Inhibitory processes in young and older adults in a picture-word task

Abstract

The present study examines changes in healthy young and healthy older adults in the ability to inhibit partially activated information in a picture/word interference paradigm. On each trial, subjects received a cue (i.e., the word PICTURE or WORD) indicating which of two stimuli the subject should attend to in an upcoming picture/word display. the display always contained a superimposed picture and word (e.g., a picture of a DEER with the word TEA printed on it). Following display offset, and depending upon the initial precue, either a test picture (e.g., KETTLE) or a test word (e.g., MOOSE) was presented. the subject's task was to determine as quickly and as accurately as possible whether the test stimulus was related to the cued dimension of the earlier picture/word display. the speed to reject an unrelated test item (e.g., picture of a KETTLE when the precue was PICTURE) that was related to the ignored dimension of the picture/word display (e.g., the word TEA in the picture/word display) was used as an index of the efficiency of the inhibitory system. the results indicated that older adults had more difficulty than younger adults inhibiting a to-be-ignored word when it was related to a picture test item, but did not have more difficulty inhibiting a to-be-ignored picture when it was related to a word test item. the results indicate that an age-related deficit in the control of interfering information is dependent upon the fluency of the processing routes.     

The transient nature of executive control processes in younger and older adults

In this paper I review data from recent studies supporting the hypothesis that executive control processes fluctuate in efficiency over time and that these fluctuations are more pervasive in older than younger adults. Patterns of response accuracy in tasks requiring selective attention and prospective memory reveal that lapses of intention are often preceded and followed by periods of goal-directed action. Analysis of response time distributions reveals that increased performance variability in older adults for task conditions requiring executive control results from an increase in the degree of positive skewing of the distribution. Together, these findings lead to the suggestion that disruptions of executive control processes supporting performance in demanding tasks are temporally limited in nature. Data from recent neurophysiological studies indicates a possible role of the prefrontal cortex in maintaining optimal levels of executive control.     

A comparison of higher order auditory processes in younger and older adults

The authors conducted 3 experiments investigating the effects of aging on higher order auditory processes. They compared younger and older adults with respect to (a) their auditory channel capacity, (b) the extent of their top-down control over auditory gain, and (c) their ability to focus attention on a narrow band of frequencies. To ensure that subclinical cochlear processing deficits in older adults (e.g., higher thresholds, poorer discrimination of frequency and intensity differences) did not limit performance, the authors used only stimuli that were perfectly discriminable by all participants. No age differences were found in any of these experiments, suggesting that some higher order auditory processes (e.g., top-down control over auditory gain, auditory attention) are preserved in normal aging, despite numerous age-related declines in peripheral auditory functionality.     

Stereotype threat strengthens automatic recall and undermines controlled processes in older adults

The threat of being judged stereotypically (stereotype threat) may impair memory performance in older adults, thereby producing inflated age differences in memory tasks. However, the underlying mechanisms of stereotype threat in older adults or other stigmatized groups remain poorly understood. Here, we offer evidence that stereotype threat consumes working memory resources in older adults. More important, using a process-dissociation procedure, we found, for the first time, that stereotype threat undermines the controlled use of memory and simultaneously intensifies automatic response tendencies. These findings indicate that competing models of stereotype threat are actually compatible and offer further reasons for researchers and practitioners to pay special attention to age-related stereotypes during standardized neuropsychological testing.     

Stress and inflammation among older adults: The moderating role of religiosity

Chronic stress weakens the immune system and leads to heightened bodily inflammation, which in turn is linked with serious health conditions. This study examined whether religiosity moderates the relationship between stress and inflammation (measured by C-reactive Protein (CRP)). A sample of 4,734 community-dwelling older adults was drawn from the 2006 wave of the Health and Retirement Study. Logistic regression was used to analyze the relationship between chronic stress (8-item index), inflammation (high CRP level), and religiosity (organizational, nonorganizational, and intrinsic), controlling for other factors. Higher levels of stress were significantly associated with high inflammation/CRP (p = .039). Further, intrinsic religiosity acted as a moderator of this relationship (p = .024), such that the relationship between stress and inflammation is lessened for persons with higher levels of intrinsic religiosity. Higher intrinsic religiosity attenuated the effects of stress on inflammation, suggesting that individuals with stronger religious commitment/motivation may better cope with stress.     

Specific effects of the Trier Social Stress Test on speech fluency in young and older adults

The notion that speech becomes less fluent during stressful speaking conditions has received little empirical test, and no research has tested this relationship in older adult participants. We analyzed speeches produced during the Trier Social Stress Test (TSST) or during a less stressful placebo (pTSST) version of the task. We measured young and older adults’ speech fillers (e.g., um), unfilled pauses (at least 1 s in duration), and other disfluencies (e.g., repetitions, repairs). Neither young nor older adult participants rated themselves as having greater stress in the TSST than pTSST condition, but behavioral effects were obtained. Participants in the TSST condition produced more mid-phrase speech fillers and unfilled pauses than participants in the pTSST condition. Young adults produced more unfilled pauses than older adults overall, and older adults produced more mid-phrase fillers than young adults. Critically, age group interacted with experimental condition, such that older speakers produced disproportionately more mid-phrase fillers than young adults in the TSST compared to the pTSST condition. In sum, the negative effects of the TSST on fluency were generally similar across age, but this specific age-related increase in mid-phrase fillers indicates that older adults’ word retrieval may have been particularly negatively affected. Findings are generally consistent with previous research and add to understanding of how factors internal to the speaker (i.e., demographic, personality, and cognitive variables) and factors external to the speaker (i.e., variables regarding the situation, context, or content of speech) combine to affect speech fluency.     

Semantic priming in young and older adults: evidence for age constancy in automatic and attentional processes

Automatic and attentional components of semantic priming and the relation of each to episodic memory were evaluated in young and older adults. Category names served as prime words, and the relatedness of the prime to a subsequent lexical decision target was varied orthogonally with whether the target category was expected or unexpected. At a prime-target stimulus-onset asynchrony (SOA) of 410 ms, target words in the same category had faster lexical decision latencies than did different category targets. This effect was not significant at a 1,550-ms SOA and was attributed to automatic processes. Expected category targets had faster latencies than unexpected category targets at the 410-ms SOA, and the magnitude of the effect increased at the 1,550-ms SOA. This effect was attributed to attentional processes. These patterns of priming were obtained for both age groups, but in a surprise memory test older adults had poorer recall of primes and targets. We discuss the implications of these results for the hypothesis that older adults suffer deficits in selective attention and for the related hypothesis that attentional deficits impair semantic processing, which causes memory decrements in old age.     

Visuomotor binding in older adults

Action integration is the process through which actions performed on a stimulus and perceptual aspects of the stimulus become bound as a unitary object. This process appears to be controlled by the dopaminergic system in the prefrontal cortex, an area that is known to decrease in volume and dopamine functioning in older adults. Although the decline should lead to reduced action integration in older adults, we found equivalent integration in both young and older adults. This indicates that older adults may be able to compensate for their dopaminergic deficiencies by activating additional neural networks that are not used by young adults.     

Representational momentum in older adults

Humans have a tendency to perceive motion even in static images that simply “imply” movement. This tendency is so strong that our memory for actions depicted in static images is distorted in the direction of implied motion - a phenomenon known as representational momentum (RM). In the present study, we created an RM display depicting a pattern of implied (clockwise) rotation of a rectangle. Young adults viewers’ memory of the final position of the test rectangle was biased in the direction of continuing rotation, but older adults did not show a similar memory bias. We discuss several possible explanations for this group difference, but argue that the failure of older adults to shown an RM effect most likely reflects age-related changes in areas of the brain involved in processing real and implied motion.     

Inhibitory processes and spoken word recognition in young and older adults: the interaction of lexical competition and semantic context.

Two experiments were conducted to examine the importance of inhibitory abilities and semantic context to spoken word recognition in older and young adults. In Experiment 1, identification scores were obtained in 3 contexts: single words, low-predictability sentences, and high-predictability sentences. Additionally, identification performance was examined as a function of neighborhood density (number of items phonetically similar to a target word). Older adults had greater difficulty than young adults recognizing words with many neighbors (hard words). However, older adults also exhibited greater benefits as a result of adding contextual information. Individual differences in inhibitory abilities contributed significantly to recognition performance for lexically hard words but not for lexically easy words. The roles of inhibitory abilities and linguistic knowledge in explaining age-related impairments in spoken word recognition are discussed.     

Search and selection processes in implicit and explicit word-stem completion performance in young, middle-aged, and older adults

In the present investigation, we sought to (1) replicate previous reports of impaired word-stem completion (WSC) priming and cued recall performance in older adults, (2) gain a better understanding of the differential roles of search and selection processes in implicit and explicit WSC, and (3) determine the particular aspects of WSC performance that are influenced by age. Experiment 1 demonstrated that older adults primed and recalled fewer items on a WSC task than middle-aged adults did, who in turn primed and recalled fewer items than young adults did. A series of item analyses indicated that choice of a stem completion is influenced by two independent sources of information: the familiarity of the completion reflected by word frequency and the cue-specific match between the stem and the completion word based on the common pronunciation of the stem. Experiment 2 demonstrated that older adults utilized cue-specific matching to the same degree as young and middle-aged adults. However, the impact of target familiarity changed across the lifespan. Older adults produced and recalled high-frequency targets as well as young adults but produced and recalled fewer low-frequency targets than did young participants. The results are consistent with the view that older adults rely on familiarity to a greater degree than do young adults.     

Sustained-attention capacity in young and older adults

The sustained-attention capacity of young (21-29 years) and older (65-78 years) adults was examined using a high-event rate digit-discrimination vigilance task presented at three levels of stimulus degradation. Increased stimulus degradation led to a reduction in the hit rate and to a greater decline in hit rate over blocks (increased vigilance decrement). Sensitivity (d') declined over blocks only at the highest level of stimulus degradation. Older adults had a lower hit rate and showed greater vigilance decrement than young adults, particularly when stimuli were highly degraded. However, both age groups showed the same pattern of stability in sensitivity when stimulus degradation was moderate, and sensitivity decrement over time when stimulus degradation was high. The results suggest that the process of sustained allocation of capacity--as reflected in temporal changes in sensitivity--operates similarly in young and older adults.     

Memory complaints in younger and older adults

Two samples of older and younger subjects were administered a series of memory tasks and questionnaires tapping their perceptions about their own memory functioning. As in previous research, memory performance was usually better in the younger than in the older sample. In contrast, perceptions about memory varied little as a function of age, and these subjective reports were not related to objective memory performances. These results are relevant to theories that metacognition plays an important role in mediating performance declines with advancing age. If metacognition is implicated in age-related memory differences, it is some aspect of metacognition other than long-term beliefs about memory functioning (e. g. short-term perceptions that occur while attempting to perform memory tasks).     

Plasticity of brain and cognition in older adults

Aging is typically related to changes in brain and cognition, but the aging process is heterogeneous and differs between individuals. Recent research has started investigating the influence of cognitive and physical training on cognitive performance, functional brain activity, and brain structure in old age. The functional relevance of neural changes and the interactions among these changes following interventions is still a matter of debate. Here we selectively review research on structural and functional brain correlates of training-induced performance changes in healthy older adults and present exemplary longitudinal intervention studies sorted by the type of training applied (i.e., strategy-based training, process-specific training, and physical exercise). Although many training studies have been conducted recently, within each task domain, the number of studies that used comparable methods and techniques to assess behavioral and neural changes is limited. We suggest that future studies should include a multimodal approach to enhance the understanding of the relation between different levels of brain changes in aging and those changes that result from training. Investigating inter-individual differences in intervention-induced behavioral and neuronal changes would provide more information about who would benefit from a specific intervention and why. In addition, a more systematic examination of the time course of training-related structural and functional changes would improve the current level of knowledge about how learning is implemented in the brain and facilitate our understanding of contradictory results.     

Training attentional control in older adults

Recent research has demonstrated benefits for older adults from training attentional control using a variable priority strategy, but the construct validity of the training task and the degree to which benefits of training transfer to other contexts are unclear. The goal of this study was to characterize baseline performance on the training task in a sample of 105 healthy older adults and to test for transfer of training in a subset (n?=?21). Training gains after 5 days and extent of transfer was compared to another subset (n?=?20) that served as a control group. Baseline performance on the training task was characterized by a two-factor model of working memory and processing speed. Processing speed correlated with the training task. Training gains in speed and accuracy were reliable and robust (ps <.001, η(2)?=?.57 to .90). Transfer to an analogous task was observed (ps <.05, η(2)?=?.10 to .17). The beneficial effect of training did not translate to improved performance on related measures of processing speed. This study highlights the robust effect of training and transfer to a similar context using a variable priority training task. Although processing speed is an important aspect of the training task, training benefit is either related to an untested aspect of the training task or transfer of training is limited to the training context.     

Predicting foreign-accent adaptation in older adults

We investigated comprehension of and adaptation to speech in an unfamiliar accent in older adults. Participants performed a speeded sentence verification task for accented sentences: one group upon auditory-only presentation, and the other group upon audiovisual presentation. Our questions were whether audiovisual presentation would facilitate adaptation to the novel accent, and which cognitive and linguistic measures would predict adaptation. Participants were therefore tested on a range of background tests: hearing acuity, auditory verbal short-term memory, working memory, attention-switching control, selective attention, and vocabulary knowledge. Both auditory-only and audiovisual groups showed improved accuracy and decreasing response times over the course of the experiment, effectively showing accent adaptation. Even though the total amount of improvement was similar for the auditory-only and audiovisual groups, initial rate of adaptation was faster in the audiovisual group. Hearing sensitivity and short-term and working memory measures were associated with efficient processing of the novel accent. Analysis of the relationship between accent comprehension and the background tests revealed furthermore that selective attention and vocabulary size predicted the amount of adaptation over the course of the experiment. These results suggest that vocabulary knowledge and attentional abilities facilitate the attention-shifting strategies proposed to be required for perceptual learning.     

Grasp force control in older adults

Diminished tactile sensibility and impaired hand dexterity have been reported for elderly individuals. Reports that younger adults with severely impaired tactile sensibility use excessive grasp force during routine grasp and manipulation tasks raise the possibility that elderly persons likewise produce large grasp forces that may contribute to impaired dexterity. Impaired pseudomotor functioning also occurs in elderly subjects and may yield a slipperier skin surface that enhances the possibility for excessive grasp force. The present study measured grasp force in 10 elderly and 9 young adult individuals, during grasp and vertical lift of a small object, using a precision (pinch) grip of the thumb and index finger. The slipperiness of the object's gripped surfaces was unexpectedly varied. Skin slipperiness was estimated by also measuring the grasp force at which the object slipped from grasp. The older subjects employed grasp forces that were, on average, twice as large as those of the young subjects, with some producing forces many times greater than the young subjects' average grip force. Grip forces also were significantly more variable across trials in older subjects. This increased variability was not caused simply by the elderly subjects' increased grip force. A portion of the increased force was due to increased skin slipperiness. The grip force that the elderly subjects produced in excess of the slip force (the "margin of safety" against object slippage) was larger than would have been predicted from their skin slipperiness, however. It is suggested that, in part, the excessive grasp forces represent a strategic response to tactile sensibility impairment. Twopoint discrimination limina in the older subjects averaged about four times greater than in the younger subjects. Increased grasp forces in elderly persons may result from other factors, such as increased variability in grip force production. The contributions of excessive grasp forces to impaired dexterity in older persons still need to be addressed experimentally.     

Both young and older adults discount suggestions from older adults on a social memory test

In the present study, we examined the impacts of participant age and confederate age on social memory processes. During a collaborative recall phase, young and older adult participants were exposed to the erroneous memory reports of a young or an older adult confederate. On a subsequent individual recall test, young and older adult participants were equally likely to incorporate the confederates’ erroneous suggestions into their memory reports, suggesting that participant age had a minimal effect on social memory processes. However, confederate age did have a marked effect: Young adult participants were less likely to incorporate misleading suggestions from older adult confederates and less likely to report “remembering” items suggested by older adult confederates. Critically, older adult participants were also less likely to incorporate misleading information from fellow older adult confederates. Both young and older adult participants discounted older adult confederates’ contributions to a memory test.     

Retrieval processes in fifth graders and adults

This research was concerned with retrieval processes which underlie conceptual clustering. In a free recall task with categorized lists, fifth graders' and adults' retrieval was examined temporally by means of interword response times. List organization and retrieval cue factors were manipulated in order to assess the developmental relevance of an hypothesized three component retrieval model. The results indicated that both age groups used a qualitatively similar retrieval strategy, involving search for and decoding of higher-order memory units. Providing retrieval cues eliminated the category search component, but also increased the likelihood of exhaustive recall attempts under random presentation conditions. The results were discussed in terms of the inter-relationships between storage and retrieval strategies. Age-related differences in retrieval time were attributed to insufficient reorganization during input and failure to attempt to recall all of a category's members.     

Treatment of depression in low-income older adults

The purpose of this study was to compare cognitive-behavioral group therapy (CBGT), clinical case management (CCM), and their combination (CBGT + CCM) to treat depression in low-income older adults (60+). Sixty-seven participants with major depressive disorder or dysthymia were randomly assigned and entered into 1 of the 3 treatment conditions for 6 months. They were followed for 18 months after treatment initiation on depression and functional outcomes. CCM and CBGT + CCM led to greater improvements in depressive symptoms than CBGT, but CBGT led to greater improvements in physical functioning. All 3 conditions resulted in similar reduction of needs. Findings suggest that disadvantaged older adults with depression benefit from increased access to social services either alone or combined with psychotherapy.