PSYC23H3 Lecture Notes - Lecture 9: Gamma-Aminobutyric Acid, Borderline Personality Disorder, Rockefeller University

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28 Jun 2015
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Week 9~ Scars that won’t heal: the neurobiology of child abuse
Maltreatment at an early age can have enduring negative effects on a child’s brain development
and function.
Until recently, psychologists believed that mistreatment during childhood led to arrested
psychosocial development and self-defeating psychic defense mechanisms in adults. New brain
imaging surveys and other experiments have shown that child abuse can cause permanent damage
to the neural structure and function of the developing brain itself.
This grim result suggests that much more effort must be made to prevent childhood abuse and
neglect before it does irrevocable harm to millions of young victims. New approaches to therapy
may also be indicated.
Extreme Personalities:
Internally it can appear as depression, anxiety, suicidal thoughts or posttraumatic stress.
it can also be expressed outwardly as aggression, impulsiveness, delinquency, hyperactivity or
substance abuse.
One of the more perplexing psychiatric conditions that are strongly associated with early ill-
treatment is borderline personality disorder.
Someone with this dysfunction characteristically sees others in black-and-white terms, often first
putting a person on a pedestal, then vilifying the same person after some perceived slight or
betrayal.
Those afflicted are also prone to volcanic outbursts of anger and transient episodes of paranoia
or psychosis.
They typically have a history of intense, unstable relationships, feel empty or unsure of their
identity, commonly try to escape through substance abuse, and experience self-destructive or
suicidal impulses.
The limbic system is a collection of interconnected brain nuclei (neural centers) that play a
pivotal role in the regulation of emotion and memory.
Two critically important limbic regions are the hippocampus and the amygdala, which lie below
the cortex in the temporal lobe.
The hippocampus is thought to be important in the formation and retrieval of both verbal and
emotional memories, whereas the amygdala is concerned with creating the emotional content of
memory—for example, feelings relating to fear conditioning and aggressive responses.
During TLE seizures, patients remain conscious while experiencing a range of psychomotor
symptoms brought on by electrical storms within these regions.
Associated effects include the abrupt onset of tingling, numbness or vertigo; motor-related
manifestations such as uncontrollable staring or twitching; and autonomic symptoms such as
flushing, nausea or the “pit in your stomach” feeling one gets in a fast-rising elevator.
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TLE can also cause hallucinations or illusions in any of the five senses.
-It is not unusual, for instance, for one afflicted with this condition to experience Alicein-
Wonderland-like distortions of the sizes or shapes of objects.
Disconnected feelings of déjà vu and mind-body dissociation are also common.
Abuse-Driven Brain Changes:
Maltreatment before age 18 had more impact than later abuse, and males and females were
similarly affected.
The irregularities arose in frontal and temporal brain regions and, to our surprise, specifically
involved the left hemisphere rather than both sides, as one would expect.
Given the important role of the hippocampus in memory function, these patients also scored
lower on verbal memory tests than the non abused group.
We observed no differences in hippocampal volume. Like Driessen’s group, however, we did
find a 9.8 percent average reduction in the size of the left amygdala, which correlated with
feelings of depression and irritability or hostility.
We asked ourselves why the hippocampus was smaller in abused subjects in studies from
Bremners, Stein’s and Dreissen’s groups but normal in De Bellis’s and in our own
investigations.
-Of the several possible answers, the most likely is that stress exerts a very gradual influence
on the hippocampus, so adverse effects may not be discernible at a gross anatomical level
until people get older.
Moreover, animal studies by Bruce S. McEwen of the Rockefeller University and Robert M.
Sapolsky of Stanford University had previously demonstrated the marked vulnerability of the
hippocampus to the ravages of stress.
Not only is the hippocampus particularly susceptible because it develops slowly, it also is
one of the few brain regions that continues to grow new neurons after birth.
Further, it has a higher density of receptors for the stress hormone cortisol than almost any
other area of the brain.
Exposure to stress hormones can significantly change the shape of the largest neurons in the
hippocampus and can even kill them.
-Stress also suppresses production of the new granule cells (small neurons), which normally
continue to develop after birth.
Experiments with rats by Christian Caldji, Michael J. Meaney of McGill University and Paul
M. Plotsky of Emory University have shown that early stress reconfigures the molecular
organization of these regions.
One major result is the alteration of the protein subunit structure of GABA receptors in the
amygdala.
These receptors respond to gamma aminobutyric acid, the brain’s primary inhibitory
neurotransmitter, and GABA attenuates the electrical excitability of neurons.
Reduced function of this neurotransmitter produces excessive electrical activity and can
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