Our brain does not go through life in a linear fashion. A vast mapping of neural wiring, established from thousands of magnetic resonance images, has just revealed the existence of four major architectural turning points that divide our mental life into five distinct phases.
This discovery comes from an analysis conducted by neuroscientists at the University of Cambridge, who studied the brain connectivity of 3,802 individuals aged 0 to 90. Using an MRI technique that traces the movement of water molecules in white matter, they were able to map the evolution of neural networks.
Illustration image Pixabay
Their work, published in
Nature Communications, outlines a novel timeline of brain development and aging, where abrupt transitions follow long periods of stability.
Childhood and the long adolescence
From birth to around nine years old, the brain is under construction. It first produces an overabundance of synaptic connections, which it then gradually refines by pruning those that are seldom used. This massive consolidation of networks is accompanied by rapid growth in gray matter and white matter volumes. This phase of high plasticity lays the foundations for the future brain architecture and corresponds to a period of intense learning, but also increased vulnerability to neurodevelopmental disorders.
Contrary to the widespread idea of adolescence ending around age 25, the data indicate that the characteristic reorganizations of this period continue well beyond. The next turning point occurs on average only at age 32. Until this age, the brain continues to optimize and specialize its communication pathways. The researchers observe that the most marked transition in terms of connection reorganization occurs around the age of thirty, showing that this period concludes an extended developmental chapter.
This long adolescent phase ends with what the team describes as the most significant topological tipping point in the entire lifespan. Around age 32, the brain reaches a peak in the efficiency of its wiring. Directional changes in connectivity are most pronounced at this time, marking the entry into a new era. This discovery provides a biological framework for the subjective feeling of a late entry into adulthood.
Adult stability and the beginnings of aging
After age 32, a long period of relative stability begins, spanning over three decades. The overall architecture of brain networks stabilizes, without undergoing major transformations. This phase corresponds to a plateau in measures of intelligence and personality stability. The adult brain, having completed its maturation, then functions with optimized and consistent efficiency, which underlies the ability to handle responsibilities and accumulate expertise.
A new, more subtle turning point is identified around age 66. It marks the beginning of a phase of "early aging." The changes are not abrupt, but a gradual reorganization of networks becomes detectable. This evolution is likely linked to the beginnings of degeneration in white matter, the brain's cables, and to reduced connectivity. This period often coincides with an increase in vascular health risks, which can influence brain health.
The last major transition occurs around age 83. The data for this age group are more limited, but they indicate a change in brain function. Overall connectivity declines further, and the brain seems to shift from an integrated functioning to a more localized reliance on certain key regions, while other communication pathways weaken. This advanced phase of aging highlights the progressive weakening of neural networks.
Article author: Cédric DEPOND