Age-related increase in top-down activation of visual features

Previous research suggests that, during visual search and discrimination tasks, older adults place greater emphasis than younger adults on top-down attention. This experiment investigated the relative contribution of target activation and distractor inhibition to this age difference. Younger and older adults performed a singleton discrimination task in which either an E or an R target (colour singleton) was present among distractor letters. Relative to a baseline condition in which the colours of the targets and distractors remained constant, an age-related slowing of performance was evident when either the colour of the target or that of the distractors varied across trials. The age-related slowing was more pronounced in response to target colour variation, suggesting that older adults place relatively greater emphasis on the top-down activation of target features.     

Age-related increase in top-down activation of visual features

Previous research suggests that, during visual search and discrimination tasks, older adults place greater emphasis than younger adults on top-down attention. This experiment investigated the relative contribution of target activation and distractor inhibition to this age difference. Younger and older adults performed a singleton discrimination task in which either an E or an R target (colour singleton) was present among distractor letters. Relative to a baseline condition in which the colours of the targets and distractors remained constant, an age-related slowing of performance was evident when either the colour of the target or that of the distractors varied across trials. The age-related slowing was more pronounced in response to target colour variation, suggesting that older adults place relatively greater emphasis on the top-down activation of target features.     

Adult age differences in visual word identification: functional neuroanatomy by positron emission tomography

Adult age differences in the neural systems mediating semantic (context-independent) memory were investigated using positron emission tomography (PET). Younger (20-29 years) and older (62-70 years) participants performed lexical decision (word/nonword discrimination) and nonsemantic (simple visual search) baseline tasks during PET scanning. Within the lexical decision task, display duration and presentation rate were varied across scans. The behavioral data suggested that although an age-related slowing was evident in visual feature and response processing, the retrieval of semantic/lexical information was similar for younger and older adults. For both age groups, lexical-related activation occurred in inferior prefrontal and occipitotemporal regions of the left hemisphere. Differential activation, as a function of age group, was observed in the left occipitotemporal pathway as a result of older adults' maintaining higher levels of neural activity in striate cortex (during visual search) and in inferior temporal cortex (during lexical decision). The prefrontal activation was similar for the two age groups. Thus, although this form of semantic memory retrieval does not undergo significant age-related decline, an age-related change in the associated pattern of neural activation is evident. These findings differ from previous neuroimaging studies of episodic (context-dependent) memory retrieval, which have suggested that age-related compensatory mechanisms are expressed primarily by greater activation of prefrontal regions for older adults than for younger adults.     

Aging and attentional guidance during visual search: functional neuroanatomy by positron emission tomography

Positron emission tomography (PET) was used to examine adult age differences in neural activation during visual search. Target detection was less accurate for older adults than for younger adults, but both age groups were successful in using color to guide attention to a subset of display items. Increasing perceptual difficulty led to greater activation of occipitotemporal cortex for younger adults than for older adults, apparently as the result of older adults maintaining higher levels of activation within the easier task conditions. The results suggest that compensation for age-related decline in the efficiency of occipitotemporal cortical functioning was implemented by changes in the relative level of activation within this visual processing pathway, rather than by the recruitment of other cortical regions.     

Adult age differences in visual search accuracy: attentional guidance and target detectability

Previous research, relying primarily on reaction time measures of highly accurate performance, suggests that both younger and older adults can increase the efficiency of visual search by guiding attention to a candidate subset of items. The authors investigated attentional guidance when accuracy was well below ceiling to focus more specifically on the role of perceptual processes. In the most difficult condition (conjunction search), the likelihood of missing a target was greater for older adults than for younger adults, and this effect was not attributable entirely to generalized slowing. Both age groups were able to improve search efficiency by attending to a distinct subset of display items, indicating that attentional guidance to perceptual features does not exhibit age-related decline. A signal-detection model of the conjunction search data demonstrated that the age difference represented an age-related decline in target detectability.     

Searching from the top down: Ageing and attentional guidance during singleton detection

Previous investigations of adult age differences in visual search suggest that an age-related decline may exist in attentional processes dependent on the observer's knowledge of task-relevant features (top-down processing). The present experiments were conducted to examine age-related changes in top-down attentional guidance during a highly efficient form of search, singleton detection. In Experiment 1 reaction times to detect targets were lower when target features were constant (feature condition) than when target features were allowed to vary between trials (mixed condition), and this reaction time benefit was similar for younger and older adults. Experiments 2 and 3 investigated possible interactions between top-down and bottom-up (stimulus-driven) processes. Experiment 2 demonstrated that search times for both age groups could be improved when targets varied on an additional feature from distractors (double-feature condition) but only when top-down control was available (feature search). In Experiment 3, the availability of top-down guidance enabled both younger and older adults to override the distracting effects of a noninformative spatial location cue. These findings indicate that top-down attentional control mechanisms interact with bottom-up processes to guide search for targets, and that in the context of singleton detection these mechanisms of top-down control are preserved for older adults.     

越老越风险规避吗？——年龄对冲动性预测决策行为的调节效应

年老化伴随着风险承担倾向的改变,而决策行为受冲动性的影响是否受到年龄的调节尚不清楚。研究采用两种不同类型的决策任务以及Barratt冲动性量表,考察老年人风险承担在自我报告和决策行为上的改变。结果显示老年人在剑桥博弈任务中更加风险寻求而在模拟充气球任务中更加风险规避。同时冲动性可以显著预测模拟充气球的行为,且该预测受到年龄的调节。研究结果提示,老年人并不是单一的更加风险规避或者风险寻求,而是与任务特异性相关。同时,冲动性可以较好的预测年轻人的决策行为,而对老年人的决策行为没有预测作用。     

Neurocognitive ageing of storage and executive processes

Converging behavioural and neuropsychological evidence indicates that age-related changes in working memory contribute substantially to cognitive decline in older adults. Important questions remain about the relationship between working memory storage and executive components and how they are affected by the normal ageing process. In several studies using positron emission tomography (PET), we find age differences in the patterns of frontal activation during working memory tasks. We find that separable age differences can be linked to different cognitive operations underlying short-term information storage, and interference resolution. Some operations are associated with age-related increases in activation, with older adults displaying bilateral activations and recruiting prefrontal areas more than younger adults. Other operations are associated with age-related decreases in activation. We consider the implications of these results for understanding the working memory system and potential compensatory processes in the ageing brain.     

注意分配与注意选择能力的年龄差异比较

为了考察注意能力的年龄差异,分别从注意分配能力和注意选择能力两个方面对青年和老年被试的表现进行了比较。结果表明：青、老年在注意分配能力上没有显着的差异;而青、老年在注意选择能力上却有显着的差异,老年的注意选择能力有显着的衰退。因此,注意能力衰退对认知年老化的影响可能更主要的是来自于注意控制能力的衰退。     

Adult age differences in the implicit and explicit components of top-down attentional guidance during visual search

Two experiments investigated adult age differences in the explicit (knowledge-based) and implicit (repetition priming) components of top-down attentional guidance during discrimination of a target singleton. Experiment 1 demonstrated an additional contribution of explicit top-down attention, relative to the implicit effect of repetition priming, which was similar in magnitude for younger and older adults. Experiment 2 examined repetition priming of target activation and distractor inhibition independently. The additional contribution of explicit top-down attention, relative to the repetition priming of distractor inhibition, was greater for older adults than for younger adults. The results suggest that some forms of top-down attentional control are preserved as a function of adult age and may operate in a compensatory manner.     

Saccadic eye movements: what do they tell us about aging cognition?

Although the relationship between age-related cognitive decline and saccadic eye movement (SEM) deficits has been outlined, specific cognitive alterations underlying age-related changes in saccadic performance remain unclear. This study attempted to better understand the nature of aging effects on SEMs. We compared SEMs in younger and older adults in prosaccade (PS) and antisaccade (AS) tasks under gap, step, and overlap conditions. We also examined relationships between these performances and several neuropsychological scores. Twenty-eight younger adults (YA), 24 older adults under 65 years (OA_<65) and 24 over 65 years (OA_>65) of age completed a neuropsychological evaluation, PS and AS tasks. Our results showed that latencies, AS cost, time to correct AS errors, and uncorrected AS, increased with aging. YA showed higher overlap effects than OA_>65 and OA_<65. Importantly, correlations and regressions revealed close relationships not only between latencies and processing speed measures but also between the AS cost and the inhibition process measures. Correct saccades and the time to correct AS errors were closely related to the inhibition process and cognitive flexibility measures. These findings suggest that the progressive age-related decline of processing speed and executive attention are associated with, and can be highlighted though SEMs in PS and AS tasks.     

Age differences in dual-task interference are localized to response-generation processes

Dual-task differences in younger and older adults were explored by presenting 2 simple tasks, with the onset of the 2nd task relative to the 1st task carefully controlled. The possibility of an age-related reduction in the ability to generate and execute 2 similar motor programs was explored by requiring either a manual response to both tasks or a manual response to the 1st and an oral response to the 2nd and was confirmed by the evidence. The age-related interference was greater than would be expected from a general slowing of processing in older adults. The possibility of an age-related reduction in the capacity to process 2 tasks in the same perceptual input modality was explored by presenting both tasks in the visual modality or the 1st task in the auditory modality and the 2nd task in the visual modality and was not supported by the evidence. There was greater interference when both tasks were in the same modality, but it was equivalent for older and younger adults. Age differences in dual-task interference appear quite localized to response-generation processes.     

New visions of the aging mind and brain

Cognitive aging is widely viewed as a process of progressive mental loss. Compelling new evidence from functional neuroimaging urges a reconsideration of this pessimistic view. In the domains of working memory and episodic memory, older adults recruit different brain regions from those recruited by younger adults when performing the same tasks. Specifically, older adults show prominent changes in the recruitment of prefrontal regions, and a conspicuous increase in the extent to which activation patterns are bilateral. These results are stimulating new hypotheses about the mechanisms underlying age-related cognitive declines and the potential for compensation. By suggesting a life-long potential for reorganization and plasticity, these discoveries might revise long-held views of functional localization.     

Neural Recruitment and CognitiveAging: Two Hemispheres Are Better Than One, Especially as You Age

Several neuroimaging studies have reported that older adults show weaker activations in some brain areas together with stronger activations in other areas, compared with younger adults performing the same task. This pattern may reflect neural recruitment that compensates for age-related neural declines. The recruitment hypothesis was tested in a visual laterality study that investigated age differences in the efficiency of bihemispheric processing. Letter-matching tasks of varying complexity were performed under two conditions: (a) matching letters projected to the same visual field (hemisphere) and (b) matching letters projected to opposite visual fields (hemispheres). As predicted by the recruitment hypothesis, older adults generally performed better in the bilateral than unilateral condition, whereas younger adults showed this pattern onlyfor the most complex task. We discuss the relation between these results and neuroimaging evidence for recruitment, and the relevance of the present bihemispheric advantage to other evidence for age-related changes in interhemispheric transfer.     

Age-related differences in idea generation and selection for propositional language

Conceptual preparation mechanisms such as novel idea generation and selection from amongst competing alternatives are critical for language production and may contribute to age-related language deficits. This study investigated whether older adults show diminished idea generation and selection abilities, compared to younger adults. Twenty younger (18–35 years) and 20 older (60–80 years) adults completed two novel experimental tasks, an idea generation task and a selection task. Older participants were slower than younger participants overall on both tasks. Importantly, this difference was more pronounced for task conditions with greater demands on generation and selection. Older adults were also significantly reduced on a semantic, but not phonemic, word fluency task. Overall, the older group showed evidence of age-related decline specific to idea generation and selection ability. This has implications for the message formulation stage of propositional language decline in normal aging.     

情绪加工老化效应的神经机制

行为学研究发现,老年人对消极情绪的辨别、注意和记忆都有所下降,而对积极情绪并未表现出类似的现象。情绪加工老化效应的神经影像学研究发现,老年人在情绪加工过程中边缘系统（尤其杏仁核）的激活强度低于年轻人,但额叶皮层区域的激活却有所增强。研究者对该结果提出了两种假说,一种是功能代偿假说,另一种是策略改变假说。功能代偿假说认为老年人额叶皮层区域的激活增强是为了弥补边缘系统功能的下降,反映了大脑功能的代偿;策略改变假说认为老年人主动使用了不同于年轻人的策略,情绪加工方式的不同导致了两组人群大脑活动的差异。未来这方面研究可以从研究层面、研究方法、研究问题等方面逐步完善     

Retrospective cues based on object features improve visual working memory performance in older adults

Research with younger adults has shown that retrospective cues can be used to orient top-down attention toward relevant items in working memory. We examined whether older adults could take advantage of these cues to improve memory performance. Younger and older adults were presented with visual arrays of five colored shapes; during maintenance, participants were presented either with an informative cue based on an object feature (here, object shape or color) that would be probed, or with an uninformative, neutral cue. Although older adults were less accurate overall, both age groups benefited from the presentation of an informative, feature-based cue relative to a neutral cue. Surprisingly, we also observed differences in the effectiveness of shape versus color cues and their effects upon post-cue memory load. These results suggest that older adults can use top-down attention to remove irrelevant items from visual working memory, provided that task-relevant features function as cues.     

Age differences in the neural response to emotional distraction during working memory encoding

Age-related declines in attention and working memory (WM) are well documented and may be worsened by the occurrence of distracting information. Emotionally valenced stimuli may have particularly strong distracting effects on cognition. We investigated age-related differences in emotional distraction using task-fMRI. WM performance in older adults was lower for emotional compared with neutral distractors, suggesting a disproportional impairment elicited by emotional task-irrelevant information. Critically, older adults were particularly distracted by task-irrelevant positive information, whereas the opposite pattern was found for younger adults. Age groups differed markedly in the brain response to emotional distractors; younger adults activated posterior cortical regions and the striatum, and older adults activated frontal regions. Also, an age by valence interaction was found for IFG and ACC, suggesting differential modulation of attention to task-relevant emotional information. These results provide new insights into age-related changes in emotional processing and the ability to resolve interference from emotional distraction.     

The development of specialized brain systems in reading and oral-language.

Functional magnetic resonance imaging (fMRI) was used to examine differences between children (9-12 years) and adults (21-31 years) in the distribution of brain activation during word processing. Orthographic, phonologic, semantic and syntactic tasks were used in both the auditory and visual modalities. Our two principal results were consistent with the hypothesis that development is characterized by increasing specialization. Our first analysis compared activation in children versus adults separately for each modality. Adults showed more activation than children in the unimodal visual areas of middle temporal gyrus and fusiform gyrus for processing written word forms and in the unimodal auditory areas of superior temporal gyrus for processing spoken word forms. Children showed more activation than adults for written word forms in posterior heteromodal regions (Wernicke's area), presumably for the integration of orthographic and phonologic word forms. Our second analysis compared activation in the visual versus auditory modality separately for children and adults. Children showed primarily overlap of activation in brain regions for the visual and auditory tasks. Adults showed selective activation in the unimodal auditory areas of superior temporal gyrus when processing spoken word forms and selective activation in the unimodal visual areas of middle temporal gyrus and fusiform gyrus when processing written word forms.     

Sensitive performance-based assessment of everyday action in older and younger adults

Everyday function is compromised by mild cognitive changes in aging. These changes predict risk for future decline and dementia but remain poorly characterized, largely due to a scarcity of sensitive, objective measures.Twenty-seven younger adults and 25 non-demented older adults completed the Naturalistic Action Test (NAT), a performance-based measure of everyday action involving simple and complex tasks. Performance was coded for overt errors and subtle inefficiencies. Participants also completed self-report functional measures and cognitive tests. Mixed ANOVAs revealed that older adults made more subtle NAT errors with high task demands; groups did not differ in overt errors. Correlations did not reveal significant relations between self-report and NAT errors, but NAT performance was correlated with learning and recall.The NAT provides a promising tool for detecting subtle age-related changes and examining decline across levels of impairment. Self-report may lack sensitivity to subtle changes, and episodic memory changes underlie early functional disruption.