Right orbitofrontal corticolimbic and left corticocortical white matter connectivity differentiate bipolar and unipolar depression - PubMed (original) (raw)

Right orbitofrontal corticolimbic and left corticocortical white matter connectivity differentiate bipolar and unipolar depression

Amelia Versace et al. Biol Psychiatry. 2010.

Abstract

Objectives: The absence of pathophysiologically relevant diagnostic markers of bipolar disorder (BD) leads to its frequent misdiagnosis as unipolar depression (UD). We aimed to determine whether whole brain white matter connectivity differentiated BD from UD depression.

Methods: We employed a three-way analysis of covariance, covarying for age, to examine whole brain fractional anisotropy (FA), and corresponding longitudinal and radial diffusivity, in currently depressed adults: 15 with BD-type I (mean age 36.3 years, SD 12.0 years), 16 with recurrent UD (mean age 32.3 years, SD 10.0 years), and 24 healthy control adults (HC) (mean age 29.5 years, SD 9.43 years). Depressed groups did not differ in depression severity, age of illness onset, and illness duration.

Results: There was a main effect of group in left superior and inferior longitudinal fasciculi (SLF and ILF) (all F > or = 9.8; p < or = .05, corrected). Whole brain post hoc analyses (all t > or = 4.2; p < or = .05, corrected) revealed decreased FA in left SLF in BD, versus UD adults in inferior temporal cortex and, versus HC, in primary sensory cortex (associated with increased radial and decreased longitudinal diffusivity, respectively); and decreased FA in left ILF in UD adults versus HC. A main effect of group in right uncinate fasciculus (in orbitofrontal cortex) just failed to meet significance in all participants but was present in women. Post hoc analyses revealed decreased right uncinate fasciculus FA in all and in women, BD versus HC.

Conclusions: White matter FA in left occipitotemporal and primary sensory regions supporting visuospatial and sensory processing differentiates BD from UD depression. Abnormally reduced FA in right fronto-temporal regions supporting mood regulation, might underlie predisposition to depression in BD. These measures might help differentiate pathophysiologic processes of BD versus UD depression.

2010 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.

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Figures

Figure 1

Figure 1

(A) Fractional anisotropy (FA) maps showing three orthogonal (coronal, sagittal, and axial) views of the main effect of group on FA in bipolar disorder (BD) depressed adults, unipolar disorder (UD) depressed adults, and healthy control adults (HC) (from top to bottom): left superior longitudinal fasciculus in inferior temporal cortex; left superior longitudinal fasciculus in primary sensory cortex; right uncinate fasciculus in orbitofrontal cortex, and left inferior longitudinal fasciculus in lateral occipital cortex. Background: Montreal Neurological Institute (MNI)152 brain and white matter skeleton used for randomized analysis (in green). The images represent findings (in red-yellow) projected onto the white matter skeleton. The red-yellow spectrum represents a significance range: 2 < f < 20. Monte Carlo simulation with the αSim approach was conducted on uncorrected F and t statistical maps (p ≤ .001), obtaining a dual thresholding of both Type I error (α; p ≤ .05) and cluster-size thresholding (CST). (B) Bar graphs show mean FA values and 95% confidence intervals for each group for each of the aforementioned four regions in which there was a main effect of group on FA. **Highlighted is the significant pairwise between-group post hoc comparison that resulted in the main effect of group in each of these four regions (BD depressed adults in red, UD depressed adults in blue, and HC in green). For each region, the third group that did not contribute to the main effect of group is also graphically represented (bar obscured) From top to bottom: pairwise comparison between BD depressed adults relative to UD depressed adults in the left superior longitudinal fasciculus in inferior temporal cortex (MNI x, y, z = –51, –38, –17); pairwise comparison between BD depressed adults relative to HC in the left superior longitudinal fasciculus in primary sensory cortex (MNI x, y, z = –40, –27, 50) and the right uncinate fasciculus in orbitofrontal cortex (MNI x, y, z = 26, 26, –11); and pairwise comparison between UD depressed adults relative to HC in the left inferior longitudinal fasciculus in lateral occipital cortex (MNI x, y, z = –28, –76, 40).

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