White matter microstructure alterations of the medial forebrain bundle in melancholic depression.
BACKGROUND
The medial forebrain bundle (MFB) is a key structure of the reward system and connects the ventral tegmental area (VTA) with the nucleus accumbens (NAcc), the medial and lateral orbitofrontal cortex (mOFC, lOFC) and the dorsolateral prefrontal cortex (dlPFC). Previous diffusion tensor imaging (DTI) studies in major depressive disorder point to white matter alterations of regions which may be incorporated in the MFB. Therefore, it was the aim of our study to probe white matter integrity of the MFB using a DTI-based probabilistic fibre tracking approach.


METHODS
22 patients with major depressive disorder (MDD) (12 melancholic-MDD patients, 10 non-melancholic-MDD patients) and 21 healthy controls underwent DTI scans. We used a bilateral probabilistic fibre tracking approach to extract pathways between the VTA and NACC, mOFC, lOFC, dlPFC respectively. Mean fractional anisotropy (FA) values were used to compare structural connectivity between groups.


RESULTS
Mean-FA did not differ between healthy controls and all MDD patients. Compared to healthy controls melancholic MDD-patients had reduced mean-FA in right VTA-lOFC and VTA-dlPFC connections. Furthermore, melancholic-MDD patients had lower mean-FA than non-melancholic MDD-patients in the right VTA-lOFC connection. Mean-FA of these pathways correlated negatively with depression scale rating scores.


LIMITATIONS
Due to the small sample size and heterogeneous age group comparisons between melancholic and non-melancholic MDD-patients should be regarded as preliminary.


CONCLUSIONS
Our results suggest that the melancholic subtype of MDD is characterized by white matter microstructure alterations of the MFB. White matter microstructure is associated with both depression severity and anhedonia.
['Bracht|Tobias|T|', 'Horn|Helge|H|', 'Strik|Werner|W|', 'Federspiel|Andrea|A|', 'Schnell|Susanne|S|', 'Höfle|Oliver|O|', 'Stegmayer|Katharina|K|', 'Wiest|Roland|R|', 'Dierks|Thomas|T|', 'Müller|Thomas J|TJ|', 'Walther|Sebastian|S|']
D000328:Adult D059445:Anhedonia D016880:Anisotropy D016022:Case-Control Studies D003865:Depressive Disorder, Major D056324:Diffusion Tensor Imaging D005260:Female D006801:Humans D008297:Male D008474:Medial Forebrain Bundle D008875:Middle Aged D009413:Nerve Fibers, Myelinated D012720:Severity of Illness Index
Diffusion tensor imaging Anhedonia Mood disorder Structural imaging