Mapping the Infant Mind: Early Brain Development Mapped

Summary: Researchers have created a set of infant cerebral cortex parcellation maps that provide an intricate look at brain development from birth to two years of age.

Using a combination of high-resolution functional and structural MRI scans, these maps reveal a fine-grained understanding of when different brain functions develop.

This research, which offers new insights into the complexity of infant brain development, paves the way for further studies of early brain development processes.

Key Facts:

1. Infant cerebral cortex parcellation maps are based on high-resolution fMRI and structural MRI scans that provide detailed insight into infant brain development from birth to two years of age.
2. The research revealed that a primitive form of brain functional networks is present by three months of age, and complex fluctuations in functional activity and network organization occur across different ages as brain function develops.
3. The cortical parcellation maps show an increase in local efficiency—the connectivity of parcels to neighboring parcels—with age, indicating increasing functional maturity.

Source: eLife

Researchers have constructed a comprehensive set of functional maps of infant brain networks that provide unprecedented detail about brain development from birth to two years of age.

The infant’s cerebral cortex parcellation map, published today in eLifehave already provided new insights into when different brain functions develop in infancy and provide valuable, publicly available references for early brain development studies.

Cortical parcellation is a means of studying brain function by dividing cortical gray matter into different locations into ‘parcels’. Functional magnetic resonance imaging (fMRI) scans are taken when the brain is in an inactive ‘resting’ state, along with measurements of brain connections, to study brain function in each bundle.

Previous studies have created parcellation maps based on resting-state fMRI connectivity in adult brains. However, these maps are unsuitable for studying infant brains due to significant differences in brain functional organization between infants and adults.

“Creating infant-specific brain parcellation maps has been challenging due to difficulties in obtaining high-resolution infant brain images and processing these images, which typically have low and rapidly changing contrast between different brain tissues during this time of development,” First explains. author Fan Wang, now associate professor at Xi’an Jiaotong University, China.

“We developed a new method that captures fine-grained functional patterns from individual infants to generate a comprehensive set of age-specific and age-independent parcellation maps that will facilitate pediatric neuroimaging research.”

Wang and colleagues used 1,064 high-resolution functional MRI scans and 394 structural MRI scans of infants from birth to two years of age, collected as part of the UNC/UMN Baby Connectome Project Consortium.

To capture detailed patterns of sharp transitions between regions of the brain, the team combined a conventional method of mapping the cortical folds (regions of the brain) across all individuals with a new algorithm that superimposes gradients of functional connectivity for each region onto the brain scans from each infant.

This allowed them to establish more accurate and meaningful connections between corresponding functional areas across individuals, resulting in a detailed characterization of the brain’s functional boundaries.

This was then used to generate infant-specific fine-grained functional parcellation maps for infants aged three months to two years, as well as age-independent maps.

The age-independent infant parcellation was very similar to some previously defined brain regions in adult parcellation maps, with parcel boundaries similar to those seen in adult brains. But the infant maps revealed new insights about the development of brain function.

First, the results suggest that a primitive form of brain functional networks is present at three months of age, when the sensory system is more developed than higher-order systems such as cognition and behavior.

The team also identified a previously unreported trend of complex fluctuations in functional activity and network organization across different ages as brain function develops, which are very different from patterns seen in early brain structural development.

These fluctuations may reflect different behavioral and cognitive milestones that emerge at different ages during infancy.

Finally, there was an increase in local efficiency—the coupling of plots to neighboring plots—with age, reflecting increasing functional maturity.

“Our method not only captured important gross patterns discovered by previous methods, but also revealed much more detailed functional boundaries with unprecedented resolution,” says senior author Gang Li, associate professor of radiology at the University of North Carolina at Chapel Hill, USA.

“The results suggest that although the functional connectivity of infants may not be as strong as that of adults, the basic units of organization are likely present in infant brains, and therefore the functional packing units of infants may be comparable in scale to those of adults.

“These infant cortical parcellation maps are a powerful platform for analyzing increasingly large cohorts of infants and higher resolution pediatric neuroimaging data, providing greater accuracy for future studies in neurodevelopment.”

“It is worth noting that our method involves an average across individuals. This inevitably introduces some registration errors into the slicing, especially in regions of high topographic variation across subjects.

“This is an important issue that exists in most population-level parcelling methods – the ultimate solution may be individualized parcelling, and we plan to work on this in the near future.” adds Li.

About this brain mapping research news

Author: Emily Packer
Source: eLife
Contact: Emily Packer—eLife
Image: Image credited to Neuroscience News

Original research: Open access.
“Fine-grained functional parcellation maps of the infant cerebral cortex” by Fan Wang et al. eLife

Abstract

Fine-grained functional parcellation maps of the infant cerebral cortex

Resting-state functional MRI (rs-fMRI) is widely used to investigate the dynamic brain functional development of infants, but these studies typically require precise cortical parcellation maps that cannot be borrowed directly from adult-based functional parcellation maps due to the substantial differences in functional brain organization between infants and adults.

Creation of infant-specific cortical parcellation maps is therefore highly desired but remains challenging due to difficulties in acquiring and processing infant brain MRIs. In this study, we utilized 1064 high-resolution longitudinal rs-fMRIs from 197 typically developing infants and toddlers from birth to 24 months who participated in the Baby Connectome Project to develop the first set of infant-specific, fine-grained, surface-based cortical functional parcellation maps.

To establish meaningful cortical functional correspondence across individuals, we performed cortical co-registration using both the cortical convolution geometric features and the local gradient of functional connectivity (FC). We then generated both age-related and age-independent cortical parcellation maps with over 800 fine-grained parcels in infancy based on fitted and averaged local gradient maps of FC across individuals.

These parcellation maps reveal complex functional developmental patterns, such as changes in local gradient, network size, and local efficiency, particularly during the first 9 postnatal months.

Our generated fine-grained infant cortical functional parcellation maps are publicly available at https://www.nitrc.org/projects/infantsurfatlas/ to advance the field of pediatric neuroimaging.