The objective of this review is to outline problems which should be considered in trying to define PTSD as neurobiological disorder with abnormal neuronal circuitry. The amygdala is the central neuronal structure for expression of fear memory and fear conditioning (emotional function). Due to the prominent connections with the cingulate and prefrontal cortex and hypothalamus, the amygdala can be considered as a part of the limbic circuitry. For regulation of contextual stimulus (cognitive function), the amygdala interacts with the memory circuit of the hippocampal cortex. Limbic circuitry, which incorporates structures of the great limbic lobe, prefrontal cortex and cingulate cortex, conveys impulses to the hypothalamus, which is the main executive structure for the interaction with endocrine pituitary and brainstem tegmental autonomic and transmitter (neuromodulatory) functions. Human stress-related changes of emotional functions show specificities related to phylogenetic specialization of the human cortex and developmental differences related to the prolonged developmental vulnerability throughout childhood and adolescence.