Measures Of Age-related Changes Research Articles

Quantifying Age-Related Changes in Brain and Behavior: A Longitudinal versus Cross-Sectional Approach.

Cross-sectional versus longitudinal comparisons of age-related change have often revealed differing results. In the current study, we used within-subject task-based fMRI to investigate changes in voxel-based activations and behavioral performance across the life span in the Reference Ability Neural Network cohort, at both baseline and 5 year follow-up. We analyzed fMRI data from between 127 and 159 participants (20–80 years) on a battery of tests relating to each of four cognitive reference abilities. We applied a Gaussian age kernel to capture continuous change across the life span using a 5 year sliding window centered on each age in our participant sample, with a subsequent division into young, middle, and old age brackets. This method was applied separately to both cross-sectional approximations of change and real longitudinal changes adopting a comparative approach. We then focused on longitudinal measurements of neural change to identify regions expressing peak changes and fluctuations of sign change across our sample. Our results revealed several regions expressing divergence between cross-sectional and longitudinal measurements in each domain and age bracket; behavioral comparisons between measurements showed differences in change curves for all four domains, with processing speed displaying the steepest declines. In the longitudinal change measurement, we found lack of support for age-related frontal increases across analysis types, instead finding more posterior regions displaying peak increases in activation, particularly in the old age bracket. Our findings encourage greater focus on longitudinal measurements of age-related changes, which display appreciable differences from cross-sectional approximations.

Microstructural Alterations in Hippocampal Subfields Mediate Age-Related Memory Decline in Humans.

Aging, even in the absence of clear pathology of dementia, is associated with cognitive decline. Neuroimaging, especially diffusion-weighted imaging, has been highly valuable in understanding some of these changes in live humans, non-invasively. Traditional tensor techniques have revealed that the integrity of the fornix and other white matter tracts significantly deteriorates with age, and that this deterioration is highly correlated with worsening cognitive performance. However, traditional tensor techniques are still not specific enough to indict explicit microstructural features that may be responsible for age-related cognitive decline and cannot be used to effectively study gray matter properties. Here, we sought to determine whether recent advances in diffusion-weighted imaging, including Neurite Orientation Dispersion and Density Imaging (NODDI) and Constrained Spherical Deconvolution, would provide more sensitive measures of age-related changes in the microstructure of the medial temporal lobe. We evaluated these measures in a group of young (ages 20–38 years old) and older (ages 59–84 years old) adults and assessed their relationships with performance on tests of cognition. We found that the fiber density (FD) of the fornix and the neurite density index (NDI) of the fornix, hippocampal subfields (DG/CA3, CA1, and subiculum), and parahippocampal cortex, varied as a function of age in a cross-sectional cohort. Moreover, in the fornix, DG/CA3, and CA1, these changes correlated with memory performance on the Rey Auditory Verbal Learning Test (RAVLT), even after regressing out the effect of age, suggesting that they were capturing neurobiological properties directly related to performance in this task. These measures provide more details regarding age-related neurobiological properties. For example, a change in fiber density could mean a reduction in axonal packing density or myelination, and the increase in NDI observed might be explained by changes in dendritic complexity or even sprouting. These results provide a far more comprehensive view than previously determined on the possible system-wide processes that may be occurring because of healthy aging and demonstrate that advanced diffusion-weighted imaging is evolving into a powerful tool to study more than just white matter properties.

TCTAP A-146 Optimal Frequency for Accurate Measurement of Age-related Changes in Electrical Impedance of Vascular Endothelial Cell by Using Micro-electrochemical Impedance Spectroscopy for Diagnosis of Senescence

Senescence is one of the major causes of cardiovascular disease. Thus, various methods have used for analysis of aging. Recently, cell electrical impedance, an electrical property, was presented as a method of quantitative measurement of cell aging by using a device which was called micro-

Skeletal Muscle Quality: Concordant Findings from Two Practical Non‐Invasive Approaches

Phase angle (θ), derived from bioelectrical impedance analysis (BIA) resistance and reactance, decreases with adult age and is associated with changes in nutritional status and skeletal muscle (SM) function. Another measure of SM quality is the light fraction (LF) measured with ultrasound (US) followed by image processing; echogenic light SM is produced with fat and fibrous tissue infiltration of normally dark SM. While the BIA system automatically measures θ, technical training is needed for operation of the US system and subsequent image analysis. The aim of this study was to examine the associations between these two age-related measures of SM quality: θ at 50 KHz using an 8-electrode multifrequency BIA system (MC980, Tanita Corp., Tokyo, Japan); US (GE LOGIC e, Milwaukee, Wisconsin; Nikon NIS Elements Advanced Research 3.22.11, Melville, NY). Subjects were 165 males and females, ages 5-80 yrs, with US measures of biceps, triceps, calf, and thigh muscles; and θ measures of each arm and leg. Significant correlations (p<0.05) were present for key associations, including: bicep LF and arm θ; triceps LF and arm θ; thigh LF and leg θ; age and biceps and thigh LF, and leg θ. Our findings thus show concordant relations between the two different measures of SM quality, θ and LF. Measurement of θ may be a simple, practical, and clinically-useful measure of age-related changes in SM quality.

Somatosensory mismatch response in young and elderly adults.

Aging is associated with cognitive decline and alterations in early perceptual processes. Studies in the auditory and visual sensory modalities have shown that the mismatch negativity [or the mismatch response (MMR)], an event-related potential (ERP) elicited by a deviant stimulus in a background of homogenous events, diminishes with aging and cognitive decline. However, the effects of aging on the somatosensory MMR (sMMR) are not known. In the current study, we recorded ERPs to electrical pulses to different fingers of the left hand in a passive oddball experiment in young (22–36 years) and elderly (66–95 years) adults engaged in a visual task. The MMR was found to deviants as compared to standards at two latency ranges: 180–220 ms and 250–290 ms post-stimulus onset. At 180–220 ms, within the young, the MMR was found at medial electrode sites, whereas aged did not show any amplitude difference between the stimulus types at the same latency range. At 250–290 ms, the MMR was evident with attenuated amplitude and narrowed scalp distribution among aged (Fz) compared to young (fronto-centrally and lateral parietal sites). Hence, the results reveal that the somatosensory change detection mechanism is altered in aging. The sMMR can be used as a reliable measure of age-related changes in sensory-cognitive functions.

Fractional anisotropy of cerebral white matter and thickness of cortical gray matter across the lifespan

We examined age trajectories of fractional anisotropy (FA) of cerebral white matter (WM) and thickness of cortical gray matter (GM) in 1031 healthy human subjects (aged 11-90 years). Whole-brain FA and GM thickness values followed quadratic trajectories with age but the relationship between them was linear, indicating that a putative biological mechanism may explain the non-linearity of their age trajectories. Inclusion of the FA values into the quadratic model of the whole-brain and regional GM thickness changes with age made the effect of the age(2) term no longer significant for the whole-brain GM thickness and greatly reduced its significance for regional GM thickness measurements. The phylogenetic order of cerebral myelination helped to further explain the intersubject variability in GM thickness. FA values for the early maturing WM were significantly better (p=10(-6)) at explaining variability in GM thickness in maturing (aged 11-20) subjects than FA values for the late maturing WM. The opposite trend was observed for aging subjects (aged 40-90) where FA values for the late maturing WM were better (p=10(-16)) at explaining the variability in GM thickness. We concluded that the non-linearity of the age trajectory for GM thickness, measured from T1-weighted MRI, was partially explained by the heterogeneity and the heterochronicity of the age-related changes in the microintegrity of cerebral WM. We consider these findings as the evidence that the measurements of age-related changes in GM thickness and FA are driven, in part, by a common biological mechanism, presumed to be related to changes in cerebral myelination.

Amperometric measures of age-related changes in glutamate regulation in the cortex of rhesus monkeys

l-glutamate (glutamate) is the principal excitatory neurotransmitter of the central nervous system and is involved in altered neural function during aging and in neurodegenerative diseases. Relatively little is known about the mechanisms of glutamate signaling in the primate brain, in part, because there is an absence of a method capable of rapidly measuring glutamate in either a non-clinical or a clinical setting. We have addressed this paucity of information by measuring extracellular glutamate at 1 Hz in the pre-motor and motor cortices of young, middle-aged, and aged monkeys using a minimally invasive amperometric recording method. In the motor cortex, mean resting glutamate levels were five times higher in the aged group compared to the young group while the pre-motor cortex showed an increasing trend in resting glutamate levels that was not statistically significant. In addition, we measured rapid, phasic glutamate release after local pressure-ejection of nanoliter volumes of either isotonic 70 mM potassium (to stimulate glutamate release) or 1 mM glutamate (to study glutamate uptake) into the pre-motor and motor cortex. In the pre-motor cortex, we measured reproducible glutamate uptake signals that had a significantly decreased (47%) rate of glutamate uptake in aged animals compared to young animals. However, following a 70 mM potassium delivery, we did not observe any consistent changes in evoked release between young versus aged animals. Using these non-clinical microelectrodes to measure glutamate signaling in the brain, our results support the hypothesis that the glutamatergic system undergoes reorganization with aging of the central nervous system.

Measurements of age-related changes of physiological processes that predict lifespan of Caenorhabditis elegans.

Aging is characterized by progressive, degenerative changes in many tissues. To elucidate the relationships among degenerative changes in Caenorhabditis elegans, we developed methods to measure age-related changes quantitatively and analyzed correlations among these changes by using a longitudinal study. The age-related declines of pharyngeal pumping and body movement were positively correlated with each other and lifespan. These findings suggest that the declines of pharyngeal pumping and body movement cause a decline in survival probability or that a shared regulatory system mediates the declines in pharyngeal pumping, body movement, and survival probability. Furthermore, measurements of these processes can be used to predict lifespan and detect premature aging. The declines of physiological processes were measured in daf-2, age-1, daf-16, eat-2, and clk-1 mutants that have altered lifespans. Each mutant strain displayed changes in one or more age-related declines, but the correlations among age-related changes were similar to WT. These measurements were used to generate a system of four stages that describes the aging process and is useful for the analysis of genetic and environmental effects on aging.

Automated measurement of age-related changes in the locomotor response to environmental novelty and home-cage activity

The likelihood to explore in an open-field environment decreases with age. Older animals tend to be less active and explore less both in novel and home-cage environments. The locomotor performance (fine movements, ambulatory movements, and rearing) of male Fischer 344 (F344) rats that were 6 ( n=6) or 22 ( n=6) months of age was evaluated by continuous automated counting of photobeam interruptions, every 30 min, during 60 consecutive hours, in standard polycarbonate cages. Novel environment performance was determined by photobeam interruption counting during the first hour in the new cage. The remaining 59 h were evaluated as home-cage activity. A significant age-related decrease in ambulatory and fine motor activity was seen during the first hour of testing (novel environment). In addition, aged rats showed a decreased number of ambulatory and fine movements in home-cage activity, predominately during the dark portion of the light cycle and during or around both light-switch periods (05:00 and 17:00). No differences were seen in rearing behavior. These findings provide a more detailed analysis and additional evidence of the activity decreases and rhythmic changes seen in aged F344 rats under uninterrupted testing conditions.

Estimating age-related changes in psychomotor function: influence of practice and of level of caloric intake in different genotypes☆

This article presents a discussion of some key considerations in the measurement of age-related changes in psychomotor function of mice. We illustrate that “standard” measures of psychomotor performance, such as running speed on a rotorod task, are highly sensitive to practice effects. Examples are cited in which failure to assess practice effects can influence conclusions regarding the magnitude and rate of change in psychomotor capacity as a function of age. A second set of examples is focused on estimating the effect of an experimental intervention, caloric restriction, on age-related changes in psychomotor performance. These examples show that psychomotor performance at a given age may vary directly, and reversibly, with the level of caloric intake. Independent of such reversible effects, the level of caloric intake can also modulate the rate of change in capacity as a function of age. It is concluded that reversible, short-term effects must be considered in estimating the effect of an experimental intervention on the rate of age-associated change in psychomotor function.

Age-related changes in human vocal tract configurations and the effects on speakers' vowel formant frequencies: a pilot study

The study aims to: (i) make accurate measurements of age-related changes in female speakers' vocal tract configurations with acoustic reflection technique (ART); (ii) obtain acoustic information of vowel formant frequency changes as a function of aging; and (iii) test the hypothesis that there are age-related vocal tract dimensional changes and concomitant decreases in all the vowel formant frequencies as people age. Preliminary findings indicate that older female subjects tend to have a more expanded pharyngeal lumen, but not longer vocal tract length, than their younger cohorts, and formant frequencies would not unanimously decrease as a function of aging. The study highlights the importance of larger-scale measurements of age-related vocal tract configuration changes and the necessity of developing new acoustic models that will delineate all the concomitant formant frequency and other acoustic changes as people age.

Methods of measuring morphological parameters in dental radiographs: Comparison between image analysis and manual measurements

Measurements of age-related changes in dental tissues are often used when estimating the age of an individual. With the new technology now available, the methods of measurement might be standardized and reproducible. The purpose of the present study was to compare the reliability of manual and computer-assisted measurements of morphological parameters in dental radiographs. Manual measurements were made conventionally using a pair of vernier callipers and a stereomicroscope with a measuring eyepiece. An image analysis software program was employed for the computer assisted measurements. Lengths and widths of tooth and pulp were measured both manually and with computer assistance on periapical radiographs from 40 patients, six teeth in each patient. Statistical analyses showed no significant intra- or inter-observer differences for the manual measurements. Statistically significant intra- and inter-observer differences were, however, found between the manual and computer-assisted measurements. The results implied that, despite advanced technology, conventional methods may be better suited for measuring linear morphological parameters in dental tissue.

Age-dependent changes of the compound action potential in the guinea pig.

As a measure of age-related changes in the most peripheral neural part of the auditory pathway, the compound action potential of the guinea pig was analyzed. In addition to a marked threshold elevation, there was a significantly lower potential amplitude in old animals. By contrast, the latency of the compound action potential was unchanged. In view of the fact that the relative amplitude increase in the intensity range tested was the same in old as in young animals, the implication is that the auditory-nerve neurons that are still excited do not exhibit functional deterioration with aging.

Infants and I scales: Inferring change from the ordinal stimulus selections of infants for configural stimuli

The analysis of I-scale preference orders of 71 infants 2 to 9 months old to four face-like stimuli suggested a common J-scale stimulus ordering for each of the four age groups. Changes in I-scale frequencies were used as a measure of age-related changes in preference orders. Results revealed no change in preference for the age period studied. Together with other data these results suggest an ageinvariant preference for organized face-like forms from at least as early as five weeks through 9 months. This finding is at variance with some theoretical expectations. A Thurstone analysis is provided as a contrast to the J-scale analysis. Assumptions of different data analyses are considered as the basis for varying results reported in the literature.