Three-dimensional analysis with MRI and PET of the size, shape, and function of the thalamus in the schizophrenia spectrum

Objective: In an exploration of the schizophrenia spectrum, the authors com pared thalamic size, shape, and metabolic activity in unmedicated patients with schizophrenia and schizotypal personality disorder to findings in age- and sex-matched healthy control subjects. Method: Coregistered magnetic re sonance imaging (MRI) and positron emission tomography scans were obtained in 27 schizophrenic patients, 13 patients with schizotypal personality diso rder, and 32 control subjects who performed a serial verbal learning test d uring tracer uptake. After thalamus edges were outlined on 1.2-mm MRI scans , a radial warping program yielded significance probability mapping in thre e dimensions. Results: Significance probability mapping (with resampling) i dentified an area in the region of the mediodorsal nucleus bilaterally with significantly lower relative metabolism in the schizophrenia group than in either the control or schizotypal personality disorder groups, which did n ot differ from each other. The three groups did not differ significantly in total thalamic volume in square millimeters or thalamic volume relative to brain volume. Shape analyses revealed that schizophrenic patients had sign ificantly fewer pixels in the left anterior region, whereas patients with s chizotypal personality disorder had significantly fewer pixels in the regio n of the right mediodorsal nucleus than did control subjects. Conclusions: Schizophrenic patients showed significant metabolism and shape differences from control subjects in selective subregions of the thalamus, whereas pati ents with schizotypal personality disorder showed only a difference in shap e. Because the mediodorsal and anterior nuclei have different connections w ith limbic and prefrontal structures, the anterior thalamic shrinkage and m ediodorsal metabolic and shape changes might relate to the different clinic al pictures in schizotypal personality disorder and schizophrenia.