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.     

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.     

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.     

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.     

Persistent repetition priming in picture naming and its dissociation from recognition memory

The current experiments investigated the longevity of repetition priming and dissociations between different memory measures. Picture-naming latencies revealed robust repetition priming in four separate studies: Previously named pictures were named faster than new pictures. The magnitude of this naming facilitation was stable across 1 to 6 weeks. The apparent temporal invulnerability of repetition priming was in marked contrast to the decline in episodic recognition memory across 6 weeks, suggesting a dissociation between implicit and explicit memory. Additional evidence of this dissociation was observed within each session: Naming facilitation for repeated pictures occurred regardless of whether those particular pictures were consciously recognized.     

Repeated study of items with and without repeated context: aging effects on memory discriminability

Presenting items multiple times during encoding is a common way to enhance recognition accuracy. Under such conditions, older adults often show an increase in false recognition that counteracts benefits of repeated study. Using a false-memory paradigm with related study items and related lures, we tested whether repetition within the same encoding task or repetition across two different encoding tasks would be more beneficial to older adults’ memory discriminability. Results showed that, compared to items not repeated at study, items repeated in the same context and items repeated across different contexts showed improvements in memory discriminability in both young and older adults. This improvement was primarily reflected in improved recollection responses for both age groups across both repeat study conditions, as compared to no repetition. Importantly, the results demonstrated that repetition can be used to successfully mitigate age-related deficits by increasing memory discriminability and without incurring a cost of false recognition specific to any one age group.     

Recognizing images: The role of motivational significance,complexity, social content,age, and gender

Memory for affective events plays an important role in determining people’s behavior and well-being. Its determinants are far from being completely understood. We investigated how recognition memory for affective pictures depends on pictures’ motivational significance (valence and arousal), complexity (figure-ground compositions vs. scenes), and social content (pictures with people vs. without people) and on observers’ age and gender. Younger, middle-aged, and older adults viewed 84 pictures depicting real-life situations. After a break, the participants viewed 72 pictures, half of which had been viewed previously and half of which were novel, and were asked to endorse whether each picture was novel or had been presented previously. Hits, false alarms, and overall performance (discrimination accuracy) were our dependent variables. The main findings were that, across participants, recognition memory was better for unpleasant than pleasant pictures and for pictures depicting people than pictures without people. Low-arousal pictures were more accurately recognized than high-arousal pictures, and this effect was significantly larger among middle-aged and older adults than younger adults. Recognition memory worsened across adulthood, and this decline was steeper among men than women. Middle-aged and older women outperformed their male counterparts. This study suggests that how well we are able to successfully discriminate previously seen pictorial stimuli from novel stimuli depends on several pictures’ properties related to their motivational significance and content, and on observer’s age and gender.     

Implicit and explicit memory in young and older adults

In three experiments, young and older adults were compared on both implicit and explicit memory tasks. The size of repetition priming effects in word completion and in perceptual identification tasks did not differ reliably across ages. However, age-related decrements in performance were obtained in free recall, cued recall, and recognition. These results, similar to those observed in amnesics, suggest that older adults are impaired on tasks which require conscious recollection but that memory which depends on automatic activation processes in relatively unaffected by age.     

Autobiographical memory specificity predicts social problem-solving ability in old and young adults

Based on recent research with young, depressed adults, age-related cognitive declines and decreased autobiographical specificity were hypothesized to predict poorer social problem-solving ability in older than in younger healthy adults. Priming autobiographical memory (ABM) was hypothesized to improve social problem-solving performance for older adults. Subsequent to cognitive tests, old and young participants' specific ABMs were tested using a cued recall task, followed by a social problem-solving task. The order of the tasks was counterbalanced to test for a priming effect. Autobiographical specificity was related to cognitive ability and predicted social problem-solving ability for both age groups. However, priming of ABM did not improve social problem-solving ability for older or younger adults. This study provides support for the hypothesis that autobiographical memory serves a directive function across the life-span.     

Autobiographical memory specificity predicts social problem-solving ability in old and young adults

Based on recent research with young, depressed adults, age-related cognitive declines and decreased autobiographical specificity were hypothesized to predict poorer social problem-solving ability in older than in younger healthy adults. Priming autobiographical memory (ABM) was hypothesized to improve social problem-solving performance for older adults. Subsequent to cognitive tests, old and young participants' specific ABMs were tested using a cued recall task, followed by a social problem-solving task. The order of the tasks was counterbalanced to test for a priming effect. Autobiographical specificity was related to cognitive ability and predicted social problem-solving ability for both age groups. However, priming of ABM did not improve social problem-solving ability for older or younger adults. This study provides support for the hypothesis that autobiographical memory serves a directive function across the life-span.     

Age differences in implicit memory: conceptual, perceptual, or methodological?

The authors examined age differences in conceptual and perceptual implicit memory via word-fragment completion, word-stem completion, category exemplar generation, picture-fragment identification, and picture naming. Young, middle-aged, and older participants (N = 60) named pictures and words at study. Limited test exposure minimized explicit memory contamination, yielding no reliable age differences and equivalent cross-format effects. In contrast, explicit memory and neuropsychological measures produced significant age differences. In a follow-up experiment, 24 young adults were informed a priori about implicit testing. Their priming was equivalent to the main experiment, showing that test trial time restrictions limit explicit memory strategies. The authors concluded that most implicit memory processes remain stable across adulthood and suggest that explicit contamination be rigorously monitored in aging studies.     

Intact and long-lasting repetition priming in amnesia.

In 2 experiments, we evaluated the ability of amnesic patients to exhibit long-lasting perceptual priming after a single exposure to pictures. Ss named pictures as quickly as possible on a single occasion, and later named the same pictures mixed with new pictures. In Experiment 1, amnesic patients exhibited fully intact priming effects lasting at least 7 days. In Experiment 2, the priming effect for both groups was shown to depend on both highly specific visual information and on less visual, more conceptual information. In contrast, recognition memory was severely impaired in the patients, as assessed by both accuracy and response time. The results provide the first report of a long-lasting priming effect in amnesic patients, based on a single encounter, which occurs as strongly in the patients as in normal Ss. Together with other recent findings, the results suggest that long-lasting priming and recognition memory depend on separate brain systems.     

Exploring the identification-production hypothesis of repetition priming in young and older adults

The identification-production hypothesis of age-related differences in repetition priming predicts reduced priming in older adults on indirect memory measures that require stimulus production (production priming) together with age constancy on indirect measures that require stimulus identification, verification, or classification processes (identification priming). Although some evidence is consistent with this hypothesis, comparisons of identification and production priming in young and older adults often confound stimulus, subject, and dependent measure factors across tasks. Consequently, repetition priming has yet to be assessed in healthy young and healthy older adults using identification and production tasks that control for these factors. The identification-production hypothesis was tested using verb generation as a measure of production priming (Experiments 1-3) and semantic classification (Experiment 1) or semantic verification (Experiments 2 and 3) as the measure of identification priming. Contrary to the identification-production hypothesis, no age-related diminutions in identification or production forms of priming were found.     

Older adults encode more,not less: evidence for age-related attentional broadening

Previous work has shown that older adults attend to and implicitly remember more distracting information than young adults; however, it is unknown whether they show a corresponding decrease in implicit memory for targets in the presence of distracters. Using implicit memory tests, we asked whether older adults show a tradeoff in memory between targets and distracters. Here, young and older adults performed a selective attention task in which they were instructed to attend to target pictures and ignore superimposed distracter words. We measured priming for distracter words using fragment completion and for target pictures using naming time. Older adults showed greater priming for distracting words compared to young adults, but equivalent priming for target pictures. These results suggest that older adults have a broader attentional scope than young adults, encompassing both relevant and irrelevant information.     

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.     

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.     

Aging selectively impairs recollection in recognition memory for pictures: evidence from modeling and receiver operating characteristic curves

Young and older adults were tested on recognition memory for pictures. The Yonelinas high threshold (YHT) model, a formal implementation of 2-process theory, fit the response distribution data of both young and older adults significantly better than a normal unequal variance signal-detection model. Consistent with this finding, nonlinear z-transformed receiver operating characteristic curves were obtained for both groups. Estimates of recollection from the YHT model were significantly higher for young than for older adults. This deficit was not a consequence of a general decline in memory; older adults showed comparable overall accuracy and in fact a nonsignificant increase in their familiarity scores. Implications of these results for theories of recognition memory and the mnemonic deficit associated with aging are discussed.     

Word-list-learning performance in younger and older adults: intra-individual performance variability and false memory

We investigated the word-list-learning performance of younger and older adults over 4 consecutive days at different times of day to study age-related differences in consistency of performance over time and the influence of circadian variation on performance. Eighteen younger (M age, 23.4 years) and 18 older (M age, 73.3 years) men and women participated. The start time of testing alternated between morning and early evening across the 4 days of testing. On each test day, participants learned a different list of 15 unrelated words over four learning trials. As expected, younger adults performed better than older adults on immediate recall, delayed recall, and recognition. Contrary to our expectations, time of day did not significantly influence recall or recognition performance in either the older or younger adults. Older adults did show a greater incidence of false memory (i.e., previously learned list intrusions in free recall and false alarms in recognition) than younger adults. Older adults also exhibited greater intra-individual performance variability on the measures of false memory across test days. This variability was not related to circadian variation. False memory and variability of performance have both been linked to frontal systems dysfunction. The findings presented here are consistent with the notion that changes in cognition with aging in part reflect age-related decline in frontal lobe function.     

Self-referencing enhances memory specificity with age

Self-referencing has been identified as an advantageous mnemonic strategy for young and older adults. However, little research has investigated the ways in which self-referencing may influence older adults' memory for details, which is typically impaired with age, beyond memory for the item itself. Experiment 1 assessed the effects of self- and other-referencing on memory for visually detailed pictures of objects in thirty-two young and thirty-two older adults. Results indicate that self- and close other-referencing similarly enhance general (item) and specific (detail) recognition for both young and older adults relative to the distant other condition. Experiment 2 extended these findings to source memory, with young and older adults encoding verbal information in self-referent, semantic, and structural conditions. Findings suggest that self-referencing provides an age-equivalent boost in general memory and specific memory for specific source details. We conclude that the mnemonic benefits of referencing the self extend to specific memory for visual and verbal information across the lifespan.     

Aging and the Deletion Function of Inhibition

The present study was adapted from the sentence completion task of Hartman and Hasher (1991). We addressed the question raised by Burke (1997): are the age-related differences in priming effects found in that task better explained by deficits in explicit memory or by inefficient inhibitory mechanisms? In the study phase, older and younger adults read high cloze sentences ending with an expected or an unexpected final word. In the second phase, participants were asked to complete sentence frames with either the final word presented during the study phase (inclusion condition) or with another, new word (exclusion condition). The third phase was an indirect memory test of perceptual identification. Finally, we compared explicit memory for recalled and inhibited words in a recognition test. In perceptual identification by older adults, priming was equivalent for recalled and inhibited words, whereas in younger adults priming was higher for recalled than for inhibited words. In the explicit memory test, recognition scores were lower for inhibited words in both age groups. These results are consistent with the view of Hasher and Zacks (1988), who assume an age-related decline in the ability to suppress no-longer-relevant information