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Greetings everybody!
Welcome to the first Biology Behind of 2014!! In the post today we will be informing you about Post Traumatic Stress Disorder otherwise known as PSTD, this is the only major mental disorder in which the cause is known. For those of you who watched the Call the Midwife christmas special will be fairly familiar with this. So lets go!!
In 1678 the Swiss diagnosed patients as having nostalgia, the Spanish physicians termed the symptoms as "Estar Roto" meaning "to be broken"until recently this disease was finally defined as its own disease known as Post Traumatic Stress Disorder. The following characteristics, are associated with PTSD.
Reduced Hippocampus:
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| Image: Biological studies of post traumatic stress disorder. |
One of the most common brain structures seen in post traumatics stress disorder patients is a reduction in the volume of the hippocampus, this reduction in cortical capacity has shown patients to have an inability to inhibit fear and associated negative responses.
The
above picture, was taken from a study were 2 pairs of twins were used
to investigate the effects of PTSD. On the left hand side there is a
twin pair that has a combat veteran with PTSD and his counterpart who
has not suffered from a traumatic event but has a high risk of PTSD and
on the right is a control pair of twins of a combat exposed twin and a
non combat exposed twin both without PTSD. Contrast A demonstrates
smaller hippocampi in the veteran with PTSD than the veteran without
PTSD. Contrast B however, compared hippocampal volumes in the pair of
twin with the combat exposed PTSD suffereing twin. Finally contrast C
compares the hippocampal volumes of no PTSD in high and low risk twins.
From this it could be suggested that a reduced hippocampal volume could
be a pr-existing vulnerability factor as apposed to a feature that
occurs after a traumatic event.
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There has been a possible link made between the severity of PTSD symptoms and the reduction of the hippocampus, this is seen in some studies that failed to observe the reduction in hippocampal volume that was seen in other PTSD patients because the selected subject in the study had less severe symptoms of PTSD. It is difficult to see this feature is children affected with PTSD and this may suggest that nerumaturational factors may have a role in hippocampal reduction. Magnetic resonance spectroscopic imaging, is able to quantify N-acetylaspartate, this is able to mark neuronal density was used in PTSD subjects and found neuronal reduction. However this is still be determined.
Sympathetic nervous system:
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Events such as the one seen above are often displayed as a cause of an exaggerated amygdala activation, you may remember the amygdala as the fear handling part of the brain. This activation is linked to noradrenergic hyper-reactivity which causes hyperarousal and re-experiencing symptoms (trauma related nightmares, flashbacks, narratives and odours) and cause the emotional and physiological reaction to traumatic cues.
A chemical protein called neuroprotein Y is the response to this hyper activity, those with a high gene expression showed a lower anxiety and reduced amygdala reactivity to trauma related stimuli. In subjects, with low or blunted neuroprotein Y a response to sympathetic activatio triggered PTSD symptoms.
Shift in brain state:
When we say a shift in brain state it refers to a change in what data the brain processes, in PTSD this shift is from processing multimodal contextual and memory retention to a more primitive amygdala-mediated, formation of time locked snesory associations and expression of a trauma specific defense response.
Such as dogs serving in the war:
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So that was Biology behind...
Biobunch,
Over and out
