Functional neuroimaging of anxiety A meta-analysis of emotional processing in PTSD, social anxiety disorder and specific phobia

Objective Find common and disorder-specific functional neurobiological deficits in anxiety disorders. Compare findings to systems engaged during anticipatory anxiety in healthy subjects.

Method A comparative quantitative meta- analysis of FMRI and PET of studies: - Post traumatic stress disorder - Social anxiety disorder - Specific phobias - Anticipatory anxiety in healthy subjects

PTSD Anxiety disorder developed after psychological trauma. Involving reexperience. (nightmares and flashbacks) Avoidance of triggers. (Stimuli that is associated with trauma) Symptoms of increased arousal. (Sleep and concentration problems) Lasting more than one month.

Social anxiety disorder Fear regarding social activities. Of being humiliated or embarrassed by their actions. Leading to avoidance of social situations.

Phobia Form Greek “phobos” meaning fear. Irrational, intense, persistent fear of certain situations, objects, activities or persons. Excessive desire to avoid the feared subject.

Anxiety Previous negative experience. Stimulus associated with this experience trigger defensive behavior. Defensive behavior involve avoiding triggers. Lead to impaired life quality if excessive.

Maintaining anxiety Operant conditioning; when we see or encounter something associated with a previous traumatic experience, anxious feelings resurface. We feel temporarily relieved when we avoid situations which make us anxious, but this only increases anxious feelings the next time we are in the same position, and we will want to escape the situation again and therefore will not make any progress against the anxiety.

Fear in the brain It has long been known that fear is associated with activation of amygdala. Studies have shown inconsistencies in the activity of other nuclei during fear response in humans.

Amygdala Research indicates that, during fear conditioning, sensory stimuli reach the Amygdala where it forms associations with memories of the stimuli. Involved in the genesis of many fear responses, including freezing, tachycardia, increased respiration, and stress-hormone release. Damage to the amygdalae impairs both the acquisition and expression of Pavlovian fear conditioning The amygdalae, especially the basolateral nuclei, are involved in mediating the effects of emotional arousal on the strength of the memory for the event

Lobus insularis The insula is believed to process convergent information to produce an emotionally relevant context for sensory experience. Functional imaging experiments have revealed that the insula has an important role in pain experience and the experience of a number of basic emotions, including anger, fear, disgust, happiness and sadness.

Results PTSD Hyperactivity in Amygdalae, Parahippocampal gyrus, Insula, Inferior parietal lobe, Mid-cingulate and Precuneus cortex. Hypoactivity in many cortical areas and some amygdalar nuclei.

Results social anxiety disorder Hyperactivity in amygdalae, parahippocampal and fusiform gyrus, globus pallidus, insula, inferior frontal and superior temporal gyrus. No hypoactivity.

Results specific phobia Hyperactivity in amygdalae, fusiform gyrus, globus pallidus, insula, inferior frontal and superior temporal gyrus. No hypoactivity.

Discussion Amygdala and insula are the only two areas showing consistent hyperactivity in the three disorders. PTSD is a complex disorder where fear is only one component. Social anxiety and phobias may be more readily described as intense fear.

Conclusion Social anxiety disorder and Phobias are comparable with fear in healthy subjects. PTSD however has fear as one component, but has a other components too.