Performance of Alzheimer's disease patients in judging word relatedness

Altered brain response for semantic knowledge in Alzheimer's disease

Word retrieval deficits are common in Alzheimer's disease (AD) and are thought to reflect a degradation of semantic memory. Yet, the nature of semantic deterioration in AD and the underlying neural correlates of these semantic memory changes remain largely unknown. We examined the semantic memory impairment in AD by investigating the neural correlates of category knowledge (e.g., living vs. nonliving) and featural processing (global vs. local visual information). During event-related fMRI, 10 adults diagnosed with mild AD and 22 cognitively normal (CN) older adults named aloud items from three categories for which processing of specific visual features has previously been dissociated from categorical features. Results showed widespread group differences in the categorical representation of semantic knowledge in several language-related brain areas. For example, the right inferior frontal gyrus showed selective brain response for nonliving items in the CN group but living items in the AD group. Additionally, the AD group showed increased brain response for word retrieval irrespective of category in Broca's homologue in the right hemisphere and rostral cingulate cortex bilaterally, which suggests greater recruitment of frontally mediated neural compensatory mechanisms in the face of semantic alteration.

Proactive and retroactive interference in young adults, healthy older adults, and older adults with amnestic mild cognitive impairment

This study investigated memory interference in amnestic mild cognitive impairment (aMCI) and normal aging. Participants were 27 young adults, 44 healthy older adults, and 15 older adults with aMCI. Memory interference was examined on the California Verbal Learning Test (CVLT) and on a modified AB-AC paradigm. Despite significant differences in memory performance on the CVLT, interference measures on this test did not distinguish individuals with aMCI and healthy older adults. The AB-AC task involved first learning a list (AB list) of 12 semantically related word pairs (e.g., knee-bone). Twenty minutes later, a second list (AC list) was learned in which the same stimulus words were paired with new response words (e.g., knee-bend). Both lists were repeated until 100% accurate recall was achieved. Finally, participants recalled the first (AB) list. Proactive interference (PI) was greater among older than younger adults, and greater still among individuals with aMCI, but the older and aMCI groups showed similar levels of retroactive interference. This study suggests that PI contributes to the memory deficits seen in aMCI and that tests sensitive to PI may assist in the early identification of aMCI. Memory interventions aimed at alleviating PI may improve memory functioning in individuals with aMCI. (JINS, 2009, 15, 83-93.).

The picture superiority effect in patients with Alzheimer's disease and mild cognitive impairment

The fact that pictures are better remembered than words has been reported in the literature for over 30 years. While this picture superiority effect has been consistently found in healthy young and older adults, no study has directly evaluated the presence of the effect in patients with Alzheimer's disease (AD) or mild cognitive impairment (MCI). Clinical observations have indicated that pictures enhance memory in these patients, suggesting that the picture superiority effect may be intact. However, several studies have reported visual processing impairments in AD and MCI patients which might diminish the picture superiority effect. Using a recognition memory paradigm, we tested memory for pictures versus words in these patients. The results showed that the picture superiority effect is intact, and that these patients showed a similar benefit to healthy controls from studying pictures compared to words. The findings are discussed in terms of visual processing and possible clinical importance.

Semantic memory deficits in low-educated patients with Alzheimer's disease

BACKGROUND/PURPOSE

Although a deficit of semantic memory is evident in the dementia of the Alzheimer's type (DAT), the underlying neuropsychologic mechanism remains controversial. Breakdown of the semantic network during the course of DAT and an inability to access semantic information have been postulated as possible explanations, but supporting data are limited, particularly in low-educated patients. This study examined semantic memory in low-educated patients with different degrees of dementia severity.

METHODS

In total, 197 adult subjects were recruited, including 165 DAT patients and 32 normal controls. Subjects were divided into four subgroups according to their dementia severity. All subjects completed an episodic memory task, the Six-Object Memory Test, and semantic memory tasks including the Object Naming Test, the Remote Memory Test and the Semantic Association of Verbal Fluency Test. One-way ANOVA and ANCOVA with a post hoc Scheffe's procedure were used to evaluate differences between groups.

RESULTS

All patients, irrespective of the degree of dementia, showed impaired performance on the Six-Object Memory Test [F (4, 163) = 69.95, p < 0.0001 for immediate recall; F (4, 163) = 41.34, p < 0.0001 for delayed recall]. On the semantic memory tasks, patients with moderate to severe dementia showed impaired performances on the Object Naming Test [F (4, 180) = 28.25, p < 0.0001] and the Remote Memory Test [F (4, 167) = 26.22, p < 0.0001 for recall; F (4, 167) = 34.80, p < 0.0001 for recognition], while all patients performed defectively on the Semantic Association of Verbal Fluency Test [F (4, 194) = 70.43, p < 0.0001].

CONCLUSION

Our results thus partially support the hypotheses that a loss of semantic structure and an inability to access semantic knowledge occur in the pathogenesis of DAT.

Information content versus relational knowledge: Semantic deficits in patients with Alzheimer's disease

Studies of semantic impairment in Alzheimer's disease (AD) have yielded conflicting results, some finding evidence of considerable deficits, others finding that semantic knowledge is relatively intact. How do we reconcile findings from picture naming tasks that seem to indicate semantic impairment in AD with results from certain sorting tasks that suggest intact semantics? To investigate the basis of the contradictory results described above, we conducted a study using two types of tasks: (1) picture naming; and (2) board sorting. The board sorting task we used is a simultaneous similarity judgment task, in which participants are asked to place more similar concepts closer together and less similar ones farther apart. We compared the performance of AD patients on these two tasks, using a number of different analyses that yield very different patterns of results. Our results indicate that whether patients show impairment or not depends on both the nature of the task and the subsequent analysis chosen. Specifically, tasks and analyses that focus on relational knowledge (e.g., dog is more related to cat than to camel) lead to different conclusions than those based on specific information about individual items. These findings suggest that the board sorting method, when coupled with multiple analyses, provides a more complete picture of the underlying semantic deficit in AD than previous studies have shown.

Effect of presentation modality on immediate and delayed recall in individuals with Alzheimer's disease

Episodic memory (EM) deficits are the hallmark of Alzheimer's disease (AD). Story-retelling tasks are particularly sensitive to EM impairments and require participants to recall a short story immediately and after a delay. The purpose of this study was to determine whether presentation modality influences story recall in AD participants. Thirty AD participants and 30 healthy elders recalled short stories in (a) auditory, (b) visual, and (c) combined auditory-visual modalities. Recall was assessed immediately as well as after 15- and 30-min delays. Presentation modality significantly influenced story recall in AD participants. AD participants demonstrated better recall after silently reading a story than after hearing an examiner tell the story or simultaneously hearing and reading the story. Clinical implications of these results are discussed.

Loss of Distinctive Features and a Broader Pattern of Priming in Alzheimer's Disease

The results of 2 experiments support the contention that patients with Alzheimer's disease (AD) show a relative loss of the semantic features that distinguish concepts from one another and that the representations of pairs of concepts consequently share a larger proportion of their associated features in AD than in normal aging. In Experiment 1, AD patients listed fewer features for a set of concepts than did healthy older adults and were more deficient at listing features if the features were distinctive to particular concepts than if they were shared by multiple concepts. In Experiment 2, AD patients showed online priming at levels of relatedness at which healthy older adults did not.

A longitudinal study of neuropsychological change in individuals with Parkinson's disease

OBJECTIVES

Neuropsychological changes in individuals with Parkinson's disease (PD) were studied longitudinally.

METHODS

Sixty-nine idiopathic PD patients, with Mini-Mental State Examination (MMSE) scores falling within normal range, and 37 elderly control participants were given neuropsychological tests twice approximately two years apart.

RESULTS

The PD group performed poorer than the control group on Semantic Fluency, Letter Fluency, Modified Wisconsin Card Sorting Task, and Block Design at test time 1. Two years later, the PD group showed significant decline in Semantic and Letter Fluency. A subset of 12 PD patients declined in mental status by second testing (>4 MMSE points). Cox proportional-hazards models were used to see if any baseline measures were associated with relative risk of decline in mental status. In the final model, Repetition performance and Age were significantly associated with cognitive decline.

CONCLUSIONS

Consistent with previous studies, executive function tasks were those most susceptible to disease progression.

A longitudinal study of neuropsychological change in individuals with Parkinson's disease

Neuropsychological changes in individuals with Parkinson's disease (PD) were studied longitudinally. Sixty-nine idiopathic PD patients, with Mini-Mental State Examination (MMSE) scores falling within normal range, and 37 elderly control participants were given neuropsychological tests twice approximately two years apart. The PD group performed poorer than the control group on Semantic Fluency, Letter Fluency, Modified Wisconsin Card Sorting Task, and Block Design at test time 1. Two years later, the PD group showed significant decline in Semantic and Letter Fluency. A subset of 12 PD patients declined in mental status by second testing (> or =4 MMSE points). Cox proportional-hazards models were used to see if any baseline measures were associated with relative risk of decline in mental status. In the final model, Repetition performance and Age were significantly associated with cognitive decline. Consistent with previous studies, executive function tasks were those most susceptible to disease progression.

Semantic versus phonological false recognition in aging and Alzheimer's disease

Patients with Alzheimer's disease (AD) have been found to exhibit lower levels of false recognition of semantic associates compared with healthy older adults. Because these patients may show impaired performance of episodic and semantic memory tasks, this finding could be explained by deficits in episodic memory, semantic memory, or both. The authors adapted a paradigm for comparison of semantic versus phonological false recognition. They found that: (a) patients with AD exhibited lower levels of corrected false recognition of semantic, phonological, and hybrid (mixed semantic and phonological) lists than older adults, and (b) patients with AD showed very similar levels of false recognition for all list types. These results suggest that only episodic memory deficits are necessary to explain the lower level of false recognition of semantic associates observed in patients with AD when compared to older adults. Additionally, (c) older adults showed greater levels of semantic, phonological, and hybrid false recognition than younger adults, extending previous false recognition research of semantically related words and categorized colored photographs to phonologically related words.

False recognition of pictures versus words in Alzheimer's disease: the distinctiveness heuristic

False recognition of semantic associates can be reduced when older adults also study pictures representing each associate. D. L. Schacter, L. Israel, and C. Racine (1999) attributed this reduction to the operation of a distinctiveness heuristic: a response mode in which participants demand access to detailed recollections to support a positive recognition decision. The authors examined patients with probable Alzheimer's disease (AD) and older adults with this paradigm. Half of the participants studied pictures and auditory words; the other half studied visual and auditory words. Older adults who studied pictures were able to reduce their false alarms compared with those who studied words only. AD patients who studied pictures were unable to reduce their false alarms compared with those who studied words only and, in fact, exhibited trends toward greater false recognition. Implications for understanding semantic memory in AD patients are discussed.

Speech errors in Alzheimer's disease: reevaluating morphosyntactic preservation

Researchers studying the speech of individuals with probable Alzheimer's disease (PAD) report that morphosyntax is preserved relative to lexical aspects of speech. The current study questions whether dividing all errors into only two categories, morphosyntactic and lexical, is warranted, given the theoretical controversies concerning the production and representation of pronouns and closed-class words in particular. Two experiments compare the speech output of 10 individuals with Alzheimer's disease to that of 15 healthy age- and education-matched speakers. Results of the first experiment indicate that the pattern of errors in the speech of participants with mild PAD reflects an across-the-board increase in the same types of errors made by healthy older speakers, including closed-class and morphosyntactic errors. In the second task, participants produced a grammatical sentence from written stimuli consisting of a transitive verb and two nouns. Only adults with Alzheimer's disease had difficulties with this task, producing many more closed-class word errors than did healthy older adults. Three of the participants with PAD produced nearly agrammatic speech in this task. These 3 people did not differ from the rest of the PAD group in age, education, working memory, or degree of semantic impairment. Further, error rates on the two tasks were highly correlated. We conclude that morphosyntax is not preserved in the speech output of individuals with PAD, but is vulnerable to errors along with all aspects of language that must be generated by the speaker. We suggest that these results best support a model of speech production in which all words are represented by semantic and grammatical features, both of which are vulnerable to failures of activation when there is damage or noise in the system as a result of pathology, trauma, or even divided attention.