Hemispheric specialization in affective responses, cerebral dominance for language, and handedness: Lateralization of emotion, language, and dexterity.

Hemispheric specialization in affective responses has received little attention in the literature. This is a fundamental variable to understand circuit dynamics of networks subserving emotion. In this study we put to test a modified "valence" hypothesis of emotion processing, considering that sadness and happiness are processed by each hemisphere in relation to dominance for language and handedness. Mood induction and language activation during functional magnetic resonance imaging (fMRI) were used in 20 right-handed and 20 nonright-handed subjects, focusing on interconnected regions known to play critical roles in affective responses: subgenual cingulate cortex, amygdala, and anterior insular cortex. We observed a consistent relationship between lateralization of affective processing, motor dexterity, and language in individuals with clear right-handedness. Sadness induces a greater activation of right-hemisphere cortical structures in right-handed, left-dominant individuals, which is not evident in nonright-handed subjects who show no consistent hemispheric dominance for language. In anterior insula, right-handed individuals displayed reciprocal activation of either hemisphere depending upon mood valence, whereas amygdala activation was predominantly left-sided regardless of mood valence. Nonright-handed individuals exhibited less consistent brain lateralization of affective processing regardless of language and motor dexterity lateralization. In contrast with traditional views on emotion processing lateralization, hemispheric specialization in affective responses is not a unitary process but is specific to the brain structure being activated.

Cluster B personality symptoms in persons at genetic risk for schizophrenia are associated with social competence and activation of the right temporo-parietal junction during emotion processing.

Personality disorders are common in nonpsychotic siblings of patients with schizophrenia, and some personality traits in this group may be associated with an increased risk for full-blown psychosis. We sought to establish if faulty right-hemisphere activation induced by social cognitive tasks, as previously described in patients with schizophrenia, is associated with specific personality symptoms in their unaffected siblings. We observed that cluster B personality symptoms in this group were inversely related to activation in the right temporo parietal junction (rTPJ, a structure critical in social cognitive processing) in response to a basic emotion processing task and also to social competence, whereas in contrast to our initial hypothesis, cluster A traits were not associated with right hemisphere activation during emotion processing or with social competence. These findings suggest the existence of clinical traits in at-risk individuals which share a common neurobiological substrate with schizophrenia, in regards to social performance.

Pattern of brain activation during social cognitive tasks is related to social competence in siblings discordant for schizophrenia.

Measures of social competence are closely related to actual community functioning in patients with schizophrenia. However, the neurobiological mechanisms underlying competence in schizophrenia are not fully understood. We hypothesized that social deficits in schizophrenia are explained, at least in part, by abnormally lateralized patterns of brain activation in response to tasks engaging social cognition, as compared to healthy individuals. We predicted such patterns would be partly heritable, and therefore affected in patients' nonpsychotic siblings as well. We used a functional magnetic resonance image paradigm to characterize brain activation induced by theory of mind tasks, and two tests of social competence, the Test of Adaptive Behavior in Schizophrenia (TABS), and the Social Skills Performance Assessment (SSPA) in siblings discordant for schizophrenia and comparable healthy controls (n = 14 per group). Healthy individuals showed the strongest correlation between social competence and activation of right hemisphere structures involved in social cognitive processing, whereas in patients, the correlation pattern was lateralized to left hemisphere areas. Unaffected siblings of patients exhibited a pattern intermediate between the other groups. These results support the hypothesis that schizophrenia may be characterized by an abnormal functioning of nondominant hemisphere structures involved in the processing of socially salient information.

Activation of brain areas concerned with social cognition during moral decisions is abnormal in schizophrenia patients and unaffected siblings.

Moral decision-making involves complex social cognitive processes which are known to be altered in patients with schizophrenia and first-degree relatives. Traditional philosophical views on human moral behavior have distinguished between utilitarian views (which emphasize outcomes) and deontological approaches (defining what is right to do according to certain norms). Since emotions have been suggested to play a determining role in moral behavior, we hypothesized patients with schizophrenia and unaffected siblings would make more utilitarian choices and show faulty activation of brain areas concerned with emotion regulation during such tasks. Unexpectedly, all participants (n = 13 per group) made the same proportion of utilitarian and deontological decisions. Brain activation common to all groups induced by moral decisions included two circumscribed portions of right ventromedial and dorsolateral prefrontal cortex, adding to previous evidence on a right prosencephalic cognitive network involved in ethical decisions. However, brain activation induced by moral decisions was different in healthy persons, schizophrenia patients, and nonpsychotic siblings in regards to areas directly concerned with emotion processing. These results seem to underscore the role of acquired norms in moral decisions, a frequently overlooked concept in the neurobiological characterization of human ethical behavior, and add to previous evidence of abnormal social cognitive processing in schizophrenia.