Brains get denser during adolescence--and that might not be a bad thing!

Efstathios (Stathis) Gennatas was the lead author on this study.

Efstathios (Stathis) Gennatas was the lead author on this study.

or technically,

Age-Related Effects and Sex Differences in Gray Matter Density, Volume, Mass, and Cortical Thickness from Childhood to Young Adulthood

[See Original Abstract on Pubmed]

Authors of the study: Gennatas ED, Avants BB, Wolf DH, Satterthwaite TD, Ruparel K, Ciric R, Hakonarson H, Gur RE, Gur RC.

Have you ever wondered what happens to your brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. during the tumultuous ride of adolescence? Along with dramatic changes of the body, there are considerable changes of the brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals.. We all know that the ability to think, learn, and make decisions improves as children grow up, so it is quite surprising to learn that parts of the brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. are actually getting smaller during this time.

BrainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. tissue can be divided into two types: gray matterA class of brain tissue made up of layers of cells typically covering the cortical surface of the brain and white matterA class of brain tissue made up of long and wire-like axons and tracts, acting as a highway of connections among the brain's cortical surface regions. Gray matterA class of brain tissue made up of layers of cells typically covering the cortical surface of the brain is a thick layer of cells, much of which tiles the surface of the brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals.. Depending on the location, gray matterA class of brain tissue made up of layers of cells typically covering the cortical surface of the brain is thought to process emotion, speech, decision-making, movement, self-control, and more. White matterA class of brain tissue made up of long and wire-like axons and tracts, acting as a highway of connections among the brain's cortical surface regions is made of the connections that act as highways among regions of gray matterA class of brain tissue made up of layers of cells typically covering the cortical surface of the brain. Because of the fatty biological materials making up these highways, white matterA class of brain tissue made up of long and wire-like axons and tracts, acting as a highway of connections among the brain's cortical surface regions looks white!

As you grow and learn, new connections form. So, it would make sense for the brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. to grow in size. Yet, this is not the case! Stathis Gennatas, a former neuroscience graduate student under the direction of Dr. Ruben Gur at the University of Pennsylvania, wondered if we were missing the full story.

There are two common ways to measure how much gray matterA class of brain tissue made up of layers of cells typically covering the cortical surface of the brain someone has, using a technique called magnetic resonance imagingA common brain imaging method that exploits different magnetic reactions of brain tissue to take pictures of the brain (MRI), which uses large magnets to make a 3D image of the brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals.. One way to measure gray matterA class of brain tissue made up of layers of cells typically covering the cortical surface of the brain is to calculate its volume from the MRI image. The second way is to measure the thickness of the gray matterA class of brain tissue made up of layers of cells typically covering the cortical surface of the brain. Over and over, teams of scientists have found that both of these measures show a dramatic decline during adolescence, despite rapid improvements in tests of memory and learning.1

Stathis and his team used MRI to scan the brainsThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. of 1189 children and adolescents from the Philadelphia area. As in prior studies, he found that both cortical thickness and gray matterA class of brain tissue made up of layers of cells typically covering the cortical surface of the brain volume did indeed decline during adolescence. However, he also looked at another measure called gray matterA class of brain tissue made up of layers of cells typically covering the cortical surface of the brain density, which measures how tightly packed gray matterA class of brain tissue made up of layers of cells typically covering the cortical surface of the brain is in the cortex. Gray matterA class of brain tissue made up of layers of cells typically covering the cortical surface of the brain density has not historically been examined in studies of brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. development, which have focused on measures of volume and thickness. Stathis actually found increases in gray matterA class of brain tissue made up of layers of cells typically covering the cortical surface of the brain density with increasing age; in fact, gray matterA class of brain tissue made up of layers of cells typically covering the cortical surface of the brain density actually showed the strongest age-related effects, meaning that it changed the most with age. This suggests that perhaps gray matterA class of brain tissue made up of layers of cells typically covering the cortical surface of the brain is not being lost during adolescence, but rather, simply being reorganized in a more tightly packed manner.

Stathis found another interesting twist in his study of brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. structure during adolescence. The brainsThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. of boys and girls appeared to be growing differently. Males at this age tend to be bigger and taller, and therefore have larger brainsThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. and more gray matterA class of brain tissue made up of layers of cells typically covering the cortical surface of the brain compared to girls. During adolescence, when gray matterA class of brain tissue made up of layers of cells typically covering the cortical surface of the brain volume decreases, female brainsThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. start out with less gray matterA class of brain tissue made up of layers of cells typically covering the cortical surface of the brain volume. Stathis found, though, that females have higher gray matterA class of brain tissue made up of layers of cells typically covering the cortical surface of the brain density on average than males, possibly compensating for their smaller average gray matterA class of brain tissue made up of layers of cells typically covering the cortical surface of the brain volume.

Increasing gray matterA class of brain tissue made up of layers of cells typically covering the cortical surface of the brain density provides an important piece of the puzzle as to why gray matterA class of brain tissue made up of layers of cells typically covering the cortical surface of the brain volume or cortical thickness decreases in adolescence. This is important because currently, gray matterA class of brain tissue made up of layers of cells typically covering the cortical surface of the brain density is not routinely considered in studies of brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. development in childhood and adolescence, when many psychiatric disorders emerge. Gray matterA class of brain tissue made up of layers of cells typically covering the cortical surface of the brain density is highly sensitive to changes with age, and thus may help us glean new insight into what changes in brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. structure accompany the development of mental disorders. These findings might also help us understand why the effects of brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. disorders on females and males differ during the rapid changes of adolescence. Examining gray matterA class of brain tissue made up of layers of cells typically covering the cortical surface of the brain density could also be really important for understanding the relationship between brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. structure and cognitive performance. More densely packed gray matterA class of brain tissue made up of layers of cells typically covering the cortical surface of the brain may allow more processing for less space, thus improving learning and memory abilities. In summary, your brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. shrinking during adolescence might not be such a bad thing.
About the brief writer: Ursula Tooley  Ursula is a PhD Candidate in  Allyson Mackey’s  and  Danielle Bassett’s labs . How does our brain change as we develop from young children to adults, and what functional networks support our ability to learn and reason about the world? How does our early environment shape this? Ursula is a fourth year student interested in the answers to these questions.

About the brief writer: Ursula Tooley

Ursula is a PhD Candidate in Allyson Mackey’s and Danielle Bassett’s labs. How does our brain change as we develop from young children to adults, and what functional networks support our ability to learn and reason about the world? How does our early environment shape this? Ursula is a fourth year student interested in the answers to these questions.

Citations:

  1. Akshoomoff, N., Newman, E., Thompson, W. K., McCabe, C., Bloss, C. S., Chang, L., ... & Gruen, J. R. (2014). The NIH Toolbox Cognition Battery: Results from a large normative developmental sample (PING). Neuropsychology, 28(1), 1.