This occurs through the release of hypothalamic corticotropin-releasing factor, also known as corticotropin-releasing hormone (CRH), from nerve terminals in the median eminence arising in the paraventricular nucleus, which stimulates adrenocorticotropin release from the anterior pituitary that in turn induces the release of cortisol from the adrenal cortex. This progressive process culminating in the release of glucocorticoids to environmental stimuli is believed to be initiated by the amygdala, which evaluates the emotional significance of observed phenomena. Released glucocorticoids provide negative feedback on the system and also the hippocampus, which in turn regulates the shutting off of this biological stress response. It is through this response that information is encoded as emotional and bodily response is initiated, making the HPA axis an important component in emotion perception. The amygdala appears to have a specific role in attention to emotional stimuli. The amygdala is a small, almond-shaped region within the anterior part of the temporal lobe. Several studies of non-human primates and of patients with amygdala lesions, in addition to studies employing functional neuroimaging techniques, have demonstrated the importance of the amygdala in face and eye-gaze identification. Other studies have emphasized the importance of the amygdala for the identification of emotional expressions displayed by others, in particular threat-related emotions such as fear, but also sadness and happiness. In addition, the amygdala is involved in the response to non-facial displays of emotion, including unpleasant auditory, olfactory and gustatory stimuli, and in memory for emotional information. The amygdala receives information from both the thalamus and the cortex; information from the thalamus is rough in detail and the amygdala receives this very quickly, while information from the cortex is much more detailed but is received more slowly. In addition, the amygdala's role in attention modulation toward emotion-specific stimuli may occur via projections from the central nucleus of the amygdala to cholinergic neurons, which lower cortical neuronal activation thresholds and potentiate cortical information processing. There is great individual difference in emotion perception and certain groups of people display abnormal processes. Some disorders are in part classified by maladaptive and abnormal emotion perception while others, such as mood disorders, exhibit mood-congruent emotional processing. Whether abnormal processing leads to the exacerbation of certain disorders or is the result of these disorders is yet unclear, however, difficulties or deficits in emotion perception are common among various disorders. Research investigating face and emotion perception in autistic individuals is inconclusive. Past research has found atypical, piecemeal face-processing strategies among autistic individuals and a better memory for lower versus upper regions of the face and increased abilities to identify partly obscured faces.