***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: BACKGROUND Functional neuroimaging studies implicate anterior cingulate and limbic dysfunction in major depressive disorder ( MDD ) and responsiveness to antidepressants . Diffusion tensor imaging ( DTI ) enables characterisation of white matter tracts that relate to these regions . AIMS To examine whether DTI measures of anterior cingulate and limbic white matter are useful prognostic biomarkers for MDD . METHOD Of the 102 MDD out- patients from the International Study to Predict Optimized Treatment for Depression ( iSPOT-D ) who provided baseline magnetic resonance imaging ( MRI ) data , 74 completed an 8-week course of antidepressant medication  ( r and omised to escitalopram , sertraline or extended-release venlafaxine ) and were included in the present analyses . Thirty-four matched controls also provided DTI data . Fractional anisotropy was measured for five anterior cingulate-limbic white matter tracts : cingulum cingulate and hippocampus bundle , fornix , stria terminalis and uncinate fasciculus . ( Trial registered at Clinical Trials.gov : NCT00693849 . ) RESULTS A cross-vali date d logistic regression model demonstrated that altered connectivity for the cingulum part of the cingulate and stria terminalis tracts significantly predicted remission independent of demographic and clinical measures with 62 % accuracy . Prediction improved to 74 % when age was added to this model . CONCLUSIONS Anterior cingulate-limbic white matter is a useful predictor of antidepressant treatment outcome in MDD Diffusion Tensor magnetic resonance imaging and computational neuroanatomy are used to quantify postnatal developmental patterns of C57BL/6J mouse brain . Changes in neuronal organization and myelination occurring as the brain matures into adulthood are examined , and a normative baseline is developed , against which transgenic mice may be compared in genotype-phenotype studies . In early postnatal days , gray matter-based cortical and hippocampal structures exhibit high water diffusion anisotropy , presumably reflecting the radial neuronal organization . Anisotropy drops rapidly within a week , indicating that the underlying brain tissue becomes more isotropic in orientation , possibly due to formation of a complex r and omly intertwined web of dendrites . Gradual white matter anisotropy increase implies progressively more organized axonal pathways , likely reflecting the myelination of axons forming tightly packed fiber bundles . In contrast to the spatially complex pattern of tissue maturation , volumetric growth is somewhat uniform , with the cortex and the cerebellum exhibiting slightly more pronounced growth . Temporally , structural growth rates demonstrate an initial rapid volumetric increase in most structures , gradually tapering off to a steady state by about 20 days . Fiber maturation reaches steady state in about 10 days for the cortex , to 30 - 40 days for the corpus callosum , the hippocampus , and the internal and external capsules Background Due to a lack of evidence , there is no consistent age of onset to define early onset ( EO ) versus later onset ( LO ) major depressive disorder ( MDD ) . Fractional anisotropy ( FA ) , derived from diffusion tensor imaging ( DTI ) , has been widely used to study neuropsychiatric disorders by providing information about the brain circuitry , abnormalities of which might facilitate the delineation of EO versus LO MDD . Method In this study , 61 pairs of untreated , non-elderly , first-episode MDD patients and healthy controls ( HCs ) aged 18–45 years old received DTI scans .  The voxel-based analysis method ( VBM ) , classification analysis , using the Statistical Package for the Social Sciences ( SPSS ) , and regression analyses were used to determine abnormal FA clusters and their correlations with age of onset and clinical symptoms . Results Classification analysis suggested in the best model that there were two subgroups of MDD patients , delineated by an age of onset of 30 years old , by which MDD patients could be divided into EO ( 18–29 years old ) and LO ( 30–45 years old ) groups . LO MDD was characterized by decreased FA , especially in the white matter ( WM ) of the fronto-occipital fasciculus and posterior limb of internal capsule , with a negative correlation with the severity of depressive symptoms ; in marked contrast , EO MDD showed increased FA , especially in the WM of the corpus callosum , corticospinal midbrain and inferior fronto-occipital fasciculus , while FA of the WM near the midbrain had a positive correlation with the severity of depressive symptoms . Conclusion Specific abnormalities of the brain circuitry in EO vs. LO MDD were delineated by an age of onset of 30 years old , as demonstrated by distinct abnormal FA clusters with opposite correlations with clinical symptoms . This DTI study supported the evidence of an exact age for the delineation of MDD , which could have broad multidisciplinary importance . Trial Registration Clinical Trials.gov BACKGROUND Neuroimaging studies have shown that major depressive disorder ( MDD ) is accompanied by structural and functional abnormalities in specific brain regions and connections ; yet , little is known about alterations of the topological organization of whole-brain networks in MDD patients . METHODS Thirty drug-naive , first-episode MDD patients and 63 healthy control subjects underwent a resting-state functional magnetic resonance imaging scan .  The whole-brain functional networks were constructed by thresholding partial correlation matrices of 90 brain regions , and their topological properties ( e.g. , small-world , efficiency , and nodal central ity ) were analyzed using graph theory-based approaches . Nonparametric permutation tests were further used for group comparisons of topological metrics . RESULTS Both the MDD and control groups showed small-world architecture in brain functional networks , suggesting a balance between functional segregation and integration . However , compared with control subjects , the MDD patients showed altered quantitative values in the global properties , characterized by lower path length and higher global efficiency , implying a shift toward r and omization in their brain networks . The MDD patients exhibited increased nodal central ities , predominately in the cau date nucleus and default-mode regions , including the hippocampus , inferior parietal , medial frontal , and parietal regions , and reduced nodal central ities in the occipital , frontal ( orbital part ) , and temporal regions . The altered nodal central ities in the left hippocampus and the left cau date nucleus were correlated with disease duration and severity . CONCLUSIONS These results suggest that depressive disorder is associated with disruptions in the topological organization of functional brain networks and that this disruption may contribute to disturbances in mood and cognition in MDD patients OBJECTIVE The polymorphism BDNF val66met of the brain derived neurotrophic factor ( BDNF ) is common , may increase the risk for depression , and affects BDNF secretion , critical for neuronal survival , plasticity , neurogenesis , and synaptic connectivity . Our objectives were : 1 ) to test the hypothesis that BDNF(val/met ) status influences the remission rate of geriatric depression ; 2 ) to explore whether the relationship between BDNF allelic status to remission is influenced by the presence of microstructural white matter abnormalities . METHOD Non-demented older subjects with major depression had a 2-week placebo period , after which those with a Hamilton Depression Rating Scale ( HDRS ) of 18 or greater received escitalopram 10 mg daily for 12 weeks . Fractional anisotropy was determined in specific regions using the Reproducible Object Quantification Scheme ( ROQS ) software that operates on non-normalized data . RESULTS BDNF(met ) carriers were more likely to achieve remission than BDNF(val/val ) homozygotes after 12 weeks of treatment with escitalopram 10 mg daily . Microstructural abnormalities in the corpus callosum , left superior corona radiata , and right inferior longitudinal fasciculum were also associated with lower remission rate . However , there were no significant interactions between BDNF(val66met ) status and microstructural abnormalities in predicting remission . LIMITATIONS Small number of subjects , focus on a single BDNF polymorphism , fixed antidepressant dose . CONCLUSIONS Depressed older BDNF(met ) carriers had a higher remission rate than BDNF(val/val ) homozygotes . This effect was not related to microstructural white matter abnormalities , which predicted remission independently . We speculate that the relationship between BDNF(val66met ) and remission is due to different effects of BDNF in brain structures related to mood regulation This study was conducted to eluci date the effects of electroconvulsive therapy ( ECT ) on frontal white matter in late-life depressed patients . Diffusion tensor imaging was performed on 8 late-life depressed patients and 12 healthy age-matched controls . The patients were scanned before and after a course of ECT .  Fractional anisotropy ( FA ) was determined in the frontal and temporal regions and the corpus callosum . A significant white matter FA reduction was found in widespread frontal and temporal brain regions in patients with depression before ECT treatment compared with controls . A significant increase in frontal white matter FA was seen following ECT treatment . A course of bilateral ECT  ameliorated white matter integrity in frontal brain regions . This suggests a strong relationship with the antidepressant action of ECT BACKGROUND Repetitive transcranial magnetic stimulation ( rTMS ) is an effective treatment for treatment-resistant depression ( TRD ) , but its therapeutic mechanisms are unclear . White matter abnormalities are thought to cause network dysfunction underlying TRD . Diffusion tensor imaging ( DTI ) is an ideal tool for examining neural connections and the integrity of white matter . Few studies have used DTI to investigate the impact of rTMS on alterations of whiter matter in TRD . METHOD 30 young treatment-resistant unipolar depression patients ( 19 males and 11 females ) were enrolled in a double-blind , r and omized high-frequency ( 15 Hz ) rTMS treatment study . Seventeen patients were treated with real stimulation , and 13 were treated with sham stimulation .  White-matter fractional anisotropy ( FA ) was evaluated using voxel-based analysis ( VBA ) of FA maps derived from DTI before and after treatment . Twenty-five age- and gender-matched subjects were examined as a control group . RESULTS In an exploratory VBA method , clusters of fifty voxels or greater that survived a family-wise error (FWE)-corrected threshold of p<0.05 were considered significant . The results revealed significantly reduced FA in the left middle frontal gyrus , with peak coordinates [ -18 46 -14 ] in TRD patients . This reduced FA was significantly improved after active rTMS treatment , but not sham stimulation . FA increases were correlated with decreased depressive symptoms . LIMITATIONS This study requires replication and further clarification in a larger patient population , and optimization of stimulation locations and methods . CONCLUSIONS These results suggest that the efficacy of rTMS on TRD is related to increased white-matter FA in the left middle frontal gyrus 
    Output:
    
Results Both pooled and subgroup meta-analyses in medication washout patients showed robust fractional anisotropy ( FA ) reductions in white matter of the right cerebellum hemispheric lobule , body of the corpus callosum ( CC ) and bilateral superior longitudinal fasciculus III ( SLF III ) , whereas FA reductions in the genu of the CC and right anterior thalamic projections were seen in only medication-naive patients .
Fibre tracking showed that the main tracts with observed FA reductions included the right cerebellar tracts , body of the CC , bilateral SLF III and arcuate fascicle .
Conclusion By excluding the confounding influences of current medication status , findings from the present study may provide a better underst and ing of the underlying neuropathology of MDD