Transcript Limbic System

Early Brain Development and Its Implications
for Working with Young Children with Sensory
Loss
Linda Alsop
SKI-HI Institute
Utah State University
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“Early experiences are so powerful that they can
completely change the way a person turns out.”
Harry Chugani
Pediatric Neurobiologist
Wayne State University
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“Genes might determine only the brain’s main
circuits, with something else shaping the trillions of
finer connections. That something else is the
environment, the myriad
messages that the brain
receives from the
outside world.”
Sharon Begley
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A person’s ability to interact,
perceive, and learn from the
environment comes from the
ability to process incoming
sensory information and react
to the information with a
motor response which, in turn,
feeds back sensory
information.
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The central nervous system
consists of the brain and the
spinal cord.
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The Brain
The brain has two basic functions:
• The first function of the brain is to communicate.
The brain communicates by receiving sensory information from the
environment via the eyes, ears, nose, mouth, position in space, and nerve
endings throughout our body. This information is then sent to other parts of
the body via the spinal cord and the peripheral nervous system.
Subsequently, the central nervous system (CNS) receives signals from the
rest of the body and then plans and sends signals back to the environment.
Such response signals may be intentional (e.g., talking, writing, signing) or
unintentional (e.g., flushing, startling, breathing heavily).
• The second function of the brain is to integrate incoming sensory
information with information already stored in the brain’s subconscious
and conscious memory banks.
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• The brain is made up of about two hundred billion interconnected
neurons or nerve cells. A typical nerve cell has a cell body which
is attached to one major fiber or axon with a number of fibrous
branches called dendrites. Dendrites receive messages coming
into the neurons which, in turn, combine and integrate the signals.
The neurons then emit outgoing signals via the axons. These
neurons communicate with each other via chemical secretions
called neurotransmitters.
• The more the brain engages in problem-solving activities, the more
it develops—not through gaining new neurons but through dendritic
branching.
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• Most of us are born with more neurons than we need, which is
good because some die off even when there is no insult to the
brain. Individuals who have suffered from severe neurological
insult have had significantly more neurons killed off than would
occur under typical conditions. Once a neuron
is damaged or dies, it cannot be revived;
however, appropriate habilitation or
rehabilitation services may assist in
promoting the dendrites of remaining
neurons to branch out more.
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The Brain and Sensory Input
• The first priority of the brain is to keep us alive.
• The second priority of the brain is to enable us to deal with our
body and its interaction with the world it senses around us.
Genetically, we are imprinted to survive.
• Humans are constantly bombarded with stimuli—environmental
information about one’s own body, light, noise, temperature, etc.
• The entire CNS needs sensory input, but the input must be
meaningful to the brain in order for it to be helpful. A confused
brain will do what it can to make sense of what it is experiencing.
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What Happens When the Brain
Receives Messages?
Corpus Callosum
The brain is divided from front to back into two hemispheres joined
together by fibrous tissues called the corpus callosum. It is responsible
for passing messages from one side of the brain to the other.
Sensory Systems
All the information we receive comes through one or more of our
sensory systems—eyes, ears, nose, mouth, position in space, and
nerve endings throughout the body.
Reticular Activating System
The incoming sensory information alerts the reticular activating
system (RAS) to be prepared to receive and transmit messages.
The RAS has to be aroused to perform its functions.
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• Anesthesia, some drugs, and
deep sleep affect the reticular
activating system, so there is no
conscious processing of the
incoming stimuli even though the
information has been received
and transmitted by the sensory
avenue(s).
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Thalamus
• The thalamus is a small brain structure that plays a major role in
determining which sensory information is going to receive the most
conscious awareness.
• All incoming sensory information, except for smell, is “sorted” by
importance.
• Information that has been encountered previously, and found to be
harmless, may be ignored. New information will require more
attention until it proves not to be a threat and/or not requiring active
attention.
• If the incoming information contradicts existing information, the rest
of the brain will be alerted to pay attention to this new information.
• The thalamus helps the rest of the brain to know what is important
to attend to and what is not important to attend to.
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• The thalamus is especially vulnerable to
insult that may have occurred in early
life, especially if there was a lack of
oxygen (anoxia).
• The thalamus, like the RAS, is highly
affected by medication.
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Limbic System
• The limbic system evaluates incoming sensory information.
It is the brain structures responsible for emotions.
• The limbic system evaluates in two primary ways:
1) The limbic system finds familiarity comfortable. Novel experiences
increase discomfort, which results in stress. The limbic system
subconsciously assesses information on a comfort continuum.
2) The limbic system is the subconscious emotional system that
provides subconscious level perceptions. If the limbic system
perceives a situation as threatening, a fight or flight response
kicks in and the limbic system sends warning signals to the basic
power plant (hypothalamus). In turn, the hypothalamus sends out
other hormonal signals to prepare for battle.
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• The brain is programmed to maintain equilibrium.
When the brain is faced with a new experience, it subconsciously/
subcortically and/or consciously/cortically evaluates the experience. If
the experience is understood in the light of previous experiences
remembered by the brain, it gets a little excited. Small to moderate
amounts of excitement/stress are alerting. (Novelty – new experience
as perceived by the brain.)
If however, the experience runs counter to what the brain already knows,
then it perceives the situation as potentially threatening, and it prepares
to defend itself.
Too much stress tips the scale the wrong way and is dangerous for
anyone. Stress is the reaction of the body to changes in the status quo.
When an individual gets angry or frightened, the body mobilizes
resources with a primitive response known as “flight or fight.” When this
situation occurs, the body automatically releases stress hormones.
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Stress Hormones
Stress hormones have wide-ranging effects on the body. They
are released into the body when the brain receives the signal
that danger is near.
One of these stress hormones is cortisol. Cortisol gets glucose
(energy) into our bodies and also helps rev up the sympathetic
nervous system (heart rate), increase our vigilance and attention
to threat, and decrease our attention for other things.
Once you get this stress response going, you have to be able to
turn it off. Here is where the hippocampus comes in. This is
really important because chronic stress with too high cortisol
levels decreases memory and the ability to control behavior and
focus attention. It also slows the immune system.
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• Indiscriminate sensory bombardment, as an educational
practice, is not justifiable with those individuals who have
significant neurological insults.
• If the brain receives too much
information and receives it too
quickly, it cannot understand,
and a state of stress will occur.
The results may well be
individuals who become more
ill than they need to be.
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• Sensory Disorganization and
Emotional Development:
Difficulty in processing and understanding sensory
information—new environments,
materials, activities, and motor
patterns—creates a reluctance
to attempt new adventures.
Situations which exacerbate
sensory disorganization can
be scary.
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• Every experience needs to be examined from the child’s perspective.
If stress is at a high level for prolonged periods of time, then the
body’s physiological defenses may be working overtime.
• If the stress is unrelenting, from the brain’s perspective, then the
immune system will be affected,
and the child may become ill more
frequently and/or more seriously.
• Messages received by the
olfactory system (smells) are
directly processed by the limbic
system. Thus, smells evoke
memories and strong emotions.
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Amygdala and Hippocampus
• The amygdala and hippocampus
are part of the limbic system.
They are critical in the role of
memory, in anticipation, and
habituation.
• These two structures and others
process events for storage in
the subconscious memory bank.
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“Stress and constant threats rewire emotion circuits.
These circuits are centered on the amygdala, a little
almond-shaped structure deep in the brain whose job is to
scan incoming sights and sounds for emotional content.
Impulses from eye and ear reach the amygdala before
they get to the rational, thoughtful neocortex. If a sight,
sound or experience has proved painful before—then the
amygdala floods the circuits with neurochemicals before
the higher brain knows what’s happening. The brain
remains on high alert. In this state, more circuits attend to
nonverbal cues—facial expressions, angry noises—that
warn of impending danger. The cortex falls behind in
development and has trouble assimilating complex
information such as language.”
Sharon Begley
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• The hippocampus and amygdala are
highly effected by anoxia at birth and
are very susceptible to seizures.
• It is critical to use techniques that will
assist the child in perceiving the routine
of individual activities. It is important to
make the situations predictable,
interesting, and challenging but
not overly stressful.
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Hypothalamus
• The hypothalamus is the involuntary center for controlling heart
rate, temperature, constriction/dilation of blood vessels, water
balance, hormone secretion, appetite, etc.—all functions that
maintain physiological equilibrium and life.
• The hypothalamus and limbic
system constantly influence
each other.
• The observable manifestations
of hypothalamic functioning are
a critical clue regarding the child’s
state of arousal, degree of stress,
and readiness for learning.
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bronchial tubes open for
deeper breathing
hair shaft may
become erect
eyes dilate for
more focused
vision
heart beats faster,
contracts strongly
EXTREME STRESS ACTIVATES
POWERFUL INTERPLAY OF
digestion slows
down
LIMBIC SYSTEM AND
blood pressure
rises
muscles contract and blood
vessels widen to
accommodate increased
oxygen needs
HYPOTHALAMUS
blood sugars
increase for
energy
other vital
organs aroused
surface vessels of
skin contract
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• Many children who have significant neurological challenges may
never talk, use sign, write, be effective with technology, or, in
extreme situations, use any form of intentional communication.
• These other indices are
subcortical, physiological
indicators. These unintentional
reactions are manifested by such
behaviors as posture, tone,
respiration, flushing, palloring,
and so forth.
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Learning
• Learning occurs on two levels: sub-cortical and cortical.
• Learning includes the development of orienting, anticipating,
and habituating responses which, in turn, rests on the ability
to discriminate, associate, and remember sub-cortically and/or
cortically.
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Orienting:
• To orient is to be aware that an event is
occurring. This is a very early indicator of
cognition—the individual recognizes that there
is a new stimulus and does something of an
autonomic nature to indicate that recognition.
• To orient to a stimulus involves the ability to
neurologically:
* be prepared to receive, organize, and interpret
incoming sensory information at some level;
* inhibit some information via the thalamus; and
* re-alert when there is an introduction of a new
experience (novelty).
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• Children with severe neurological challenges may orient, but have
great difficulty recognizing and remembering a routine. Many of these
children will demonstrate the same level of arousal each time the same
stimulus is present, and this level of arousal may not lower. These
children may not be learning; they may just orient to the stimulus and
be aroused. The stimulus, under these situations, does not lose its
novelty.
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Anticipating:
• Anticipation is a higher level of subcortical
neurological functioning critical to the
learning process. Anticipation is the ability
to guess, within a system of predictability,
what the next event will be. Anticipation
requires attentional processing and the
ability to remember an event or a sequence
of events.
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Habituating:
• The systems of the brain regulate a process called “habituation,” a
process in which a response to a stimulus becomes automatic.
• The child learns:
* to recognize a stimulus that has been given repeatedly
* to respond to it in an automatic manner.
• This is the most basic process of learning. It involves sensory
receptivity, sensory awareness, attention, discrimination, and
memory.
• The ability to learn requires the ability to habituate. Habituation is
the process by which the brain gradually adapts to a new event or
sensation and no longer consciously notices it, because the event
or sensation has been integrated with other information and
experiences.
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• In teaching situations, there is a critical need to carefully monitor
and control the sensory-motor demands of each event and each
material within each activity in order to
maximize participation and minimize
startling, fatiguing, and/or stressing.
• Memory can be enhanced by:
* setting up a sequence of very
routinized activities;
* presenting sequenced activities in
a very routinized manner; and
* careful monitoring of and
responding to communicative
physiological, visual, and motor
cues.
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Attachment:
• Attachment develops from an environment that is predictable and people
who are responsive to the cues the child provides. If people and life are
confusing and nonresponsive, then people and objects cannot be trusted.
• A critical area that frequently is affected by significant neurological
insult is attachment. Attachment to a primary
or significant person ties in with conditioning
and learning.
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Educators can take the principles of normal learning
and systematize them to promote the learning of
individuals who are deafblind and/or have multiple
disabilities by:
1. Aiding the child in discriminating one adult from
another;
2. Establishing routines; feelings of security and
reduction of stress come from being able to
anticipate what is going to happen. We can only
anticipate when we perceive some pattern and
remember it; and
3. Systematic and salient association of certain
objects with certain events.
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The neurological approach, when viewed from an educational
perspective, is concerned with the child’s:
• strategies in receiving and processing sensory information;
• capacities in managing increasingly more complex sensorymotor demands;
• discrimination, memory, and association abilities;
• states of arousal;
• behavioral organization;
• level of stress;
• attending behaviors;
• anticipatory behaviors;
• motivation;
• stereotypic and self-abusive behaviors; and
• physiological and motor communicative signals.
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Working with Children who have Experienced
Significant Neurological Insults:
1) The child’s reactions and responses may be extremely variable; not
just day to day but also moment to moment.
2) Energy levels may be extremely variable.
3) The child’s attention may vary widely depending on:
* difficulties encountered in managing the sensory/motor demands of
the task; and
* preference for the activity and/or individual. Sustained attention is a
derivative of sustained motivation. Start activities with what the child
knows. Gradually introduce novelty in small increments.
4) Motor limitations make it difficult to plan and execute motor
responses in a timely manner.
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5) Rate and timing of responses by the child may be frequently
delayed. Others may step in before the child has had time to
process the incoming stimuli, plan and execute a response. The
responses of others may be misunderstood by the child.
6) Individuals who have a hard time managing information from the
environment may become anxious, stereotypic in their behaviors,
and internalized.
7) Health may be affected by stress.
8) Reading communicative signals of a child who has significant
neurological dysfunctioning is difficult. It is important to listen to
the physiological and motor cues of the child.
9) Consider the sensory environment. Some environments may be
overly aggressive from the child’s perspective.
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10) Multi-sensory experiences may not be the best teaching route.
Introduce one sensory-modality at a time, and build slowly.
11) Consistency and predictability are critical.
The introduction of appropriate new (novel)
experiences is also critical.
12) Slow down. Pace the interactions.
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References:
• Understanding Deafblindness: Issues, Perspectives, and Strategies;
L. Alsop (Ed.), SKI-HI Institute, Logan, UT, 2002.
• Communicating Research to Practice and Practice to Research:
From theoretical contributions to therapeutic interventions. Jude
Nicholas, Resource Center for the Deafblind, Norway.
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