Axonal myelin increase in the callosal genu in depression but not schizophrenia

Abnormalities in the anterior inter-hemispheric connectivity have previously been implicated in major depressive disorder. Disruptions in fractional anisotropy in the callosum and fornix have been reported in schizophrenia and major depressive disorder. Oligodendrocyte density and overall size of th...

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Bibliographic Details
Published in:Psychological medicine 2015-07, Vol.45 (10), p.2145-2155
Main Authors: Williams, M. R., Sharma, P., Fung, K. L., Pearce, R. K. B., Hirsch, S. R., Maier, M.
Format: Article
Language:English
Subjects:
Adult
Brain
Brain - pathology
Cohort Studies
Corpus Callosum - pathology
Depression
Depressive Disorder, Major - pathology
Female
Humans
London
Male
Mental depression
Microscopy, Polarization
Middle Aged
Myelin Sheath - pathology
Nerve Fibers, Myelinated - pathology
Original Articles
Regression Analysis
Schizophrenia
Schizophrenia - pathology
Tissue Banks
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Summary:Abnormalities in the anterior inter-hemispheric connectivity have previously been implicated in major depressive disorder. Disruptions in fractional anisotropy in the callosum and fornix have been reported in schizophrenia and major depressive disorder. Oligodendrocyte density and overall size of the callosum and fornix show no alteration in either illness, suggesting that gross morphology is unchanged but more subtle organizational disruption may exist within these brain regions in mood and affective disorders. Using high-resolution oil-immersion microscopy we examined the cross-sectional area of the nerve fibre and the axonal myelin sheath, and using standard high-resolution light microscopy we measured the density of myelinated axons. These measurements were made in the genu of the corpus callosum and the medial body of the fornix at its most dorsal point. Measures were taken in the sagittal plane in the callosal genu and in the coronal plane at the most dorsal part of the fornix body. Cases of major depressive disorder had significantly greater mean myelin cross-sectional area (p = 0.017) and myelin thickness (p = 0.004) per axon in the genu than in control or schizophrenia groups. There was no significant change in the density of myelinated axons, and no changes observed in the fornix. The results suggest a clear increase of myelin in the axons of the callosal genu in MDD, although this type of neuropathological study is unable to clarify whether this is caused by changes during life or has a developmental origin.
ISSN:0033-2917
1469-8978
DOI:10.1017/S0033291715000136