Tag Archives: LTP

Learning & the Brain – Frances Jensen, second part (teen brain)

[July 28, 2008 Update: I just came upon this wonderful interview with Frances Jensen on the teen brain. She responds to ten questions, and you can watch the brief video clips for each response or read the corresponding text.]

My previous post provided a primer in cellular learning as a beginning to understanding how the teen brain develops. As part of this process Frances Jensen describes:

The Paradox of the Teen Brain

Cell (neuronal) based learning is at its height in the teen brain
but
the network coordination is not fully connected up yet.

What does this mean? Essentially, teenagers – who, Jensen stressed, are not small adults – have superior learning skills to adults but their prefrontal cortex is still developing. As a result, then tend to have difficulty with impulse control and are not the best at making informed decisions.

As the brain develops, it matures from back to front, so the prefrontal cortex is the last to develop, becoming fully developed around age twenty-four. This explains why teenagers do not always act in what adults would consider a rational manner. Jensen also explained that the “excitation system peaks in early childhood, which is also when many affective disorders begin, while the inhibitory system continues to develop into adulthood.

Long term potentiation, described in my previous post, peaks two to three years earlier with girls (ages 10 to 14) than with boys (ages 12 to 17). Thus, “adolescent synaptic plasticity is “way better” than adults.” Because LTP is widely influenced by the environment, teenagers may be wired for optimal learning but also have the highest susceptibility to negative influences.

If you recall from the previous post, LTP is why repetition works. Imagine a fertile brain, still developing, and highly attuned to learning. Now expose this brain to drugs or alcohol or addiction or sleep deprivation or stress or multitasking. The teen brain is primed to learn and not primed to make informed decisions. With repetitive exposure to these negative influences, the teen brain learns to want continued exposure to these influences. Jensen states it succinctly: the “Adolescent brain responds too robustly to addiction, much more so than the adult brain.”

Jensen touched on some of the specifics of these negative influences. For instance, marijuana negatively impacts the sending and receiving of neuronal signals. “The effects may linger for days, so if you get high on Saturday this may impact your test taking four days later.” (I’ll bet that’s a surprise to any teenage readers!)

She shared a story about stress: Consider a mouse in a cage, with a cat hovering just outside the cage, and imagine the stress level of the mouse. Now simply replace the mouse with a student in a classroom, and replace the cat with either a teacher or a parent, and imagine the stress level of the student. Perhaps it will not surprise you to learn that high levels of stress in adolescence can cause depression later on in adulthood.

Lastly, Jensen talked about chronic sleep deprivation. According to her, two days of deprivation can lead to no LTP taking place; that means no real learning being consolidated over night. The simple solution is to get to sleep early and be sure to get sufficient amounts of sleep. Reviewing information at night, just before falling asleep, leads to sleep-induced replay which facilitates LTP. I have read about this many times and, while not testing it out in terms of preparing for a test, have done my own experiment for remembering. Instead of writing myself a note before bed, I have repeated to myself out loud what I want to remember in the morning. And guess what, in the morning I have remembered my message to myself from the night before.

At the National Institute for Health site you can view a time lapse movie of consolidated brain MRI scans showing 15 years of normal brain development from ages 5 through 20.

“Red indicates more gray matter, blue less gray matter. Gray matter wanes in a back-to-front wave as the brain matures and neural connections are pruned. Areas performing more basic functions mature earlier; areas for higher order functions mature later. The prefrontal cortex, which handles reasoning and other “executive” functions, emerged late in evolution and is among the last to mature. Studies in twins are showing that development of such late-maturing areas is less influenced by heredity than areas that mature earlier.”

What does all of this mean in terms of teenage brains and their education? As Jensen summarized:

  • Teenagers have exceptional skill for cellular learning (better than an adult, not as good as a young child).
  • Connectivity is a work in progress (better than a young child, not as good as an adult).
  • There is a paradoxical state in the teen brain (impulsive, enhanced susceptibility to environmental effects).
  • Schools and teachers should take genetic differences and school hours into consideration (girls develop two years sooner than boys, and all teens tend to have circadian rhythms that have them most alert and awake by ten o’clock in the morning).

Learning & the Brain – Frances Jensen, first part (cellular learning)

As a teacher of teenagers and a mother of two sons, one who is currently a teenager, I was primed for Frances Jensen’s session The Paradox of Learning in the Teen Brain: Unique Vulnerabilities and Strengths. Jensen is a doctor at Harvard’s Children’s Hospital and is on a mission to share current research on teen brains with those who would most benefit from the information – teenagers, their parents, and their teachers.

Just this past Friday, I shared the bulk of her talk in a class I co-teach with an upper school colleague, Frontiers in Science. Once a week I give a talk on what’s new in technology, and volunteered to give a talk on what’s new in brain research. To best understand the paradox of the teen brain, it helps to first have a sense of how the brain learns.

Jensen provided a quick primer in cellular learning. Essentially, information in the form of a signal is received by a neuron via its dendrites, and then information in the form of a signal is fired through the neuron’s axon and out via its axon terminals. This communication between neurons happens across the synapse, which is the space between the neurons. Coating the axon is myelin, which protects the axon and assists with communication.

Not all brain cells fire; some send excitatory signals and some send inhibitory signals. According to Jensen, in order for learning to take place there needs to be:

  • a synapse
  • a patterned input
  • enough excitation to induce a response
  • and alterations in the activated cell that is long lasting and leads to long term potentiation (LTP)

What, exactly, is Long Term Potentiation? Potentiation refers to increased effectiveness or potency. In terms of LTP, it means the ability of information to retain its strength over time, in other words, for information to be remembered. To better understand what this means in terms of learning, consider that LTP (the following comes directly from Jensen)

  • consists of a practice effect or memorization
  • is why repetition works
  • explains why multiple inputs into a cell enhances learning
  • and is why multiple methods of teaching should be utilized (my addition)

With LTP the synapse gets altered to be larger, faster and newer, with more receptors.

In my next post I’ll share more of what Frances Jensen said about the teen brain, in particular how it differs from the child and adult brain. Meanwhile, feel free to check out Teen Brain’s Ability to Learn Can Have a Flip Side on The Dana Foundation site. The article shares a number of reports that lend

support to the idea that the remarkable adaptability of the adolescent brain can be a double-edged sword: The dramatic remodeling of the brain during adolescence holds tremendous opportunities for growth and learning but also appears to increase a teen’s vulnerability to the long-term effects of environmental influences such as stress and drug experimentation.

Another article on the topic of teen brains, Understanding the Temporary Insanity of Adolescence, appeared recently in The New York Times, and I suspect there will be more and more doctors deciding to specialize in this area of medicine, just as there are pediatricians and gerontologists who specialize by a general age range of patients.

Plasticity and the Brain: Merzenich and Taub

Michael Merzenich blogs at On the Brain, where he never seems to mince words as he gets right down to the subject at hand. PositScience: The Science with Dr. Merzenich is a 9 minute video during which Merzenich talks about the development of the brain, brain change, and plasticity.

His current company, PositScience, is focused on how to maintain plasticity and encourage brain change and growth for aging adults, with the goal of improving memory. If you are interested, there are a number of YouTube videos about this, including interviews with neuroscientists and users of the PositScience program.

[October 11, 2008 update – in going through my files I found a May, 6, 2007 NY Times article about Merezenich and his company, entitled Muscular Metaphor, which provides background on the company.]

Merezenich is another one of the neuroscientists featured in Norman Doidge’s book, The Brain That Changes Itself, and may best be known for his work on developing the cochlear implant.

What interests me most, though, are the findings of his research.

‘You cannot have plasticity in isolation … it’s an absolute impossibility.’ His experiments have shown that if one brain system changes, those systems connected to it change as well. The same ‘plastic rules’ – use it or lose it, or neurons that fire together wire together – apply throughout. Different areas of the brain wouldn’t be able to function together if that weren’t the case.

Within the same chapter, Doidge explains the brain chemistry that takes place during learning and unlearning, both of which take place as a function of plasticity. As you learn something, the neurons involved in the learning fire together and thus wire together. This is facilitated in cells by LTP (long-term potentiation), which is the chemical process of strengthening the synaptic connections. When the brain is poised for unlearning, the opposite takes place due to LTD (long-term depression), where the synaptic connections are weakened and disconnected.

Another neuroscientist who brightens the pages of Doidge’s book is Edward Taub. His research and innovation in stroke treatment pioneered CI (constraint induced) therapy, which exploits the brain’s plasticity. You can listen to Taub explain his work in an interview on The Brain Science Podcast, where there are also a number of links and references posted.

Taub’s research supported Merzenich’s findings that “when a brain map is not used, the brain can reorganize itself so that another mental function takes over that processing space.” In addition, with specific application to stroke patients and anyone who had some form of brain damage, “Not only could the brain respond to damage by having single neurons grow new branches within their own small sectors, but, the experiment showed, reorganization could occur across very large sectors.”

Hazaah!

Greenleaf Presentation.2 – Brains Learn

There were a number of clever sounding one liners uttered by Bob Greenleaf during his presentation. The thing is, while they sound clever, they are also easy to remember, and make total practical sense.

Lungs breathe, hearts pump, brains learn.

I have heard that sentiment several times, but none put so succinctly. Our brains are learning machines; they improve with the learning process. The act of building synapses and connections is the act of learning. According to Eric Jensen:

For the most part, long-term potentiation (LTP) has been accepted as the physical process of learning. … LTP means a neuron’s response to another neuron has been increased. It has “learned” to respond. Each future event requires less work to activate the same memory networks. … In short, learning happens at a micro level through the alteration of synaptic efficacy. Excited cells will excite other nearby cells.

Greenleaf went on to explain that when one area of the brain is busy processing, this benefits the other areas of the brain because the brain is an interconnected organ. All areas of the brain participate all the time in processing, though depending upon what is being processed some areas will be more active at any given time.

And as for the right-brain, left-brain theory, in actuality this is more of a personality or learning style description rather than a description of how the brain truly functions.

Next post: Pithy statement number two.