An unparalleled study led by scientists from the University of California, Riverside, has generated comprehensive maps of infant brain networks, shedding light on brain development from birth to two years old.
Researchers say these infant brain cortex parcellation maps provide crucial information on the timing of different brain functions during infancy and serve as essential references for early brain developmental studies. Cortical parcellation involves dividing up cortical grey matter into distinct ‘parcels’ to study brain function.
The researchers used functional magnetic resonance imaging (fMRI) scans of the brain in an inactive ‘resting’ state, alongside measurements of brain connectivity, to examine brain function within each parcel.
Previous studies created parcellation maps based on resting state fMRI connectivity in adult brains. Of course, these were not suitable for studying infant brains due to significant differences in functional organization between the two age groups.
“Creating infant-specific brain parcellation maps has been challenging due to difficulties in acquiring high-resolution infant brain images and processing them,” explains lead author Fan Wang explains in a statement. “We developed a novel method that captures fine-grained functional patterns from individual infants, generating comprehensive age-specific and age-independent parcellation maps.”
The researchers utilized 1,064 high-resolution fMRI scans and 394 structural MRI scans of infants from birth to two years old. They combined a conventional method of mapping cortical folds with a novel algorithm that overlays gradients of functional connectivity for each region onto brain scans. This allowed them to establish accurate connections between corresponding functional areas, resulting in detailed brain functional boundaries.
The infant-specific parcellation maps revealed several key findings. First, a primitive form of brain functional networks was present at three months old, with the sensory system more developed than higher-order systems like cognition and behavior. Second, complex fluctuations in functional activity and network organization were observed across different ages, reflecting different milestones of behavior and cognitive ability during infancy. Finally, local efficiency, or the connection of parcels to neighboring parcels, increased with age, indicating increasing function maturity.
These infant cortical parcellation maps provide a powerful platform for future studies in neurodevelopment. Gang Li, the senior author, emphasizes that the method not only captured important patterns discovered by previous methods but also revealed more detailed functional boundaries at unprecedented resolution.
Li also notes that the method involves averaging across individuals, introducing some registration errors into the parcellation. Future work will aim to address this issue by exploring individualized parcellation methods.
The study is published in eLife.