Sources of priming in text rereading: intact implicit memory for new associations in older adults and in patients with Alzheimer's disease

Bilingual language intrusions and other speech errors in Alzheimer's disease

The current study investigated how Alzheimer's disease (AD) affects production of speech errors in reading-aloud. Twelve Spanish-English bilinguals with AD and 19 matched controls read-aloud 8 paragraphs in four conditions (a) English-only, (b) Spanish-only, (c) English-mixed (mostly English with 6 Spanish words), and (d) Spanish-mixed (mostly Spanish with 6 English words). Reading elicited language intrusions (e.g., saying la instead of the), and several types of within-language errors (e.g., saying their instead of the). Patients produced more intrusions (and self-corrected less often) than controls, particularly when reading non-dominant language paragraphs with switches into the dominant language. Patients also produced more within-language errors than controls, but differences between groups for these were not consistently larger with dominant versus non-dominant language targets. These results illustrate the potential utility of speech errors for diagnosis of AD, suggest a variety of linguistic and executive control impairments in AD, and reveal multiple cognitive mechanisms needed to mix languages fluently. The observed pattern of deficits, and unique sensitivity of intrusions to AD in bilinguals, suggests intact ability to select a default language with contextual support, to rapidly translate and switch languages in production of connected speech, but impaired ability to monitor language membership while regulating inhibitory control.

Differential age effects for implicit and explicit conceptual associative memory

Older adults show disproportionate declines in explicit memory for associative relative to item information. However, the source of these declines is still uncertain. One explanation is a generalized impairment in the processing of associative information. A second explanation is a more specialized impairment in the strategic, effortful recollection of associative information, leaving less effortful forms of associative retrieval preserved. Assessing implicit memory of new associations is a way to distinguish between these viewpoints. To date, mixed findings have emerged from studies of associative priming in aging. One factor that may account for the variability is whether the manipulations inadvertently involve strategic, explicit processes. In two experiments we present a novel paradigm of conceptual associative priming in which subjects make speeded associative judgments about unrelated objects. Using a size classification task, Experiment 1 showed equivalent associative priming between young and older adults. Experiment 2 generalized the results of Experiment 1 to an inside/outside classification task, while replicating the typical age-related impairment in associative but not item recognition. Taken together, the findings support the viewpoint that older adults can incidentally encode and retrieve new meaningful associations despite difficulty with the intentional recollection of the same information.

Context effects in auditory implicit memory

The context effect in implicit memory is the finding that presentation of words in meaningful context reduces or eliminates repetition priming compared to words presented in isolation. Virtually all of the research on the context effect has been conducted in the visual modality but preliminary results raise the question of whether context effects are less likely in auditory priming. Context effects in the auditory modality were systematically examined in five experiments using the auditory implicit tests of word-fragment and word-stem completion. The first three experiments revealed the classical context effect in auditory priming: Words heard in isolation produced substantial priming, whereas there was little priming for the words heard in meaningful passages. Experiments 4 and 5 revealed that a meaningful context is not required for the context effect to be obtained: Words presented in an unrelated audio stream produced less priming than words presented individually and no more priming than words presented in meaningful passages. Although context effects are often explained in terms of the transfer-appropriate processing (TAP) framework, the present results are better explained by Masson and MacLeod's (2000) reduced-individuation hypothesis.

New norms for a new generation: cognitive performance in the framingham offspring cohort

A previous publication presented normative data on neuropsychological tests stratified by age, gender, and education based on the Original Cohort of the Framingham Heart Study. Many contemporary investigations include subject samples with higher levels of education, a factor known to affect cognitive performance. Secular change in education prompted the reexamination of norms in the children of the Original Cohort. The study population consisted of 853 men and 988 women from the Offspring Study, free of clinical neurological disease, who underwent a neuropsychological examination, which included tests given to their parents in 1974 to 1976 as well as additional newer tests to provide a more comprehensive battery. The Offspring population overall was more evenly distributed by gender and better educated. Their performance on cognitive tests was superior to that of the Original Cohort. Multivariable analyses revealed that more years of education explained only a part of the cohort differences. These findings suggest that continued surveillance of each generation is necessary to document the impact that unique social and economic variables have on cognitive function. Here, the authors provide updated normative data.

Local-global processing in Alzheimer's disease: an examination of interference, inhibition and priming

Impairments of memory, praxis, gnosis, language and executive functioning are well documented in Alzheimer's disease (AD). Functions, such as attention, however, have only recently been systematically investigated. We used Navon-type stimuli (large "global" digits composed of smaller "local" digits) to assess 12 AD participants' plus age-matched controls' ability to focus and alter the scale of their spatial attention. In the first experiment, participants responded to either the global or local characters within a block, ignoring characters at the other spatial scale. Healthy young adults (n=12) demonstrated the normal 'global precedence' effect on this task. In contrast, participants with AD and their age-matched controls were significantly faster on the local task than on the global task, suggesting in these groups a 'local precedence' effect. This consisted of both a local advantage and a local-on-global interference effect. In a second experiment, participants searched for designated targets which occurred unpredictably at either the local or global spatial scale. Participants with AD were significantly slower and more error-prone than older controls. In addition, participants with AD showed a greater cost in reaction time (RT) when required to switch spatial scales on consecutive trials, compared to no switch responses at the same spatial scale on consecutive trials. Thus, AD may impair the ability to process global figures, due perhaps to involvement of posterior parietal areas. Further, participants with AD were poor at inhibiting irrelevant stimuli and at inhibiting attentional allocation to an irrelevant spatial scale, which may relate to prefrontal pathology.

Memory rehabilitation in Alzheimer's disease: a review of progress

BACKGROUND

Memory rehabilitation is a sadly misrepresented area of applied research in Alzheimer's disease.

OBJECTIVES

To gather and evaluate recent evidence for the clinical effectiveness or ecologically validity of memory rehabilitation for mild to moderate Alzheimer's patients.

METHODS

Computerised searches and some handsearching were conducted spanning the last five years, from 1995 to 2000, inclusively. Criteria for inclusion in this overview involved the use of a precise memory rehabilitation technique within an experimental study design applied to Alzheimer's patients with pre- and post-treatment evaluation.

FINDINGS

Three potential levels of memory rehabilitation procedures with proven clinical or pragmatic efficacy were identified. The first level bears on the facilitation of residual explicit memory with structured support both at encoding and at subsequent recall; the second level of memory rehabilitation exploits the relatively intact implicit memory system (priming and procedural memory); the last deals with finding ways of coping with the patient's limited explicit memory capacities through the use of external memory aids. A proposal of suggestions for good practice and future research in memory rehabilitation is also offered with the hope to spur further development in this rapidly expanding area of applied research.

CONCLUSION

The available evidence shows that alternative and innovative ways of memory rehabilitation for Alzheimer's patients can indeed be clinically effective or pragmatically useful with a great potential for use within the new culture of a more graded and proactive type of Alzheimer's disease care.