Adolescence is the period between childhood and adulthood. This stage of life is marked by increased cognitive abilities, social sensitivity, and increasing independence. These changes make this time particularly perplexing to some adults, as they struggle to make sense of stereotypical adolescent behaviors such as risk taking, increased allegiance to peers and other behaviors that are sometimes described as ‘knuckle-headed’.
Twenty years ago, adolescent behavior was discussed as being influenced by “raging hormones.” In today’s world, we discuss adolescent behavior in terms of the “teenage brain “. But what makes the teenage brain different from the child or adult brain? And do these differences have implications for education, learning and social interaction?
Here’s some latest research in adolescent brain development and how the current evidence might inform education during the teenage years. Using neuroscience, we’ve gained some interesting information about the physical changes that take place in the brain during adolescence.
The most important consideration to keep in mind regarding the brain during adolescence is that the brain continues to change. There is evidence for this from multiple lines of research, including cellular work on post-mortem human brain tissue, as well as longitudinal magnetic resonance imaging (MRI) studies of brain structure and function.
With MRI, we have the ability to see how the living human brain changes from birth to old age by taking different kinds of pictures. One kind of picture we can take is of the structure–or anatomy–of the human brain, and we can use this picture to look specifically at two components of the brain’s structure: one component is grey matter, which is largely made up of brain cell bodies and their connections. And the other is white matter, which is primarily the long connecting fibers that carry signals between brain regions.
There have been a few studies now where hundreds of participants had their brains scanned multiple times across development, and we know from these studies that the amount of grey matter is greatest during childhood, but decreases during adolescence before roughly stabilizing in the mid- to late- twenties. We also know that the amount of white matter increases almost linearly across adolescence. These are two major changes happening in the structure of our brain during adolescence.
We have also learned that these changes don’t all happen at once. Structural changes are not occurring at the same time across the whole brain. Actually, areas of the brain that are involved in basic sensory processing or movement develop earlier than areas of the brain involved in more complex processes such as inhibiting inappropriate behavior, planning for the future, and understanding other people. These and other complex processes rely on areas in the prefrontal, temporal and parietal cortices, which are continuing to change in structure across the second decade of life.
So, how do these changes happen?
We still do not know the specific cellular mechanisms that underlie developmental changes in measures of grey or white matter, but it is often thought that these decreases in grey matter reflect, at least in part, changes in connectivity between brain cells. These changes include decreases in dendritic spine density (which is basically a proxy for how interconnected cell bodies are in the grey matter) and other cellular processes involved in synaptic pruning (which is the way that connections in the brain are broken). Histological work, which involves studying the cells using microscopes, has given us a better understanding of the cellular changes occurring in the human brain across the lifespan.
Is this a bad thing? Not necessarily. The continued reduction in synapses seen in the prefrontal cortex means that the brain is still undergoing changes in organization during adolescence. As humans, we have an excess amount of brain connections when we are children, and almost half of these connections can be lost in adolescence. We know that experience influences what connections are kept and subsequently strengthened. Thus we can think of adolescence as a time of transition rather than a time of loss in certain areas of the brain.
MRI can also be used to see how blood flows in the brain, which allows researchers to get a sense of how the brain is working. So if MRI alone reveals brain structure, you can think of fMRI (or “functional MRI”) as revealing brain function. Many fMRI studies have also shown changes in brain functionality across adolescence. For example, how we use areas of the brain involved in understanding other people changes between adolescence and adulthood.
This is especially true for “the social brain”. There are a number of cognitive processes that are involved in interacting with and understanding other people, and we can use functional MRI to see what areas of the brain are active when we engage in important social tasks like understanding the intentions or emotions behind facial expressions or understanding social emotions like guilt or embarrassment. Tasks like these consistently recruit a number of brain regions in the prefrontal and temporal cortex, which is sometimes referred to as the “social brain.”
Although adolescents and adults use the same areas of the brain during a number of social tasks like understanding intentions and social emotions, these tasks all show a similar decrease in activity across age in this medial prefrontal cortex area, which is a part of the brain often related to social processing Adolescents seem to use this part of the prefrontal cortex more than adults when doing certain social tasks.
So what does it all mean?
Neuroscience has helped us learn how the brain is changing in both its structure and function during adolescence, highlighting in particular the changes involved in areas of the brain used when we attempt to understand the thoughts, intentions and feelings of other people. These changes are relevant because of the developmental tasks that adolescents must accomplish. One of the major developmental tasks of adolescence is to learn how to successfully navigate our highly social world.
So, hang in there parents, having a malleable brain during adolescence is exactly how your teenager gains new social skills as well as higher levels of cultural rules and expectations. It’s just not going to happen overnight….