Age-related total gray matter and white matter changes in normal adult brain. Part I: volumetric MR imaging analysis.
ABSTRACT A technique of segmenting total gray matter (GM) and total white matter (WM) in human brain is now available. We investigated the effects of age and sex on total fractional GM (%GM) and total fractional WM (%WM) volumes by using volumetric MR imaging in healthy adults.
Fifty-four healthy volunteers (22 men, 32 women) aged 20-86 years underwent dual-echo fast spin-echo MR imaging. Total GM, total WM, and intracranial space volumes were segmented by using MR image-based computerized semiautomated software. Volumes were normalized as a percentage of intracranial volume (%GM and %WM) to adjust for variations in head size. Age and sex effects were then assessed.
Both %GM and %WM in the intracranial space were significantly less in older subjects (> or =50 years) than in younger subjects (<50 years) (P <.0001 and P =.02, respectively). Consistently, %GM decreased linearly with age, beginning in the youngest subjects. %WM decreased in a quadratic fashion, with a greater rate beginning only in adult midlife. Although larger GM volumes were observed in men before adjustments for cranium size, no significant differences in %GM or %WM were observed between the sexes.
GM volume loss appears to be a constant, linear function of age throughout adult life, whereas WM volume loss seems to be delayed until middle adult life. Both appear to be independent of sex. Quantitative analysis of %GM and %WM volumes can improve our understanding of brain atrophy due to normal aging; this knowledge may be valuable in distinguishing atrophy of disease patterns from characteristics of the normal aging process.
SourceAvailable from: Jennifer K E Steeves[Show abstract] [Hide abstract]
ABSTRACT: Retinoblastoma is typically diagnosed before 5 years of age and is often treated by enucleation (surgical removal) of the cancerous eye. Here, we sought to characterize morphological changes of the cortex following long-term survival from early monocular enucleation. Nine adults with early right-eye enucleation (≤48 months of age) due to retinoblastoma were compared to 18 binocularly intact controls. Surface area, cortical thickness, and gyrification estimates were obtained from T1 weighted images and group differences were examined. Early monocular enucleation was associated with increased surface area and/or gyrification in visual (i.e., V1, inferior temporal), auditory (i.e., supramarginal), and multisensory (i.e., superior temporal, inferior parietal, superior parietal) cortices compared with controls. Visual cortex increases were restricted to the right hemisphere contralateral to the remaining eye, consistent with previous subcortical data showing asymmetrical lateral geniculate nucleus volume following early monocular enucleation. Altered morphological development of visual, auditory, and multisensory regions occurs subsequent to long-time survival from early eye loss.
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ABSTRACT: A new technique - Z-spectrum Analysis Provides Proton Environment Data (ZAPPED) - was used to map cross-relaxing free and restricted protons in nine healthy subjects plus two brain tumor patients at 3T. First, MT data were acquired over a wide symmetric range of frequency offsets, and then a trio of quantitative biomarkers, i.e., the apparent spin-spin relaxation times (T2,f, T2,r) in both free and restricted proton pools as well as the restricted pool fraction Fr, were mapped by fitting the measured Z-spectra to a simple two-Lorentzian compartment model on a voxel-by-voxel basis. The mean restricted exchangeable proton fraction, Fr, was found to be 0.17 in gray matter (GM) and 0.28 in white matter (WM) in healthy subjects. Corresponding mean values for apparent spin-spin relaxation times were 785 µs (T2,f) and 17.7 µs (T2,r) in GM, 672 µs (T2,f) and 23.4 µs (T2,r) in WM. The percentages of Ff and Fr in GM are similar for all ages, whereas Fr shows a tendency to decrease with age in WM among healthy subjects. The patient ZAPPED images show higher contrast between tumor and normal tissues than traditional T2-weighted and T1-weighted images. The ZAPPED method provides a simple phenomenological approach to estimating fractions and apparent T2 values of free and restricted MT-active protons, and it may offer clinical useful information.PLoS ONE 10(3):e0119915. DOI:10.1371/journal.pone.0119915 · 3.53 Impact Factor
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ABSTRACT: Research has shown that patients diagnosed with Major Depressive Disorder have reduced gray matter volume in a variety of brain regions including the hippocampus, basal ganglia, and medial prefrontal cortex. In particular, a number of recent meta-analyses have consistently observed reduced medial prefrontal cortical volumes in major depression, which has been hypothesized to be linked to stress-initiated hypercortisolemic glucocorticoid-mediated cell death. In healthy individuals, stress is associated with lower levels of gray matter volume in the medial prefrontal cortex. However, it remains unclear as to whether variability in normative levels of non-clinical depression is related to variability in medial prefrontal cortex gray matter volume. Therefore, the aim of this study was to examine whether non-clinical levels of depression were related to medial prefrontal cortical volumes. In a sample of 42 normative individuals, we used T1-weighted magnetic resonance imaging to measure brain volume and assessed participants’ level of depression via a self-report questionnaire. Voxel-based morphometry was used to identify voxels which correlated with depressive symptoms. We found a cluster within the medial prefrontal cortex where greater levels of depression were associated with lower gray matter volumes. This relationship with the medial prefrontal cortex was not observed for measures of anxiety and stresssuggesting a unique association between medial prefrontal gray matter volume and depression. The results of this experiment support the hypothesis that even within a non-clinical sample, individuals who have higher levels of depressive traits tend to have lower levels of gray matter volume in the medial prefrontal cortex.Cognitive Neuroscience; 04/2014