Aging is associated with progressive losses in function across multiple systems, including sensation, cognition, memory, motor control, and affect. The traditional view has been that functional decline in aging is unavoidable because it is a direct consequence of brain machinery wearing down over time. In recent years, an alternative perspective has emerged, which elaborates on this traditional view of age-related functional decline. This new viewpoint--based upon decades of research in neuroscience, experimental psychology, and other related fields--argues that as people age, brain plasticity processes with negative consequences begin to dominate brain functioning. Four core factors--reduced schedules of brain activity, noisy processing, weakened neuromodulatory control, and negative learning--interact to create a self-reinforcing downward spiral of degraded brain function in older adults. This downward spiral might begin from reduced brain activity due to behavioral change, from a loss in brain function driven by aging brain machinery, or more likely from both. In aggregate, these interrelated factors promote plastic changes in the brain that result in age-related functional decline. This new viewpoint on the root causes of functional decline immediately suggests a remedial approach. Studies of adult brain plasticity have shown that substantial improvement in function and/or recovery from losses in sensation, cognition, memory, motor control, and affect should be possible, using appropriately designed behavioral training paradigms. Driving brain plasticity with positive outcomes requires engaging older adults in demanding sensory, cognitive, and motor activities on an intensive basis, in a behavioral context designed to re-engage and strengthen the neuromodulatory systems that control learning in adults, with the goal of increasing the fidelity, reliability, and power of cortical representations. Such a training program would serve a substantial unmet need in aging adults. Current treatments directed at age-related functional losses are limited in important ways. Pharmacological therapies can target only a limited number of the many changes believed to underlie functional decline. Behavioral approaches focus on teaching specific strategies to aid higher order cognitive functions, and do not usually aspire to fundamentally change brain function. A brain-plasticity-based training program would potentially be applicable to all aging adults with the promise of improving their operational capabilities. We have constructed such a brain-plasticity-based training program and conducted an initial randomized controlled pilot study to evaluate the feasibility of its use by older adults. A main objective of this initial study was to estimate the effect size on standardized neuropsychological measures of memory. We found that older adults could learn the training program quickly, and could use it entirely unsupervised for the majority of the time required. Pre- and posttesting documented a significant improvement in memory within the training group (effect size 0.41, p<0.0005), with no significant within-group changes in a time-matched computer using active control group, or in a no-contact control group. Thus, a brain-plasticity-based intervention targeting normal age-related cognitive decline may potentially offer benefit to a broad population of older adults.

Brain plasticity and functional losses in the aged: scientific bases for a novel intervention.

Neural bases of visual deficits during aging.

David B. Elliott* and Mark A. Bullimore\Purpose. To gather information regardin the reliabilityg , discriminative ability an,d validit oyfdisability glare tests.Methods. The following glare tests were evaluated the Miller-Nadler: , Vistech MCT8000 Ber, -keley, van den Berg Straylightmeter, and the Brightness Acuity Tester used with the Pelli-Rob-son and Regan charts. Three test evaluation criteria wer (1e used) repeatability—comparin: gtest score osn two visits (2; ) discriminative ability—the tests' abilit to differentiaty e betweenyoung and old subjects and between old normal and cataract subjects; (3) validity—comparingcataract test scores wit thhe reference standar odf the van den Berg Straylightmeter. Threesubject groups were evaluated: young normals (n = 24, mean age 24.3 ± 3.3 yr), older normals(n = 22, mean age 66.0 ± 6.2 yr), and early cataract ( n = 33, mean age 70.6 ±8.1 yr).Results and Conclusions. Data indicate that contrast sensitivit or loyw contrast acuity measuredin the presence of glare are superior to disability glare scores in assessing cataract patients withnormal neural function. Under glare conditions, contras and lot sensitivitw contrast acuity yscores from the Pelli-Robson, Regan, and Berkeley tests provide similarly reliable, discrimina-tive, and valid measure osf visual assessmen it n cataract. The Miller-Nadler glare tester poorlydetects and measures subtle change ins the ocular media, such as early cataract, becaus ofe itslarge step sizes at low contrast thresholds. The poor reliabilit of they Vistech MCT8000 limitsits usefulness Th. e study suggests that unless good chart an desigd psychophysicn s are used,the geometry and intensit oyf the glare source are of little importance. Invest Ophthalmol VisSci. 1993;34:108-119.v>«ontrast sensitivity (CS) and glare tests are beingused more frequently to clinically evaluate patientswith media opacities, such as after refractive surgeryand in patients with corneal edema, cataract, and cap-sular opacification. In some cases, they also are used to

Assessing the reliability, discriminative ability, and validity of disability glare tests.

Publisher Summary This chapter provides a contemporary overview of one aspect of sensory aging, namely age-related changes in vision and low-level visual information processing. The ability to cope effectively with the environment begins with the capacity to process sensory input. Indeed, the senses have been carefully crafted by the forces of nature to effortlessly extract critical information from the world. Unfortunately, advancing adult aging brings with it systematic reductions in the efficiency of our sensory systems. This lost efficiency of low-level, automatic processing capacity often necessitates effortful, high-level compensatory processes that may tax already limited cognitive resources. Hence, sensory aging is of potentially great interest at all levels of psychological analysis. This focus on vision does not discount the critical role played by the other major sensory systems. Important domains of investigative inquiry are sampled with a focus on basic aspects of vision and aging that have received significant attention in the research literature during the past decade. Several excellent reviews of the sensory aging literature prior to the contemporary period are also presented in the chapter.

Vision and aging.

Neural contribution to spatiotemporal contrast sensitivity decline in healthy ageing eyes.

Contrast sensitivities were measured in human observers of different ages in response to sinusoidal grating patterns generated by laser interferometer and cathode ray tube (c.r.t.). The former method bypasses the effects of the optical media to assess directly the contrast sensitivity of the retina/visual system, while the over-all assessment including optical media is made to the c.r.t. display. The ratio of the two sets of values gives the contrast ratio of the optical media. The latter assessment does not include the effects of wide-angle light scattering which were measured by comparing the responses of eyes with a Perspex lens implant or without any lens at all (i.e. without the major source of scattering) with natural eyes. With increasing age, c.r.t. contrast sensitivities remained steady until the sixth decade when they declined while laser interference fringe contrast sensitivities declined continuously, apart from some abnormally low results for teenage observers. In contrast, the optical contrast did not vary systematically with age nor did its rate of change with spatial frequency vary. The latter was always less than the rate for laser interference fringe contrast sensitivities indicating that the retina/visual system always sets the limit to visual resolution. Wide-angle light scattering was not found to contribute significantly to the changes in ageing nor did reduced retinal illumination, as reproduced by reduced pupil diameter or viewing through a neutral density filter. We therefore conclude that the age-related deterioration is primarily caused by changes within the central nervous system rather than the optical media, the transmission quality of which remains unaffected.

C. McGrath

Papers

Assessment of the optical contributions to the age-related deterioration in vision.