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Table 4 Diffusion tensor imaging studies excluded from meta-analysis conducted in patients with both major depressive disorder and late-life depression (age >65 years) using other forms of analysis such as regions of interest or tractographya

From: Meta-analysis of diffusion tensor imaging studies shows altered fractional anisotropy occurring in distinct brain areas in association with depression

Study Method Participants Results Comments
Lu et al. [39] Tractography
1.5 Tesla
13 non-colinear directions
23 MDD patients, 24 controls Increased neural connections between areas involved in mood regulation in MDD subjects, such as right superior frontal gyrus to right pallidum and left superior parietal gyrus to right superior occipital gyrus Increased neural connections in MDD patients in brain areas associated with mood regulation
Cullen et al. [38] Tractography and voxel-based analysis
3.0 Tesla
30 non-colinear directions
14 healthy MDD adolescents, 14 controls Reduced FA in WM tracts connecting subgenual ACC to amygdala in right hemisphere and right and left uncinate to supragenual cingulum Altered frontolimbic neural pathways in adolescent depression
Shimony et al. [37] ROI analysis superficial: superior, middle and inferior frontal gyri, medial and lateral orbital frontal, dorsal, ventral and ACC, mesial frontopolar cortex, motor cortex, medial temporal gyrus, fusiform gyrus, auditory cortex, somatosensory cortex and posterolateral intraparietal sulcus, occipital pole and visual cortex
Deep: ventral, dorsal, and posterior frontal lobes, temporal and parietal lobes
1.5 Tesla
6 directions
73 LLD subjects, 23 controls Reduced FA in prefrontal regions compared to controls DTI abnormalities may be correlated with reduced cognitive processing speed
Yang et al. [17] ROI analysis: DLPFC, parahippocampal gyrus and genu and body of corpus callosum
1.5 Tesla
25 diffusion-weighted directions
31 LLD subjects, 15 controls Significantly reduced FA values in superior and middle frontal gyrus and right parahippocampal gyrus Microstructural abnormalities in temporal and frontal areas of brain are associated with LLD
Nobuhara et al. [10] ROI analysis: frontal WM 8 mm above AC-PC, on AC-PC, 8 mm below AC, genu and splenium
Bilaterally: temporal WM, parietal WM and occipital WM
1.5 Tesla
6 non-colinear directions
13 LDD patients, matched controls Significantly reduced FA in the WM of frontal, temporal and occipital brain regions and corpus callosum of LLD individuals Frontal, temporal and orbitofrontal WM deficits may play a role in symptom severity in LLD
Li et al. [35] ROI analysis: prefrontal WM at 4 mm inferior to and at 0, 4, 8, 12, 16 and 20 mm superior to AC-PC plane
1.5 Tesla
13 non-colinear directions
51 LDD individuals Significantly reduced FA values in prefrontal WM at bilateral 20 mm, right
16 mm and right 12 mm above AC-PC. No significant correlation
between FA and illness course or severity
Prefrontal WM abnormalities may occur early in the course of MDD and may play a role in the pathophysiology
Murphy et al. [36] Voxel-based analysis
1.5 Tesla
8 diffusion sensitization directions
51 LDD individuals, no controls Reduced FA in WM lateral to ACC and posterior cingulate cortex and in prefrontal, insular and parahippocampal
regions
Alterations in the frontostriatal-limbic networks may be associated with
executive dysfunction of LLD as measured on the Stroop task
Bae et al. [34] ROI analysis: WM of superior and middle frontal gyri of DLPFC, anterior corpus callosum and anterior limb of internal capsule
1.5 Tesla
6 diffusion-weighted directions
106 LLD subjects, 84 elderly euthymic controls Significantly reduced FA in WM of the right ACC, bilateral superior frontal gyri, and left middle frontal gyrus Reduced FA in dorsolateral prefrontal cortex and ACC suggests altered brain connections are associated with LLD
Taylor et al. [16] ROI analysis bilaterally: periventricular WM, frontal WM, anterior parietal WM, posterior parietal WM and caudate thalamus
1.5 Tesla
6 non-colinear
directions
29 LLD patients and 20 controls Depressed nonremitting subjects showed fewer changes in ACC Nonremitting subjects showed fewer FA changes, which may reflect antidepressant failure
  1. aMDD, major depressive disorder; FA, fractional anisotropy; WM, white matter; ROI, region of interest; LLD, late-life depression; DTI, diffusion tensor imaging; DLPFC, dorsolateral prefrontal cortex; ACC, anterior cingulate cortex; AC, anterior commissure; PC, posterior commissure.