Neuropsychological and neuroradiological distinctions between Alzheimer's and Huntington's diseases.

Examined neuropsychological and magnetic resonance imaging (MRI) differences among 23 Ss (mean age 70 yrs) with Alzheimer's disease (AD), 9 Ss (mean age 49.2 yrs) with Huntington's disease (HD), and 13 normal controls (mean age 71.7 yrs). Neuropsychological results show that HD Ss' episodic and semantic memory deficits were attributable to retrieval deficiencies, whereas AD Ss' impairments reflected a lack of storage and a breakdown in the structure of semantic knowledge. MRI results show that these cognitive changes were mirrored by significant group differences in striatal and cortical degeneration. AD Ss evidenced more widespread cortical damage, and HD Ss showed more striatal destruction. Both groups evidenced significant deterioration in medial temporal lobe and diencephalic structures. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Anomia as a marker of distinct semantic memory impairments in Alzheimer's disease and semantic dementia.

Objective: Many neurologically constrained models of semantic memory have been informed by two primary temporal lobe pathologies: Alzheimer's disease (AD) and Semantic Dementia (SD). However, controversy persists regarding the nature of the semantic impairment associated with these patient populations. Some argue that AD presents as a disconnection syndrome in which linguistic impairment reflects difficulties in lexical or perceptual means of semantic access. In contrast, there is a wider consensus that SD reflects loss of core knowledge that underlies word and object meaning. Object naming provides a window into the integrity of semantic knowledge in these two populations. Method: We examined naming accuracy, errors and the correlation of naming ability with neuropsychological measures (semantic ability, executive functioning, and working memory) in a large sample of patients with AD (n = 36) and SD (n = 21). Results: Naming ability and naming errors differed between groups, as did neuropsychological predictors of naming ability. Despite a similar extent of baseline cognitive impairment, SD patients were more anomic than AD patients. Conclusions: These results add to a growing body of literature supporting a dual impairment to semantic content and active semantic processing in AD, and confirm the fundamental deficit in semantic content in SD. We interpret these findings as supporting of a model of semantic memory premised upon dynamic interactivity between the process and content of conceptual knowledge. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

A multidimensional scaling analysis of the development of animal names.

Investigated developmental changes in semantic structure using the INDSCAL multidimensional scaling procedure. Dissimilarity judgments of all possible parts of 10 animal names were obtained from 39 1st-, 3rd-, 6th-grade, and college students. The overall scaling solution revealed a semantic space consisting of the features of size, domesticity, and predativity. Further analyses revealed that this structure changes with development inasmuch as the perceptual feature of size becomes less salient and the more abstract features of predativity and domesticity becomes more salient. This finding is compared to those from earlier research in which other techniques were used, and it is concluded that multidimensional scaling is a useful tool for determining developmental changes in semantic structure. (16 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Use of semantic context by patients with Alzheimer's disease.

Used semantic-priming procedures to examine limitations in the use of semantic context by 18 patients (mean age 68.9 yrs) with Alzheimer's disease (AD) and to determine whether any such contextual effects were mediated solely through automatic processes or whether attentional processes were also involved. Three tasks were applied to examine the effect of semantic context on the performance of 18 normal elderly Ss (mean age 67.2 yrs), 18 normal young Ss (mean age 24.1 yrs), and the AD Ss. When normal and AD Ss were asked to decide whether a given item was a member of a certain category, their response times were equally affected by the item's dominance in the category. The time that AD Ss took to recognize a word was actually affected more by the semantic context provided by a priming sentence than was that of normal Ss. When asked to generate the final word of an incomplete sentence, AD Ss performed very poorly unless potential responses were highly constrained by sentence context. (31 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Deterioration of generic knowledge in patients with Alzheimer's disease: evidence from the Number Information Test

Semantic memory for generic knowledge was assessed in patients with probable Alzheimer's disease (AD; n = 142) and elderly normal control (NC; n = 78) subjects using the Number Information Test (NIT), a test that consists of 24 general knowledge questions that require a single number for an answer (e.g., "How many days are in a year?"). The results showed that patients with AD were impaired, even in the mildest stage of dementia, and that this impairment grew as the severity of their dementia increased over time. In addition, patients with AD were highly consistent in the individual items they missed in subsequent test sessions conducted 1 or 2 years later. These results indicate that semantic memory for generic knowledge is impaired relatively early in AD, deteriorates throughout the course of the disease, and may be due to a loss of knowledge rather than to a retrieval deficit.     

Verb confrontation naming and word-picture matching in Alzheimer's disease.

Patients with Alzheimer's disease (AD) were asked to name pictures and perform a multiple-choice word–picture matching task with verbs and nouns. AD patients were significantly more impaired with verbs than nouns for both naming and word–picture matching, and their patterns of semantic naming errors differed for verbs and nouns. One subgroup of AD patients was compromised on both naming and word–picture matching consistent with a semantic memory deficit. Naming was worse for verbs than for nouns in these patients, and they produced significantlv fewer hierarchically related semantic substitutions for verbs than for nouns. Other AD patients without semantic memory difficulty did not demonstrate these form class-sensitive patterns. The investigators hypothesize that form class-specific effects in AD patients' naming are due in part to differences in processing verbs and nouns in semantic memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Do ability-performance relationships differentiate age and practice effects in visual search?

Investigated relationships between abilities and performance in visual search for 70 young (aged 17–31 yrs) and 70 old adults (aged 65–80 yrs). Ss received extensive practice on a category search task. A consistent version allowed development of an automatic attention response; a varied version allowed general performance improvements. Transfer conditions assessed learning. General ability, induction, semantic knowledge, working memory, perceptual speed, semantic memory access, and psychomotor speed were assessed. LISREL models revealed that general ability and semantic memory access predicted initial performance for both age groups. Improvements on both the consistent and the varied tasks were predicted by perceptual speed. Ability–performance relationships indexed performance changes but were not predictive of learning (i.e., automatic process vs general efficiency). Qualitative differences in the ability-transfer models suggest age differences in learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Semantic memory: Facts and models.

Contends that the database of semantic memory is richer and more consistent internally than indicated by W. Kintsch (1980) and describes major explanatory models of semantic memory in relationship to this database. Findings on category size, typicality, false-relatedness, and false production-frequency effect are presented and reconsidered. Such a systematic reassessment has been lacking in the semantic memory literature, leading to a knowledge base that is difficult to interpret. The main outcome of this review is a restoration of some of the early claims of a category size effect and the establishment of a novel fast-true effect. Current models of semantic memory described in this context are hierarchical-network, predicate-intersections, feature-comparison, marker-search, spreading-activation, and property-comparison. (66 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Semantic fluency in Alzheimer's, Parkinson's, and Huntington's disease: Dissociation of storage and retrieval failures.

Patients with Alzheimer's disease (AD), Huntington's disease (HD), and Parkinson's disease (PD), and normal controls were compared on 2 versions of a semantic fluency task: a standard, uncued version and a version in which Ss were cued with subordinate categories. All patients were impaired relative to controls on the standard version. On the cued version, PD and HD patients improved significantly, but AD patients did not. AD patients' fluency, but not PD or HD patients', correlated significantly with confrontation naming ability. Impairment exhibited by PD and HD patients on standard semantic fluency tasks may be due to a retrieval deficit, whereas that of AD patients may be due to degradation of semantic memory stores. In addition, the pattern of performance exhibited by a nonaphasic patient with bilateral frontal lobe lesions suggests that the retrieval functions involved may depend on integrity of the prefrontal cortex. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of long-term vocabulary instruction on lexical access and reading comprehension.

To examine the relationship between knowledge of word meanings and semantic processes, 27 4th-grade children were taught 104 words over a 5-mo period. Following instruction, Ss performed tasks designed to require semantic processes ranging from single word semantic decisions to simple sentence verification and memory for connected text. On all these tasks, instructed Ss performed at a significantly higher level than controls matched on pre-instruction vocabulary knowledge and comprehension. Thus, instructed Ss gave evidence both of learning word meanings taught by the program and of being able to process instructed words more efficiently in tasks more reflective of comprehension. Implications for vocabulary instruction and the role of individual word meanings in comprehension are discussed. (18 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Lexical semantic and associative priming in Alzheimer's disease.

Semantic memory impairment was investigated in patients with probable Alzheimer's disease (AD) using a threshold oral word reading task to assess priming of different lexical relationships. Healthy elderly controls showed significant priming for associatively related nouns (tempest-teapot) and also for nouns semantically related either because both designate basic-level exemplars of a common superordinate category (cousin-nephew) or because the target names the superordinate category of the prime (daughter-relative). AD patients, in contrast, showed preserved priming of lexical associates but impaired priming of certain semantic relationships. They showed no priming between words designating coordinate exemplars within a category, despite preserved priming of the superordinate category label. Findings are consistent with the view that at least part of the semantic deficit in AD is due to disruption of semantic knowledge that affects relationships among basic-level concepts, more than the relationships between these concepts and their corresponding superordinate category of membership. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Intact text-specific implicit memory in patients with Alzheimer's disease.

The ability of patients with Alzheimer's disease (AD) to acquire and retain text-specific knowledge was investigated in a rereading study. Ten AD patients (aged 59–84 yrs) and 10 normal control Ss read 2 passages 3 times, each as quickly as possible, and answered recognition memory questions after the 3rd reading of each passage. The AD patients had poor explicit memory as evidenced by impaired recognition memory for the passages. In contrast, normal decreases in the times required for successive readings of each passage for AD patients indicated intact implicit memory for the passages. The absence of facilitation across passages indicated that the rereading effect was text specific, suggesting that AD patients may retain the ability to form certain kinds of implicit new associations. Alternative accounts of the mechanism underlying text-specific priming, and of the nature of intact and impaired implicit memory in AD, are considered. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Contextual constraint and schizophrenic language.

Compared 16 hospitalized schizophrenic patients and 16 nonpsychiatric patients for the degree of facilitation of contextual constraint in memory. Ss were matched for intelligence, age, education, duration of illness, and socioeconomic level. All Ss listened to 4 taped word passages of different linguistic structure: normal and anomalous sentences, and semantically related and random word-strings. Ss differed in recall on all conditions, with the greatest difference between S groups occurring on normal sentences. Both S groups showed greater recall on passages emphasizing semantic components than on those with syntactic. Results suggest that the schizophrenic difficulty in communication may be influenced by lack of memory facilitation due to contextual constraints. (24 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Perseverative behavior in Alzheimer's disease and subcortical ischemic vascular dementia.

Perseverative behavior has not been extensively studied in patients with dementia. In this study, perseverative behavior was elicited with the dementia version of the Graphical Sequence Test. A control group and participants with Alzheimer's disease (AD) and subcortical ischemic vascular dementia (IVD) were studied. A factor analysis revealed a 3-factor model consisting of perseverations related to semantic knowledge, motor functioning, and a third, intermediary factor. IVD participants made more total perseverations than did AD participants. Perseverations made by AD participants were correlated with deficits on tests of semantic knowledge, whereas the perseverations made by IVD participants were correlated with motor and frontal systems tests. Results are consistent with the view that perseverative behavior is hierarchically arranged in terms of specific levels of cognitive complexity and the overall pattern of cognitive deficits associated with each type of dementia. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Assessment of semantic processing in patients with Alzheimer's type dementia: The release-of-proactive-inhibition paradigm.

Investigated memory functioning in 10 patients with dementia of Alzheimer's type (DAT [aged 54–87 yrs]) and 20 age-matched normal controls (CTLs) by using the release-from-proactive-interference paradigm. DAT Ss exhibited lower correct recall and higher intrusion rates than did CTLs. DAT Ss did not show the expected build-up and release from proactive interference when correct recall was considered but showed the expected pattern when intrusion rate was considered. CTLs showed evidence of semantic processing on both measures. Results are discussed in relation to the defects in semantic memory hypothesized in Alzheimer's disease. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Preserved organization of semantic attributes in Alzheimer's disease.

This study investigated whether Alzheimer's disease (AD) disrupts the basic organization of the semantic attributes of concepts. Young and normal older Ss and AD patients were presented with a target concept followed by a stimulus word and were to decide whether the stimulus was related to the target. On those trials where it was, the stimulus was either a high-, medium-, or low-dominance attribute of the target. The higher the normative dominance, the more important the attribute to concept meaning. In all 3 S groups, decision time varied as a function of dominance. The higher the dominance, the faster the decision. Attribute dominance affected the performance of AD patients more than that of normal Ss. These results suggest that AD patients retain their knowledge of the relative importance that the different attributes of a concept have for concept meaning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The disparate effects of Alzheimer's disease and Huntington's disease on semantic memory.

Alzheimer's disease (AD) and Huntington's disease (HD) impair performance on semantic memory tasks, but researchers disagree on whether AD and HD cause these impairments in the same manner. According to one view, AD disrupts the storage of semantic memories, whereas HD disrupts the retrieval of semantic memories. Dissenters argue that AD, like HD, disrupts retrieval. In this study, participants generated category exemplars (e.g., kinds of fruits) for 1 min, and response latencies were examined. Relative to healthy controls, the 12 AD patients produced a larger proportion of responses earlier in the recall period, consistent with the view that AD patients quickly exhaust their limited supply of items in storage. By contrast, the 12 HD patients produced a larger proportion of their responses late in the recall period, consistent with the view that HD slows retrieval. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Semantic networks for odors and colors in Alzheimer's disease.

Objective: Impairment in odor-naming ability and in verbal and visual semantic networks raised the hypothesis of a breakdown in the semantic network for odors in Alzheimer's disease (AD). The current study addressed this hypothesis. Method: Twenty-four individuals, half patients with probable AD and half control participants, performed triadic-similarity judgments for odors and colors, separately, which, utilizing the multidimensional scaling (MDS) technique of individual difference scaling analysis (INDSCAL), generated two-dimensional configurations of similarity. The abilities to match odors and colors with written name labels were assessed to investigate disease-related differences in ability to identify and conceptualize the stimuli. In addition, responses on attribute-sorting tasks, requiring the odor and color perceptions to be categorized as one polarity of a certain dimension, were obtained to allow for objective interpretation of the MDS spatial maps. Results: Whereas comparison subjects generated spatial maps based predominantly on relatively abstract characteristics, patients with AD classified odors on perceptual characteristics. The maps for patients with AD also showed disorganized groupings and loose associations between odors. Their normal configurations for colors imply that the patients were able to comprehend the task per se. The data for label matching and for attribute sorting provide further evidence for a disturbance in semantic odor memory in AD. The patients performed poorer than controls on both these odor tasks, implying that the ability to identify and/or conceptualize odors is impaired in AD. Conclusion: The results provide clear evidence for deterioration of the structure of semantic knowledge for odors in AD. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of Alzheimer's disease on the recognition of novel versus familiar words: Neuropsychological and clinico-metabolic data.

This study explored recognition memory performance for novel versus familiar words in Alzheimer's disease (AD) patients and normal controls (NCs), using an adaptation of E. Tulving and N. Kroll's (1995) procedure. Results showed that both groups exhibited more hits and more false alarms for familiar than for novel words. The groups did not differ in the recognition of familiar words, reflecting preserved familiarity processes in AD. However, AD patients made more false alarms than NCs in the recognition of novel words, reflecting impairment of recollection processes in AD. A positron emission tomography analysis of clinico-metabolic correlations in AD patients showed a correlation between recognition of novel words and right hippocampal activity, whereas recognition of familiar words was more related to metabolic activity in the left posterior orbitofrontal cortex. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of intentionality and strategy on memory for frequency.

Several studies have examined whether Ss who learn a list of words incidentally remember frequency as well as those who learn the words intentionally. Conflicting results have been found. This discrepancy is examined in the present 3 experiments with a total of 105 undergraduates. Results of Exps I and II indicate that intentional-learning Ss exhibited an advantage in memory for frequency only if the instructions emphasized the importance of good performance on the memory task. Results of Exp III show that intentionality influenced memory for frequency within a list of items and that a strategy that involved semantic processing led to improved frequency estimation. It is concluded that these results are inconsistent with formulations of the claim that frequency information is encoded automatically and demonstrate that instructions play a crucial mediating role in memory for frequency. (55 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)