Short- and long-term implicit memory in aging and Alzheimer's disease

Implicit memory processes were investigated via picture naming in healthy young and older adults and in persons with mild Alzheimer's disease (AD). Repetition priming in picture-naming was intact in all groups over the course of a short retention interval (seconds), and only the AD group revealed a deficit over a longer interval (72 hours). In addition, the AD group showed impaired procedural memory, with no benefit of practice on picture-naming. Impaired long-term priming was related to severity of AD. Both theoretical and methodological implications are discussed.     

Assessment of associative relations in alzheimer's disease: Evidence for preservation of semantic memory

Abstract

Semantic priming was assessed in Alzheimer's disease (AD), elderly control, and young control subjects with three lexical decision, continuous priming experiments. the stimuli were intracategory, associated pairs in Experiments 1 and 2 and varied types of associated pairs in Experiment 3. AD priming effects were equal to those of elderly control subjects; elderly and young control priming effects were also equal. We interpret this as evidence for the relative preservation of the semantic memory network in early AD, as in normal aging, at least to the extent necessary for normal access of concept nodes and normal automatic spreading activation between concept nodes. In a final study (Experiment 4) knowledge of the associations between the targets and related primes used in Experiments 1 and 2 was explicitly assessed; 20 out of 22 AD subjects showed perfect or close to perfect performance.     

Memories defining the self in Alzheimer’s disease

ABSTRACT

There is a debate over the extent to which personal identity or the self is preserved in patients with Alzheimer’s disease (AD). Autobiographical memory deficits at early stages of AD could contribute to altering patients’ self. However, the nature of the relationship between autobiographical memory deficits and the self in AD has not been much investigated experimentally. In the present study, we aimed to investigate the integrative meaning of self-defining memories (SDMs) in early stages of AD and to analyse its relationship with the self-concept. The results showed that, when compared to the control group, AD patients less frequently extracted meaning from their SDMs and the meaning was less frequently tied to the self. Patients exhibited some altered aspects of the self-concept (i.e., complexity and strength), though some other components still persisted (i.e., valence and certainty). Correlation analyses showed that the impaired integrative meaning in the AD group was correlated with some changes in self-concept. We suggest that integrative meaning may act as a bridge between autobiographical memories and the self-concept, with reduced integration abilities appearing as a potential mechanism for the deterioration of the self-concept in AD.     

Effects of age of acquisition and priming on picture naming

Four experiments examined the interaction of age of acquisition (AoA) and priming on picture naming. Experiment 1 found that initial-letter priming and AoA significantly affected picture-naming latencies, but there was no interaction between them. Experiment 2 found that initial-phoneme priming and AoA significantly affected picture-naming latencies, but again there was no interaction. Experiment 3 repeated Barry, Hirsh, Johnston, and Williams's (2001) priming study using a very short interval between prime and target. Experiment 3 replicated previous findings of a significant interaction between priming and AoA. Experiment 4 repeated this investigation with a procedure that did not require participants to articulate the prime. Once again, there were significant effects of priming, AoA, and the interaction between them. The implications of these findings in relation to accounts of AoA and its locus of effect are discussed.     

Effects of age of acquisition and priming on picture naming

Four experiments examined the interaction of age of acquisition (AoA) and priming on picture naming. Experiment 1 found that initial-letter priming and AoA significantly affected picture-naming latencies, but there was no interaction between them. Experiment 2 found that initial-phoneme priming and AoA significantly affected picture-naming latencies, but again there was no interaction. Experiment 3 repeated Barry, Hirsh, Johnston, and Williams's (2001) priming study using a very short interval between prime and target. Experiment 3 replicated previous findings of a significant interaction between priming and AoA. Experiment 4 repeated this investigation with a procedure that did not require participants to articulate the prime. Once again, there were significant effects of priming, AoA, and the interaction between them. The implications of these findings in relation to accounts of AoA and its locus of effect are discussed.     

The dissociation of repetition priming and recognition memory in language/learning-disabled children.

Recent research has found that the performance of learning-disabled and non-disabled children is dissociated on explicit and implicit tests of memory (Lorsbach & Worman, 1989). The current study further examined this phenomenon by comparing language/learning-disabled (L/LD) and nondisabled children (NLD) on tasks measuring primed picture-naming and item recognition. Included within the design of the experiment was the manipulation of both presentation format (pictures or words) and retention interval (immediate or 1 day). Children were initially presented with pictures and words. Performance was measured both immediately and following a 1-day retention interval on a picture naming task, an item recognition task, and a supplementary measure of memory for presentation format. The magnitude of facilitation associated with primed picture-naming was found to be independent of item recognition performance. In addition, the effects of population (L/LD and NLD) and retention interval (immediate test or 1 day) each produced dissociations between the magnitude of naming facilitation and item recognition performance. Results were discussed in terms of their implications for our understanding of the nature of memory difficulties in L/LD children.     

Convergent behavioral and neuropsychological evidence for a distinction between identification and production forms of repetition priming

Four experiments examined a distinction between kinds of repetition priming which involve either the identification of the form or meaning of a stimulus or the production of a response on the basis of a cue. Patients with Alzheimer's disease had intact priming on picture-naming and category-exemplar identification tasks and impaired priming on word-stem completion and category-exemplar production tasks. Division of study-phase attention in healthy participants reduced priming on word-stem completion and category-exemplar production tasks but not on picture-naming and category-exemplar identification tasks. The parallel dissociations in normal and abnormal memory cannot be explained by implicit-explicit or perceptual-conceptual distinctions but are explained by an identification-production distinction. There may be separable cognitive and neural bases for implicit modulation of identification and production forms of knowledge.     

Appraisal of Memory Functioning and Memory Performance in Healthy Ageing and Early-Stage Alzheimer's Disease

ABSTRACT

Background/Aims: To compare memory evaluations in healthy older people and people with Alzheimer's disease (AD) and present standardised individual and dyadic methods for classifying degree of memory awareness in the participants with dementia. Methods: Cross-sectional study evaluating awareness of memory functioning and performance and providing normative data for healthy individuals and couples, together with comparison data from people with AD. Results: As a group, older people are reasonably accurate raters of their own memory functioning and performance, although considerable individual differences can be observed, and control dyads show good comparative accuracy. Comparing normative data from the control group to data from participants with AD confirms that significant overestimation is a frequent feature among people with dementia, with approximately two-thirds showing this pattern, although significant under-estimation is also reliably observed in a small proportion of people with dementia. Different types of measure elicit different profiles of memory awareness in participants with dementia. Conclusion: Normative data from older individuals and couples provides useful percentile-based indices for determining level of memory awareness in people with dementia.     

Semantic priming occurs for word but not location pronunciation in the postcue task

Semantic priming refers to the finding that a word response is facilitated if it is preceded by a related word compared to when it is preceded by an unrelated word. Dallas and Merikle (Can J Psychol 30: 15–21 1976a; Bull Psychon Soc 8: 441–444 1976b) demonstrated that semantic priming occurred under conditions in which a pair of simultaneously displayed words was previewed for over a second prior to the onset of a cue indicating which of the words should be pronounced aloud (postcue task). In contrast, semantic interference effects have been reported for postcue picture-naming tasks (Dean et al. in J Exp Psychol Learn Mem Cogn 27: 733–743, 2001; Humphreys et al. in J Exp Psychol Learn Mem Cogn 21: 961–980, 1995). According to Dean et al., the semantic interference effects in postcue picture naming occur because the integration of the object and the cued attribute in memory is more difficult for categorically related pictures than for unrelated pictures. The aim of this experiment was to determine whether this idea was true for postcue word pronunciation tasks. Participants completed two postcue tasks, one requiring pronunciation of the target word indicated by a locational cue and another requiring pronunciation of the location of a centrally presented word. Results indicated a semantic priming effect only for the locational cue condition suggesting that the integration of the cue and identity information was unaffected by word context. These data suggest that priming in a postcue word pronunciation task may be due to feedback from residual activation within the semantic system facilitating access to the target word’s phonology.     

Visual Imagery Processing and Knowledge of Famous Names in Alzheimer's Disease and MCI

ABSTRACT

The study of memory for famous people and visual imagery retrieval was investigated in patients in the early stages of Alzheimer's disease (AD) and in the prodromal stage of AD, so-called Mild Cognitive Impairment (MCI). Fifteen patients with AD (MMSE ≥23), 15 patients with amnestic MCI (a-MCI) and 15 normal controls (NC) performed a famous names test designed to evaluate the semantic and distinctive physical features knowledge of famous persons. Results indicated that patients with AD and a-MCI generated significantly less physical features and semantic biographical knowledge about famous persons than did normal control participants. Additionally, significant differences were observed between a-MCI and AD patients in all tasks. The present findings confirm recent studies reporting semantic memory impairment in MCI. Moreover, the current findings show that mental imagery is lowered in a-MCI and AD and is likely related to the early semantic impairment.     

Transfer of processing in repetition priming: some inappropriate findings.

Transfer effects in repetition priming were found with both picture and word naming, but varied with the type of prime list. Unmixed lists of word or picture primes produced equivalent intra-modal and cross-modal repetition priming in both picture-naming (Experiment 1) and word-naming (Experiment 5) tasks. However, mixing word and picture primes resulted in greater intra-modal than cross-modal priming for both picture-naming (Experiment 2) and word-naming (Experiment 6) tasks. This mixed-list difference between intra-modal and cross-modal priming was reduced by blocking prime types at input (Experiment 3). These findings suggest that differences in priming as a function of prime stimulus format should be cautiously interpreted when mixed prime lists are used.     

The usefulness of the story recall test in patients with mild cognitive impairment and Alzheimer's disease

ABSTRACT

Background: The story recall test (SRT) is one of the most reliable neuropsychological assessments for evaluating verbal memory function in order to distinguish between individuals with normal aging, mild cognitive impairment (MCI), and Alzheimer's disease (AD). The SRT is analogous to the logical memory test in Wechsler Memory Scale-III, which has recently been developed and standardized to apply to older adults in Korea. The purpose of this study was to examine the usefulness of the SRT and its ability to discriminate between normal cognitive aging and patients with MCI or AD. Methods: One hundred and twelve patients with MCI, 97 patients with AD, and 53 healthy elderly adults participated in this study. The SRT was compared with the Clinical Dementia Rating (CDR), Global Deterioration Scale (GDS), Korean version of the Mini Mental State Examination (K-MMSE), and the Korean version of the Hopkins Verbal Learning Test (K-HVLT). Results: The SRT was well-correlated with the dementia rating scales and the K-HVLT. However, the sensitivity and specificity of the SRT was greatly influenced by the level of education of the subjects. Conclusions: The SRT is a sensitive measurement of verbal memory function that can be used in clinical settings to discriminate between normal memory functioning and the very early and moderate stages of AD in a Korean population. Moreover, it is important to recognize that the SRT is more appropriate for subjects with a high level of education rather than a low level of education to differentiate normal cognitive aging from MCI or AD.     

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.     

Differential Memory Test Sensitivity for Diagnosing Amnestic Mild Cognitive Impairment and Predicting Conversion to Alzheimer's Disease

ABSTRACT

Episodic memory is the first and most severely affected cognitive domain in Alzheimer's disease (AD), and it is also the key early marker in prodromal stages including amnestic mild cognitive impairment (MCI). The relative ability of memory tests to discriminate between MCI and normal aging has not been well characterized. We compared the classification value of widely used verbal memory tests in distinguishing healthy older adults (n = 51) from those with MCI (n = 38). Univariate logistic regression indicated that the total learning score from the California Verbal Learning Test-II (CVLT-II) ranked highest in terms of distinguishing MCI from normal aging (sensitivity = 90.2; specificity = 84.2). Inclusion of the delayed recall condition of a story memory task (i.e., WMS-III Logical Memory, Story A) enhanced the overall accuracy of classification (sensitivity = 92.2; specificity = 94.7). Combining Logical Memory recognition and CVLT-II long delay best predicted progression from MCI to AD over a 4-year period (accurate classification = 87.5%). Learning across multiple trials may provide the most sensitive index for initial diagnosis of MCI, but inclusion of additional variables may enhance overall accuracy and may represent the optimal strategy for identifying individuals most likely to progress to dementia.     

Musical Memory in Alzheimer Disease

ABSTRACT

This study examines musical memory in 12 patients with moderate or severe AD and 12 healthy, older adult controls. Participants were asked to distinguish familiar from novel tunes, to identify distortions in melodies, and to sing familiar tunes. Comparison of the AD and control groups showed significant impairment of the AD participants. However, a more complex picture emerged as we compared each individual case to the control group. Five of the AD group performed within the control group range on most tasks. An additional four participants showed partial sparing in that they performed below the range of control participants, but their scores were above the level of chance. The final three participants showed near complete loss of musical memory, as their performance was consistently at or near the level of chance. These results are discussed in terms of the literature on the heterogeneity of cognitive presentation in AD.     

Time-dependent forgetting in visual short-term memory

ABSTRACT

Whether visual short-term memory can be lost over an unfilled delay, in line with time-dependent forgetting, is controversial and prior work has yielded mixed results. The present study explored time-dependent forgetting in visual short-term memory in relation to other factors. In three experiments, participants compared single target and probe objects over a 2 s or 10 s retention interval. The objects across trials were either similar or dissimilar (Experiment 1) and had to be remembered in the presence of an additional distractor (Experiment 2) or under conditions where the amount of time separating trials varied (Experiment 3). In all experiments, the retention interval manipulation made the biggest contribution to performance, with accuracy decreasing as the retention interval was lengthened from 2 s to 10 s. These results pose problems for interference and temporal distinctiveness models of memory but are compatible with temporal forgetting mechanisms such as decay.     

Mental representation and learning: The influence of practice on the development of mental representation structure in complex action

ObjectivesRecent research has elicited distinct differences in mental representations between athletes of different skill levels. Such differences suggest that the structure of mental representations changes as a function of skill level. However, research examining how such mental representation structures develop over the course of learning is lacking. In the present study, we examine the effects of practice on the development of one's mental representation of a complex action during early skill acquisition.DesignFor this purpose, we created a controllable learning situation, using a repeated-measures design with a control group. More specifically, novice golfers were randomly assigned to either a practice group (n = 12) or a control group (n = 12). Both groups were tested before and after an acquisition phase of three days as well as after a three day retention interval.MethodsMental representation structures of the putt were recorded, employing the structural dimensional analysis of mental representation (SDA-M), which provides psychometric data on the structure and grouping of action concepts in long-term memory. In addition, outcome performance of the practice group was measured, using two-dimensional error scores of the putt.ResultsFindings revealed a significant improvement in task performance, as well as functional changes in the structure of the practice group's mental representation. In contrast, no functional adaptations were evident in the mental representation of the control group.ConclusionOur findings suggest that motor skill acquisition is associated with functional adaptations of action-related knowledge in long-term memory.     

Gender Priming in Picture Naming: Modality and Baseline Effects

Gender priming in speech production relates to the issue of whether retrieval of a noun is facilitated by preactivation of its grammatical gender. Such gender-to-lexical entry priming has been considered the mechanism underlying the gender-identity effect in word substitution errors (i.e., a substituted word tends to have the same gender as the target word.) Gender priming was explored in two primed picture-naming experiments with German participants. Primes were presented either visually or auditorily and differed in whether they carried grammatical gender information or not. Unlike inhibition from a gender-incongruent prime, facilitation from a gender-congruent prime was weak, not reliable, and dependent on the baseline and prime modality. Implications for the interpretation of the gender-identity effect are discussed.     

Five weeks of immersive reminiscence therapy improves autobiographical memory in Alzheimer’s disease

ABSTRACT

We examined the effects of a new Immersive Reminiscence Therapy (IRT) programme on cognitive function, including autobiographical memory, in a sample Alzheimer’s disease (AD) patients. A total of 43 AD patients with mild to moderate disease severity were randomly assigned to either an intervention group (n?=?22, MMMSE?=?20.77), or a control group (n?=?21, MMMSE?=?19.24). The intervention group received one weekly group-based session of IRT for five weeks in an authentic 1950s style museum environment, matching the time of the participants’ youth. IRT included semi-structured conversations about the past. The control group received standard care. We assessed performance on cognitive function and autobiographical memory at baseline and post-intervention. Five weeks of IRT enhanced subsequent autobiographical memory performance, when participants were cued by concrete objects dated to their youth. Object-cued memories reported post intervention included a significantly higher degree of episodic details and higher word counts. The intervention showed no effect on the Autobiographical Memory Interview or word-cued recall. Global cognitive function and semantic autobiographical memory performance increased across time for both groups. Our findings demonstrate that immersion into a setting, rich on concrete cues dated to the participants’ youth can improve autobiographical remembering.     

Long-term positive and negative identity priming: Evidence for episodic retrieval

An episodic retrieval account of negative priming (Neill, 1997; Neill & Valdes, 1992) was evaluated in three experiments. Duringpractice, regular word pairs were presented to subjects differing numbers of times. The subjects named specific target words while they ignored specific distractor words. Following a 5-min retention interval, memory for practice was revealed:Test responses for target words exhibited positive priming that increased with increases in the number of times that the words had been attended. Test responses for distractor words exhibited either positive priming (Experiment 1) or negative priming (Experiments 2–3) that also increased with increases in the number of times that the words had been ignored. The type of priming that abstractors exhibited was determined by several contextual similarities between the practice environment, in which distractors were ignored initially, and the test environments, in which they were processed subsequently. Negative priming that spanned a 5-min interval, increased with increases in the number of times that a distractor was ignored, and was sensitive to contextual changes indicated that the direction of the effect was temporally backward because the test probe cued memory for earlier processing of the priming stimulus when the distractor had been ignored.