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The Amazing Human Brain and Human Development
 

   
 
Lesson 5: Plasticity, Memory, and Cortical Modulation in the Brain

Brain Plasticity

Welcome back. Last time we talked about how human communication works in relation to the brain and also how different parts of the brain are affected by traumatic experience.

This week we'll go a little deeper to discuss how the brain stores those experiences and how it adapts as a result of them.

Plastic Fantastic

The human brain is very plastic, meaning that it is capable of changing in response to patterned, repetitive activation. Reading, hearing a new language, and learning a different motor skill such as typing are all examples of the brain's plasticity in action. But not all parts of the brain are equally plastic.

As areas of the brain increase in complexity, they become more plastic. Image courtesy of Bruce D. Perry, M.D., Ph.D.
As areas of the brain increase in complexity, they become more plastic. Image courtesy of Bruce D. Perry, M.D., Ph.D.

The Cortex Is the Most Plastic

The malleability of specific human brain areas is different. The most complex area of the brain -- the cortex -- is the most plastic. We can modify some cortex-related functions throughout life with minimal effort. For example, even a 90-year-old person can learn a new phone number.

The lower parts of the brain, which mediate core regulatory functions, are not very plastic. And that is for good reason. It would be very destructive for these basic and life-sustaining functions to be easily modified by experience once they were organized. A lesion that kills one million neurons in the cortex can be overcome. For instance, people recover language and motor skills following a stroke. Conversely, a lesion in the brainstem that killed as many cells would result in death.

Brain Plasticity Is Related to Two Main Factors

The degree of brain plasticity is related to two main factors: the stage of development and the area or system of the brain. Once an area of the brain is organized, it is much less responsive to the environment, or plastic. A critical concept related to memory and brain plasticity is the differential plasticity of various brain systems.



 


Remember!

Remember that the brain is not just one large mass of equivalent tissue. It has a hierarchical and complex organization.


State Dependent Storage and Recall

The brain changes in a use-dependent fashion. All parts of the brain can modify their functioning in response to specific patterns of activation -- or to chronic activation. These use-dependent changes in the brain result in equivalent changes in cognition. This is what we recognize as cognitive learning. Similarly, emotional functioning (social learning), motor-vestibular functioning (e.g., the ability to write, type, ride a bike) and state-regulation capacity (e.g., resting heart rate) all exemplify the brain's ability to make use-dependent changes.

Conversely, you cannot change any part of the brain that you are not activating! No one could learn to play golf by sitting in a classroom and listening to Tiger Woods talk about how to shoot a low score. In order to learn -- to change the brain -- the experience has to activate the part of the brain that mediates the function you are trying to learn; the right parts of the cortex must be activated and receptive to learn traditional "cognitive" concepts such as we teach in schools, for example.

A mismatch between modality of teaching and the receptive portions of a specific child's brain can occur. This is particularly true when considering the learning experiences of the traumatized child. Classroom learning cannot occur if the child is in either a persistent state of arousal and anxiety, or of dissociation. When in this state, the key parts of the cortex are not receptive to cognitive information that is not relevant to survival. The traumatized child's brain is essentially unavailable to process efficiently the complex cognitive information being conveyed by the teacher.

Trauma Impairs Interpretation

The traumatized child frequently has significant impairment in social and emotional functioning. Hyper-vigilant children frequently develop remarkable non-verbal skills in proportion to their verbal skills (street smarts). They often over-read (misinterpret) non-verbal cues. Eye contact is read as a threat, or a friendly touch is interpreted as an antecedent to seduction and rape. These assessments might have been accurate in the world they came from.

During early development, these traumatized children spent so much time in a low-level state of fear that they were focused primarily on non-verbal cues. Once out of such an environment, it is still difficult for the child's brain to interpret (relearn) these innocent looks and touches as benign.

 These children are often labeled as learning disabled. These difficulties with cognitive organization contribute to a more primitive, less mature style of problem solving -- with violence often being employed as a "tool."

This principle is critically important in understanding why a traumatized child -- in a persistent state of arousal -- can sit in a classroom and not learn. The brain of this child has different areas activated -- different parts of the brain controlling his functioning. The capacity to internalize new verbal cognitive information depends upon having portions of the frontal and related cortical areas activated, which in turn requires a state of attentive calm. Sadly, this is a state that the traumatized child rarely achieves.

Various developmental stages as they pertain to the brain and behavior. Image courtesy of Bruce D. Perry, M.D., Ph.D.
Various developmental stages as they pertain to the brain and behavior. Image courtesy of Bruce D. Perry, M.D., Ph.D.

The above table illustrates the various developmental stages as they pertain to the brain and behavior. Note that when a child is threatened, he or she is likely to act in an "immature" fashion. Regression, a retreat to a less-mature style of functioning and behavior, is commonly observed in all of us when we are physically ill, sleep-deprived, hungry, fatigued, or threatened. When we regress -- in response to a real or perceived threat -- our behavior is mediated (primarily) by less-complex brain areas.

Baseline State of Arousal

If a child has been raised in an environment of persistent threat, the child will have an altered baseline such that the internal state of calm is rarely obtained. The traumatized child will have a "sensitized" alarm response, over-reading verbal and non-verbal cues as threatening. This increased reactivity will result in dramatic changes in behavior in the face of seemingly minor provocative cues. Often, over-reading of threat will lead to a "fight or flight" reaction and impulsive violence. The child will view his violent actions as defensive.

Children exposed to significant threat will "re-set" their baseline state of arousal such that even when no external threats or demands are present, they will be in a physiological state of persistent alarm. As external stressors are introduced (e.g., a complicated task at school, a disagreement with a peer) the traumatized child will be more "reactive." Even a relatively small stressor can instigate a state of fear or terror. The cognition and behavior of the child will reflect his or her state of arousal.

No part of the brain can change without being activated. You can't instruct someone in the French language while they are asleep, nor can you teach a child to ride a bike by drawing a picture on a blackboard.

The increased baseline level of arousal and increased reactivity in response to a perceived threat plays a major role in the various behavioral and cognitive problems associated with traumatized children.



 


Life as a Constant Test

Children in a state of fear retrieve information from the world differently than children who feel calm. We all are familiar with test anxiety. Imagine what life would be like if all experiences invoked a similar and persistent feeling of anxiety. If a child has information stored in cortical areas, but is very fearful at a specific moment, the information becomes inaccessible.


Cortical Modulation

The human brain works through inhibitory mechanisms. The majority of the brain's structural organization takes place in childhood. This development is characterized by both sequential development and "sensitivity" (from the brainstem to the cortex), and by the "use-dependent" organization of these various brain areas.

As the brain grows and organizes, the higher, more complex areas begin to control and modulate the more reactive, primitive functioning areas of the lower parts. The person becomes less reactive, less impulsive, and more thoughtful. Any factors that increase the activity or reactivity of the brainstem (e.g., chronic traumatic stress) or decrease the moderating capacity of the limbic or cortical areas (e.g., neglect, brain injury, mental retardation) will increase an individual's aggression, impulsivity, and capacity to be violent (see the graphic below).

Cortical Modulation Is Age-Related

The capacity to moderate frustration, impulsivity, aggression, and violent behavior is age-related. With sufficient motor, sensory, emotional, cognitive, and social experiences during infancy and childhood, the mature brain develops (in a use-dependent fashion) a mature, humane capacity to tolerate frustration, contain impulsivity, and channel aggressive urges.

A frustrated three-year-old (with a relatively unorganized cortex) will have a difficult time modulating the reactive, brainstem-mediated state of arousal and will scream, kick, bite, throw, and hit. However, the older child, when frustrated, may feel like kicking, biting, and spitting, but has "built in" the capacity to modulate and inhibit those urges.

As the brain develops and the more complex areas organize, they begin to moderate and control the more primitive and reactive lower portions of the brain. Image courtesy of Bruce D. Perry, M.D., Ph.D.
As the brain develops and the more complex areas organize, they begin to moderate and control the more primitive and reactive lower portions of the brain. Image courtesy of Bruce D. Perry, M.D., Ph.D.

Sequential Development

All theoretical frameworks in developmental psychology describe this sequential development of ego-functions and super-ego. Simply stated, inhibitory capabilities gradually develop so as to modulate the more primitive, less mature, reactive impulses of the human brain.

Loss of cortical function through any variety of pathological processes (e.g., stroke, dementia) results in regression. Further, any deprivation of optimal developmental experience that leads to the underdevelopment of cortical, sub-cortical, and limbic areas will result in persistence of primitive, immature behavioral reactivity and predisposition to aggressive behavior.

Coming Up

So, what do you make of all this? How is the information coming together in your brain? How do you think this new knowledge will help you in your work with children? Please visit the Message Board and share your thoughts.

In our next (and last) lesson, we'll go over some of the many resources available for learning more about children and the incredible brains we all possess. We'll tie up the course with a few brainy factoids, and you and your brain will be on your way.

Image courtesy of Bruce D. Perry, M.D., Ph.D.
Image courtesy of Bruce D. Perry, M.D., Ph.D.


 


Use it or Lose it

A key neurodevelopmental factor that plays a major role in determining the brain's moderating capacity is its amazing ability to organize and change in a "use-dependent" fashion.


   
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