Brain folds begin to form in the womb and deepen substantially throughout the first year of human life. In a new study we find that folds which emerge earlier in gestation—during roughly the 16th to 19th gestational weeks, such as the calcarine sulcus—are already relatively deep at birth and then show little to no additional deepening over the first postnatal year. By contrast, sulci that appear later in utero tend to deepen more rapidly after birth than those that formed earlier. This postnatal sulcal deepening reflects a complex, multicomponent process involving coordinated morphological changes and underlying microstructural development.

https://doi.org/10.1038/s42003-026-09536-8.

Want to learn how microstructural tissue properties develop in the visual cortex during the first year of human life? Our new study shows that microstructure in the gray matter and the adjacent white matter of brain regions across the dorsal, lateral, and ventral visual processing streams becomes denser after birth. This pattern indicates substantial tissue growth in the brain following an infant’s birth. Within each stream, early visual areas appear more mature at birth than higher-level areas, yet they show slower postnatal development compared with those higher-level areas. This hierarchical organization may be a core feature of the visual system as newer processes build on and refine older ones. We hypothesize that if microstructural maturation is tied to functional specialization, that functional development may follow a similar hierarchical course.

https://doi.org/10.1007/s00429-025-03054-9.