Structural and Functional Abnormalities of the Amygdala in Schizophrenia

Abstract: Schizophrenia is characterized by delusions and hallucinations, which tend to respond to treatment with dopamine receptor blockers, and a loss of motivation and affect, which do not. Structural magnetic resonance imaging (sMRI) has convincingly demonstrated reduced volumes of the amygdala‐hippocampal complex (AHC) and other limbic and paralimbic structures, on both manual tracing and automated analyses. The Edinburgh High‐Risk Study (EHRS) of initially healthy adolescents with at least two affected relatives has found that AHC volumes are reduced pre‐morbidly but not to schizophrenic levels, suggesting that further volume reductions may be associated with the onset of schizophrenia. AHC volumes appear to be genetically mediated in families with a dominant pattern of transmission, whereas prefrontal lobe and basal ganglia volumes are related to genetic liability to schizophrenia in the generality of high‐risk subjects. Temporal lobe volumes may fall as psychotic symptoms develop, in the context of drug abuse and stress. Neuropsychological testing has also demonstrated pre‐morbid impairments and symptom‐related deterioration. More detailed analyses of the temporal lobe changes on sMRI and fronto‐temporal dysconnectivity on fMRI are in progress. These findings are discussed with reference to other indications of pre‐morbid developmental disturbance in our high‐risk subjects, animal models of schizophrenia, and reliable findings from neuropathological, neuropsychological, and functional imaging studies of patients with schizophrenia.