Resting state functional connectivity and treatment response in late-life depression

Indices of functional connectivity in the default mode network (DMN) are promising neural markers of treatment response in late life depression. We examined the differences in DMN functional connectivity between treatment responsive and treatment resistant depressed older adults. Forty-seven depressed older adults underwent MRI scanning pre- and posi-pharmacotherapy. Forty six never depressed older adults underwent MR scanning as comparison subjects. Treatment response was defined as achieving a Hamilton Depression Rating Scale of 10 or less post treatment. We analyzed resting state functional connectivity using the posterior cingulate cortex as the seed region-of-interest. The resulting correlation maps were employed to investigate between group differences. Additionally we examined the association between white matter hyperintensity burden and functional connectivity results. Comparison of pre- and post treatment scans of depressed participants revealed greater post treatment functional connectivity in the frontal precentral gyrus. Relative to treatment-responsive participants, treatment-resistant participants had increased functional connectivity in the left striatum. When adjusting for white matter hyperintensity burden, the observed differences lost significance for the PCC-prefrontal Functional connectivity, but not for the PCC-striatum functional connectivity. The post-treatment frontalization or the DMN connectivity suggests a normalizing effect of antidepressant treatment. Moreover, our study confirms the central role of white matter lesions in disrupting brain functional connectivity. (C) 2013 Elsevier Ireland Ltd. All rights reserved.