Finding the patterns of white matter growth that support children’s cognitive development

Joëlle Bagautdinova was the lead author on this study. Joëlle is broadly interested in brain development and how this may go awry in psychiatric disorders. For her PhD in Dr. Ted Satterthwaite’s lab, Joëlle is using neuroimaging to study the mechanisms underlying brain development, cognition and psychiatric disorders. She is particularly interested in understanding the potential role of sleep as a risk factor in the emergence of mental illness.

or technically,

Development of white matter fiber covariance networks supports executive function in youth

[See Original Abstract on Pubmed]

Authors of the study: Joëlle Bagautdinova, Josiane Bourque, Valerie J. Sydnor, Matthew Cieslak,Aaron F. Alexander-Bloch, Maxwell A. Bertolero, Philip A. Cook, Raquel E. Gur, Ruben C. Gur, Fengling Hu, Bart Larsen, Tyler M. Moore, Hamsanandini Radhakrishnan, David R. Roalf, Russel T. Shinohara, Tinashe M. Tapera, Chenying Zhao, Aristeidis Sotiras, Christos Davatzikos, and Theodore D. Satterthwaite

Recently, many neuroscientists have been trying to uncover the developmental “blueprint” of the brain’s gray matter, or the specific ways in which brain regions grow and change over the course of adolescence. However, less attention has been paid to the brain’s white matter, which is the insulated, wire-like “tracts” that connect one brain region to another. NGG student Joëlle Bagautdinova and her colleagues in the Satterthwaite lab filled this gap by investigating white matter’s structural development in MRI scans from almost 1000 people ages 8 to 22 years.

While it famously does NOT imply causation, correlation can show parts of the brain have similar structures and, therefore, might be following the same developmental blueprint. So, Joëlle and her colleagues decided to cluster every point along the brain’s white matter tracts (Figure 1) into groups with similar structures (Figure 2). Specifically, they grouped points with similar fiber density, or how many “wires” are packed together to make the tract, and cross-section, or how thick the tract is (Figure 1); they refer to the combination of these measurements as “FDC”. She also tested to see how each group’s FDC values changed across adolescence.

Figure 1. White matter tracts can be measured by their density and cross-section.

Figure 2. Points of white matter can be grouped by how similar their FDC (fiber density and cross-section) values are.

Usually, researchers assume that all points along a tract will develop similarly; however, because Joëlle determined her groups based on how similar the points are, different points along the same tract could be put into different groups, while points from more than one tract could be lumped together. This allowed her to uncover brand new relationships between different white matter tracts and unique subsections that develop differently than the white matter tract. For instance, she found that FDC in the lower part of the corticospinal tract, which connects the brain and spinal cord, was different than the FDC in the upper corticospinal tract, and each portion had its own unique growth trajectory. All in all, the researchers found 14 different groups of similarly-structured white matter regions, 12 of which showed significant structural changes across this period of adolescent development.

The age at which each white matter group developed most also seems to follow a pattern. Specifically, they found that the white matter in the lower back area of the brain matures earlier in adolescence while the white matter in the upper front area of the brain doesn’t mature until a bit later. These early-maturing white matter tracts tend to connect parts of the brain that do what scientists call “lower-order functions” like vision processing, basic movement, and emotions – all things that children can do pretty well. Meanwhile, the later-maturing white matter tracts tend to connect brain regions that do “higher order” functions like complex reasoning. Overall, the fact that white matter maturation seems to progress “basic” to “complex” tracts suggests that white matter may play a big role in the brain’s development across adolescence.

Finally, Joëlle and her colleagues wanted to see if these white matter structures helped kids’ executive function, which is one of these “higher order” cognitive functions that includes planning, organizing, and impulse control. They found that if you remove the effects of age, kids with better executive function tend to have higher FDC in all but one white matter group. This means that white matter tracts that are thicker and/or more tightly packed do a better job of sending signals between brain regions, especially those in the front of the brain that are responsible for cognition, and that this enhanced signaling may allow children to have stronger executive functions.

By using new, cutting-edge analyses, Joëlle and her collaborators were able to: uncover brand-new, biologically-based relationships between white matter areas; chart how these areas develop over adolescence; and show which white matter structures seem to help with cognitive function. All in all, this work fills in important gaps in our understanding how the brains we’re born with mature into the brains of capable, full-grown adults.

About the brief writer: Margaret Gardner

Margaret is a PhD student in the Brain-Gene-Development Lab working with Dr. Aaron Alexander-Bloch. She is interested in studying how different biological and demographic factors influence people’s brain development and their risk for mental illnesses.

Want to learn more about this exciting research? Check out Joëlle’s paper here!

Understanding the brain during mindfulness

Dale Zhou was the lead author on this study. Dale is interested in how the brain network compresses and reconstructs information as network structure changes across the lifespan. He aims to account for computations of memory and reward as network functions of dimensionality reduction and expansion using experimental, naturalistic, and clinical data.

or technically,

Mindful attention promotes control of brain network dynamics for self-regulation and discontinues the past from the present

[See Original Abstract on Pubmed]

Authors of the study: Dale Zhou, Yoona Kang, Danielle Cosme, Mia Jovanova, Xiaosong He, Arun Mahadevan, Jeesung Ahn, Ovidia Stanoi, Julia K. Brynildsen, Nicole Cooper, Eli J. Cornblath, Linden Parkes, Peter J. Mucha, Kevin N. Ochsner , David M. Lydon-Staley, Emily B. Falk, and Dani S. Bassett

In recent years, the practice of meditation has received a lot of attention for its health benefits, both physically and mentally. One popular form of meditation, mindfulness meditation, teaches individuals to focus on, and attend to the present moment. The ability to shift focus depends on the ability to orchestrate shifts in neural activity, and has been previously called executive function. While the benefits of mindfulness meditation are widely recognized, what’s going on in the brain is much less clear.

In order to understand how mindfulness is represented in the brain, Dale Zhou, a recent NGG graduate, and his collaborators recruited healthy college students who identified as social drinkers and asked them to perform a task rating from 1 to 5 how much they would crave an alcoholic drink, presented to them on a computer screen. Dale simultaneously measured the activity patterns in participants’ brains using functional magnetic resonance imaging, or fMRI, while they completed this task. One group of participants was instructed to practice mindfulness while rating their cravings by “mentally distancing themselves by observing the situation and their response to it with a more impartial, nonjudgmental, or curious mindset, and without getting caught up in the situation or response”. The other group was instructed to rate their cravings with their natural gut reaction to the drink.  For some trials, participants in the mindful group were asked to switch to their gut reaction instead, allowing Dale and his colleagues to compare which brain areas were simultaneously active or quiet during the different reactions. This allowed them to draw some interesting conclusions about how the brain represents mindfulness.

Figure 1: Simplified representation of brain states. In this example, the brain has only two areas and the brain state is defined by the activity of region 1 and region 2.

Before Dale analyzed the results from the experiment, he first asked how mindfulness can be measured in the brain and if the “amount” of mindfulness in our brains impacts our day-to-day behaviors. To answer this question, he used average brain activity from the participants’ scans to calculate a measure of the executive function called controllability. To understand controllability, it is helpful to think of the brain as having different “brain states” (Figure 1). When a person is doing some activity, like walking, the brain exists in a particular brain state - some brain areas are very active and some are quiet. When the same person is doing a different activity, like eating, the brain exists in a different brain state - a different set of brain areas are active and quiet. Dale and his colleagues defined controllability as how readily the brain can switch into any possible brain state. By calculating controllability for each participant, and tracking their drinking behavior weeks after the brain scan, Dale found that the participants with higher controllability tended to have fewer drinks than those with lower controllability, suggesting that perhaps mindfulness does impact our day to day behaviors in a positive manner. 

Now back to the experiment. Dale asked whether there were differences in controllability, and therefore brain activity, between the two groups.  To do this, he calculated the amount of effort, or control, it took for participants in each group to enter either a mindful state or gut reaction state while reacting to the alcohol cue. He found that participants instructed to react mindfully took more effort to enter this brain state after being prompted than participants instructed to react naturally took to enter their gut reaction brain state. This was exactly what they expected to see, since it is known that achieving a state of mindfulness initially requires more thought and brain activity. However, he also found that when participants from both groups were instructed to react naturally, those who had previously reacted mindfully still required more effort to enter this gut reaction brain state than those who had not. This suggests that practicing mindfulness might make us more effortful in attention, even when we are not actively trying or instructed to. 

Finally, Dale found that brain areas that use more effort had shorter episodes of neural activity. These shorter episodes suggested that there was less influence of the past in these areas. Furthermore, these quick episodes were typically found in brain areas that help us sense the world around us rather than areas that help us think about past experiences or plan for the future. Practicing mindfulness, therefore, may put us in a more effortful state of attention which is more focused on the present moment rather than on the past or future. 

In conclusion, Dale’s hard work on this project has allowed us to take a glimpse at the brain during mindfulness and how it might be benefiting our behavior. His work reminds us that, although the brain is composed of many different brain areas, human behavior is a product of these various areas interacting with one another, producing unique states of mind such as mindfulness. Work similar to his will hopefully lead the way to a better understanding of some of the brain’s other complex functions.

About the brief writer: Jafar Bhatti

Jafar is a PhD Candidate in Long Ding and Josh Gold’s lab. He is broadly interested in brain systems involved in sensory decision-making. 

Want to learn more about how these researchers study mindfulness? You can find Dale’s paper here!

Does the size of your social network predict how big certain parts of your brain are?

Camille was the lead author on this study. She is a 5th year graduate student at the University of Pennsylvania with Dr. Michael Platt. She wants to understand the evolution and neurobiological mechanisms of social relationships in primates using approaches from behavioral ecology of primates in the wild to single cell electrophysiology in the lab!

or technically,

Social Connections predict brain structure in a multidimensional free-ranging primate society

[See original abstract on PubMed]

Authors of the study: Camille Testard, Lauren J. N. Brent, Jesper Andersson, Kenneth L. Chiou, Josue E. Negron-Del Valle, Alex R. DeCasien, Arianna Acevedo-Ithier, Michala K. Stock, Susan C. Antón, Olga Gonzalez, Christopher S. Walker, Sean Foxley, Nicole R. Compo, Samuel Bauman, Angelina V. Ruiz-Lambides, Melween I. Martinez, J. H. Pate Skene, Julie E. Horvath, Cayo Biobank Research Unit, James P. Higham, Karla L. Miller, Noah Snyder-Mackler, Michael J. Montague, Michael L. Platt, Jérôme Sallet

When I think of neuroscience, I think of scientists in white lab coats examining brains under a microscope. While it’s true that neuroscience these days typically takes place in a laboratory environment, some would argue that this isn’t the best way to study the brain. If we want to study how the brain works naturally, why would we study it in an artificial environment, such as a lab?

While of course there are some topics that are better suited to be studied in labs like how individual neurons in the brain function and work together, topics like social behavior, which is what Camille and her colleagues were interested in, may benefit from more naturalistic experimental conditions. In particular, Camille and her colleagues wanted to know how the size of an individual’s social network can affect their brain structure and function. To do this they studied the behavior and brains of rhesus macaque monkeys living in a semi-free range colony on Cayo Santiago Island in Puerto Rico. 

In their paper, the researchers examined the behavior of a single social group composed of 103 individual monkeys of which 39 were male and 64 were female. For each monkey in the colony, the researchers looked at two measures of social behavior. The first measure was the monkey’s social network, which was based on the number of grooming interactions a given monkey had with other monkeys. The more grooming partners a monkey had, the larger its network was. The second measure they looked at was the monkey’s social status, which was based on aggressive interactions given and received that a given monkey encountered with others (threats, chases, submissions, etc.). 

Camille and her team observed each monkey’s behavior for 3 months prior to  measuring their brain structure using a technique known as MRI, or magnetic resonance imaging. With this technique, they were able to determine the size of different brain areas in each monkey. Then, they wanted to see if there was a relationship between a given monkey’s social behavior and any part of the monkey’s brain. 

Interestingly, the researchers found that there was a positive correlation between the social network size (i.e, number of grooming partners) of a monkey and the size of two specific brain regions (see Figure 1). The first brain region is called the mid superior temporal sulcus (mid-STS, for short). In previous studies, the mid-STS has been found to be involved in responding to social scenes. This region is also thought to be involved in deciding whether to cooperate versus compete with a partner. The second brain region is called the ventral dysgranular insula (vd-insula, for short). In previous studies, this region has been found to be involved in grooming behavior in macaques and empathy in humans!

Because social interactions between monkeys are multi-faceted, just as in humans, Camille also looked at several other nuances of the monkeys’ social network to see if they predicted the size of these brain regions. For example, they looked at “betweenness” (was a given monkey able to bridge connections between distant members of the colony?) and “closeness” (how close was a given monkey to every other monkey in the colony?). These other measures did not correlate with any brain region in these monkeys. Because of this, the researchers took a closer look at social network size, which did show a correlation with brain size. Since this measure was determined by grooming interactions, they were curious if the direction of the grooming mattered: whether the monkey actively groomed other individuals or was being groomed. When they looked at the data this way, they found that how many individuals in the colony that groomed a given monkey more closely predicted its brain size. 

Finally, the researchers wondered if the relationship that they found between social network size and brain size in adult monkeys was also true for infant monkeys. These monkeys are too young to form complex social networks so the researchers instead used the social network of the mothers of these infants. They reasoned that they might still see a relationship because previous studies showed that an infant macaque’s social network mimick the social network of his/her mother. However they found no clear relationship between a mother’s social network and her infant’s brain size. The authors suggested that the infants were perhaps too young for their brains to have fully developed and any size differences to be observable. These results led the researchers to believe that the brain-size differences that they see in adult macaques are due to the increased sociability that occurs during development. 

In summary, Camille’s research offers incredible insight into how the size of specific brain regions is related to the ability of mammals to form large social networks in their natural environment. Her team determined the social network size of each monkey in the colony and found a significant correlation with two socialization-related brain regions, the mid-STS and the vd-Insula. Furthermore, this relationship could not be found in infant monkeys, leading them to believe that increased sociability during development leads to the observed differences in brain structure seen in adult monkeys. Camille’s work is important because her discoveries in wild, free-ranging monkeys emphasize that complex social forces, for instance in human societies, can powerfully drive the physical expansion of socially related areas in the brain.

About the brief writer: Jafar Bhatti

Jafar is a PhD Candidate in Maria Geffen’s lab. I’m broadly interested in brain networks involved in auditory processing and decision-making.

Want to learn more about how these researchers study the social behavior and brains of free ranging monkeys? You can find Camille’s full paper here!

How different levels of brain development help adolescent cognition - or don’t

Adam Pines was the lead author on this study. Adam is a postdoctoral fellow in the Stanford PanLab for Precision Psychiatry and Translational Neuroscience. He completed his Ph.D. in Neuroscience at UPenn in 2022. His other research interests include developmental neuroscience, brain-environment interactions, and adaptive plasticity in the brain.

or technically,

Dissociable multi-scale patterns of development in personalized brain networks

[See Original Abstract on Pubmed]

Authors of the study: Adam R. Pines, Bart Larsen, Zaixu Cui, Valerie J. Sydnor, Maxwell A. Bertolero, Azeez Adebimpe, Aaron F. Alexander-Bloch, Christos Davatzikos, Damien A. Fair, Ruben C. Gur, Raquel E. Gur, Hongming Li, Michael P. Milham, Tyler M. Moore, Kristin Murtha, Linden Parkes, Sharon L. Thompson-Schill, Sheila Shanmugan, Russell T. Shinohara, Sarah M. Weinstein, Danielle S. Bassett, Yong Fan & Theodore D. Satterthwaite

You don’t need to be a scientist to know that kids get smarter as they grow up - they get better at things like problem-solving, thinking flexibly, and remembering information. But what exactly is changing in the brain to make these cognitive skills, which researchers call “executive function” easier?

Like instruments in a band, different areas of the human brain have different roles and will perform together in different combinations to everything from processing what your eyes see, to controlling your muscles, to solving a crossword, to feeling emotions. A group of brain regions that work together is called a functional brain network. Some functional brain networks perform easier, or “lower-order”  tasks, like sensing pain when you get a cut. Others perform harder, more complex tasks, like solving physics equations or learning a language, which are considered “higher-order”. 

Dr. Adam Pines, who recently graduated from the Neuroscience Graduate Group, wanted to know how all these functional networks mature as kids age and how this pattern of development relates to kids’ improving executive function. To study this, Adam had two challenges. First, we don’t know how many functional networks there “really” are in the brain; you can divide the brain up into different numbers of chunks and still do a good job of grouping regions that activate together and separating those that don’t (Figure 1, Columns). Second, the layout of everyone’s functional networks is a tiny bit different: one network may take up a little more space in one person, for instance, or the parts of the brain that do a certain task on one person may be just a little bit more to the left on another (Figure 1, Rows). Therefore, Adam made personalized functional networks (PFNs), which are maps of a person’s unique functional network layout, for every subject in the study. He also tried grouping the brain into different numbers of networks to see whether this would change his results.

Figure 1: Illustration of personalized functional networks mapped for varying numbers of networks.

Adam mapped the unique functional networks of each person in the study (PFNs), as shown in the rows. He also divided the brain’s activity into different numbers of networks, with maps of 4, 7, and 13 networks pictured. Different colors show that the brain regions are part of different functional networks.

To make personalized functional networks (PFNs) for each subject (Figure 1, Rows), Adam and his colleagues mapped the layout of every functional network in the average person and mathematically tweaked the layout to fit each participant’s unique pattern of brain activation. Then, they repeated this step using different numbers of networks in their baseline map (Figure 1, Columns) and labeled whether each network did lower- or higher-order functions. In the end, they had 29 brain maps for each person (each dividing brain activity into 2 to 30 functional networks), that they could compare to each participant’s age and score on a test of executive function.

First, Adam compared PFNs across participants ages 8 through 23 and found that lower- and higher-order networks tended to develop differently. Lower-order networks (each of which does an easier task) became more interconnected over the course of adolescence, while higher-order networks (each of which does a harder task) became less interconnected. Next, he tested how these PFN patterns were related to kids’ executive function. Interestingly, he found executive function tends to be better when very low-order and very high-order networks are distinct, but networks that fall in the middle (ones that do medium-complexity tasks) are more interconnected. Dividing the brain into a greater number of PFNs, Adam saw this effect grow stronger, especially in lower-order networks.

Taken together, Adam’s results are surprising because, while aging makes higher-order networks more distinct (which is better for executive function), lower-order networks actually become more interconnected (which is worse for executive function)! This may mean that while increasingly distinct higher-order networks allow kids’ executive function to improve as they grow up, their brains’ lower-order networks are already starting to decline. These findings will be important for future scientists studying how kids’ executive function develops and may help uncover why some kids struggle with cognitive development.

About the brief writer: Margaret Gardner

Margaret is a PhD student in the Brain-Gene-Development Lab working with Dr. Aaron Alexander-Bloch. She is interested in studying how different biological and demographic factors influence people’s brain development and their risk for mental illnesses.

Want to read Adam’s work for yourself? You can find the full article (complete with equations and pretty brain pictures) here!

Human brain imaging highlights a relationship between excitatory and antioxidant neurochemicals and psychosis

Valerie Sydnor was the lead author on this study. Valerie is a PhD candidate in Ted Satterthwaite’s lab studying how brain plasticity changes throughout neurodevelopment. Valerie aims to uncover how developmental programs contribute to the emergence of youth psychiatric disorders.

or technically,

A meta-analysis of ultra-high field glutamate, glutamine, GABA and glutathione 1HMRS in psychosis: Implications for studies of psychosis risk

[See Original Abstract on Pubmed]

Authors of the study: Valerie Sydnor & David Roalf

PsychosisA symptom of mental illness in which the person loses touch with reality and thinks or behaves in bizarre ways. Psychosis is a complex brain disorder that typically presents in adolescence or early adulthood with devastating impacts on social, occupational, and daily functioning. is a complex and neurodevelopmental brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. disorder that typically presents in adolescence or early adulthood. Characterized by disorganized thought and behavior, low motivation, and the presence of hallucinations or delusions, psychosisA symptom of mental illness in which the person loses touch with reality and thinks or behaves in bizarre ways. Psychosis is a complex brain disorder that typically presents in adolescence or early adulthood with devastating impacts on social, occupational, and daily functioning. can have a devastating impact on social, occupational, and daily functioning. It’s also more common than you may think. According to the National Alliance on Mental Illness, approximately 100,000 young people experience psychosisA symptom of mental illness in which the person loses touch with reality and thinks or behaves in bizarre ways. Psychosis is a complex brain disorder that typically presents in adolescence or early adulthood with devastating impacts on social, occupational, and daily functioning. each year in the U.S. alone. In addition to affecting basic day-to-day life, episodes of psychosisA symptom of mental illness in which the person loses touch with reality and thinks or behaves in bizarre ways. Psychosis is a complex brain disorder that typically presents in adolescence or early adulthood with devastating impacts on social, occupational, and daily functioning. are associated with changes in both brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. structure and brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. function. For example, psychosisA symptom of mental illness in which the person loses touch with reality and thinks or behaves in bizarre ways. Psychosis is a complex brain disorder that typically presents in adolescence or early adulthood with devastating impacts on social, occupational, and daily functioning. has been linked with changes in the way neuronsA nerve cell that uses electrical and chemical signals to send information to other cells including other neurons and muscles in the brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. are both connected to (structural change) and communicate with (functional change) one another. Interestingly, these structural and functional changes have been found not only in patients with psychosisA symptom of mental illness in which the person loses touch with reality and thinks or behaves in bizarre ways. Psychosis is a complex brain disorder that typically presents in adolescence or early adulthood with devastating impacts on social, occupational, and daily functioning., but also in youth at genetic or clinical risk for developing psychosisA symptom of mental illness in which the person loses touch with reality and thinks or behaves in bizarre ways. Psychosis is a complex brain disorder that typically presents in adolescence or early adulthood with devastating impacts on social, occupational, and daily functioning.. This finding means that it may be possible to use information about the brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. to predict and diagnose psychosisA symptom of mental illness in which the person loses touch with reality and thinks or behaves in bizarre ways. Psychosis is a complex brain disorder that typically presents in adolescence or early adulthood with devastating impacts on social, occupational, and daily functioning. as well as to inform psychosisA symptom of mental illness in which the person loses touch with reality and thinks or behaves in bizarre ways. Psychosis is a complex brain disorder that typically presents in adolescence or early adulthood with devastating impacts on social, occupational, and daily functioning. treatment strategies, which represents a huge step forward for psychiatry.

So, what exactly are these psychosisA symptom of mental illness in which the person loses touch with reality and thinks or behaves in bizarre ways. Psychosis is a complex brain disorder that typically presents in adolescence or early adulthood with devastating impacts on social, occupational, and daily functioning.-related brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. changes? Well, Neuroscience Graduate Group (NGG) student Valerie Sydnor, her co-author Dr. David Roalf, and many others in the field, think that a neurochemical called glutamatethe most abundant excitatory neurotransmitter plays a critical role in psychosisA symptom of mental illness in which the person loses touch with reality and thinks or behaves in bizarre ways. Psychosis is a complex brain disorder that typically presents in adolescence or early adulthood with devastating impacts on social, occupational, and daily functioning.. Glutamatethe most abundant excitatory neurotransmitter is the brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals.’s main excitatory neurotransmitterchemicals released by neurons; can have an excitatory or inhibitory effect, meaning it plays a large role in neuronal communication. (It’s present at approximately 80% of synapsesthe site of transmission of electric nerve impulses between two nerve cells (neurons) that form the basis for neuronal communication, which serve as the point of communication between neuronsA nerve cell that uses electrical and chemical signals to send information to other cells including other neurons and muscles!) Recently, the receptorsReceives an input some stimulus and transmits a the information to other cells or neurons. that bind glutamatethe most abundant excitatory neurotransmitter to enable this neuronal communication have also been shown to bind drugs, like ketamine, that induce a mental state similar to that of acute psychosisA symptom of mental illness in which the person loses touch with reality and thinks or behaves in bizarre ways. Psychosis is a complex brain disorder that typically presents in adolescence or early adulthood with devastating impacts on social, occupational, and daily functioning.. It is this functional link between glutamatethe most abundant excitatory neurotransmitter receptorsReceives an input some stimulus and transmits a the information to other cells or neurons. and a psychotic-like state that clued Valerie and others into a potential role for glutamatethe most abundant excitatory neurotransmitter in this perplexing disorder. Importantly, in addition to its role in communication throughout the brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals., glutamatethe most abundant excitatory neurotransmitter can also influence other neurochemicals, including glutamine (a glutamatethe most abundant excitatory neurotransmitter metabolite), gamma aminobutyric acid (GABA; the main inhibitory neurotransmitterchemicals released by neurons; can have an excitatory or inhibitory effect), and glutathione (an antioxidant that protects the brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. from oxidative stressdamage done to the body due to a build-up of unstable oxygen-containing molecules). This means that alterations in brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. glutamatethe most abundant excitatory neurotransmitter levels, which are thought to occur in psychosisA symptom of mental illness in which the person loses touch with reality and thinks or behaves in bizarre ways. Psychosis is a complex brain disorder that typically presents in adolescence or early adulthood with devastating impacts on social, occupational, and daily functioning., may result in changes in any (or all) of these other three neurochemicals. So, in order to get a complete picture of the relationship between glutamatethe most abundant excitatory neurotransmitter and psychosisA symptom of mental illness in which the person loses touch with reality and thinks or behaves in bizarre ways. Psychosis is a complex brain disorder that typically presents in adolescence or early adulthood with devastating impacts on social, occupational, and daily functioning., it’s necessary to systematically investigate an entire group of neurochemicals.

However, if we want to use these neurochemicals to help predict, diagnose, and treat psychosisA symptom of mental illness in which the person loses touch with reality and thinks or behaves in bizarre ways. Psychosis is a complex brain disorder that typically presents in adolescence or early adulthood with devastating impacts on social, occupational, and daily functioning., we need a way to measure them in the brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals.. Fortunately, with the development of new technology, we can do just that! Recent advances in ultra-high field MRI technology (think: more than two times stronger than the magnetic field of your average MRI scanner) and proton magnetic resonance spectroscopy (1HMRS) techniques (which enable non-invasive assessment of regional brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. chemistry) allow researchers to more accurately and reliably quantify neurochemical levels in the brainsThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. of humans. With this promising leap in neurochemical-based brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. imaging, there has been an emergence of research applying the technology to psychiatric disorders like psychosisA symptom of mental illness in which the person loses touch with reality and thinks or behaves in bizarre ways. Psychosis is a complex brain disorder that typically presents in adolescence or early adulthood with devastating impacts on social, occupational, and daily functioning.. To date, nine studies have used ultra-high field 1HRMS to investigate neurochemical concentrations in psychosisA symptom of mental illness in which the person loses touch with reality and thinks or behaves in bizarre ways. Psychosis is a complex brain disorder that typically presents in adolescence or early adulthood with devastating impacts on social, occupational, and daily functioning.. With the goal of synthesizing results across these studies, Valerie and David conducted a meta-analysis. By leveraging available data and quantitatively summarizing the findings, their work provides insight into whether concentrations of the brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals.'s main neurotransmitterschemicals released by neurons; can have an excitatory or inhibitory effect -- glutamatethe most abundant excitatory neurotransmitter and GABA -- and their associated metabolites are altered in psychosisA symptom of mental illness in which the person loses touch with reality and thinks or behaves in bizarre ways. Psychosis is a complex brain disorder that typically presents in adolescence or early adulthood with devastating impacts on social, occupational, and daily functioning..

So, what did Valerie’s meta-analysis find? After combining data from all individuals who participated in the nine available 1HMRS imaging studies, there were a total of 255 individuals with psychosisA symptom of mental illness in which the person loses touch with reality and thinks or behaves in bizarre ways. Psychosis is a complex brain disorder that typically presents in adolescence or early adulthood with devastating impacts on social, occupational, and daily functioning. and 293 healthy participants without psychosisA symptom of mental illness in which the person loses touch with reality and thinks or behaves in bizarre ways. Psychosis is a complex brain disorder that typically presents in adolescence or early adulthood with devastating impacts on social, occupational, and daily functioning.. Comparing metabolite levels for glutamatethe most abundant excitatory neurotransmitter, GABA, glutathione, and glutamine between these two groups, Valerie found that the concentration of both glutamatethe most abundant excitatory neurotransmitter and glutathione was reliably lower in patients with psychosisA symptom of mental illness in which the person loses touch with reality and thinks or behaves in bizarre ways. Psychosis is a complex brain disorder that typically presents in adolescence or early adulthood with devastating impacts on social, occupational, and daily functioning.. This finding adds to a growing body of evidence from animal models, post-mortem brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. tissue, and genetic studies suggesting that glutamatethe most abundant excitatory neurotransmitter system dysfunction contributes to psychosisA symptom of mental illness in which the person loses touch with reality and thinks or behaves in bizarre ways. Psychosis is a complex brain disorder that typically presents in adolescence or early adulthood with devastating impacts on social, occupational, and daily functioning.. It also provides insight into why psychosisA symptom of mental illness in which the person loses touch with reality and thinks or behaves in bizarre ways. Psychosis is a complex brain disorder that typically presents in adolescence or early adulthood with devastating impacts on social, occupational, and daily functioning. may emerge during late stages of neurodevelopment, given that these maturational stages are characterized by extensive changes in neuronsA nerve cell that uses electrical and chemical signals to send information to other cells including other neurons and muscles that communicate using glutamatethe most abundant excitatory neurotransmitter. Valerie’s work paves the way for future research, which could leverage this non-invasive technique to collect longitudinal samples of brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. chemistry in order to better understand the developmental time course of these neurochemical alterations. With these kinds of efforts, it won’t be long until concentrations of neurochemicals, like glutamatethe most abundant excitatory neurotransmitter, can be incorporated into individualized psychosisA symptom of mental illness in which the person loses touch with reality and thinks or behaves in bizarre ways. Psychosis is a complex brain disorder that typically presents in adolescence or early adulthood with devastating impacts on social, occupational, and daily functioning. risk calculators, serve as biological predictors of the transition from at-risk for developing psychosisA symptom of mental illness in which the person loses touch with reality and thinks or behaves in bizarre ways. Psychosis is a complex brain disorder that typically presents in adolescence or early adulthood with devastating impacts on social, occupational, and daily functioning. to a formal psychosisA symptom of mental illness in which the person loses touch with reality and thinks or behaves in bizarre ways. Psychosis is a complex brain disorder that typically presents in adolescence or early adulthood with devastating impacts on social, occupational, and daily functioning. diagnosis, and function as druggable targets for decreasing psychosisA symptom of mental illness in which the person loses touch with reality and thinks or behaves in bizarre ways. Psychosis is a complex brain disorder that typically presents in adolescence or early adulthood with devastating impacts on social, occupational, and daily functioning. risk.

About the brief writer: Kara McGaughey

Kara is a PhD candidate in Josh Gold’s lab studying how we make decisions in the face of uncertainty and instability. Combining electrophysiology and computational modeling, she’s investigating the neural mechanisms that may underlie this adaptive behavior.

Want to learn more about imaging neurochemicals in the brain and their implications for mental health? You can find Valerie’s full paper here!

How do the brain’s structure and function develop together through adolescence?

or technically,

Development of structure-function coupling in human brain networks during youth

[See Original Abstract on Pubmed]

Authors of the study: Graham L. Baum, Zaixu Cui, David R. Roalf, Rastko Ciric, Richard F. Betzel, Bart Larsen, Matthew Cieslak, Philip A. Cook, Cedric H. Xia, Tyler M. Moore, Kosha Ruparel, Desmond J. Oathes, Aaron F. Alexander-Bloch, Russell T. Shinohara, Armin Raznahani, Raquel E. Gur, Ruben C. Gur, Danielle S. Bassett, and Theodore D. Satterthwaite

An important part of learning about the brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. is not just understanding the way one individual brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. region works, but also how different brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. regions connect to each other. For example, our eyes receive visual information, but you only know what objects you are looking at because that visual information is also associated with your other senses and your memories. The connections between brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. regions are not completely set once a person is born, they develop as that person grows. There are several ways that these connections can develop. One way is structural, which is the physical connections between regions. These are the 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 connections that stretch from region to region and the synapsesthe point of communication between neurons; the tiny gap between two neurons, where nerve impulses are relayed formed between cells in different regions. Another type of connection between regions is functional. This means that when one region is active and doing a task, the other region is active as well. When the structure between brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. regions also supports the functional connections between those regions, that is called structure-function coupling. Graham Baum, Neuroscience Graduate Group student and member of the Satterthwaite lab, wanted to know how structure-function coupling develops in youth.

BrainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. regions can be classified in groups based on what they process. If a brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. region only focuses on a single simple thing such as light, heat or taste, then it is called unimodal. If a brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. region associates multiple types of information that come from different brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. regions, that brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. region can be called transmodal. When children grow up, the senses are among the first parts of the brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. to develop since they are more concrete; they require less abstract thought. The more evolved transmodal 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 the ones that develop later in life. It is also possible to measure how much a transmodal region is connected to other brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. regions, which is called the brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. region’s participation coefficient. Graham’s study focused on the differences in development of unimodal and transmodal types of brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. regions.

To study structure-function coupling, Graham scanned people from ages 8 to 23 using MRI imaging. He made two maps for each person. The first map was a structural map, made with diffusion weighted imagingA method for imaging and measuring properties of white matter using magnetic resonance imaging.. This map showed the physical connections between regions of the brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals.. The next map was a functional map. To make this map, each participant was scanned with a MRI machine while they were doing a task where they needed to remember a number of things and then repeat them back to the experimenter. That allowed Graham to make a map of the brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. to see how each region of the brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. communicated with every other region of the brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. during this task. The last step was to correlate the structural connections with the functional connections. Each region in the brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. then had a number to represent its structure-function coupling. This final value is what Graham measured and compared between participants.

The first thing Graham found was that regions that were unimodal had stronger structure-function coupling compared to transmodal areas. The more regions that one brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. region was communicating with, the weaker structure-function coupling it had. This was true across all ages. He next wanted to know how structure-function associations would change with age. To do this, he compared the structure-function coupling between younger participants and older participants. BrainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. regions that were unimodal did not change much with age. The regions that changed the most with age were the transmodal areas that support complex thought.

These age differences in structure-function coupling were exciting, but they were done across different people of different ages. Graham added to this by scanning a group of participants and then scanning those same participants about 2 years later. For most adolescents, 2 years can be a significant amount of time to change in terms of brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. development. When Graham scanned the same people twice, he confirmed that transmodal brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. regions within the same individuals developed stronger structure-function coupling over time.

The last thing Graham wanted to know is whether these structure-function connections would actually be related to behavior. He looked at how people actually did on the behavioral task that he used to make the functional maps. He found that higher structure-function coupling in a region called the rostrolateral prefrontal cortex (rlPFC) was associated with better performance on the task. The structure-function coupling of the rlPFC could also predict how two people of the same age would do on the task.

Graham’s work shows us something we didn’t know before, how the development of 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 helps to support the way that the brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. develops its cognitive abilities. This work gives us the ability to predict brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. function as humans age and develop. Additionally, this work can help us try to understand disorders that are defined by the disconnect between structural and functional development such as certain neuropsychiatric disorders.

About the brief writer: Rebecca Somach

Rebecca is a PhD Candidate in Akiva Cohen’s lab. She is interested in using electrophysiology to answer interesting and novel questions in neuroscience. Her current research focuses on how mild traumatic brain injury alters the neuronal circuitry of sleep.

Want to learn more about structure-function coupling, and how it changes as we develop? Check out Graham’s paper here.

Improving how we visualize brain changes from youth to adulthood

or technically,

Adam Pines was the lead author on this study. Adam is a PhD candidate in Ted Satterthwaite's Lab. He is interested in understanding how psychopathology emerges from neurocognitive development

Leveraging multi-shell diffusion for studies of brain development in youth and young adulthood

[See Original Abstract on Pubmed]

Authors of the study: Adam R. Pines, Matthew Cieslak, Bart Larsen, Graham L. Baum, Philip A. Cook, Azeez Adebimpe, Diego G. Dávila, Mark A. Elliott, Robert Jirsaraie, Kristin Murtha, Desmond J. Oathes, Kayla Piiwaa, Adon F.G. Rosen, Sage Rush, Russell T. Shinohara, Danielle S. Bassett, David R. Roalf, Theodore D. Satterthwaite

As people grow from childhood to adolescence, most changes are pretty clear: you might see a niece or nephew again after a couple years and find they have changed quite a bit, whether they are several inches taller or sporting new favorite phrases and hobbies. During this time of growing up, there are many complex changes happening in the brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. that are less visible.

One of the things that changes across development is the strength of connections between brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. regions. Why does this matter? Well, different parts of your brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. communicate with each other to produce the thoughts and actions that guide our daily life. When a brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. region communicates more with a particular brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. region than another, that connection gets stronger. The changes in these connections usually follow a reliable pattern across development, with some individual differences based on our unique experiences. It is important to know what changes to expect in the connections between different brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. regions during development, so that we can learn to spot when things go awry. Adam Pines of the UPenn Neuroscience Graduate Group and member of the Satterthwaite lab was interested in finding the best ways to measure changes in these connections across development by comparing several methods for analysis.

To visualize the connections between brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. regions, scientists look at a type of tissue called 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. To understand what 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 and why it is important, we need to zoom in and start with the basic building block of the brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals.: the neuronA nerve cell that uses electrical and chemical signals to send information to other cells including other neurons and muscles. NeuronsA nerve cell that uses electrical and chemical signals to send information to other cells including other neurons and muscles are a specialized kind of brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. cell. The communication between neuronsA nerve cell that uses electrical and chemical signals to send information to other cells including other neurons and muscles is what drives most everything we see, think, and do. The part of the neuronA nerve cell that uses electrical and chemical signals to send information to other cells including other neurons and muscles that makes up 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 often covered in an insulating coating called myelin. Myelin helps signals travel faster from one end of a neuronA nerve cell that uses electrical and chemical signals to send information to other cells including other neurons and muscles to the other. Collectively, these connections are called 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 because the coating makes them appear white.

Techniques have been developed to image 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 using an odd-sounding but effective principle: “follow the water.” You may not think of water when you think of the inner-workings of the brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals., but 73% of the brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. is actually water.¹ In areas of the brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. without this myelin coating, water is going in all directions. However, myelin is resistant to water, so it essentially forms little water slides in the brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals.. Only where there is 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 the water moving in one direction more than all others. Researchers take advantage of this and “follow the water” to measure 1) the direction of the water and 2) how fast it is going. This tells them the direction of the connection between brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. regions and the strength of those connections. This technique is called diffusion weighted imagingA method for imaging and measuring properties of white matter using magnetic resonance imaging.. With these basic principles, diffusion weighted imagingA method for imaging and measuring properties of white matter using magnetic resonance imaging. is able to map out where 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 and measure its properties.

Although it is a powerful tool, interpreting the results of diffusion weighted imagingA method for imaging and measuring properties of white matter using magnetic resonance imaging. requires a lot of complex modelling. Not all models are best suited for studying brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. development. The best model would be the one that showed changes in the brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. with age and that was not affected too much by people moving while they were in the scanner (called in-scanner motion). Imaging of the brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. has the same problem you do when taking a picture of anything moving - things get blurry. Lots of people can get fidgety in the scanner but especially kids, making finding a metric that isn’t affected by in-scanner motion extra important when studying brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. development. Adam wanted to figure out which diffusion weighted imagingA method for imaging and measuring properties of white matter using magnetic resonance imaging. measures researchers should be using to study brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. development.

Adam tested different methods by seeing how the output of each related to age and to in-scanner motion. Each method had a slightly different set of outputs or metrics that he looked at. He found that the metrics of each related to age and in-scanner motion differently. Some metrics were more affected by the age of the participant than others whereas other metrics were more affected by in-scanner motion. Remember, in order to study brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. development, the best metrics would be the ones that were most affected by age and least affected by in-scanner motion. Adam found that each metric varied quite a bit in how well it was associated with age. However, he found that one particular method, the Laplacian-regularized Mean Apparent Propagator (MAPL), was less affected by in-scanner motion than the other methods he tested. MAPL is a relatively new method and, before Adam’s study, no one was sure how well it would work for measuring brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. development.

Based on Adam’s work, other researchers now know what metrics are best to study 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 to determine what is happening in the brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. during development. This work is important because it allows future research on brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. development to be more reliable by leading researchers away from model metrics that would miss the effects they are most interested in. By looking at 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 during development using previous methods, researchers have already discovered different pathways that are related to normal development, anxiety and depression, and more. Adam’s work will allow for many more future discoveries like these that help us better understand problems that occur during development!

About the brief writer: Sara Taylor

Sara Taylor is a PhD Candidate in Ted Brodkin’s lab. She is interested in understanding how behaviors associated with Autism Spectrum are related to each other as well as their genetic basis.

Citations:

1. Mitchell, H. H., Hamilton, T. S., Steggerda, F. R., & Bean, H. W. (1945). The chemical composition of the adult human body and its bearing on the biochemistry of growth. Journal of Biological Chemistry, 158(3), 625-637.

   
   You can find the paper here.

Want to learn more about how these methods for studying brain development work? You can find Adam Pines’ full paper here!

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

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.

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.