The Complicated Case of Adolescent Drug Abuse: Implications of Brain Plasticity


Comments   |   Blog, Substance Abuse

by Erich Engelhardt M.A. and Joseph Shrand, MD

Brain imageIt never made sense what my teachers in medical school were telling me back in the late 1980’s about the brain: that brain cells did not replicate and once dead were therefore not replaced.  Practically all other parts of the body have some way of reproducing.  From our skin to our blood, cells replicate.  Our gut cells die and are replaced by new ones.  You have all had the experience of a sun burn, having the old skin peel off only to be replaced by new skin.  Imagine if this didn’t happen!  The liver, the kidneys, our bones, all of us are in some ways brand new every few months.

There is a huge evolutionary premium to be able to replicate our cells.  It is the way to ensure longer term survival: organisms that had a way to repair themselves survived longer than organisms that did not.  To think that our brains, arguably the most important organ in our body, would be precluded from this ability just seemed silly.

But new research has shown that our intuitive belief that the brain had to have some mechanism to reproduce and adapt does indeed happen.  Important families of brain cells called glial cells actually have the ability to replicate, and some stem-cell glial cells can be prompted to mature into neurons.

(SIDE BAR:  Remember that phrase we only use ten percent of our brain?  Nonsense!  This belief is a response to a misunderstanding of the function of glial cells.  The brain is composed basically of two types of cells.  Neurons, the name of which precedes suffix words like neuroscience and neurology, comprise ten percent of our brain, the ten percent we thought we used.  Neurons were believed to be the cells that took information from the outside world, translated it, and then transmuted it into a thought, feeling, and action. For a hundred years, neurons, the ten percent of the brain, have been seen as royalty and leaders.  And just like royalty, they needed the support of serfs, a complex network of servants responsible for feeding them, nurturing them, protecting them, and getting rid of their garbage.  The other 90 percent of the brain were seen as no more than chaff: the lowly glial cells.)

Glial cells are now coming into their own (Koob, 2009)  Responsible for much more than being a garbage scow, they are actually a family of cells with grand names like astrocytes because of their star like shape, or oligodendrocytes that coat the neuron with the fatty sheath of myelin which we talk about in more depth later in the blog.  It is the glial cells that appear to be receiving the information transmitted from the neurons, and then telling the neurons what to do.  And it is the glial cell that is replicating, dying, being replaced, and in some cases transforming into neurons.

This has enormous implications for the brain.  With each moment our brains are receiving information, processing and interpreting that information, and then responding in action to that information.  These responses actually change, at a microcellular (really, really small) level the intricate interconnections of our brain. The brain is not static but constantly evolving, adapting, and changing.

Called   Neuroplasticity, this concept has replaced the old ideology that the brain is the brain is the brain, never changing, immutable. It just makes so much more sense than the idea I was taught, that the brain does not re-generate. This new understanding has enormous implications, none more so than for the brain of the adolescent.

For now, however, we will focus on neurons and their role in “neuroplasticity.”  (At some point I am sure scientists will change the phrase to “glialplasticity,” but not today!)

Koob, A (2009) The Root of Thought: Unlocking Glia- the Brain Cell That Will Help Us Sharpen Our Wits, Heal Injury, and Treat Brain Disease. FT Press 2009