Hundreds of scientists around the globe have shared data to create the world's first brain growth chart. The project incorporated MRI scans from subjects of all ages to offer a unique portrait of how our brains change over the course of a lifetime.
Parents are probably incredibly familiar with child growth charts. Tracking weight, height and other metrics helps doctors and parents keep tabs on whether a child is growing normally or falling behind on something. These markers are often communicated as percentile ranks, and scientists have a good picture on the normal spectrum of development in adolescent human bodies from decades of research.
While we do know that the human brain undergoes a number of significant changes over a lifetime, doctors have no resource to understand the spectrum of normal brain development at different ages. What does a normal healthy brain look like at 15 years of age compared to 45? Richard Bethlehem, from the University of Cambridge, and Jakob Seidlitz, from the University of Pennsylvania, worked with hundreds of researchers from around the globe to rectify this problem.
To create a series of charts tracking average brain development over the course of a lifetime, the researchers first needed to amass a huge dataset. Because fMRI brain imaging is a costly and time-consuming process, there was no way a single team could gather the necessary data. So the researchers looked to collaborate with hundreds of scientists around the world, each doing their own brain scan research.
“We sought to address this by stitching together data across the largest possible combination of existing studies,” explained Bethlehem and Seidlitz in an article for The Conversation. “We contacted many researchers to see if they would be willing to contribute to these reference charts. As evident from our large dataset, these requests were met with overwhelming enthusiasm. This turned a grassroots project into a collaborative global effort spanning six continents and dozens of institutions.”
The massive project ultimately gathered 123,984 MRI scans from more than 100,000 human subjects. The scans spanned subjects as old as 100 years and as young as a fetus at 15 weeks.
The findings, published through an open source website called Brain Chart, offer the first set of reference charts tracking structural brain changes over a human lifespan. And the scale of dataset has allowed the researchers to calculate percentile scores identifying normal spectrums of brain sizes for different age ranges.
The new research found, for example, the volume of gray matter in a human brain peaks at the age of six, but white matter continues to grow until around 29 years. At around the age of 50 the volume of white matter in a brain begins to decrease at a rapid pace.
Pulling all this data together and combining it with WHO-style growth modelling we were able to create a fully life-spanning set of reference trajectories and map out several important developmental milestones. pic.twitter.com/V3nR5PlYEu
— Richard Bethlehem (@rai_bethlehem) April 6, 2022
Bethlehem said it is too soon for the brain charts to be used as a clinical tool by doctors. More data is needed to better address diverse populations of patients but in the future it may be possible for doctors to take MRI scans of patients and use these reference charts to detect abnormal brain changes.
“This should effectively allow the neurologist to answer the question ‘this area looks atypical but atypical by how much?’,” said Bethlehem. “As the tool is standardized, it shouldn’t matter where you have your brain scan – you should still be able to compare it.”
At this point in time MRI brain imaging is not a simple or cheap diagnostic tool. So even as the Brain Chart builds its dataset and refines its models, there are technological hurdles to overcome before the resource can be used to monitor brain development.
Recent engineering innovations have introduced new portable MRI machines that bring this kind of detailed brain imaging one step closer to something accessible to all. According to Bethlehem and Seidlitz, the research team will continue to update and improve this set of novel data so it will be ready once technology has caught up and brain scans become a regular clinical practice.
“As brain scanning becomes cheaper and increasingly accessible (even portable), we hope our brain charts will enable more quantitative standards and aid neuroscientific discoveries to parallel these exciting technological advances,” write Bethlehem and Seidlitz. “One day, if brain scanning becomes a normal part of pediatric practice, we hope to be ready with the necessary methods and tools to provide meaningful insights for patients and their families.”
The new study was published in Nature.
Sources: The Conversation, King’s College London
