1. amygdalar division: feeding, food-search, angry
and
defensive behaviors related to obtaining food;
2. septal division: sexual pleasure, grooming, courtship, and maternal
behavior ;
3. thalamo-cingulate division: play, vocalization and maternal behavior;
4. The hypothalamus: nonverbal behaviors;
5. The hippocampus: aquisition of data into new skills; language
development .
The Limbic System
(definitions)
1. Those interlinked modules and pathways of the brain in charge of
emotions, feelings, and moods.
2. The "entire neuronal circuitry that controls emotional behavior and
motivational drives" (Guyton 1996:752).
3. The emotional core of the human nervous system (Cytowic 1993).
Functions of the Limbic System
A great deal of our nonverbal communication reflects happenings in the
limbic system. Nonverbal signs, signals, and cues disclose limbic
emotions and attitudes more openly and with greater honesty than words.
Evolution: In human beings, the limbic system grew in tandem with the
cerebral cortex (Armstrong 1986). Thus, ours is the most emotional - as
well as the most intellectual - species on Earth.
1. The limbic system 'plays a key role in the evolutionary survival and
eventual success of hominids' (Eccles 1989).
2. Regarding nonverbal behavior: a. the limbic system's amygdalar
division
promotes feeding, food-search, angry and defensive behaviors related to
obtaining food; b. The septal division promotes sexual pleasure,
genital swelling,
grooming, courtship, and maternal behavior; and c. The thalamocingulate
division
promotes play, vocalization (e.g., the separation cry), and maternal
behavior
(MacLean 1993).
3. 'While the cortex contains our model of reality and analyzes what
exists outside ourselves, it is the limbic brain that determines the
salience of that information' (Cytowic 1993:156).
4. The cerebral cortex 'has more inputs from the limbic system than the
limbic
system has coming from the cortex' (Cytowic 1993).
5. Many emotional systems, in addition to the limbic system, may exist
in
the brain (LeDoux 1996).
6. Phylogenetically, the limbic lobe is the oldest part of the cerebral
cortex
(Willis 1998).
7. The limbic system includes the amygdala, anterior thalamic nucleus,
cingulate gyrus, fornix, hippocampus, hypothalamus, mammillary bodies,
medial forebrain bundle, prefrontal lobes, septal nuclei, and other
areas and pathways of
the brain. The hypothalamus, a key player, mediates nonverbal behaviors
through the brain-stem reticular nuclei. When excited, the reticular
nuclei arouse cerebral as well as spinal circuits. (N.B.: An important
two-way link between the limbic system and brain stem is the medial
forebrain bundle.)
Copyright © 1998 - 2001 (David B. Givens; Center for
Nonverbal
Studies)
Amygdala and Immune
system
'In the present study we examined the role of the central nucleus of
the
amygdala in hypothalamic-pituitary-adrenal axis responses to an immune
challenge
in the form of systemic administration of the proinflammatory cytokine
interleukin-1beta
(1 microg/kg). We found that bilateral ibotenic acid lesions of the
central
amygdala substantially reduced adrenocorticotropin hormone release and
hypothalamic corticotropin-releasing factor and oxytocin cell c-fos
expression responses
to interleukin-1,8 suggesting a facilitatory role for this structure in
the generation of hypothalamic-pituitary-adrenal axis responses to an
immune
challenge. Since only a small number of central amygdala cells project
directly
to the paraventricular nucleus, we then examined the effect of central
amygdala
lesions on the activity of other brain nuclei that might act as relay
sites
in the control of the hypothalamic-pituitary-adrenal axis function. We
found
that bilateral central amygdala lesions significantly reduced
interleukin-1beta-induced c-fos expression in cells of the ventromedial
and ventrolateral subdivisions
of the bed nucleus of the stria terminalis and brainstem catecholamine
cell
groups of the nucleus tractus solitarius (A2 noradrenergic cells) and
ventrolateral
medulla (A1 noradrenergic and C1 adrenergic cells). These findings, in
conjunction
with previous evidence of bed nucleus of the stria terminalis and
catecholamine
cell group involvement in hypothalamic-pituitary-adrenal axis
regulation,
suggest that ventromedial and ventrolateral bed nucleus of the stria
terminalis cells and medullary catecholamine cells might mediate the
influence of the central amygdala on hypothalamic-pituitary-adrenal
axis responses to an immune challenge. Thus these data establish that
the central amygdala influences hypothalamic-pituitary-adrenal axis
responses to a systemic immune
challenge but indicate that it primarily acts by modulating the
activity
of other control mechanisms.'
[The central amygdala modulates
hypothalamic-pituitary-adrenal
axis responses to systemic interleukin-1beta administration; Xu et al]
The Limbic System in Autism
Autopsy and MRI studies have revealed an
ímmature
development of many structures of the limbic system, including
amygdala,
gyrate nucleus, and hippocampus, but no damage or loss of neurons. The
limbic
system represents the mammalian development of emotional attachment,
parenting
and social behaviors, as well as learning and language development. As
warm-blooded
mammals, we are dependant on the development of emotional attachment to
the
parents. We feel good when we are safe, well fed and we know where our
parents
are. In that state of well being, we learn and develop language and
social
skills. Conversely, when we are lost, hungry and in danger, we
experience
panic. That panic involves the immune system and begins with an
adrenalin
release. The immune system takes over from the emotional system, and we
revert
to a more primitive state of fight-or-flight, survival instinct. In
that
state, learning, language development and social skills are not
important
to survival. We believe that in autism, the immune system is reacting
to
lutein as if it were a life-threatening pathogen. The particular type
of
immune response involves the 'alternative pathway activation pathway'
(APAP)
and is the type of reaction we would see to a cobra venom - it is a
life
or death situation. The immune system takes charge of the body's vital
functions
- digestion, metabolism, breathing, heart rate, temperature - and all
superfluous
activity, including social activity, stops until the reaction ceases.
But
for the autist, the reaction doesn't cease because lutein is coming
into
the body too often. In the infant, there are generally few exposures to
lutein,
but during the second and third years lutein-containing foods begin to
enter
the diet frequently. The response to the first exposures might be
fever,
and many parents report fevers during early childhood. The child often
begins
to refuse some foods. The altered immune system often over-reacts to
immune
challenges as is seen in the frequent reports of adverse reactions to
vaccinations.
Then, as the lutein exposure becomes continual, the immune system has
to
adapt, as continual high fever is dangerous to the brain. The response
changes
from acute to chronic - control of the digestion, metabolism, hormone
and
enzyme production. Serotonin transport to the brain is controlled to
reduce
arousal of the pituatary system to a minimum. The primary focus of the
immune
system becomes systematic removal of the pigment pathogen and it's
breakdown
products. This is seen in increased excretion of neopterin and
biopterin,
prurigo-type eruptions on the skin, and recurrent ear inflamation. Lab
reports
show unusual patterns of fatty acid and amino acid excretion, Vitamin C
metabolism,
signs of gut flora imbalance and production of unusual opioid chemicals
which
the immune system is manufacturing as endogenous stress and
pain-reducers.
With an ongoing immune system activity, the limbic system switches over
to
a state of defensiveness and survival. Development of social behavior
is
arrested in favor of survival, defensive and coping strategies to
minimise
arousal and social expectactions. Depending on the innate strength of
the
individual, mental and intellectual functioning may develop, despite
the
social handicap, in idiosyncratic ways. For some high functioning
autists,
the strategy of avoidance takes the form of developing unique skills,
or
intensive reading and studying, or focus on a particular branch of math
or
science or music.
Removal of lutein from the diet is the first step towards recovery and
healing,
but there is often a long way to go. After approximately 4 months, the
parents
report that the child is calmer, happier, more social, more interested.
It
takes a while longer for language development to move forward,
especially
for those who were always non-verbal. Our experience after many years
into
recovery is that the immune system never fully relinquishes control,
but
coping skills and obsessive behaviors slowly diminish, and focus on
normal
enjoyment and pleasure increases. Body language becomes more normal and
easier
to interpret in others. All the senses improve, from a state of
confusion
and conflict to clarity and sharpness and emotional significance. Our
lives
take on real meaning and we become less fearful and reclusive and more
social
and positive in our outlook. Having worked with many thousands of
people,
we have seen how emotional development increases year on year, so that
after
5 years on the diet, a 15 year old may exhibit the typical emotional
and
social development of a 5 year old, the sexual interests of a 15 year
old
and the intellectual level of a college student. Although we do not
intend
to become 'normal', we see the potential of all autists to find meaning
and
fulfillment, joy and happiness in their lives.
