fMRI of sensitization to angry faces.

This study examined what is communicated by facial expressions of anger and mapped the neural substrates, evaluating the motivational salience of these stimuli. During functional magnetic resonance imaging, angry and neutral faces were presented to human subjects. Across experimental runs, signal adaptation was observed. Whereas fearful faces have reproducibly evoked response habituation in amygdala and prefrontal cortex, angry faces evoked sensitization in the insula, cingulate, thalamus, basal ganglia, and hippocampus. Complementary offline rating and keypress experiments determined an aversive rank ordering of angry, fearful, neutral, and happy faces and revealed behavioral sensitization to the angry faces. Subjects rated angry faces, in contrast to other face categories such as fear, as significantly more likely to directly inflict harm. Furthermore, they rated angry faces as significantly less likely to produce positive emotional outcomes than the other face categories. Together these data argue that angry faces, a directly aversive stimulus, produce a sensitization response.

Response and habituation of the human amygdala during visual processing of facial expression.

We measured amygdala activity in human volunteers during rapid visual presentations of fearful, happy, and neutral faces using functional magnetic resonance imaging (fMRI). The first experiment involved a fixed order of conditions both within and across runs, while the second one used a fully counterbalanced order in addition to a low level baseline of simple visual stimuli. In both experiments, the amygdala was preferentially activated in response to fearful versus neutral faces. In the counterbalanced experiment, the amygdala also responded preferentially to happy versus neutral faces, suggesting a possible generalized response to emotionally valenced stimuli. Rapid habituation effects were prominent in both experiments. Thus, the human amygdala responds preferentially to emotionally valenced faces and rapidly habituates to them.

Experimental allergic encephalomyelitis in Lewis rats bearing avian sarcoma virus-induced brain tumors.

Lewis rats bearing avian sarcoma virus (ASV)-induced brain tumors were injected with guinea pig spinal cord emulsion and complete Freund's Adjuvant to determine if they remained susceptible to induction of experimental allergic encephalomyelitis (EAE). The incidence of EAE among rats with small, and moderate sized gliomas was similar to non-tumor-bearing controls (P less than 0.5; P less than 0.9) while 18 of 24 (75%) animals with large gliomas developed EAE as compared to 31 of 33 (93%) controls (P less than 0.05). The histologic features and geographical distribution of "ordinary' EAE were seen in controls and were maintained in tumor-bearing rats. The presence of an intracranial tumor did not significantly alter the ability of Lewis rats to develop EAE.

The dexamethasone suppression test as a diagnostic aid in late onset paranoia.

A case of acute paranoia in a 64-year-old woman with a previous history of one depressive episode is described. Accurate diagnosis was hampered by her illogical and tangential answers to questions and the development of an organic brain syndrome while on neuroleptics and anticholinergics. She did not tolerate tricyclic antidepressants and was unresponsive to three electroconvulsive therapy (ECT) treatments. Because of the previous history of depression and the presence of some depressive symptoms, the possibility of a depression underlying her paranoid psychosis was considered. A dexamethasone suppression test (DST) was performed to confirm this and was found to be abnormal. ECT was then continued with the eventual result of complete remission in symptoms. The authors discuss the potential usefulness of the DST in confirming a diagnosis of depression in selected cases of late onset psychosis.