Download Trainee Content for Day 1, Segment 4C

Trainee Content for Day 1, Segment 4C
Principles of Neurodevelopment
1. Neurodevelopment proceeds from genetic and environmental influences:
Genetics provide the blueprint, but the environment will shape how genes are
expressed. When experiences are provided in a structured, patterned, and
appropriately timed way, genetic potential can be expressed and neural systems which
mediate various functions will develop.
2. Neurodevelopment is sequential: The brain develops in a sequential and
hierarchical fashion, organizing itself from least (brainstem) to most complex (limbic,
cortical area). These different areas develop, organize, and become fully functional at
different times during childhood. The brainstem, which regulates cardiovascular and
respiratory functions, is functional at birth, while cortical areas responsible for
abstract cognition will not mature for years. Each brain area has its own timetable for
development. The neurons for the brainstem have to migrate, differentiate, and
connect before the neurons for the cortex. This has profound implications for
maltreatment: for example, if nurturing is absent for the first three years of a child’s
life, the love and care that the child then receives when adopted may not be enough to
overcome the malorganization of the neural systems that mediate socio-emotional
functioning.
3. Neurodevelopment is activity-dependent: The brain organizes in a use-dependent
way. Lack, or disruption, of critical cues can alter the neurodevelopmental processes
of neurogenesis, migration, differentiation, and synaptogenesis—all of which can
contribute to malorganization and diminished functional capabilities in the specific
neural system where development has been disrupted. This can lead to compromised
functioning throughout life.
4. Neurodevelopment involves windows of opportunity and windows of
vulnerability: Sensitive periods for neural systems (and the functions they mediate)
will be when that system is in the midst of organizing itself (the developmental ‘hot
zone’). Since the brainstem must organize key systems by birth, the sensitive period
for those brainstem-mediated functions is during the prenatal period. The neocortex,
in contrast, has systems and functions organizing throughout childhood and into adult
life. The sensitive periods for these cortically-mediated functions are likely to be
very long. Although the brain remains sensitive to experience throughout life, it is
most receptive to environmental input (plastic) during early childhood. Different
parts of the brain are more plastic (cortex) or less plastic (brainstem) than others.
“Experience can change the mature brain—but experience during the critical periods of
early childhood organizes brain systems!”
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Illustration. Synaptic density in the human brain
At birth
Six years old
14 years old
Adapted from: Perry, B.P. (2002). Childhood Experience and the Expression of Genetic Potential: What Childhood
Neglect Tells Us About Nature and Nurture. Brain and Mind, 3, 79-100, to supplement the screening of Dr. Perry’s
videotape and Childhood Trauma, the Neurobiology of Adaptation and Use-Dependent Development of the
Brain: How States Become Traits by Bruce D. Perry M.D., Ph.D., et al.
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Trainee Content for Day 1, Segment 4C
Architecture and Functions of the Brain
The brain is the most complex part of the human body. Scientists have learned more
about the brain in the last few years than in all previous centuries of study due to the
accelerating pace of neurological and behavioral science, and the development of new
research techniques, such as positron emission tomography (PET) scans and magnetic
resonance imaging (MRI). An understanding of the brain’s structure and function will
help to create a framework for understanding the impact that maltreatment or trauma may
have on the developing child.
Overview
The brain’s structures mirror evolutionary history through its organizational hierarchy
from older to newer, lower (primitive) to higher (advanced), and in the positioning of the
structures in the skull. (Siegel, 1999; Solms & Turnbull, 2002 in Applegate & Shapiro,
2005). There are three main interdependent brain systems: (1) the brainstem, (2) the
limbic system, and (3) the cortex.
Brainstem
Location: The base of the brain contains the lower structures, which include the neural
circuits of the brainstem, a direct extension of the spinal cord.
Functions: The brain’s oldest structure in evolutionary terms, the brainstem is
responsible for monitoring and regulating basic physiological process such as heart rate,
respiration, body temperature, and sleep cycles. (Siegel, 1999; Solms & Turnbull, 2002
in Applegate & Shapiro, 2005).
Cerebellum
Location: The cerebellum is connected to the back, and slightly above, the brainstem.
Function: The cerebellum helps coordinate motor, social, emotional, and cognitive
functioning. Collectively, the brainstem and cerebellum are referred to as the reptilian
brain due to their resemblance to the brains of contemporary reptiles. (Stien & Kendall,
2004)
Example of function: When you play the piano or hit a tennis ball, you are activating the
cerebellum.
Limbic System
Location: The limbic system is located between the brainstem and the cerebral cortex
and coordinates their activities. It forms a ring around the brainstem. Key regions of the
limbic system include the orbitofrontal cortex, the anterior cingulate, and the amygdala.
The limbic system also contains the hippocampus.
Functions: These regions perform the function of integrating and regulating a wide
variety of mental and emotional processes, including attachment, and are believed to
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enhance the human capacity for assigning meaning to internal and external stimuli. The
hippocampus is a sub-system that mediates access to conscious forms of memory (Siegel,
1999 in Applegate & Shapiro, 2004). The limbic system is sometimes referred to as the
mammalian brain since it first appeared in mammals. It is alternatively called the
emotional brain, because it remains the source of our urges, appetites, and emotions.
(Stien & Kendall, 2004). The most basic emotions of life, such as fear, activate the limbic
system. Dysfunction in limbic structures underlies most psychiatric disorders, such as
depression.
Cerebral Cortex
Location: The newest and most advanced parts of the brain constitute the higher
structures, principally the cerebral cortex found on the outer layer of the brain.
Functions: This area of the brain is responsible for the formation of ideas and mental
representations of self, others, and the environment.
Development: The cerebral cortex is sculpted postnatally, in the context of positive and
negative interactions with the social and physical environments. (Siegel, 1999; Solms &
Turnbull, 2002 in Applegate & Shapiro, 2005).
Other facts: When people talk about gray matter in the brain, they are talking about the
cerebral cortex. The cortex is gray because nerves in this area lack the insulation that
makes most other parts of the brain appear to be white. The folds in the brain add to its
surface area, and therefore increase the amount of gray matter and the quantity of
information that can be processed.
Orbitofrontal Cortex
Location: The orbitofrontal cortex lies just behind the orbit of the eye at the apex of the
limbic system where the cortex and subcortical areas meet.
Functions: The orbitofrontal cortex is important in affect regulation and has been
nicknamed the senior executive of the social-emotional brain. It contains neurons that
process facial and vocal information and is believed to be critical in social adjustment,
the control of mood, and the regulation and storage in memory of affective responses to
events. It is expanded in the right hemisphere, and dominant for unconscious processes
(Schore, 2003 in Applegate & Shapiro, 2005).
Left and Right Hemispheres
Location: The cerebral cortex is made up of two large hemispheres that are connected by
filaments of white matter, called the corpus callosum.
Functions: Although the two hemispheres appear identical, their functions are different.
Left hemisphere: The left hemisphere specializes in identifying and processing the
details of a situation. Its specialty is processing the semantic aspects of language,
making causal connections between phenomena, and coordinating fine motor
movements (Pally, 2000; Siegel, 1998 in Applegate & Shapiro, 2005).
Right hemisphere: The right hemisphere specializes in processing global aspects of
information: it gets the big picture of a situation, and is particularly adept at
processing emotional experience, nonverbal communication such as gesture or tone
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of voice, and somatic sensations such as touch, pressure, and overall body
positioning.
Functions and Characteristics Associated
with the Right and Left Cerebral Hemispheres
Left Hemisphere
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Positive, optimistic emotions (e.g., happiness)
Motivational tendency to approach, explore, and tack action
Involved in the processing of verbal communication, words, and numbers
Has the capacity to analyze, problem solve, and process information sequentially
Allows for the elaboration and provides detailed perspective
Right Hemisphere
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Negative, pessimistic emotions (e.g., fear or despair)
Motivational tendency to withdraw and avoid
Involved in the processing of nonverbal, emotional communication, imagery, and
visual-spatial information
Limited capacity to think analytically
Provides global perspective
Courtesy of Haworth Press, http://www.haworthpress.com.
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Triune Brain. An evolutionary perspective of brain development, by Paul Maclean, which
emphasizes that the human brain evolved from the bottom up. Each new layer added new
functions that helped in the struggle to survive and dominate. As the fetal brain develops, it
repeats the evolutionary development of the species- the primitive lower layers mature first and
the cortex develops last. The cerebellum also evolved from an area that initially controlled
movement to a structure that plays a significant role in thinking, emotional regulation, and
communication. Image and text provided courtesy of Haworth Press,
http://www.haworthpress.com.
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The Four Lobes of the Brain
The cerebral cortex is divided into four lobes. Each has different functions and is
represented in both hemispheres:
(1) the occipital lobes, involved in processing visual stimuli
Example of function: As you look at the words and pictures in the illustration, the
occipital lobes are processing images from your eyes and linking that information
with images stored in memory. Damage to the occipital lobes can cause blindness.
(2) the temporal lobes, which mediate auditory, language, and memory functions
Location: The temporal lobes lie in front of the visual areas and nest under the
parietal and frontal lobes.
Examples of functions: Whether you appreciate symphonies or rock music, your
brain responds through the activity of these lobes. At the top of each temporal lobe is
an area responsible for receiving information from the ears. The underside of each
temporal lobe plays a crucial role in forming and retrieving memories including those
associated with music.
(3) the parietal lobes, which link sensory and motor functions and provide a sense of the
spatial location of the body
Examples of functions: When you enjoy a good meal—the taste, aroma and texture
of the food—the parietal lobes are at work. The forward parts of these lobes, just
behind the motor areas, are the primary sensory areas. These areas receive
information about temperature, taste, touch, and movement from the rest of the body.
Reading and arithmetic are also functions in the repertoire of each parietal lobe.
(4) the frontal lobes, sometimes called the executive center of the brain, which mediate
motor behavior, language, abstract reasoning, and directed attention (Cozolino, 2002
in Applegate & Shapiro, 2005).
Location: The frontal lobes lie directly behind the forehead.
Examples of functions—Frontal lobes: When you plan a schedule, imagine the
future, or use reasoned arguments, these two lobes are working. The frontal lobes
appear to act as short-term storage sites allowing one idea to be kept in mind, while
other ideas are considered.
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Functional Areas. Contemporary mapping of the mind is based on two types of studies: those
using functional imaging techniques that visually record neural activity as an individual is
performing a mental and/or behavioral task, and those that show the effects of damage to
particular areas of the brain and the effects of stimulating specific brain regions. The brain is a
complex, interactive, and dynamic system. Remarkably, functional areas can change—given the
right circumstances—and one are can take over the work of another. Image and text provided
courtesy of Haworth Press, http://www.haworthpress.com.
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