Emotion endophenotypes in bipolar and schizophrenic disorders

Because of its proximity to the vulnerability model hypotheses and its correlation to functional outcome, emotional processing has emerged as a major topic of research in bipolar as well as schizophrenia disorders. By experimental necessity, the somewhat vague notion of emotion has been parceled into several dimensions. Thus, the aptitude to perceive and decrypt emotional stimuli has been artificially differentiated between the emotional feelings reported by subjects and the concomitant physiological changes. A large literature has been built to characterize a singular emotional profile combining a deficit in facial affect recognition with preserved or even enhanced emotional experience of negative emotions. Even though emotional disturbances tend to be intuitively associated with bipolar disorders, this latter profile is far better documented in schizophrenia. Furthermore, several studies of high-risk individuals or of relatively healthy populations allow for selecting some of these emotional disturbances as endophenotypes. Conversely, functional imaging works have explored the cortico-limbic circuit underlying these functions in both the acute and stabilized phases of these illnesses. Here again, a fairly common pattern seems to emerge in both disorders with hyperactivity of the limbic system and failure to activate the modulating regions of the prefrontal cortex. However, inconsistencies in results need to be addressed, and neuroimaging works on healthy relatives or high-risk individuals are still very scarce. These results are discussed in light of the models of shared genetic vulnerability between schizophrenia and bipolar disorders. (C) L'Encephale, Paris, 2012