Retrieval from long-term memory in senile dementia; cued recall revisited

Long-term memory cuing to reduce visuo-spatial disorientation in Alzheimer's disease patients in a special care unit

Visuo-spatial disorientation typically occurs relatively early in Alzheimer's disease patients, and is usually reported by families who fear that the individual may leave the house and get lost. It is often this deficit which frightens the family members into consideration of a long term care facility. However, disorientation to place can occur within a long term care facility as well as outside of it. This study will examine whether prominently displayed personal memorabilia of long term significance to each resident will serve as orientation cues to help identify his or her bedroom. The results indicate that four out of 10 residents were more successful in locating their rooms with significant memorabilia items than with nonsignificant ones.

Pattern separation and pattern completion in Alzheimer's disease: evidence of rapid forgetting in amnestic mild cognitive impairment

Over the past four decades, the characterization of memory loss associated with Alzheimer's disease (AD) has been extensively debated. Recent iterations have focused on disordered encoding versus rapid forgetting. To address this issue, we used a behavioral pattern separation task to assess the ability of the hippocampus to create and maintain distinct and orthogonalized visual memory representations in patients with amnestic mild cognitive impairment (aMCI) and mild AD. We specifically used a lag-based continuous recognition paradigm to determine whether patients with aMCI and mild AD fail to encode visual memory representations or whether these patients properly encode representations that are rapidly forgotten. Consistent with the rapid forgetting hypothesis of AD, we found that patients with aMCI demonstrated decreasing pattern separation rates as the lag of interfering objects increased. In contrast, patients with AD demonstrated consistently poor pattern separation rates across three increasingly longer lags. We propose a continuum that reflects underlying hippocampal neuropathology whereby patients with aMCI are able to properly encode information into memory but rapidly lose these memory representations, and patients with AD, who have extensive hippocampal and parahippocampal damage, cannot properly encode information in distinct, orthogonal representations. Our results also revealed that whereas patients with aMCI demonstrated similar behavioral pattern completion rates to healthy older adults, patients with AD showed lower pattern completion rates when we corrected for response bias. Finally, these behavioral pattern separation and pattern completion results are discussed in terms of the dual process model of recognition memory.

Lexical Priming in Alzheimer's Disease and Aphasia

Lexical priming was examined in patients with Alzheimer's disease and in aphasic patients. Control participants were divided into young and elderly [cf. Arroyo-Anlló et al.: Eur J Cogn Psychol 2004;16:535-553]. For lexical priming, a word-stem completion task was used. Normal elderly participants had lexical priming scores that were significantly lower than those of young individuals. Analysis of covariance with age and educational level as covariates showed that the control participants, aphasic and Alzheimer patients did not differ significantly on the lexical priming task. Our results suggest that performance in the lexical priming task diminishes with physiological aging, but is not significantly affected by mild or moderate Alzheimer's disease or by fluent or non-fluent aphasia.

Stem-completion priming in Alzheimer's disease: the importance of target word articulation

Stem-completion priming performance in patients with Alzheimer's type dementia (DAT) was explored in three experiments in which both the standard repetition priming effect and a novel indirect form of priming, cohort priming, were measured. In the first experiment, in which study stimuli were words, both priming effects were found to be markedly attenuated in the DAT group. In the second experiment, the study stimuli were specially constructed nonwords, and it was found that cohort priming was present at normal levels in the DAT group. In a third experiment we tested the specific hypothesis that the requirement to overtly articulate target stimuli during the study phase was critical for the appearance of normal cohort priming in the DAT group in Experiment 2, and also for the normal levels of repetition priming which have been reported in some published studies. Two encoding conditions were compared, one in which subjects simply had to read aloud the target words and a second in which subjects were required to make evaluative (pleasantness) ratings for each of the target words (identical to that used in Experiment 1). Stem-completion priming performance following the latter condition was significantly attenuated in the DAT group relative to a healthy control group, but following the "read aloud" encoding condition, normal levels of repetition and cohort priming were observed. It is suggested that the most fruitful approach to understanding the performance of DAT subjects on lexical repetition priming tasks will involve a detailed analysis of language functions and how they interact with other, possibly mnemonic, processes in the generation of primed responses.

Event-related desynchronization (ERD) patterns during memory processes: effects of aging and task difficulty

Event-related desynchronization (ERD) was studied in 10 young (mean age = 19.1) and 10 older (mean age = 62.8) subjects during two recognition tasks: verbal and visuo-spatial. The difficulty of these tasks varied according to the difficulty to distinguish between targets and distractors. EEGs recorded from 29 electrodes were used to compute ERDs from 14 source derivations in 125 msec intervals. Thereafter, they were displayed as spatio-temporal maps. The results show that desynchronization was more widespread in the visuo-spatial compared to the verbal task. This was observed in the two age groups, although it was more pronounced in the young subjects. The effect of task complexity was also influenced by the kind of material to be remembered: more differences between the two levels of difficulty were observed during the verbal task. The results revealed significant influences of the task and time variables on the ERD patterns. A distinct time course of the desynchronization phenomenon was observed to be related to the kind of recognition task. Age and task complexity interacted with the other variables.

Implicit verbal memory in Alzheimer's disease

Word stem completion and word identification were used in two repetition priming experiments to evaluate the implicit memory performance of Alzheimer's disease (AD) patients. This issue was also approached using various meta-analyses combining and contrasting previously reported data. While the experimental results suggested that AD patients present preserved repetition priming in both tasks, the meta-analytic approach showed an impairment in stem completion in comparison to word identification. Converging evidence cautiously suggested to accept the results of the meta-analysis. The above dissociation has been interpreted as showing differences in the specific contribution of data- and conceptually-driven processes in the two implicit tasks. A further meta-analysis on the effect of reduced perceptual availability of the study material on the same two tasks indicated that this variable affected repetition priming in word identification more heavily than in stem completion. The impact of such a dissociation on theories of implicit memory is discussed.

Event-related desynchronization (ERD) patterns during verbal memory tasks: effect of age

Event-related desynchronization (ERD) was studied in 10 young (mean age = 19.1) and 10 older (mean age = 62.8) subjects during a verbal recognition task. The attention load of the task varied according to the difficulty of discriminating between targets and distractors. EEG recorded from 29 electrodes was used to compute ERD from 14 source derivations in 125 ms intervals. Thereafter, it was displayed as spatiotemporal maps. The results show that attention influences the characteristics of EEG desynchronization. In young subjects, ERD is more pronounced and more widespread when the attentional load is high. In the elderly, differences between the two attention conditions are less marked. ANOVA reveals main effects of attention and time. The significant 'attention x time x age group' interaction confirms the presence of different brain activation patterns in the two age groups in relation to attention load.

Patients with dementia involving families to maximize nursing care

Incorporating family members in the care of patients with dementia provided pertinent psychosocial data, led to mutual decision-making regarding care, and produced changes in the responses of the residents with dementia, as well as in the family and nursing staff. The experimental group experienced increases in psychosocial nursing diagnoses with planning and interventions to meet the problems, more extensive problem description, and an active focus on interaction and change in the nurse's notes. As a result of collaborative nursing and family involvement, personal articles were brought from home; family collateral visits and interaction increased; families were more involved in the unit, medical center, and support groups; and p.r.n. medication use was decreased. As health-care technology prolongs the life of patients with chronic illness and sequelae such as dementia, nurses will need to continue to include families as collaborators in providing quality care.

Memory deficits in Alzheimer's patients: a comprehensive review

Despite considerable experimental work on Alzheimer's disease (AD), the underlying cognitive mechanisms as well as the precise localization of neuropathological changes critical for memory loss remains undefined. A review of the neuropsychological literature on long-term memory deficits in AD patients suggests that AD patients display (a) a pervasive deficit of explicit memory, (b) a partial deficiency of implicit memory for verbal and visuoperceptual material (as measured by repetition priming procedures), and (c) a substantial sparing of implicit memory for visuomotor skills. The explicit memory loss is likely a result of encoding as well as consolidation difficulties. A faulty lexical-semantic knowledge structure appears responsible for deficient repetition priming effects. Since neuropathological changes diffusely affect the brain of AD patients, establishing a clear relationship between localization of cerebral lesions and memory deficits is particularly difficult. Nevertheless, data suggest that extensive involvement of the hippocampal-amygdala complex plays a major role in explicit memory loss. Damage to associative cortical areas likely is involved in repetition priming deficits. The relative integrity of primary motor and sensory cortical areas and of the basal ganglia likely subsume, by contrast, the normal learning of visuomotor skills.

Encoding specificity, depth of processing, and cued recall in Alzheimer's disease

Unlike normal aging, Alzheimer's disease (SDAT) subjects typically show no benefit in free recall from semantic depth of processing cues at acquisition, but their recall is enhanced by semantic cues at both acquisition and retrieval. However, this apparent encoding-specificity effect might result from cued recall alone. SDAT and control subjects studied pictures in a design comparing depth of processing, cued recall, and encoding specificity. Cued recall alone was ineffective for SDAT subjects but, consistent with other studies, the encoding specificity condition did enhance recall. Both control and SDAT subjects also showed a levels of processing effect in free recall, modified by recency of presentation. Conclusions were: (a) though impaired in the capacity spontaneously to do so, SDAT subjects can be assisted to exploit semantic aspects of material in memory; (b) for optimal remembering in SDAT, substantial cued support should be provided at both ends of the processing continuum.

Explicit and implicit memory in dementia and normal ageing

In two experiments, young subjects, healthy elderly subjects (spouses), and highly intelligent elderly subjects (elite elderly), were compared with dementia patients in a variety of explicit and implicit memory tasks, to investigate two issues: whether priming in Alzheimer-type dementia is contingent upon the presence of pre-existing representations, and whether intelligence modulates performance in explicit memory tasks in healthy ageing. Dementia patients performed as well as spouses in a homo-phone-spelling task. Moreover, they established new contextual associations when memory was tested by word-stem completion. The hypothesis that priming in dementia is contingent upon pre-existing memory representations was not supported. Spouses, elite elderly, and young subjects did not differ in their ability to recognize correctly recently heard stimuli or to complete word stems. However, recall of lists of words and paired associates was better in both young and elite elderly subjects than in spouses. It is concluded that intellectual capacity rather than chronological age in healthy subjects modulates performance in explicit-memory tasks.

Direct and indirect memory performance in patients with senile dementia

The performance of patients with a presumptive clinical diagnosis of Senile Dementia of the Alzheimer's Type was compared to that of a group of normal elderly on several memory and neuropsychological tasks. The patients were impaired on tasks of free and cued recall, but exhibited normal performance on a word-completion procedure similar to that used by Graf et al. (1984). Reasons for the discrepancy between these findings and those from related research which reports impairment of word completion in patients with Alzheimer's Disease are discussed. Of particular interest is the role the orientating task plays in word-completion performance.

Cued recall and memory disorders in dementia

Memory functioning of normal elderly subjects and patients with suspected malignant memory disorders were examined using a cued recall memory assessment procedure. Levels of psychosocial functioning were rated by a multidisciplinary team. Ability to engage in free and cued recall was studied to determine the relationship between problems of acquisition and retrieval. Normal and impaired elderly showed strong differences on free recall and total recall resulting in 90.58% and 79.06% rates of accuracy of prediction of group membership. There were significant multivariate and univariate differences among the memory-impaired groups defined in terms of their psychosocial functioning. These findings indicate that differences in acquisition and retrieval are associated with increasing impairment of psychosocial functioning. Patients whose psychosocial functioning was rated as falling within the questionable range exhibited only deficits in retrieval. Patients whose psychosocial functioning was rated as more severely impaired, exhibited problems of retrieval and acquisition.

Cognitive and brain imaging measures of Alzheimer's disease

Diagnosis of Alzheimer's disease (AD) during life relies upon clinical and neurobehavioral symptoms but is presumptive without microscopic verification of neuropathology. Studies in this review observed considerable heterogeneity in AD symptoms and did not agree on how to detect the earliest symptoms. Problems exist in diagnosis. Differences in symptoms and diagnosis result from how AD is defined neurobehaviorally and on the model used for description. The studies reviewed have been considered under three basic models: A severity (staging) model; a heterogeneity (subtyping) model; and an information processing model. Differences in model intent have resulted in differences in disease description. Brain imaging measures have not invalidated models but add the neural substrate needed to examine correlation of measures within each model.

Cognitive functioning in Parkinson's disease: in relation to prevalence of dementia and psychiatric diagnosis

Forty-three neurologically and psychiatrically assessed patients with idiopathic Parkinson's disease (PD) underwent detailed cognitive assessment. Cognitive deficits typical of senile dementia of Alzheimer's type (SDAT) were found in 7% but the majority showed definite impairments not typical of SDAT. Cognitive impairment was significantly more likely in those with more severe PD symptoms. There was substantial agreement between psychiatric diagnosis and psychological picture of SDAT and some links were found between other diagnostic categories and nature of cognitive functioning. However, cognitive deficits were also found in two-thirds of patients with no psychiatric diagnosis.

The memory deficits in Alzheimer-type dementia: a review

This review is an account of recent experimental studies of memory deficits at the early stages of Alzheimer-type dementia, evaluating these studies in relation to current theories of memory functioning in humans. Whilst memory deficits are found to be widespread, some aspects are more resilient to impairment than others. For example, the processes associated with articulatory rehearsal in working memory are unimpaired despite a reduction in performance on most tests of primary memory. The “implicit” aspects of secondary memory appear to remain unimpaired, in contrast to a marked decline in “explicit” or “episodic” memory. In addition, there is evidence that the rate of forgetting from secondary memory is normal. Some aspects of episodic and semantic memory are found to be impaired as a consequence of a decline in the efficient organisation and processing of verbal material at encoding or retrieval. It is concluded that the deficits share particular features found in organic amnesia, but with additional deficits which relate to impairments in other domains of functioning.

Controlled and automatic information processing in senile dementia: a review

The evidence on cognitive decline in senile dementia is reviewed with respect to the distinction between controlled and automatic processing. It is argued that controlled processing, which requires the attentional resources of the individual, declines in early senile dementia. However, automatic processing, which does not require attentional resources, is well maintained until late in the disorder. Implications of this view are drawn for the development of effective screening instruments which can be used for the early detection of dementia in the general population.

Cued recall and the nature of the memory disorder in dementia

The study investigated the retrieval deficit hypothesis of forgetting in senile dementia, using a cued recall technique. Memory for lists of words was tested with either no cues given at the time of recall, or alternatively by cueing the patient either with the word's first letter or its semantic category. Results do not support a retrieval deficit explanation of forgetting in dementia, but instead suggest the possibility of a processing deficit at the acquisition stage.