Perception of negative affect in schizophrenia--functional and structural changes in the amygdala. Review

Despite the evidence for impaired perception of negative affect in schizophrenia, there have been a few functional neuroimaging studies so far examining neural responses to facial negative emotional stimuli in this illness. These studies have demonstrated that schizophrenic patients relative to healthy controls fail to activate the amygdala in response to facial expressions of fear, and also during a sadness induction paradigm. These recent findings reflect functional amygdala abnormalities in overt displays of fear in schizophrenic patients. Lack of amygdala activation in obvious aversive stimuli and enhanced amygdalar response to ambiguous stimuli might be explained by an altered threshold at which the amygdala responds to fearful stimuli. Morphological change of bilaterally amygdala volume has been found using MRI although some researchers have found only unilateral reduction or enlargement in the left amygdala. To conclude, brain imaging literature focused on amygdala abnormalities in schizophrenia is full of inconsistencies due to incomplete understanding of the illness itself, different techniques and stimuli used.