Aging affects word-stem completion and recognition but not category generation

In this study, we investigated the effect of aging on two implicit memory tasks, word-stem completion and category generation, and on explicit recognition. We compared the performance of young and older adults on these implicit memory tasks with those of explicit recognition. We expected better performance of young than older adults in the explicit memory task and similar priming in both implicit memory tasks. The results showed that young adults performed better than older adults in the recognition task. Moreover, both age groups showed priming in the implicit memory tasks, although priming was greater in young adults compared to older adults in the word-stem completion memory task, whereas both age groups showed similar levels of priming in the category generation task. The present results showed dissociations as a function of age not only between the explicit and the implicit tasks but also between the implicit tasks.     

Further considerations regarding inhibitory processes, working memory, and cognitive aging

The present study explored the relationship between inhibitory processing (as indexed by identity negative priming in a letter-naming task), working memory, discourse processing, and cognitive aging effects. Consistent with several other recent reports, this study found evidence of intact inhibitory processing, as measured by negative priming, in older adults as well as younger adults. This intact negative priming occurred in conjunction with diminished working memory span and impaired memory in the discourse processing task in the same sample of older adults, further arguing against the likelihood that declines in these areas are caused by impairments in the inhibitory processes measured by negative priming. The implications of these results for theories of cognitive aging and possible reasons for inconsistent findings regarding negative priming effects among the elderly are discussed.     

Age-Related Differences in Memory Illusions: Revelation Effect

Older adults are often more susceptible to various illusions and distortions of memory than young adults. In the experiments reported here, we explored the question of whether normal aging was associated with a larger revelation effect, an illusion of memory in which items that are revealed gradually during a recognition test are more likely to be called old than unrevealed items that are shown in their entirety. Contrary to expectations, older adults were not susceptible to this memory illusion. A revelation effect occurred for young but not older adults, even when older adults were similar to young adults on measures of recognition and repetition priming. When data across experiments were combined, there was evidence for a negative revelation effect in older adults in which revealed items were less likely called old than unrevealed items. These results place boundary conditions on the claim that older adults are more susceptible than young adults to memory illusions, and imply that one or more mechanisms underlying the revelation effect are age sensitive.     

Effects of aging on priming and skill learning.

This study examined the effects of aging on 2 kinds of implicit memory; repetition priming and skill learning. In Experiment 1, older adults showed less improvement in the skill of reading inverted words than did young adults, but priming performance did not differ for the 2 age groups. Similarly, in Experiment 2, in a partial-word identification task, skill learning was observed only for young adults, whereas there was no age difference in priming. Experiments 1a and 2a, however, showed that when older adults were presented with more perceptual information than were young adults, the age deficit in skill learning was eliminated. These results indicate that skill learning is impaired under data-limited conditions, whereas priming is unaffected under these conditions. It is proposed that the age deficit in skill learning is related to a deficit in perceptual organization and reorganization.     

Children do show negative priming: further evidence for early development of an intact selective control mechanism

Reactions to stimuli that were shortly before presented as distractors are usually slowed down; this phenomenon is known as negative priming. Negative priming is an accepted index for tapping into selective control mechanisms. Although this effect is well established for adults, it has been claimed that children do not show negative priming. Recently, however, V. E. Pritchard and E. Neumann challenged this view and concluded that selective control mechanisms are already fully developed in young children. The authors of the present study analyzed differences between older studies, in which no negative priming had been observed, and the Pritchard and Neumann (2004) study. In sum, the present study yielded further evidence for an intact selective control mechanism in young children. The authors also linked this empirical finding to the broader literature on negative priming by a direct comparison with an adult sample.     

Target selection difficulty, negative priming, and aging

It has been recently suggested that the presence of identity negative priming effects in old adults could occur when there is substantial processing of the distracting information in a selective attention task (J. M. Kieley & A. A. Hartley, 1997). In three experiments, using a letter identification task, it was found that making target selection more difficult increased the magnitude of the negative priming effect to a similar extent in both young and old adults. Moreover, the size of the negative priming effect did not differ between young and elderly participants. These results are discussed with respect to the issue of age-related deficits in the mechanisms underlying negative priming.     

Auditory negative priming in younger and older adults

Two experiments are reported in which performance of old and young adults in an auditory negative priming task was compared. Auditory negative priming was not smaller in old than in young adults. This result was independent of whether or not conditions were present that had previously been assumed to favour episodic retrieval, as opposed to inhibitory processes, as a basis of the negative priming phenomenon. The data from the present auditory negative priming experiments are incompatible with the global assumption that the efficiency of inhibitory attentional processes in general diminishes across the adult life span.     

Attentional modulation of masked repetition and categorical priming in young and older adults

Three experiments examined the effects of temporal attention and aging on masked repetition and categorical priming for numbers and words. Participants' temporal attention was manipulated by varying the stimulus onset asynchrony (i.e., constant or variable SOA). In Experiment 1, participants performed a parity judgment task and a lexical decision task in which categorical priming and repetition priming were, respectively, tested. Experiment 2 used a semantic categorization task testing categorical priming. In Experiment 3, repetition and categorical priming were tested in the same semantic categorization task with the same stimuli. The results of the three experiments showed that masked repetition priming is insensitive to manipulations of temporal attention whereas categorical priming is. Furthermore, no differences were found between young and older adults in repetition priming effects, again contrasting with the categorical priming results for which older adults were more sensitive to attentional manipulations than young adults.     

Picture priming in normal aging and Alzheimer's disease

The present study investigated age invariance for naming pictures and whether implicit memory is spared in Alzheimer's disease (AD). During the study phase, young adults, AD patients, and older controls were shown outlines of familiar pictures. After a distracter task, implicit memory was assessed incidentally. The results showed similar visual priming for the three groups, although young adults responded faster than the two older groups. Moreover, the number of errors was smaller for studied than for non-studied pictures. This pattern of results was repeated across the three groups, although AD patients produced more errors than young adults and older controls, and there were no differences between these latter groups. These results confirmed previous visual and haptic findings showing unimpaired perceptual priming in normal aging and AD patients when implicit memory is assessed using identification tasks. These results are interpreted from a cognitive neuroscience perspective.     

保留的跨通道启动与老化：对于近期观点的总结

通道内重复启动的研究提示老年人内隐记忆未受损, 这不只体现在视觉通道上还包括其他感觉通道(例如触觉、听觉和嗅觉)。然而很少有研究考察启动任务是否具有通道特异性。在以年轻人为被试的研究中发现跨通道迁移(视觉到触觉和触觉到视觉)和通道内迁移(视觉到视觉, 触觉到触觉)具有相似性。一项最近的研究进一步探索老年人在跨通道启动任务上是否受损。结果显示视觉和触觉间的跨通道启动在年轻被试和老年被试上都是保留的且具有对称性。并且, 对于自然声响、图片的通道内和跨通道启动任务随着年老化发展仍旧保留。这些行为结果和其它最近神经科学结果显示跨通道启动发生于枕叶后纹状皮层区, 而这一区域在老年人中未损坏。这一领域未来的研究方向包括利用不同知觉通道间、利用熟悉的和新异的刺激并结合行为的和脑成像的方法, 通过设计完善的跨通道启动来研究正常老人与阿尔兹海默病人, 还包括将设计得完善的启动任务包括在用于改善老年人记忆功能的项目中。     

Age-Related Influences on Repetition Priming in the Verb Generation Task: Examining the Role of Response Competition

ABSTRACT

The identification-production framework suggests that aging is associated with a decline in production forms of repetition priming, particularly under test conditions that maximize response competition. The present study examined this prediction by testing young and healthy older adults in a single-encoding version of the verb generation task in which some items had one dominant verb response (low competition) or had no such dominant response (high competition). Further analyses examined whether priming and error rates were related to performance on neuropsychological tests purported to measure frontal lobe functioning. Priming was invariant across age groups and was not related to frontal lobe status in older adults, but frontal lobe status did predict task performance: low-frontal older adults made more errors than high-frontal older adults, particularly for high-competition items and items with high association strength. These results are not consistent with the identification-production framework, but are consistent with the conclusions that (a) aging is associated with invariance in the processes that support repetition priming in the verb generation task and (b) frontal lobe status in aging is related to verb generation performance.     

Age-related differences in medial prefrontal activation in response to emotional images

Research has suggested that aging results in a "positivity effect," with young adults dwelling on negative information, and older adults attending to positive information. In order to understand age-related changes in emotional processing underlying this effect, the present fMRI study compared neural activity in young and older adults as they viewed positive, negative, and neutral images. Results indicated a striking age-related reversal in the valence of information eliciting activity within the ventromedial prefrontal cortex (VMPFC). Negative in comparison with positive images activated the VMPFC more for young adults, whereas positive in comparison with negative images activated the VMPFC more for the older adults. The VMPFC is a region associated with the processing of emotional information, and more specifically, with emotion generation and emotion regulation. Therefore, the present results suggest that age-related changes in these processes implemented by the VMPFC contribute to older adults' "positivity effect."     

Production and identification repetition priming in amnestic mild cognitive impairment

The experiment reported here examined implicit memory function, as measured through repetition priming, in amnestic mild cognitive impairment (MCI) to examine whether impairments exist in this aspect of memory function. Young adults, healthy older controls, Alzheimer's disease patients, and MCI participants were asked to perform two types of implicit memory tests (word stem completion and threshold identification repetition priming tasks), as well as a recognition test for studied items. As expected, young adults performed better than the other participants on the recognition test and the word stem completion task; there was equivalent priming across groups on the word identification task. While both the older control and MCI participants showed lower levels of priming on the word stem completion task relative to the young adults, the magnitude of priming was equivalent for these two groups, and reliably greater than that of the dementia participants. These results suggest that not all aspects of memory function are impaired in MCI relative to healthy aging.     

Aging affects both perceptual and lexical/semantic components of word stem priming: An event-related fMRI study

In this event-related fMRI study, brain activity patterns were compared in extensive groups of young (N=25) and older (N=38) adults, while they were performing a word stem completion priming task. Based on behavioral findings, we tested the hypothesis that aging affects only the lexical/semantic, but not the perceptual component of word stem priming. To this end, we distinguished between priming-related activity reductions in posterior regions involved in visual processing, and regions associated with lexical/semantic retrieval processes, i.e., left lateral temporal and left prefrontal regions. Both groups revealed significant priming-related response time reductions. However, in accordance with earlier findings, a larger priming effect was found in the group of young participants. In line with previous imaging studies, the groups showed common priming-related activity reductions in the anterior cingulate, and the left inferior prefrontal cortex extending into the anterior portion of the left superior temporal gyrus, and at lower thresholds also in the right occipital lobe. However, when directly comparing the groups, greater priming-related reductions were found for the young group in the left anterior superior temporal gyrus and the right posterior occipital lobe. These findings suggest that, converse to current psychological views, aging affects both perceptual and lexical/semantic components of repetition priming.     

Repetition priming across the adult lifespan--the long and short of it

Previous reports suggest that repetition priming (i.e., enhanced processing of a stimulus after experience with that stimulus) is long lasting and impervious to the effects of age, in contrast to the pattern found with explicit memory. However, the nature of repetition priming in aged individuals remains unclear, as conflicting findings have also been reported. We used a longitudinal design to examine how repetition priming is affected by multiple stimulus repetitions (three presentations) and different delay intervals (no delay, 1 day, 1 week, and 1 month) in young adults, as well as in two groups of aging adults (young-elderly and old-elderly). Our findings extend previous reports that priming is long lasting, even when 1 month intervenes between the initial experience with an item and the subsequent priming test of that item (Cave, 1997), and is relatively impervious to the effects of age (Mitchell, et al., 1990). In addition, a more detailed characterization of priming and the effects of aging was revealed. Although priming is long lasting, remaining significant even at the month delay for all groups, it did decline over time and the rate of that decline differed with age. Both young-elderly and old-elderly groups showed a marked drop-off at 1 day, whereas young adults did not show a decline until 1 week. All groups benefited from multiple repetitions; however, this benefit disappeared at the month delay (in contrast to recognition memory, where the benefit remained significant). These findings support the assertion that repetition priming and explicit memory reflect the operation of distinct systems, and that these systems may undergo different rates of change in aging.     

Production and Identification Repetition Priming in AmnesticMild Cognitive Impairment

ABSTRACT

The experiment reported here examined implicit memory function, as measured through repetition priming, in amnestic mild cognitive impairment (MCI) to examine whether impairments exist in this aspect of memory function. Young adults, healthy older controls, Alzheimer's disease patients, and MCI participants were asked to perform two types of implicit memory tests (word stem completion and threshold identification repetition priming tasks), as well as a recognition test for studied items. As expected, young adults performed better than the other participants on the recognition test and the word stem completion task; there was equivalent priming across groups on the word identification task. While both the older control and MCI participants showed lower levels of priming on the word stem completion task relative to the young adults, the magnitude of priming was equivalent for these two groups, and reliably greater than that of the dementia participants. These results suggest that not all aspects of memory function are impaired in MCI relative to healthy aging.     

Explicit and implicit stereotype activation effects on memory: do age and awareness moderate the impact of priming?

Two studies examined the effects of implicit and explicit priming of aging stereotypes. Implicit primes had a significant effect on older adults' memory, with positive primes associated with greater recall than negative primes. With explicit primes, older adults were able to counteract the impact of negative stereotypes when the cues were relatively subtle, but blatant stereotype primes suppressed performance regardless of prime type. No priming effects under either presentation condition were obtained for younger adults, indicating that the observed implicit effects are specific to those for whom the stereotype is self-relevant. Findings emphasize the importance of social-situational factors in determining older adults' memory performance and contribute to the delineation of situations under which stereotypes are most influential.     

A speed-accuracy analysis of word recognition in young and older adults

To measure age differences in the rate of semantic priming, studies vary the prime-target interval in lexical decision (LD) tasks. This provides no time limit on the target response. Thus, older adults' greater response times (RTs) could offer them more accumulated priming at the response compared with younger, faster adults. This study used a response deadline procedure in an LD task to equalize processing time across age groups. Although RTs did not significantly differ across age groups, older adults showed larger semantic priming effects than young adults. Semantic priming was also found with response accuracy (d'), but did not differ across age.     

Loss of negative priming following sleep deprivation

It has been argued that one night of sleep loss in young healthy adults produces changes similar to that associated with normal, healthy ageing—in particular, that young sleep-deprived adults perform similarly to 60-year-old sleep-satiated adults on some tasks of frontal lobe function. This proposition was examined using a protocol viewed by many to be a direct probe of nonvolitional attention mechanisms associated with frontal lobe function. A negative priming (NP) procedure was used to compare performance between non-sleep-deprived (NSD) and sleep-deprived (SD, 34 hr) young, healthy adults. This protocol allowed for exploration of two theories of the NP effect based on inhibitory or memorial processes. Under conditions believed to facilitate inhibitory processes a normal NP effect was found for NSD(16 ms) and SD (9 ms) participants. Under conditions believed to rely on memorial processes there was no NPeffect following SD, compared with a normal NP effect for NSD participants (11 ms). Distractor interference was also greater following SD. These findings do not suggest a similar pattern of change following sleep loss in healthy young adults to that of normal, healthy, non-sleep-deprived aged groups.