The Brain Dynamically Changes Size Throughout Life
Post by D. Chloe Chung
The takeaway
Researchers have created a growth chart of the human brain, reflecting how the brain changes size throughout the lifespan. This chart can be used as a reference tool for the neuroimaging and clinical communities.
What's the science?
The advancement of neuroimaging techniques such as magnetic resonance imaging (MRI) has helped many clinicians, patients, and researchers over the past decades. However, unlike how we understand the change of height and weight throughout our lives, there has been no standard reference of what the brain looks like at a certain age. An inclusive map that describes developmental milestones and aging-related changes of the brain will benefit both researchers and clinicians. This week in Nature, Bethlehem and colleagues comprehensively examined how our brain dynamically changes its size throughout our lifespan by analyzing more than 100,000 MRI scans of the brain.
How did they do it?
The authors collected 123,984 MRI scans from 101,457 human participants (with or without medical conditions), aged from 16 weeks after conception to 100 years old. These brain scans were obtained from both primary studies and publicly available open databases. To create the brain size chart over the lifespan, the scans were quantified for structural changes in the brain and how fast these changes occur through aging. For this analysis, the authors adapted a modeling approach recommended by the World Health Organization that can help neutralize differences in measurement derived from diverse techniques and machines used across studies. The final brain chart was made into an interactive tool that can be used to analyze additional MRI datasets generated by tool users in the future.
What did they find?
The authors found that, up to 6 years of age, grey matter rapidly increases in its volume and thickness. The white matter volume also showed strong growth during early childhood but in a more delayed fashion than grey matter, peaking in size at around 30 years of age. The authors noted that these changes early in brain development highlight grey/white matter volume differentiation. After their respective peaks, both grey and white matter volume began to decrease over the rest of the lifespan. In contrast to these early developmental milestones, the authors found that the amount of cerebrospinal fluid in the brain ventricles that maintains its plateau throughout life starts to exponentially increase from around 60 years of age. In addition to defining developmental milestones using the brain chart, the authors demonstrated the utility of their brain chart in studying brain-related conditions. For example, the authors observed a faster decrease of the grey matter volume in Alzheimer’s disease patients, especially those who are biologically female, compared to non-patients of the same age.
What’s the impact?
This study generated a comprehensive growth chart of the human brain by examining the largest collection of MRI brain scans to date covering a 100-year age range. This brain chart will serve as a highly useful, standardized reference for neuroimaging in the future. The authors pointed out that even this brain chart is not inclusive enough as it covers mostly European and North American populations because neuroimaging tools are not as readily available to all global communities. Future studies will hopefully improve demographic and socioeconomic diversity in MRI research.
