Functional Deficits in Individual Thalamic Nuclei in Schizophrenia and the Relationship to Structure and Cognition
Andrews, J., Csernansky, J. G., Wang, L., Barch, D. M.
Functional MRI during working memory, encoding, and recognition tasks was used to investigate the role of thalamic function in individuals with schizophrenia and healthy controls. Specifically, we were interested in the degree to which cognitive-task related alterations in thalamic activity occurred in the same thalamic nuclei that have been found to show altered volume and shape measures in schizophrenia, namely the anterior nucleus (AN), the mediodorsal nucleus (MDN), and the pulvinar (PUL). Thirty-six patients and 28 healthy controls matched on age, gender, race and parental socioeconomic status participated in the study. All subjects underwent structural and functional scanning while performing a series of memory tasks, including a 2-back version of the N-back task (working memory), intentional memorization of a series of pictures or words (episodic encoding), and a yes-no recognition task. Whereas previously published studies report global activation differences between the two groups (Barch et al, 2002), the current study focused on activation patterns within 7 individual thalamic regions of interests defined by anatomical and functional criteria.
Decreased functional activation within the AN and the MDN was found in patients. These nuclei overlap with sub-regions of the thalamic surface that we previously reported to exhibit morphological abnormalities in schizophrenia (Csernansky et al, 2004). However, there were no significant correlations between specific measures (i.e. eigenvectors) used to capture information about variation in the surface and the corresponding activation patterns within thalamic nuclei. Better behavioral performance during the working memory task among patients was associated with increased functional activation in the AN, the MDN, and the PUL. These results suggest important correspondences between morphological and functional alterations in the thalamus in schizophrenia, and highlight the importance of investigating relationships between brain structure and function.
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