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64. Thalamic nuclei volumes and neuropsychological functioning in psychotic disorders.
Reduced thalamic volume is one of the most robust findings in neuroimaging studies of schizophrenia. Models of thalamic dysfunction in schizophrenia emphasize the mediodorsal nucleus (MD) and pulvinar nuclei. However, very few studies have investigated the specificity of MD and pulvinar volume reduction in schizophrenia and other psychotic disorders, or whether reduced volumes are associated with cognition. Using a developmental version of Freesurfer, which includes enhanced segmentation of thalamic subnuclei derived from ex vivo MRI scans and histological data, we extracted MD and pulvinar volumes from people with schizophrenia (n=201), bipolar I disorder with psychotic features (n=88), and healthy individuals (n=177). Ventral lateral and ventral anterior nuclei volumes were included as control regions. We found a group by nuclei volume interaction (F(6,1374)=4.85, p<.001), with only the MD and pulvinar showing significant differences between groups. MD and pulvinar volumes were smaller in schizophrenia (p’s<.001), but not bipolar disorder. Overall neuropsychological functioning correlated with MD and pulvinar volumes independent of group membership (R(partial)=.131 and p=.006 and R(parital)=.149, p=.002 respectively). Our findings support two hypotheses: reduced thalamic volume in schizophrenia is specific rather than global and changes of the MD and pulvinar nuclei are associated with cognitive dysfunction in schizophrenia.