Age-Related Changes in Electroencephalographic Signal Complexity

The study of active and healthy aging is a primary focus for social and neuroscientific communities. Here, we move a step forward in assessing electrophysiological neuronal activity changes in the brain with healthy aging. To this end, electroencephalographic (EEG) resting state activity was acquired in 40 healthy subjects (age 16–85). We evaluated Fractal Dimension (FD) according to the Higuchi algorithm, a measure which quantifies the presence of statistical similarity at different scales in temporal fluctuations of EEG signals. Our results showed that FD increases from age twenty to age fifty and then decreases. The curve that best fits the changes in FD values across age over the whole sample is a parabola, with the vertex located around age fifty. Moreover, FD changes are site specific, with interhemispheric FD asymmetry being pronounced in elderly individuals in the frontal and central regions. The present results indicate that fractal dimension well describes the modulations of brain activity with age. Since fractal dimension has been proposed to be related to the complexity of the signal dynamics, our data demonstrate that the complexity of neuronal electric activity changes across the life span of an individual, with a steady increase during young adulthood and a decrease in the elderly population.     

Electroencephalographic Changes in Epileptics while Viewing Television

Ten consecutive epileptic patients who showed abnormal electroencephalographic (E.E.G.) responses to intermittent photic stimulation have been studied while watching television. Though only two gave a history of television epilepsy nine exhibited spike-wave discharges in the E.E.G. during viewing. This effect occurred when the set was functioning normally but was increased in five subjects when the screen was deliberately caused to flicker.     

Changes in Retinal Glial Cells with Age and during Development of Age-Related Macular Degeneration

Age is the major risk factor in the age-related macular degeneration (AMD) which is a complex multifactor neurodegenerative disease of the retina and the main cause of irreversible vision loss in people over 60 years old. The major role in AMD pathogenesis belongs to structure-functional changes in the retinal pigment epithelium cells, while the onset and progression of AMD are commonly believed to be caused by the immune system dysfunctions. The role of retinal glial cells (Muller cells, astrocytes, and microglia) in AMD pathogenesis is studied much less. These cells maintain neurons and retinal vessels through the synthesis of neurotrophic and angiogenic factors, as well as perform supporting, separating, trophic, secretory, and immune functions. It is known that retinal glia experiences morphological and functional changes with age. Age-related impairments in the functional activity of glial cells are closely related to the changes in the expression of trophic factors that affect the status of all cell types in the retina. In this review, we summarized available literature data on the role of retinal macro- and microglia and on the contribution of these cells to AMD pathogenesis.     

Developmental and Age-Related Changes in Rat Brain Glycosaminoglycans

The quantities of each major class of glycosaminoglycan were determined in rat cerebrum from postnatal day 5 to 30 months of age. Chondroitin sulphate, dermatan sulphate, heparan sulphate, heparin, and hyaluronate were found, but no keratan sulphate was detected. Large and rapid changes in glycosaminoglycan content were observed during the period of brain maturation, and thereafter relatively steady levels were maintained until after the age of 12 months. The most remarkable change in the aged rat cerebrum was the ratio by weight of hyaluronate to chondroitin sulphate, which was approximately 1:1 from postnatal day 10 to 18 months but increased to 2.6:1 by the age of 30 months. In immature rats, the proportion of nonsulphated and 6-sulphated disaccharides derived from chondroitinase AC digests of brain glycosaminoglycans was much greater than in adults. In mature rats, chondroitin sulphate was composed almost entirely of 4-sulphated disaccharide subunits. The possibility that these changes could affect the permeability properties of the cerebral extracellular space and ionic equilibria in the brain is discussed.     

Age-Related Changes in Task Related Functional Network Connectivity

Aging has a multi-faceted impact on brain structure, brain function and cognitive task performance, but the interaction of these different age-related changes is largely unexplored. We hypothesize that age-related structural changes alter the functional connectivity within the brain, resulting in altered task performance during cognitive challenges. In this neuroimaging study, we used independent components analysis to identify spatial patterns of coordinated functional activity involved in the performance of a verbal delayed item recognition task from 75 healthy young and 37 healthy old adults. Strength of functional connectivity between spatial components was assessed for age group differences and related to speeded task performance. We then assessed whether age-related differences in global brain volume were associated with age-related differences in functional network connectivity. Both age groups used a series of spatial components during the verbal working memory task and the strength and distribution of functional network connectivity between these components differed across the age groups. Poorer task performance, i.e. slower speed with increasing memory load, in the old adults was associated with decreases in functional network connectivity between components comprised of the supplementary motor area and the middle cingulate and between the precuneus and the middle/superior frontal cortex. Advancing age also led to decreased brain volume; however, there was no evidence to support the hypothesis that age-related alterations in functional network connectivity were the result of global brain volume changes. These results suggest that age-related differences in the coordination of neural activity between brain regions partially underlie differences in cognitive performance.     

Exploring BOLD Changes during Spatial Attention in Non-Stimulated Visual Cortex

Blood oxygen level-dependent (BOLD) responses were measured in parts of primary visual cortex that represented unstimulated visual field regions at different distances from a stimulated central target location. The composition of the visual scene varied by the presence or absence of additional peripheral distracter stimuli. Bottom-up effects were assessed by comparing peripheral activity during central stimulation vs. no stimulation. Top-down effects were assessed by comparing active vs. passive conditions. In passive conditions subjects simply watched the central letter stimuli and in active conditions they had to report occurrence of pre-defined targets in a rapid serial letter stream. Onset of the central letter stream enhanced activity in V1 representations of the stimulated region. Within representations of the periphery activation decreased and finally turned into deactivation with increasing distance from the stimulated location. This pattern was most pronounced in the active conditions and during the presence of peripheral stimuli. Active search for a target did not lead to additional enhancement at areas representing the attentional focus but to a stronger deactivation in the vicinity. Suppressed neuronal activity was also found in the non distracter condition suggesting a top-down attention driven effect. Our observations suggest that BOLD signal decreases in primary visual cortex are modulated by bottom-up sensory-driven factors such as the presence of distracters in the visual field as well as by top-down attentional processes.     

Age-Related Changes in Expectation-Based Modulation of Motion Detectability

Expecting motion in some particular direction biases sensitivity to that direction, which speeds detection of motion. However, the neural processes underlying this effect remain underexplored, especially in the context of normal aging. To address this, we examined younger and older adults'' performance in a motion detection task. In separate conditions, the probability was either 50% or 100% that a field of dots would move coherently in the direction a participant expected (either vertically or horizontally). Expectation and aging effects were assessed via response times (RT) to detect motion and electroencephalography (EEG). In both age groups, RTs were fastest when motion was similar to the expected direction of motion. RT tuning curves exhibited a characteristic U-shape such that detection time increased with an increasing deviation from the participant''s expected direction. Strikingly, EEG results showed an analogous, hyperbolic curve for N1 amplitude, reflecting neural biasing. Though the form of behavioral and EEG curves did not vary with age, older adults displayed a clear decline in the speed of detection and a corresponding reduction in EEG N1 amplitude when horizontal (but not vertical) motion was expected. Our results suggest that expectation-based detection ability varies with age and, for older adults, also with axis of motion.     

Age-Related Changes in Attention and Impulsivity in Young Schoolchildren

Normative values of attention, impulsivity, response time, and response time variability were determined for seven- to ten-year-old children with the continuous performance Test of Variables of Attention (TOVA). An age-related increase in attention and a decrease in impulsivity, response time, and its variability were revealed. Differences in TOVA scores were studied for students of gymnasia and schools providing general education.     

Changes in Chromatin Organization during Early Development and Carcinogenesis

Similar changes in chromatin organization take place during development and carcinogenesis. The size of chromatin loop domains fixed on the nuclear skeleton (matrix) increased from 20 to approximately 200 kb. These changes are accompanied by an increased size of replicons and altered specificity of loop attachment to the nuclear matrix. During carcinogenesis, inverse changes in the chromatin structure are observed, neoplastic cells are dedifferentiated and return to the initial state. In this review, we consider new experimental data on organization of the DFNA loops and nuclear matrix in embryogenesis and carcinogenesis.     

Age-Related Changes in Corneal Deformation Dynamics Utilizing Scheimpflug Imaging

PurposeTo study age-related changes in corneal deformation response to air-puff applanation tonometry.MethodsFifty healthy subjects were recruited for a prospective study and divided into two equal age groups (≤ 28 and ≥ 50 years old). Up to three measurements by a corneal deformation analyser based on the Scheimpflug principle were performed on the left eye of each subject. Raw Scheimpflug images were used to extract changes in anterior and posterior corneal profiles, which were further modelled by an orthogonal series of Chebyshev polynomial functions. Time series of the polynomial coefficients of even order exhibited a dynamic behavior in which three distinct stages were recognized. A bilinear function was used to model the first and the third stage of corneal dynamics. Slope parameters of the bilinear fit were then tested between the two age groups using Wilcoxon rank sum test and two-way non-parametric ANOVA (Friedman) test.ResultsStatistically significant changes (Wilcoxon test, P<0.05) between the age groups were observed in the phase of the second applanation dynamics for the posterior corneal profile. In a two-way comparison, in which the corneal profile was used as a dependent variable, statistically significant changes (ANOVA/Friedman test, P = 0.017) between the groups were also observed for that phase.ConclusionCorneal biomechanics depend on age. The changes in corneal deformation dynamics, which correspond to mostly free return of the cornea to its original shape after the air pulse, indicate that the age related differences in corneal biomechanics are subtle but observable with high speed imaging.     

Age-Related Changes in Microglia of the Rat Spinal Cord

Journal of Evolutionary Biochemistry and Physiology - The aim of this study was to evaluate age-related changes in microglial cells in various regions of the cervical spinal cord in young (4...     

Epigenetic Changes and Its Intervention in Age-Related Neurodegenerative Diseases

Cellular and Molecular Neurobiology - Epigenetic mechanisms involving the modulation of gene activity without modifying the DNA bases are reported to have lifelong effects on mature neurons in...     

Age-Related Changes in Collagen and Glycosaminoglycans of Rat Gingiva1

Age-related changes in collagen and glycosaminoglycans (GAGs) of rat gingiva were studied biochemically and histologically. The components of isolated GAGs were identified as dermatan sulphate, hyaluronic acid, and heparan sulphate. In histological studies, hyaluronic acid was present in all regions of the gingiva, whereas dermatan sulphate and heparan sulphate were present only in gingival connective tissue. However, there was no significant difference in the relationship between aging, and the content or distribution of GAGs. On the other hand, histological findings showed that collagen fibers were markedly increased in number and the vascular composition was decreased with increasing age. In biochemical studies, the content of collagen, especially of insoluble collagen, was greatly increased with age, whereas collagen biosynthesis and collagenolytic activity were markedly decreased. In addition, lysyl oxidase activity was also significantly decreased with age. The results indicate that the rate of collagen turnover decreases and collagen fibers increase in stability in rat gingiva with increasing age. These observed age-related changes may affect the ability of gingiva to respond to local irritants.     

Electroencephalographic and Plasma Electrolyte Changes After Cardiac Surgery in Children

Serial electroencephalographic studies were carried out during the first few days following open heart surgery in 53 children who had an uneventful surgical procedure and postoperative recovery. While the E.E.G. taken a few hours after the end of the operation was comparable to the preoperative one, an increase in slow activity subsequently occurred in all patients and reached its maximum on the first or second postoperative day. This increase in slow activity was not commonly associated with any obvious altered state of consciousness and the preoperative E.E.G. patterns reappeared within one week. A fall in plasma sodium level with a comparable fall in plasma chloride usually occurred around the second postoperative day, returning to the preoperative levels by the fourth postoperative day.It is suggested that both events are part of a normal reversible physiological response to the operative trauma. The presence of generalized slow activity in the E.E.G. in the first few days after heart surgery does not necessarily imply that there has been cerebral damage from anoxia.     

Exploring Responses to Art in Adolescence: A Behavioral and Eye-Tracking Study

Adolescence is a peculiar age mainly characterized by physical and psychological changes that may affect the perception of one''s own and others'' body. This perceptual peculiarity may influence the way in which bottom-up and top-down processes interact and, consequently, the perception and evaluation of art. This study is aimed at investigating, by means of the eye-tracking technique, the visual explorative behavior of adolescents while looking at paintings. Sixteen color paintings, categorized as dynamic and static, were presented to twenty adolescents; half of the images represented natural environments and half human individuals; all stimuli were displayed under aesthetic and movement judgment tasks. Participants'' ratings revealed that, generally, nature images are explicitly evaluated as more appealing than human images. Eye movement data, on the other hand, showed that the human body exerts a strong power in orienting and attracting visual attention and that, in adolescence, it plays a fundamental role during aesthetic experience. In particular, adolescents seem to approach human-content images by giving priority to elements calling forth movement and action, supporting the embodiment theory of aesthetic perception.