Static and dynamic visual sensitivity in older adults.

Many visual changes accompany the aging process, even in the absence of known visual pathology. One such change which has attracted recent attention is that "normal" older adults, on average, exhibit diminished contrast sensitivity (CS). This loss is not of a general nature, but rather is restricted to intermediate and higher spatial frequencies. Age-related decline in CS has been attributed to both optical (e.g., retinal illuminance, light scatter) and neural factors (e.g., cell loss in higher-order neurons). Three experiments evaluated CS in adults of varying ages. These experiments were intended to 1) establish provisional age norms for the Vistech Contrast Test System, a recently developed method for CS evaluation; 2) assess the convergent and construct validity of the Vistech charts against an optical/neural model of age-related differences in spatial vision; and 3) determine the degree to which these age-deficits in CS were magnified in a dynamic contrast sensitivity (DCS) task where bifoveal fixation requires accurate smooth pursuit. Results demonstrate that the Vistech charts appear to possess good convergent validity with respect to age differences in spatial vision. In addition to declines in spatial vision, older adults are less able to smoothly pursue a moving stimulus. This decline in smooth pursuit accuracy suggested that age differences in CS would be magnified when the elderly were required to discern contrast in a moving stimulus. Two studies have produced results which are consistent with this argument. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hemispheric asymmetry in the visual contribution to postural control in healthy adults

This study was carried out in order to test the hypothesis of a right hemisphere dominance in the visual control of body balance. Eight healthy adults were subjected to a self-regulated lateral balance task, performed while sitting on a rocking platform. Four visual conditions were tested: open eyes with normal vision, closed eyes in the dark, left visual field-right hemisphere and right visual field-left hemisphere. Head and support displacements in the roll plane were recorded by means of an optoelectronic system. Two main results emerged from this study: (1) head stabilization in space was much more efficient in the left visual field-right hemisphere condition than in the three other visual conditions, and (2) although vision played an important role in the body stability whatever the anatomical level, there was no right hemisphere dominance at the pelvic level. A clear right hemisphere dominance was thus demonstrated as regards the visual contribution to head stabilization in space.     

Generalizability of the limits of stability test in the evaluation of dynamic balance among older adults

OBJECTIVE: Reliability of platform posturography tests is essential for the identification and treatment of balance-related disorders. The purposes of this study were to establish the reliability of the limits of stability (LOS) test and to determine the relative variance contributions from identified sources of measurement error. DESIGN: Generalizability theory was used to calculate (1) variance estimates and percentage of variation for the sources of measurement error, and (2) generalizability coefficients. Random effects repeated measures analysis of variance (RM ANOVA) was used to assess consistency of measurements across both days and targets. PARTICIPANTS: Thirty-eight community-dwelling older adults with no recent history of falls. MAIN OUTCOME MEASURES: Outcome measures derived from the LOS tests included movement velocity (MV), maximum center of gravity (COG) excursion (ME), end point COG excursion (EE), and directional control (DC). RESULTS: Estimated generalizability coefficients for 2 and 3 days of testing ranged from .69 to .91. Relative contributions of the day facet were minimal. The RM ANOVA results indicated that for three of the movement variables, no significant differences in scores were observed across days. CONCLUSIONS: The 75% and 100% LOS tests are reliable tests of dynamic balance when administered to healthy older adults with no recent history of falls. Dynamic balance measures were generally consistent across multiple evaluations.     

Age, executive functions, and visuospatial functioning in healthy older adults.

Visuospatial test performance declines with age, whereas verbal test performance remains fairly constant. This pattern has been attributed to an age-related decline in either right-hemisphere functioning or executive functions (EFs), which may be associated with prefrontal cortical decline. Timed and untimed EF tests, and visuospatial tests requiring substantial integrative skill (I-VS) or little or no integrative skill (non-I-VS) were administered to young-old (aged 74 yrs and younger) and old-old (aged 75 yrs and older) healthy volunteers. Groups differed on I-VS tests and on many EF tests but not on non-I-VS tests. I-VS tests correlated highly with tests of EFs, but non-I-VS tests did not. These results are interpreted as supporting the proposal that an age-related decline in EF underlies the decline in visuospatial test performance observed with advancing age. Other issues regarding the relationship between age and EF are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effect of a 12-week dynamic resistance strength training program on gait velocity and balance of older adults

This study tested whether a 12-week dynamic resistance strength training program can change gait velocity and improve measures of balance among adults age 65 and older. Fifty-five community-dwelling adults (mean age = 71.1) were randomized into an exercise (n = 25) or control (n = 30) group. The exercisers were requested to complete three bouts of strength training per week for 12 weeks using elastic tubing. At posttest the exercisers demonstrated slower gait velocity, enhanced balance, and an improved ability to walk backward, although none of these posttest measures was significantly different from the control group.     

Training older adults to search more effectively: Scanning strategy and visual search in dynamic displays.

The authors examined the ability of older adults to modify their search strategies to detect changes in dynamic displays. Older adults who made few eye movements during search (i.e., covert searchers) were faster and more accurate compared with individuals who made many eye movements (i.e., overt searchers). When overt searchers were instructed to adopt a covert search strategy, target detection performance increased to the level of natural covert searchers. Similarly, covert searchers instructed to search overtly exhibited a decrease in target detection performance. These data suggest that with instructions and minimal practice, older adults can ameliorate the cost of a poor search strategy. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Intraindividual variability in cognitive performance in older adults: Comparison of adults with mild dementia, adults with arthritis, and healthy adults.

Intraindividual variability in latency and accuracy of cognitive performance across both trials and occasions was examined in 3 groups of older adults: healthy adults, adults with arthritis, and adults diagnosed with mild dementia. Participants completed 2 reaction-time and 2 episodic-memory tasks on 4 occasions. Results indicated that intraindividual variability in latency was greater in individuals diagnosed with mild dementia than in adults who were neurologically intact, regardless of their health status. Individual differences in variability were stable over time and across cognitive domains. Intraindividual variability was also related to level of performance and was uniquely predictive of neurological status, independent of level of performance. Results suggest that intraindividual variability may be a behavioral indicator of compromised neurological mechanisms. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Chronic strain, locus of control, and distress in older adults.

In this study, I examined whether locus of control beliefs buffer or mediate the impact of chronic financial strain on psychological well-being. Data are from a longitudinal survey of a random community sample of older adults. Findings suggest that elderly people with internal locus of control beliefs are less likely to suffer from the deleterious effects of chronic financial strain than are older adults with external locus of control orientations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Multisensory training of standing balance in older adults: I. Postural stability and one-leg stance balance

BACKGROUND: The effects of standing balance training on the ability to maintain stability in both static two-leg and one-leg stance were tested in healthy older adults. METHODS: Subjects (age range 65-90 years) were randomly assigned to a training (n = 12) or control group (n = 12). Training subjects received a 10-hour balance training program which selectively manipulated sensory inputs from the visual, vestibular, and somatosensory systems. RESULTS: Training subjects showed significantly improved stability (root-mean-square values of anteroposterior platform torque) after training in five of the eight training conditions (when somatosensory inputs were changed or when two or more sensory systems were simultaneously manipulated) (p < .006). When tested 4 weeks after completion of training, subjects (a) fell less frequently when the ankle/foot somatosensory inputs were minimized and (b) stood longer on one leg than the control group (p < .001). CONCLUSIONS: Balance training designed to improve intersensory interaction could effectively improve balance performance in healthy older adults.     

Isometric pinch force control and learning in older adults

The learning of a dynamic isometric pinch force task was investigated in young adults (aged 19 to 29 years) and older adults (aged 64 to 75 years) through use of a visuo-motor tracking paradigm. Both groups significantly improved performance over trials, retained what was learned 1 week later, successfully transferred to a new target, and demonstrated interlimb transfer of training effects, reflecting a strong central component to this task that is apparently intact in older adults. However, performance differences between the two groups remained throughout the trials. Although it appeared that older adults were able to utilize a model-based strategy to predict the target path, as evidenced by minimal response lag, their absolute performance was inferior to that of young adults relative to an overall root mean square error score, a correlation coefficient, and their increased use of high-frequency components in the tracking signal. The age-related performance differences may be attributable to a peripheral decrement in tactile sensibility and/or muscle reorganization as well as a slowness in processing afferent information.     

Priming of two-dimensional visual motion is reduced in older adults.

Previously, Y. Jiang, P. Greenwood, and R. Parasuraman (1999) reported that priming of rotating three-dimensional visual objects is age sensitive. The current study investigated whether there is also an age-related difference in priming with simple two-dimensional (2-D) moving stimuli (i.e., whether a prime stimulus moving in a particular direction causes a subsequent ambiguous target stimulus to be seen moving in the same direction as the prime). In 2 experiments, younger and older adults judged the directions of moving sine-wave gratings. Groups differed neither in determining the direction of a single 2-D movement nor in detecting motion reversals in successively moving gratings. However, the older group showed a significant reduction in the extent of 2-D motion priming. The decrement in older adults for visual motion priming may reflect age-related changes in temporal processing in human visual cortex. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Structure of four executive functioning tests in healthy older adults.

The authors examined the factor structure of 4 indicators of executive functioning derived from 2 new (i.e., Hayling and Brixton) and 2 traditional (i.e., Stroop and Color Trails) tests. Data were from a cross-sectional sample of 55- to 85-year-old healthy adults (N=427) from the Victoria Longitudinal Study. Confirmatory factor analysis (LISREL 8.52) tested both a 2-factor model of Inhibition (Hayling, Stroop) and Shifting (Brixton, Color Trails) and a single-factor model. The 2-factor model did not fit the data because the covariance matrix of the factors was not positive definite. The single-factor model fit the data well, χ2(2, N=427)=0.32, p=.85, root-mean-square error of approximation (RMSEA)=.00, comparative fit index (CFI)=1.00, goodness-of-fit index (GFI)=1.00. Moreover, the single-factor structure of executive functioning was invariant (configural and metric) across gender, and invariant (configural with limited metric) across age. Structural relations showed that poorer executive functioning performance was related to older age and lower fluid intelligence, χ2(11, N=418)=23.04, p=.02, RMSEA=.05, CFI=.97, GFI=.98. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Association between aerobic fitness and visuospatial performance in healthy older adults.

Examined whether chronic physical exercise activity is associated with better neurocognitive performance in older adults. 105 men participated in 1 of 3 age groups (18–28, 35–45, and 60–73 yrs). For each age group, Ss were classified as high or low in fitness on the basis of self-reported activity levels and the results of a submaximal bicycle ergometer test. A comprehensive battery of neuropsychological tests was administered to each S, and older Ss scored significantly lower than the younger groups on most tests. Significant differences between high- and low-fit Ss were found only on tasks with heavy visuospatial demands, and these differences were most notable in the older adult group. These findings suggest that participation in aerobic exercise activity selectively preserves some cognitive functions that normally decline with age. The benefits of activity appear to be most evident on tasks that require visuospatial processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of resistance training on strength, postural control, and gait velocity among older adults

The purpose of this study was to examine the effects of a 14-week resistance training program on the ankle strength, training intensity, postural control, and gait velocity of older adults. Forty-two older adults (mean age = 72), 21 in the resistance and control groups, completed the 14-week project. The resistance training group participated in 14 weeks of resistance training three times per week using elastic bands (Theraband) for resistance. Isokinetic ankle strength, training intensity, postural stability, and gait velocity were measured prior to and following the 14-week intervention. Following the training, the resistance group exhibited improved ankle dorsiflexion, training resistances, and gait velocity, but showed no change in plantar flexion or postural control. The control group also exhibited improvements in dorsiflexion, but these gains were approximately one-half of the gains observed in the resistance training group. Finally, when adjusted for baseline differences, subjects in the resistance training group demonstrated no changes in the dependent measures over the control group.     

The effect of strength and endurance training on gait, balance, fall risk, and health services use in community-living older adults

BACKGROUND: The study tested the effect of strength and endurance training on gait, balance, physical health status, fall risk, and health services use in older adults. METHODS: The study was a single-blinded, randomized controlled trial with intention-to-treat analysis. Adults (n = 105) age 68-85 with at least mild deficits in strength and balance were selected from a random sample of enrollees in a health maintenance organization. The intervention was supervised exercise (1-h sessions, three per week, for 24-26 weeks), followed by self-supervised exercise. Exercise groups included strength training using weight machines (n = 25), endurance training using bicycles (n = 25), and strength and endurance training (n = 25). Study outcomes included gait tests, balance tests, physical health status measures, self-reported falls (up to 25 months of follow-up), and inpatient and outpatient use and costs. RESULTS: There were no effects of exercise on gait, balance, or physical health status. Exercise had a protective effect on risk of falling (relative hazard = .53, 95% CI = .30-.91). Between 7 and 18 months after randomization, control subjects had more outpatient clinic visits (p < .06) and were more likely to sustain hospital costs over $5000 (p < .05). CONCLUSIONS: Exercise may have beneficial effects on fall rates and health care use in some subgroups of older adults. In community-living adults with mainly mild impairments in gait, balance, and physical health status, short-term exercise may not have a restorative effect on these impairments.     

Age and the sense of control among older adults

Older adults are expected and frequently found to report less control than younger adults. In this study, we decompose this negative relationship between age and sense of control using nested multivariable linear regression models that serially introduce sociodemographic characteristics, socioeconomic factors, health status, and subjective religiosity and religious beliefs in a sample of 1,051 older adults attending the general medicine clinics of a major medical center. The results indicate that the effect of age is suppressed in the bivariable model. In the final multivariable model, educational attainment has the largest relative effect (i.e., beta; .253), followed by age (-.210), mental health (.174), subjective religiosity (.113), being an African American (-.100), perceived health (.082), and being Catholic (.068). Future research should focus on the inflection point in the relationship between age and the sense of control that apparently occurs at about 50 years of age.     

Lexical, sublexical, and implicit memory processes in healthy young and healthy older adults and in individuals with dementia of the Alzheimer type.

Five groups of participants—healthy young, healthy young-old, healthy old-old, very mildly demented, and mildly demented individuals of the Alzheimer type (DAT)—participated in a 2-phase experiment that entailed a rhyme judgment task followed by a lexical decision task, in which half of the stimuli were earlier presented in the rhyme judgment task. The results of the rhyme task indicated that healthy young and older adults did not produce an influence of word frequency on rhyme decisions. However, the 2 groups of DAT individuals produced large word-frequency effects primarily for the nonrhyming pairs. The results of the lexical decision task indicated that (a) repetition facilitated lexical decisions to words, whereas there was evidence of inhibition for nonwords; and (b) there was an increasing influence of word frequency across the 5 groups of participants. The results are interpreted with respect to attentional control of appropriate (lexical and sublexical) processing pathways and the nature of processes that are disrupted and those that remain uninfluenced in healthy aging and DAT. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Recognition of posed and spontaneous dynamic smiles in young and older adults.

In 2 studies, we investigated age effects in the ability to recognize dynamic posed and spontaneous smiles. Study 1 showed that both young and older adult participants were above chance in their ability to distinguish between posed and spontaneous smiles in young adults. In Study 2, we found that young adult participant performance declined when judging a combination of both young and older adult target smiles, while older adult participants outperformed young adult participants in distinguishing between posed and spontaneous smiles. A synthesis of results across the 2 studies showed a small-to-medium age effect (d = ?0.40), suggesting that older adults have an advantage in discriminating between smile types. Mixed stimuli (i.e., a mixture of young and older adult faces) may impact accurate smile discrimination. In future research, both the sources (cues) and behavioral effects of age-related differences in the discrimination of positive expressions should be investigated. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Context processing in older adults: Evidence for a theory relating cognitive control to neurobiology in healthy aging.

A theory of cognitive aging is presented in which healthy older adults are hypothesized to suffer from disturbances in the processing of context that impair cognitive control function across multiple domains, including attention, inhibition, and working memory. These cognitive disturbances are postulated to be directly related to age-related decline in the function of the dopamine (DA) system in the prefrontal cortex (PFC). A connectionist computational model is described that implements specific mechanisms for the role of DA and PFC in context processing. The behavioral predictions of the model were tested in a large sample of older (N = 81) and young (N = 175) adults performing variants of a simple cognitive control task that placed differential demands on context processing. Older adults exhibited both performance decrements and, counterintuitively, performance improvements that are in close agreement with model predictions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Generation effects and source memory in healthy older adults and in adults with dementia of the Alzheimer type.

Recognition and source memory were explored in healthy older adults, adults diagnosed with very mild dementia of the Alzheimer type (DAT), and adults diagnosed with mild DAT. Two sentence-completion tasks were used. In Task 1, half of the sentences were completed (clozed) by the participant, and half by the experimenter. In Task 2, half were participant clozed, and half were participant read (already clozed). Recognition of the cloze words and accuracy of categorizing them as participant generated or experimenter generated (Task 1) and participant generated or participant read (Task 2) were measured (source discriminalion). Contrary to previous reports, the DAT groups showed the generation effect, that is, better recognition for participant-generated words than experimenter-generated words (Task 1) or read words (Task 2). Source discrimination was disproportionately impaired in the DAT groups. (PsycINFO Database Record (c) 2010 APA, all rights reserved)