Physiological neuronal decline in healthy aging human brain - An in vivo study with MRI and short echo-time whole-brain (1)H MR spectroscopic imaging.

Knowledge of physiological aging in healthy human brain is increasingly important for neuroscientific research and clinical diagnosis. To investigate neuronal decline in normal aging brain eighty-one healthy subjects aged between 20 and 70years were studied with MRI and whole-brain (1)H MR spectroscopic imaging. Concentrations of brain metabolites N-acetyl-aspartate (NAA), choline (Cho), total creatine (tCr), myo-inositol (mI), and glutamine+glutamate (Glx) in ratios to internal water, and the fractional volumes of brain tissue were estimated simultaneously in eight cerebral lobes and in cerebellum. Results demonstrated that an age-related decrease in gray matter volume was the largest contribution to changes in brain volume. Both lobar NAA and the fractional volume of gray matter (FVGM) decreased with age in all cerebral lobes, indicating that the decreased NAA was predominantly associated with decreased gray matter volume and neuronal density or metabolic activity. In cerebral white matter Cho, tCr, and mI increased with age in association with increased fractional volume, showing altered cellular membrane turn-over, energy metabolism, and glial activity in human aging white matter. In cerebellum tCr increased while brain tissue volume decreased with age, showing difference to cerebral aging. The observed age-related metabolic and microstructural variations suggest that physiological neuronal decline in aging human brain is associated with a reduction of gray matter volume and neuronal density, in combination with cellular aging in white matter indicated by microstructural alterations and altered energy metabolism in the cerebellum.

Reconstructing atmospheric Hg levels near the oldest chemical factory in central Europe using a tree ring archive.

The Chemical Factory in Marktredwitz (CFM) is known as the oldest chemical factory in Germany (1778-1985), and from the beginning of the 20th century focused primarily on the production of mercury (Hg) compounds. Due to extensive pollution, together with employee health issues, the CFM was shut in 1985 by a government order and remediation works proceeded from 1986 to 1993. In this study, tree ring archives of European Larch (Larix decidua Mill.) were used to reconstruct changes of air Hg levels near the CFM. Mercury concentrations in larch boles decreased from 80.6 µg kg-1 at a distance of 0.34 km-3.4 µg kg-1 at a distance of 16 km. The temporal trend of atmospheric Hg emissions from the CFM reconstructed from the tree ring archives showed two main peaks. The first was in the 1920s, with a maximum tree ring Hg concentration 249.1 ± 43.9 µg kg-1 coinciding with when the factory had a worldwide monopoly on the production of Hg-based seed dressing fungicide. The second peak in the 1970s, with a maximum tree ring Hg concentration of 116.4 ± 6.3 µg kg-1, was associated with a peak in the general usage and production of Hg chemicals and goods. We used the tree ring record to reconstruct past atmospheric Hg levels using a simple model of Hg distribution between the larch tree rings and atmosphere. The precision of the tree ring model was checked against the results of air Hg measurements during the CFM remediation 30 years ago. According to the tree ring archives, the highest air Hg concentrations in the 1920s in Marktredwitz were over 70 ng m-3. Current air Hg levels of 1.18 ng m-3, assessed in the city of Marktredwitz, indicate the lowest air Hg in the past 150 years, underscoring the effective remediation of the CFM premises 30 years ago.

Age-related Brain Metabolic Changes up to Seventh Decade in Healthy Humans : Whole-brain Magnetic Resonance Spectroscopic Imaging Study.

PURPOSE: To study brain metabolic changes under normal aging and to collect reference data for the study of neurodegenerative diseases. METHODS: A total of 55 healthy subjects aged 20-70 years (n ≥ 5 per age decade for each gender) underwent whole-brain magnetic resonance spectroscopic imaging at 3T after completing a DemTect test and the Beck depressions inventory II to exclude cognitive impairment and mental disorder. Regional concentrations of N-acetylaspartate (NAA), choline-containing compounds (Cho), total creatine (tCr), glutamine and glutamate (Glx), and myo-inositol (mI) were determined in 12 brain regions of interest (ROIs). The two-sided t­test was used to estimate gender differences and linear regression analysis was carried out to estimate age dependence of brain regional metabolite contents. RESULTS: Brain regional metabolite concentrations changed with age in the majority of selected brain regions. The NAA decreased in 8 ROIs with a rate varying from -4.9% to -1.9% per decade, reflecting a general reduction of brain neuronal function or volume and density in older age; Cho increased in 4 ROIs with a rate varying from 4.3% to 6.1%; tCr and mI increased in one ROI (4.2% and 8.2% per decade, respectively), whereas Glx decreased in one ROI (-5.1% per decade), indicating an inhomogeneous increase of cell membrane turnover (Cho) with altered energy metabolism (tCr) and glutamatergic neuronal activity (Glx) as well as function of glia cell (mI) in normal aging brain. CONCLUSION: Healthy aging up to the seventh decade of life is associated with regional dependent alterations of brain metabolism. These results provide a reference database for future studies of patients.

Regional Metabolite Concentrations in Aging Human Brain: Comparison of Short-TE Whole Brain MR Spectroscopic Imaging and Single Voxel Spectroscopy at 3T.

PURPOSE: The aim of this study was to compare a recently established whole brain MR spectroscopic imaging (wbMRSI) technique using spin-echo planar spectroscopic imaging (EPSI) acquisition and the Metabolic Imaging and Data Analysis System (MIDAS) software package with single voxel spectroscopy (SVS) technique and LCModel analysis for determination of relative metabolite concentrations in aging human brain. METHODS: A total of 59 healthy subjects aged 20-70 years (n ≥ 5 per age decade for each gender) underwent a wbEPSI scan and 3 SVS scans of a 4 ml voxel volume located in the right basal ganglia, occipital grey matter and parietal white matter. Concentration ratios to total creatine (tCr) for N­acetylaspartate (NAA/tCr), total choline (tCho/tCr), glutamine (Gln/tCr), glutamate (Glu/tCr) and myoinositol (mI/tCr) were obtained both from EPSI and SVS acquisitions with either LCModel or MIDAS. In addition, an aqueous phantom containing known metabolite concentrations was also measured. RESULTS: Metabolite concentrations obtained with wbMRSI and SVS were comparable and consistent with those reported previously. Decreases of NAA/tCr and increases of line width with age were found with both techniques, while the results obtained from EPSI acquisition revealed generally narrower line widths and smaller Cramer-Rao lower bounds than those from SVS data. CONCLUSION: The wbMRSI could be used to estimate metabolites in vivo and in vitro with the same reliability as using SVS, with the main advantage being the ability to determine metabolite concentrations in multiple brain structure simultaneously in vivo. It is expected to be widely used in clinical diagnostics and neuroscience.

Perception of emotional speech in Parkinson's disease.

Nonmotor symptoms in Parkinson's disease (PD) involving cognition and emotionality have progressively received attention. The objective of the present study was to investigate recognition of emotional prosody in patients with PD (n = 14) in comparison to healthy control subjects (HC, n = 14). Event-related brain potentials (ERP) were recorded in a modified oddball paradigm under passive listening and active target detection instructions. Results showed a poorer performance of PD patients in classifying emotional prosody. ERP generated by emotional deviants (happy/sad) during passive listening revealed diminished amplitudes of the mismatch-related negativity for sad deviants, indicating an impairment of early preattentive processing of emotional prosody in PD.