Amygdala has a dual sensory input system running from our sense organs to thalamus. From the thalamus these two inputs diverge. One pathway leads directly to the amygdala and the other to the cortex.
Pathway connections between the cortex and the amygdala are less well developed than are connections from amygdala to the cortex. This means that the amygdala exerts a greater influence on the cortex than vice versa and once the amygdala is turned on, it is difficult for the cortex to turn it off.
Information from senses, internal and external, received by thalamus. If based on our past conditioning, memories and our temperament the stimuli is recognized as significant and dangerous; the thalamus directs it to the amygdala, which initiates the body's fight-flight response.
An activated amygdale does not wait around for instructions from the logical mind and triggers a body wide emergency response with in milliseconds.
Impulses from the amygdala are sent to the hypothalamus. Once the hypothalamus is aware of the potential danger it activates two different pathways simultaneously. It activates the sympathetic nervous system (SNS) in the spinal cord which affects heart rate, respiration, vasoconstriction, sweating, etc. Hypothalamus also sends signals to the pituitary gland. Pituitary gland in turn secretes hormones which signal other glands in the body such as the adrenal gland to flood the bloodstream with stress hormones like epinephrine, nor epinephrine and cortisol affecting blood pressure, body temperature, metabolism etc.
The net effect of this fear reaction on our mind-body system is multiple. Within our mind, the activation of this fear response, based on our past conditioning, memory and our genetic make up leads to a series of fearful thoughts. These thoughts lead to feelings of anxiety, caution, anger, worry, panic, etc. Our body shuts down the non- emergency functions such as digestion in favor of directing the body's resources to increasing our heart rate, respiration, muscle strength, etc. All of this allows our body to move quickly for attack or escape.
The stress hormones also act on the brain to form a memory of the stressful event. Amygdala tells the brain to make a strong memory of the perceived threat. The more significant the event the stronger the memory of it.
Children psychologically abused or neglected were found to have abnormalities in the left side of the temporal region
It is postulated that left hemisphere dysfunction in children may result in greater use or dependence on the right hemisphere. Increased dependence on the right frontal lobes may, in turn, lead to increased perception and expression of negative emotion and may facilitate unconscious storage of painful childhood memories
The brainstem was found to be 'dysregulated' in traumatized patients which in turn results in a host of signs and symptoms related to abnormal brainstem functioning, including: altered cardiovascular regulation, affective ability, behavioral impulsivity, increased anxiety, increased startle response and sleep abnormalities.
Alterations in the noradrenergic and dopaminergic neurotransmitter systems and the stress response of the hypothalamic-pituitary-adrenal axis are well documented in PTSD - adrenergic dyregulation, enhanced thyroid function, and altered HPA activity
Also affects the immune system
Subjects with PTSD excreted significantly greater amounts of urinary free
cortisol and catecholamines. These biological stress measures
correlated positively with duration of the PTSD trauma and symptoms
of intrusive thoughts, avoidance, and hyper-arousal
May lead to permanent changes in the NS
Amnesia seen in PTSD is likely to be caused by
excessive norepinephrine (NE) release at
the time of the trauma
Secretion of endogenous opioids may account for
emotional responses being blunted during the traumatic stimulus
“ Some mental representation of the experience is probably laid down by means of a system that records affective experience but has no capacity for symbolic processing or placement in space or time. It is theorized that the failure of semantic memory leads to the organization of memory on a somatosensory level--such as somatic sensations, behavioral enactments, nightmares, and flashbacks.”
“ Research suggests the emotional memory may be indelible but is held in check by cortical and hippocampal inhibitory control. Decreased inhibitory control may occur under a variety of circumstances such as under the influence of drugs and alcohol, during sleep, with aging, and after exposure to strong reminders of the traumatic event. Traumatic memories could then emerge as affect states, somatic sensations, or flashbacks. Such somatosensory memories are timeless and unmodified by further experience”