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Functional neuroimaging

PET: [15O]H2O or FDG

Panic PTSD

PTSD Baseline

Yohimbine

Decrease in volume

Temporal lobe abnormalities Hippocampus

Decrease in blood flow/metabolism

Resting flow in temporal and prefrontal cortex

Temporal and parietal cortex

Orbitofrontal and prefrontal cortex

Hippocampus

Traumatic scripts Medial prefrontal cortex

Right hippocampus

Anterior cingulate

Orbitofrontal cortex

Combat slides/sounds Left inferior frontal cortex

Anterior cingulate

Medial prefrontal cortex

Left-right parahippocampus

Left inferior parietal cortex

Left-right hippocampal ratio

Increase in volume

Increase in blood flow

Right amygdala/insula

Posterior cingulate and motor cortex

Panic Lactate infusion

Phobias Exposure

Temporal pole, orbitofrontal cortex Visual association cortex

SPECT: [99m Tc] HMPAO Panic

Proton MRS Panic

Neurochemical and neuroreceptor

SPECT Panic

Baseline Yohimbine Lactate infusion

Hyperventilation Bz binding

Hippocampal perfusion Blunted frontal cortical activation Blunted global and normalized in occipital cortex

Left occipital cortex

Right-left inferior frontal asymmetry

Decrease in binding

Left hippocampal Precuneus

Prefrontal, orbitofrontal

Lactate levels Increase in binding to these scripts showed decreased blood flow in mPFC (areas 24 and 25) and failure of activation in anterior cingulate (area 32), with increased blood flow in posterior cingulate and motor cortex and anterolateral prefrontal cortex. These areas are known to modulate emotion and fear responsiveness through inhibition of amygdala responsiveness. At the same time, these women also had decreased blood flow in the right hippocampus, parietal, and visual association cortex. These findings replicated findings in combat veterans with PTSD exposed to combat-related slides and sound (Fig. 2).

One study found amygdalar activation, but overall findings of amygdalar activation are mixed. These findings point to a network of related regions as mediating symptoms of anxiety. Dysfunction of the

Normal PTSD

Figure 1 Part of an MRI scan of the hippocampus in a normal control and patient with combat-related PTSD. The hippocampus is visibly smaller in PTSD. Overall, there was an 8% reduction in the right hippocampal volume in PTSD.

Normal PTSD

Figure 1 Part of an MRI scan of the hippocampus in a normal control and patient with combat-related PTSD. The hippocampus is visibly smaller in PTSD. Overall, there was an 8% reduction in the right hippocampal volume in PTSD.

mPFC areas may represent a neural correlate of a failure of extinction to fearful stimuli in PTSD. Posterior cingulate plays an important role in visuo-spatial processing and is therefore an important component of preparation for coping with a physical threat. The posterior cingulate gyrus has functional connections with hippocampus and adjacent cortex, which led to its original classification as part of the limbic brain.

Findings from imaging studies may also be relevant to the failure of extinction to fear responding that is characteristic of PTSD and other anxiety disorders. Following the development of conditioned fear, as in the pairing of a neutral stimulus (bright light, CS) with a fear-inducing stimulus (electric shock, UCS), repeated exposure to the CS alone normally results in the gradual loss of fear responding. Extinction to conditioned fear has been hypothesized to be secondary to the formation of new memories that mask the original conditioned fear memory. The extinguished memory is rapidly reversible following reexposure to the CS-UCS pairing even 1 year after the original period of fear conditioning, suggesting that the fear response did not disappear but was merely inhibited. The extinction is mediated by cortical inhibition of amygdala responsiveness. mPFC has inhibitory connections to the amygdala that play a role in extinction of fear responding. Auditory association cortex (middle temporal gyrus) also has projections to amygdala that seem to be involved in extinction. Anterior cingulate activation represents a "normal" brain response to traumatic stimuli that serves to inhibit feelings of fearfulness when there is no true threat. Failure of activation in this area and/or decreased blood flow in adjacent subcallosal gyrus may lead to increased fearfulness that is not appropriate for the context.

In PD activation studies have revealed the involvement of many brain areas, depending on the condition and the paradigm. However, the orbitofrontal cortex/ anterior insula and the anterior cingulate are implicated in all the studies and may represent the nodal point between somatic and cognitive symptoms of panic but also any other form of anxiety. Most studies of binding at the Bz-GABA(A) receptor are difficult to interpret because of substantial methodological problems; however, regional and/or global reductions are the most consistent finding in PD.

Figure 2 Anxiety response in O15 PET scanning in veterans with PTSD during memories of war using audiovisual cues of war. There is decreased blood flow in the medial prefrontal cortex, medial temporal gyrus, and anterior cingulate indicative of a failure of inhibition of limbic structures such as amygdala (areas displayed with z score >3.00; p<0.001).

Figure 2 Anxiety response in O15 PET scanning in veterans with PTSD during memories of war using audiovisual cues of war. There is decreased blood flow in the medial prefrontal cortex, medial temporal gyrus, and anterior cingulate indicative of a failure of inhibition of limbic structures such as amygdala (areas displayed with z score >3.00; p<0.001).

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Free Yourself from Panic Attacks

Free Yourself from Panic Attacks

With all the stresses and strains of modern living, panic attacks are become a common problem for many people. Panic attacks occur when the pressure we are living under starts to creep up and overwhelm us. Often it's a result of running on the treadmill of life and forgetting to watch the signs and symptoms of the effects of excessive stress on our bodies. Thankfully panic attacks are very treatable. Often it is just a matter of learning to recognize the symptoms and learn simple but effective techniques that help you release yourself from the crippling effects a panic attack can bring.

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