Scientists around the world joined forces to complete the world's first step-by-step "brain development map" showing how a mammalian brain is built. Covering everything from lab mice to humans, the map is expected to provide key clues to understanding early brain development and uncovering the causes of neurodevelopmental disorders such as autism and attention-deficit/hyperactivity disorder (ADHD).
An international research team participating in the U.S. National Institutes of Health (NIH) BRAIN Initiative published a total of 12 papers on the 6th in the journal Nature and its sister journals.
About 15% of children and adolescents worldwide currently have neurodevelopmental disorders that affect cognition, language, behavior, and motor skills. Representative examples are autism spectrum disorder (ASD) and ADHD.
In particular, because the human brain develops over a much longer period than other animals, problems that arise early in development can lead to lifelong neurological illness. Scientists say properly understanding this period is the first step to preventing and treating brain disorders.
The researchers analyzed brain cells from various animals to track when and where cells turn genes on and off. As a result, they detailed how millions of cells in the brain differentiate, migrate, and consolidation over time.
For example, neurons that secrete GABA (gamma-aminobutyric acid) act as a brake by inhibiting neural signals and controlling excessive brain activity. Analyzing data from more than 1.2 million mouse brain cells, the team traced the lineage of GABA cells and found that some GABA cells continue to develop long after birth and are involved in emotion, decision-making, and learning. In other words, there is more time after a child is born for brain circuits to change than previously thought.
Another study examined the cellular development of the visual cortex, the brain region that processes visual information. By analyzing about 770,000 cells from mouse childhood to adulthood, the team mapped developmental trajectories. The results showed that exposure to light and experiences that recognize the world after birth have a greater impact on brain development than before birth. It shows how important a child's environment and stimuli are to brain development.
The fact that the environment can change brain structure also emerged from an analysis of genes across millions of neurons. This study likewise found that sensory experiences such as visual stimuli are deeply involved in shaping the areal identity of the brain.
With a precise brain development map at the cellular level now complete, scientists can pinpoint the critical periods of brain development more concretely. These are times when the brain is particularly sensitive and present important opportunities to steer it in a better direction through treatment, education, or stimulation.
Joshua Gordon, chair of psychiatry at Columbia University and former director of the U.S. National Institute of Mental Health, said, "These maps are vitally important resources we urgently need to understand the mechanisms that govern the developing brain in health and disease," adding, "They will provide a foundation for building a deeper understanding of autism, schizophrenia, and other conditions known to arise during brain development."
References
Nature (2025), DOI: https://doi.org/10.1038/s41586-025-09652-1