Thomas Armstrong

Consultant

Cloverdale, CA

Interests: Brain and learning,...

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Six Key Facts About the Adolescent Brain

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This is a transcript of my video:  The Power of the Adolescent Brain, Part 2:  Six Key Facts About the Adolescent Brain  -

In this video, I explore six key findings from recent research into how the adolescent brain functions and develops over time.  To further explore these issues, see my book The Power of the Adolescent Brain:  Strategies for Teaching Middle and High School Students.   Below is the transcript of the video:  Click here to watch the actual video.  


Hi, I’m Dr. Thomas Armstrong, and this is Part 2 of my video series on the adolescent brain entitled 6 key facts about the adolescent brain.  In the last video we noted that up until the 1990’s most scientists thought that the brain was pretty much fully developed by the end of the childhood.  In this video we’ll explore some of the new discoveries of the past fifteen years that have transformed our understanding of the changes going on in the adolescent brain.

The first key fact coming out of neuroscience research is that gray matter in the brain is decreasing during adolescence.  Gray matter refers to the cell body of the neuron or brain cell, as well as the dendrites (a word meaning ‘’branches’’) and axons which extend out of the cell body that connect with other neurons or brain cells – in this slide it would include the areas colored in burgundy.  This decrease in gray matter comes about largely as a result of ‘’pruning’’ or the selective elimination of dendrite connections between brain cells, a process which seems like it should lead to less brain power, but which actually results in a fitter brain that is better adapted to the individual’s local environment. We’ll come back to this idea of ‘’pruning’’ when we talk about the neuroplasticity of the adolescent brain.

The second key fact that neuroscientists have discovered about the adolescent brain is that white matter in the brain is increasing.   White matter refers to, among other things, the myelin or insulation (indicated in this slide by the color yellow) that covers the axons which connect to the dendrites of other brain cells.  This process of insulation, referred to as myelination, allows for quicker and more efficient transmission of nerve impulses from cell to cell throughout the brain, thus creating a more effective brain.

The third key fact about the adolescent brain is that new brain cells are being created, a process called neurogenesis.  In 1998, a brain researcher named Fred Gage at the Salk Institute in La Jolla, California demonstrated that brain cells are being created throughout the life span, something that hadn’t previously been thought possible. This slide depicts the neurogenesis of a brain cell taking place within the hippocampus, a structure important for the processing of emotion and memory.

The fourth important fact about the adolescent brain is that the process of ‘pruning’ that we discussed earlier moves over the course of childhood and adolescence in a wave-like manner from the back of the brain to the front. In this diagram, color is used to refer to the volume of gray matter in the brain.  The blue and purple regions indicate areas with less volume of gray matter, less because of the pruning process described above, where dendrites, one form of gray matter, are being eliminated.  Note how the blues and purples increase over time, sweeping over the whole brain from age 5 to age 20, and notice especially how that movement proceeds from the back area of the brain to the front (in the case of the brains shown below the diagonal arrow, from the bottom to the top).

The fifth key fact is that because the pruning of the brain proceeds from back to front, the front area of the brain—which is the primary reasoning area– is the last region to mature.  This front area is called the prefrontal cortex (just behind the forehead) and is considered to be the seat of rationality.  It contrasts with the limbic system, a group of structures underneath the cortex (that includes the amygdala among others), that collectively have been called the ‘’emotional brain.”

These two brain systems mature at different times – a fact which helps explain some of the problems associated with the adolescent years.  The emotional brain matures first – in early adolescence – and is associated with such things as risk-taking, motivation, sensation seeking, impulsivity, and emotionality.  The prefrontal cortex, which we might call the ‘’reasoning brain’’ on the other hand is associated with decision-making, planning, inhiibiting impulses, reflecting, and self-control, and other higher-order cognitive processes.  This area doesn’t fully mature until the early to mid-twenties.  So here we have a situation where the emotional brain – which we might compare to the ‘’gas pedal’’ of a car – is fully developed while the ‘’reasoning brain’’ – which according to our analogy would be the ‘’brakes’’ of a car – haven’t yet been fully installed.  It’s this gap between the development of these two brain systems that encapsulates the dilemma faced by parents and teachers of adolescents.  How to manage all that emotion while helping teens develop their ability to regulate it through reasoning.

The sixth and final key fact of this video is the most important one because it suggests that we can do something about this dilemma.  The processes I’ve talked about in this video, including pruning, myelination, and neurogenesis, are all affected by inputs from the environment, including parenting and education.  In other words, the way in which the adolescent brain is wired has a lot to do with the kinds of environmental inputs it gets.  This flexibility to being shaped by the environment is called neuroplasticity. Jay Giedd, a neuroscientist who has been in the forefront of research on the adolescent brain over the past twenty years talked about adolescent neuroplasticity in this way:

’…the pruning-down phase is perhaps even more interesting, because our leading hypothesis for that is the “Use it or lose it” principle. Those cells and connections that are used will survive and flourish. Those cells and connections that are not used will wither and die.  So if a teen is doing music or sports or academics, those are the cells and connections that will be hard-wired. If they’re lying on the couch or playing video games or MTV, those are the cells and connections that are going [to] survive.’’ 

This means that we have a responsibility as parents and teachers, to do all we can to make sure teens have the best and most positive learning and growing environment within which to thrive.  In future videos, we’re going to talk about specific strategies that can be implemented at the middle school and high school levels to maximize the chances that the adolescent brain will wire itself for success. 

If you want to find out about those strategies right now, or get further information about the material we just covered in this video get my book The Power of the Adolescent Brain:  Strategies for Teaching Middle and High School Students.  Thanks for watching, and I hope that you’ll look for my other videos in this series on adolescent brain development.

For Further Information:  Thomas Armstrong, The Power of the Adolescent Brain: Strategies for Teaching Middle and High School Students. (ASCD)

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