Implicit memory in Alzheimer's disease

Exploring why "memory loss" is a misleading descriptor of people living with dementia and can lead to dysfunctional care

Amidst goals for prevention and improved treatment for people living with dementia, much remains needed to enhance the quality of life of those currently diagnosed, especially the transfer of accurate information from professionals to the public. Although many healthcare professionals understand the various types of memory and which are likely to be more affected than others during the progression of dementia, lay persons are more frequently unaware of that important information. The terms used to describe the symptoms of dementia can have a great impact on perceptions of faculties that are absent, compromised, or preserved. Understanding the nuances of preserved memory faculties and other cognitive abilities retained by persons with dementia is important in this regard. The term "memory loss" as a descriptor of the syndrome of dementia and ascribing it to persons with dementia connotes an inability to form new memories and participate in meaningful social interactions, which is detrimental to their personhood. From a multidisciplinary approach drawn from neurology, neurobiology, psychology, and case vignettes, we aim herein to highlight the ways in which the term "memory loss" can be inaccurate, counterproductive and potentially promote dementia-related misperceptions, malignant positioning and malignant social psychology. Persons with dementia unequivocally struggle with explicit memory, or recalling on demand, but retain implicit memory, as evidenced by research and everyday actions. Therefore, we propose the use of alternative medical language to reflect accurately memory impairment and preservation of some important memory capabilities.

Why is music therapeutic for neurological disorders? The Therapeutic Music Capacities Model

Music has cognitive, psychosocial, behavioral and motor benefits for people with neurological disorders such as dementia, stroke, Parkinson's disease (PD) and Autism Spectrum Disorder (ASD). Here we discuss seven properties or 'capacities' of music that interact with brain function and contribute to its therapeutic value. Specifically, in its various forms, music can be engaging, emotional, physical, personal, social and persuasive, and it promotes synchronization of movement. We propose the Therapeutic Music Capacities Model (TMCM), which links individual properties of music to therapeutic mechanisms, leading to cognitive, psychosocial, behavioral and motor benefits. We review evidence that these capacities have reliable benefits for people with dementia, stroke, PD and ASD when employed separately or in combination. The model accounts for the profound value that music affords human health and well-being and provides a framework for the development of non-pharmaceutical treatments for neurological disorders.

Event perception: Translations and applications

Event segmentation is the parsing of ongoing activity into meaningful events. Segmenting in a normative fashion-identifying event boundaries similar to others' boundaries-is associated with better memory for and better performance of naturalistic actions. Given this, a reasonable hypothesis is that interventions that improve memory and attention for everyday events could lead to improvement in domains that are important for independent living, particularly in older populations. Event segmentation and memory measures may also be effective diagnostic tools for estimating people's ability to carry out tasks of daily living. Such measures preserve the rich, naturalistic character of everyday activity, but are easy to quantify in a laboratory or clinical setting. Therefore, event segmentation and memory measures may be a useful proxy for clinicians to assess everyday functioning in patient populations and an appropriate target for interventions aimed at improving everyday memory and tasks of daily living.

The effect of natural environments upon agitation and aggression in late stage dementia patients

Agitated aggressive behavior in late stage dementia occurs in 30 to 50 percent of patients. This behavior often results in the use of chemical and physical restraints (which have a high degree of untoward side effects) and caregiver burnout. Interventions for agitated aggressive behavior are needed that do not have these side effects, which are readily available in nursing homes and are effective and acceptable to caregivers. Environmental psychologists have proposed that natural elements within the environment decrease agitation in the nondemented as well as the demented Since the shower bath is often a time of great agitation in dementia patients, natural elements were used to modify care during the shower bath (n = 31). There was a significant decrease in mean difference scores from baseline to treatments one and two, with the treatment group demonstrating an overall decline in agitated aggressive behavior Additional randomized trials of the effects of natural environments upon agitation and aggression in dementia are needed.

Awareness Deficits in Alzheimer's Disease: Issues in Assessment and Intervention

Unawareness of deficits is a challenging problem frequently encountered in individuals with Alzheimer's disease (AD). Understanding mediating and causative factors of unawareness is important for accurate assessment and effective intervention. However, clinicians should also consider the variability that is often present between and within AD patients and should avoid the use of dichotomous classifications of unawareness. In this article, current knowledge generated by both neurosciences and behavioral sciences provides the basis for identifying issues and offering recommendations pertinent to assessment and intervention of awareness deficits m AD. Remedial and compensatory efforts used with head-injured patients may have potential application to dementia patients with awareness deficits, especially for those in earlier stages. Knowledge in this area is still in an early stage of investigation. As more is known about the nature of awareness deficits, it will be possible to design more effective approaches based on the characteristics of individual patients.

Object-location memory in adults with autism spectrum disorder

This study tested implicit and explicit spatial relational memory in Autism Spectrum Disorder (ASD). Participants were asked to study pictures of rooms and pictures of daily objects for which locations were highlighted in the rooms. Participants were later tested for their memory of the object locations either by being asked to place objects back into their original locations or into new locations. Proportions of times when participants choose the previously studied locations for the objects irrespective of the instruction were used to derive indices of explicit and implicit memory [process-dissociation procedure, Jacoby, 1991, 1998]. In addition, participants performed object and location recognition and source memory tasks where they were asked about which locations belonged to the objects and which objects to the locations. The data revealed difficulty for ASD individuals in actively retrieving object locations (explicit memory) but not in subconsciously remembering them (implicit memory). These difficulties cannot be explained by difficulties in memory for objects or locations per se (i.e., the difficulty pertains to object-location relations). Together these observations lend further support to the idea that ASD is characterised by relatively circumscribed difficulties in relational rather than item-specific memory processes and show that these difficulties extend to the domain of spatial information. They also lend further support to the idea that memory difficulties in ASD can be reduced when support is provided at test.

Automatic and Controlled Uses of Memory in Alzheimer's Disease

This study used the process-dissociation procedure (Jacoby, 1991) to examine the contribution of automatic and controlled uses of memory to a stem completion task in 16 patients with Alzheimer's disease (AD) and a matched group of healthy elderly subjects (EC). In an inclusion task subjects attempted to use a studied word to complete three-letter word stems, in an exclusion task they were instructed to complete stems with unstudied words. Relative to patients with AD, EC subjects produced more target word completions under inclusion conditions, and less target word completions under exclusion conditions. The probability of the AD group using studied words to complete stems was invariant across inclusion and exclusion conditions. Estimates derived from the process-dissociation calculations, showed that the performance of the AD patients was mediated entirely by automatic uses of memory, whereas for EC subjects controlled and automatic processes codetermined task performance. Both estimates of controlled and to a lesser extent automatic uses of memory were greater for the EC than the AD subjects, indicating that the stem completion impairment in AD may not be entirely attributable to a deficiency in controlled memory processes but also due to reduced automatic processing.

Word-stem completion task to investigate semantic network in patients with Alzheimer's disease

Semantic impairment in patients with Alzheimer's disease (AD) is revealed by tasks of verbal naming, verbal fluency, and semantic knowledge. Causes of the deficit remain unclear in spite of many studies to investigate whether AD patients suffer from the inability to have voluntary access to an almost intact semantic store or from its break down. Word-stem completion (WSC) tasks have been utilized in healthy subjects in order to study semantic memory and network by exploiting the possibility of the involuntary access to them. Available conflicting data refer to the presence of semantic prime in AD patients. To explore the semantic network in AD, patients were requested to complete with the first word that sprang to their mind a stem submitted immediately after presentation of the word prime, as a WSC task. Stems consisted of the three beginning letters of words that were semantically related to primes. We compared data obtained with this task from patients with mild to moderate AD with those from normal controls (NC). AD patients completed less stems (P<0.001) with the expected words than NC, suggesting a break down of the semantic network rather than a deficit in the access to the semantic store.

Implicit and explicit memory for spatial information in Alzheimer's disease

There is abundant evidence that memory impairment in dementia in patients with Alzheimer's disease (AD) is related to explicit, conscious forms of memory, whereas implicit, unconscious forms of memory function remain relatively intact or are less severely affected. Only a few studies have been performed on spatial memory function in AD, showing that AD patients' explicit spatial memory is impaired, possibly related to hippocampal dysfunction. However, studies on implicit spatial memory in AD are lacking. The current study set out to investigate implicit and explicit spatial memory in AD patients (n=18) using an ecologically valid computer task, in which participants had to remember the locations of various objects in common rooms. The contribution of implicit and explicit memory functions was estimated by means of the process dissociation procedure. The results show that explicit spatial memory is impaired in AD patients compared with a control group (n=21). However, no group difference was found on implicit spatial function. This indicates that spared implicit memory in AD extends to the spatial domain, while the explicit spatial memory function deteriorates. Clinically, this finding might be relevant, in that an intact implicit memory function might be helpful in overcoming problems in explicit processing.

Use of preferred music to decrease agitated behaviours in older people with dementia: a review of the literature

AIMS AND OBJECTIVES

This paper reviews study findings of preferred music on agitated behaviours for older people with dementia and provides implications for future research and practice.

BACKGROUND

Music has been suggested as a feasible and less costly intervention to manage agitated behaviours in older people with dementia. However, no review of the literature focusing on study findings of preferred music on agitated behaviours in older people with dementia had been reported.

METHODS

A review was undertaken using electronic databases with specified search terms for the period of 1993-2005. The references listed in the publications selected were also searched for additional studies.

RESULTS

Eight research-based articles met the inclusion criteria and were included in the review. The preferred music intervention demonstrated positive outcomes in reducing the occurrence of some types of agitated behaviours in older people with dementia. The findings from these studies were relatively consistent in finding improvement in agitated behaviours although the findings in one study did not reach statistical significance. The small sample sizes and some variations in the application of the preferred music intervention mean that caution is needed in drawing conclusions from these studies.

CONCLUSIONS

This review highlights that preferred music has positive effects on decreasing agitated behaviours in older people with dementia; however, the methodological limitations indicate the need for further research.

RELEVANCE TO CLINICAL PRACTICE

Findings from the review highlight the beneficial outcomes of preferred music in reducing agitated behaviours for older people with dementia. The incorporation of preferred music has the potential to provide a therapeutic approach to the care of older people with dementia.

Implicit memory and familiarity among elders with dementia

PURPOSE

To propose a framework for familiar environment as a cue for maintaining or maximizing functional abilities in elders with dementia.

ORGANIZING CONSTRUCT

The organizing construct is the sense of familiarity. Although a feeling of familiarity can be processed in both explicit and implicit memory in normal populations, it is retrieved more frequently and efficiently in the implicit memory system than through explicit memory in elders with dementia.

METHODS

The model was developed using sources identified through a literature search of relevant topics in Medline, PsycInfo, and CINAHL, as well as through clinical observations and experiences.

CONCLUSIONS

Evidence from neuro- and cognitive psychology indicates that elders with dementia or Alzheimer's disease (AD) have impaired explicit memory but preserved implicit memory. For initiating an intervention related to spared implicit memory, we propose that implicit memory can be used therapeutically in patients with dementia. The sense of familiarity as a form of implicit memory is used as an exemplar. Producing or introducing the sense of familiarity into a new or strange environment as well as maximizing familiarity in an existing environment is proposed as a viable nursing strategy.

The impact of semantic impairment on word stem completion in Alzheimer's disease

Both the extent of semantic memory impairment and the level of processing attained during encoding might constitute critical factors in determining the amount of word-stem completion (WSC) priming encountered in Alzheimer's disease (AD) subjects. We investigated the impact of varying encoding level in AD and elderly normal subjects, using a set of stimuli ranked as "intact" or "degraded" in terms of each subject's semantic knowledge on probe questions. For both shallow and deep encoding conditions, overall priming in the two subject groups was equivalent. However, for the deep encoding condition, consisting of a semantic judgment task performed on each target word, the priming effect noted in AD subjects was significantly smaller for semantically degraded items than for semantically intact items. Results indicate that the degree of semantic impairment represents one important variable affecting the amount of WSC priming which results when deep encoding procedures are used at study.

Rates of forgetting in Alzheimer dementia

Patients diagnosed with Alzheimer's disease (AD) were compared with healthy controls on a picture recognition task, a forced choice word recognition task, a forced choice design recognition task, a picture recall task and a stem completion task. Performance on recognition and word stem completion was assessed at 1, 10 and 20 min after exposure to experimental stimuli, as these are delays across which previous studies had suggested there might be differing forgetting rates. AD patients did not show significantly faster rates of forgetting relative to controls on picture recognition, design recognition, word recognition or stem completion, after levels of learning had been matched as closely as possible. Moreover, once initial learning was equated in a small number of subjects, there were no qualitative differences between AD patients and controls following inclusion and exclusion instructions on the stem completion task. In particular, those AD patients who were matched to controls for initial levels of "recollection" showed comparable forgetting rates in recollection (or cued recall). Although matching was more difficult for a picture recall task, both the main analysis and subgroup analysis indicated faster forgetting in the AD group than controls, suggesting a difference between "free recall" and recognition or cued recall measures, comparable with the finding in a parallel study of organic amnesia.

Automatic influences of memory in Alzheimer's disease

Automatic and controlled influences of memory were examined in 12 patients with early Alzheimer's disease (AD) and 12 control subjects. The subjects studied a list of words and then received three-letter word stems in three different retrieval tasks. In an indirect memory task (word-stem completion priming), they were asked to produce the first word that came to mind in response to each stem. In an inclusion task, they were required to produce a studied word in response to each stem, and in an exclusion task they were asked to produce a new, unstudied word for each stem. The performance of the subjects with AD was equal in the inclusion and exclusion conditions, showing no evidence of controlled recollection for the studied words, while their automatic memory as well as priming were preserved. The results provide neuropsychological support for the distinction between controlled and automatic memory processes.

Word-stem completion priming for perceptually and conceptually encoded words in patients with Alzheimer's disease

This study examined whether the frequently reported word-stem completion priming deficit of Alzheimer's disease (AD) patients could be characterized as either a semantic encoding deficit or a conceptual priming deficit. AD patients and normal elderly control subjects studied words in two conditions: (1) reading visually presented words aloud, which maximizes perceptual encoding of seen words, and (2) generating words aloud from definitions, which maximizes conceptual encoding of words not seen but retrieved on the basis of semantic context. Recognition accuracy was greater for words that were generated at study, and word-stem completion priming was greater for words that were read at study. For the AD patients, recognition accuracy was impaired and word-stem completion priming was intact for words encoded in both conditions. The findings are discussed in terms of discrepant results about word-stem completion priming in AD.

Perceptual priming in Alzheimer's and Parkinson's diseases

The present study focused on perceptual identification priming (implicit memory) in early stages of dementia by studying demographically and cognitively matched patients with Alzheimer's disease (AD) and Parkinson's disease (PD). The AD and PD groups performed normally on perceptual identification priming, whereas their explicit recognition memory was equally impaired compared to normal controls. These results imply that priming in perceptual identification relies on the perceptual memory system which can resist not only impairments of explicit memory but also widespread cognitive deterioration induced by the neurodegenerative processes in AD or PD.