The 5 Brain Epochs: Development From Birth to Old Age
Advanced analytics with rich data sets reveal nuances of human development.
Updated November 27, 2025 | Reviewed by Devon Frye
We have many models of human development, from personality and psychosocial ones to those based on neuroscientific and developmental research. Freud (1937), envisioning a scientific model for psychoanalysis and the mind, discussed our capacity for growth and development in Analysis Terminable and Interminable. Certain people are able to change to varying degrees, likening working with them to a sculptor working in "hard stone or soft clay." Of those who are inflexible, he presciently writes:
"In another group of cases we are surprised by an attitude in our patients which can only be put down to a depletion of the plasticity, the capacity for change and further development, which we should ordinarily expect. We are, it is true, prepared to find in analysis a certain amount of psychic intertia... But with the patients I here have in mind, all the mental processes, relationships and distributions of force are unchangeable, fixed and rigid. One finds the same thing in very old people, in which case it is explained as being due to what is described as force of habit or an exhaustion of receptivity—a kind of psychical entropy. But we are dealing here with people who are still young. Our theoretical knowledge does not seem adequate to give a correct explanation of such types. Probably some temporal characteristics are concerned—some alterations of a rhythm of development in psychical life which we have not yet appreciated ." [italics added for emphasis]
Mind-Bending Developmental Research
Now, a population-level analysis in Nature Communications (Topological turning points across the human lifespan; Mousley et al., 2025) is making big waves. Analyzing diffusion MRIs (a form of magnetic resonance imaging looking at "tractography," or the flow among brain regions and networks) from 4,216 people, ages 0 to 90, maps how structural brain networks evolve.
This work, complex and elegant, reveals four "turning points"—around ages 9, 32, 66, and 83—comprising five “epochs,” each with a distinct fingerprint. Rather than chasing single peaks, this multivariate, non‑linear model shows how many brain network features shift together at key ages—capturing complexity and nuance.
Epoch 1 (0–9): From exuberance to organization
Developmental/clinical correlates:
Epoch 2 (9–32): The long adolescence of the connectome
Developmental/clinical correlates:
Epoch 3 (32–66): Midlife consolidation and rebalancing
Developmental/clinical correlates:
Epoch 4 (66–83): Aging reorganization accelerates
Developmental/clinical correlates:
Epoch 5 (83–90+): Diverging paths
Developmental/clinical correlates:
The illustration below captures the major findings, with age and epoch on the vertical axis, and different measured parameters horizontally. Overall level of brain integration, how modular different subsystems are, how interconnected subsystems are globally and locally, how "smart" the clustering is for speed and coherence of processing ("small world structure"), and how much each epoch has main brain areas which serve as key hubs (centrality and betweenness centrality, related to network resilience, as having too much function tied to one hub could lead to catastrophe if that hub is knocked out).
Takeaways and Caveats
The ages are averages; individuals follow unique paths shaped by biology, experience, and choices. At birth, the brain is hyper-connected, with abundant synapses that are pruned over time for greater global efficiency going into adolescence. Later, modularity increases with some rigidity. From adolescence to mid‑adulthood—peaking near 32 when the greatest shift occurs—the brain is receptive, and further developing as the mid-life phase approaches.
From about 32 until 66, directions stay similar, but white‑matter integrity declines with cognition as shown in prior work and implied by findings in this research, while modularity rises, favoring specialization over broad adaptability. After 83, changes stabilize: Modularity settles, and subgraph centrality adds redundancy in select regions, supporting steadiness and emotional sturdiness at the cost of flexibility. Staying healthy and mentally challenged matters as networks adopt aging patterns that can tilt positive or negative.
Findings align with prior gray‑ and white‑matter work. Limits include the study's cross‑sectional design; its strengths are in its nuanced, multifactorial analytics.
Future longitudinal studies might test which factors shift trajectories, employing emerging artificial intelligence -enabled analytic tools and richer data sets, as well as additional measures of brain function, enabling precision prevention and intervention and timing support for learning, resilience, and treatment to protect cognition and mental health across the lifespan.
Without stretching the imagination too far, we might imagine precision interventional psychiatric (PIP) approaches incorporating neuromodulation, like transcranial magnetic stimulation (TMS), among may others, with office-based measurement tools such as functional near-infrared spectroscopy (fNIRS) and electroencephalograpy (EEG), to allow us to "program" desirable connectivity patterns, beyond disease for regenerative medicine and performance enhancement.
Facebook image: Vimaliss/Shutterstock
Freud, S. (1937). Analysis terminable and interminable. The International Journal of Psychoanalysis, 18, 373–405.
Mousley, A., Bethlehem, R.A.I., Yeh, FC. et al. Topological turning points across the human lifespan. Nat Commun 16, 10055 (2025). https://doi.org/10.1038/s41467-025-65974-8
ExperiMentations Blog Post ("Our Blog Post") is not intended to be a substitute for professional advice. We will not be liable for any loss or damage caused by your reliance on information obtained through Our Blog Post. Please seek the advice of professionals, as appropriate, regarding the evaluation of any specific information, opinion, advice, or other content. We are not responsible and will not be held liable for third-party comments on Our Blog Post. Any user comment on Our Blog Post that, in our sole discretion, restricts or inhibits any other user from using or enjoying Our Blog Post is prohibited and may be reported to Sussex Publishers/Psychology Today. Grant H. Brenner. All rights reserved.
Share this post Facebook Bluesky Linkedin Email
There was a problem adding your email address. Please try again.
By submitting your information you agree to the Psychology Today Terms & Conditions and Privacy Policy
Grant Hilary Brenner, M.D., a psychiatrist and psychoanalyst, helps adults with mood and anxiety conditions, and works on many levels to help unleash their full capacities and live and love well.
Get the help you need from a therapist near you–a FREE service from Psychology Today.
This article is part of the Bringwise Psychology Journal — daily insights on human behavior, mental health, and personal growth.