain goes through changes just like the body does.

"Understanding that the brain's structural journey is not a question of steady progression, but rather one of a few major turning points, will help us identify when and how its wiring is vulnerable to disruption," he said.