Charting the progression in semantic dementia: Implications for the organisation of semantic memory

Abstract

A patient, JL, with the syndrome of semantic dementia was assessed longitudinally over a two-year period. The data presented here address the controversy concerning the hierarchical organisation of semantic memory. On a range of category fluency tests, when first tested JL was just within the normal range on the broadest categories of animals and household items, but was virtually unable to produce any instances of specific categories such as breeds of dog or musical instruments. Longitudinal fluency data for the animal category demonstrate that while JL continued to produce the most prototypical responses (cat, dog, horse), other animal labels dropped out early from his vocabulary. On the picture-sorting tests from our semantic memory test battery, JL's discrimination between living things and man-made objects was preserved for a substantial time in conjunction with a marked decline in his sorting ability for more specific categories, particularly features or attributes (e.g. size, foreign-ness, or ferocity of animals).

An analysis of naming responses to the 260 Snodgrass and Vanderwart pictures on four occasions suggests a progressive loss of the features of semantic representations that enable discrimination between specific category instances. There was a progressive decline in circumlocutory and category co-ordinate responses with a rise in broad superordinate and cross-category errors. The latter are of particular theoretical interest; on session I, all cross-category errors respected the living/man-made distinction, but by session IV almost half of such errors failed to respect this distinction. The emergence of category prototypes was another notable feature, particularly in the living domain: at one stage, land (or four-legged) animals were all named either cat, dog, or horse. By contrast, within the man-made domain, items were frequently described in terms of their broad use or function, until eventually no defining features were produced. These findings are discussed in the context of competing theories of semantic organisation.     

Emotion knowledge and autobiographical memory across the preschool years: a cross-cultural longitudinal investigation

Knowledge of emotion situations facilitates the interpretation, processing, and organization of significant personal event information and thus may be an important contributor to the development of autobiographical memory. This longitudinal study tested the hypothesis in a cross-cultural context. The participants were native Chinese children, Chinese children from first-generation Chinese immigrant families in the U.S., and European American children. Children's developing emotion knowledge and autobiographical memory were assessed three times at home, when children were 3, 3.5, and 4.5 years of age. Children's emotion knowledge uniquely predicted their autobiographical memory ability across groups and time points. Emotion knowledge further mediated culture effects on autobiographical memory. The findings provide important insight into early autobiographical memory development, and extend current theoretical understandings of the emotion-memory interplay. They further have implications for the phenomenon of infantile amnesia and cross-cultural differences in childhood recollections.     

Accessing semantic knowledge in dementia: evidence from a word definition task

We examine production of word definitions by people with probable Alzheimer's disease (pAD). In the first experiment, healthy young adults defined concrete, imageable nouns to provide a baseline of definitional ability. Analysis of these definitions identified the key defining features of each target item. In the second experiment, pAD participants and elderly controls produced definitions of the same items. In the third experiment, healthy young participants rated the adequacies of these definitions. Although as expected the pAD participants produced fewer good definitions than the other two groups, most of their responses still contained some relevant information. pAD definitions contained fewer pieces of information and the information they produced was more tangential to the primary concept than that provided by the young or elderly participants. We identify two possible explanations in semantic loss and metalinguistic impairment. We consider metalinguistic impairment to provide the more plausible explanation of pAD patients' definitional performance.     

Pattern of semantic memory impairment in dementia of Alzheimer's type

The specific pattern of semantic memory impairment in patients with dementia of Alzheimer's type (DAT) remains unclear. Specifically, the presence of a category-specific deficit for biological concepts (reflected in anomia for these concepts) has been questioned. We studied 9 DAT patients using a semantic association judgement test in which they had to decide which of the two given words was most like a target word (e.g., lamb: goat, sheep). The 150 target words were drawn from 6 categories: animals, clothing and furniture, fruits and vegetables, tools, action verbs, and abstract nouns. Age- and education-matched control subjects performed equivalently (between 86 and 90% correct) in all categories. Compared to control subjects, DAT patients made significantly more errors in abstract and biological nouns, but not in verbs and man-made artifacts. This pattern of semantic memory impairment--a sparing of verbs and a selective deficit of nouns in the biological category--has been documented in patients with temporal lobe damage, suggesting a critical dysfunction in the temporal lobes of DAT.     

Verbal mediation of number knowledge: evidence from semantic dementia and corticobasal degeneration

Patients with corticobasal degeneration (CBD) appear to have impaired number knowledge. We examined the nature of their number deficit while we tested the hypothesis that comprehension of larger numbers depends in part on verbal mediation. We evaluated magnitude judgments and performance on number conservation measures rooted in Piagetian theory in nonaphasic patients with CBD (n=13) and patients with a fluent form of progressive aphasia known as semantic dementia (SD; n=15). We manipulated the numbers of the arrays and the visual-spatial properties of the stimuli being compared during magnitude judgments and Piagetian conservation measures. CBD patients were consistently impaired judging the magnitudes of larger numbers (4-9), while they had minimal difficulty with smaller numbers (magnitudes < or = 3). By comparison, SD patients performed all measures of number knowledge at a ceiling level regardless of number magnitude. Neither patient group was significantly impacted by manipulations of the spatial properties of the stimuli. CBD patients' impairment with larger numbers despite minimal aphasia, and SD patients' intact performance despite an aphasia, challenge the proposal that understanding larger numbers depends on verbal mediation.     

The role of semantic knowledge and working memory in everyday tasks

We present a single case study of a patient, HG, who was severely impaired on routine everyday tasks, such as cleaning his teeth and preparing a cup of tea. We used the Action Coding System developed by Schwartz et al. (1991) to provide quantitative and qualitative measures of his performance in a number of experimental manipulations: (a) with task-congruent objects only, (b) with task-congruent objects and semantic distractors, (c) with a set of written commands to follow, (d) when he was given one command at a time, (e) when he was shown how the task should be performed before starting himself, and (f) when the task was divided into smaller subgoals. In general, the majority of HG's errors were step omissions, perseverations, sequence errors, and semantic errors. These semantic errors are particularly interesting since HG was able to name, gesture to, and define all the objects when they were presented in isolation or in task-congruent arrays. We suggest that semantic errors may arise for a number of reasons: (1) impaired access from semantic memory to a network representing action schema, (2) degradation of stored schema, and (3) behavior that is abnormally driven by the goal, by preceding actions, or by salient objects rather than by an appropriate association between these elements in working memory.     

Naming and categorical knowledge in Alzheimer''s disease: The process of semantic memory deterioration

Semantic memory deterioration in Alzheimer's disease (AD) has been theorized to proceed from a loss of object attribute knowledge to a loss of category knowledge. The theory is based on the belief that naming is a computational process requiring object attribute knowledge. It is strengthened by reports that AD patients misname by giving category information and perform poorer on tests of attribute than category knowledge. The purpose of this study was to test the theory's validity by administering naming and category knowledge tasks to AD and normal elderly control subjects. Results revealed a theoretically unexpected outcome, that is, naming became easier relative to the recall and recognition of category information.     

A person‐centred approach to investigate the development trajectories of job‐related affective well‐being: A 10‐year follow‐up study

The primary aim of this three‐wave 10‐year follow‐up study was to investigate the intra‐individual change trajectories of job‐related affective well‐being among Finnish managers (n= 402). Job‐related affective well‐being as indicated by anxiety, depression, comfort, and enthusiasm was measured in 1996, 1999, and 2006. The characteristics of the trajectories were sought from experienced career disruptions (i.e., periods of unemployment or lay‐offs) and perceived job insecurity. The growth mixture modelling (GMM) revealed altogether three latent trajectories that differed from each other in their mean levels and regard to changes in job‐related affective well‐being over time: (1) high and improving well‐being (n= 347), (2) decreased well‐being (n= 32), and (3) low and improving well‐being (n= 23). The associations between job‐related affective well‐being trajectories and career disruptions depended upon the timing of the career disruptions. In addition, perceived job insecurity is associated with concurrently decreased occupational well‐being. Overall, the results highlighted both typical and untypical development trajectories of job‐related affective well‐being and related career characteristics.     

The semantic‐similarity effect in children: Influence of long‐term knowledge on verbal short‐term memory

The present research was designed to highlight the relation between children's categorical knowledge and their verbal short‐term memory (STM) performance. To do this, we manipulated the categorical organization of the words composing lists to be memorized by 5‐ and 9‐year‐old children. Three types of word list were drawn up: semantically similar context‐dependent (CD) lists, semantically similar context‐independent (CI) lists, and semantically dissimilar lists. In line with the procedure used by Poirier and Saint‐Aubin (1995) , the dissimilar lists were produced using words from the semantically similar lists. Both 5‐ and 9‐year‐old children showed better recall for the semantically similar CD lists than they did for the unrelated lists. In the semantic similar CI condition, semantic similarity enhanced immediate serial recall only at age 9 but contributed to item information memory both at ages 5 and 9. These results, which indicate a semantic influence of long‐term memory (LTM) on serial recall from age 5, are discussed in the light of current models of STM. Moreover, we suggest that differences between results at 5 and 9 years are compatible with pluralist models of development.     

Memory for internally generated words in Alzheimer-type dementia: breakdown in encoding and semantic memory

The "generation effect" is a phenomenon in which words that are generated by the subject are remembered better than words which are read. The present experiments examined this effect in patients with mild-to-moderate dementia of the Alzheimer type (DAT), healthy elderly adults, and young adults under a variety of different encoding and retrieval conditions. Experiment 1 employed an intentional learning task with multiple study/test trials using the same list of words. While both the young and elderly adults exhibited higher recall for internally generated words than read words, the DAT patients failed to demonstrate the effect even after repeated exposures to the same stimulus list. Experiment 2 replicated this same pattern of results using an incidental learning paradigm with both recall and recognition tests. Various explanations as to why the DAT patients failed to show the generation effect were discussed with particular emphasis placed on the role of semantic memory and encoding failure.     

Domain‐specific and domain‐general precursors of mathematical achievement: A longitudinal study from kindergarten to first grade

Background. Many contributing factors, both domain specific and domain general, influence children's performance in school achievement. Aims. This research aims to verify the importance of kindergarten measures of cognitive abilities and numerical competence in the role of predicting mathematical school achievement at the end of first grade. Sample and Methods. A total of 70 children (38 females and 32 males) took part in the study. We tested the children at the beginning of their last year of kindergarten (time 1) on the following cognitive abilities: IQ, phonology, counting skills, verbal short‐term memory, visuo‐spatial short‐term memory, working memory, and processing speed. Then, we tested the same children at end of their last year of kindergarten (time 2) on a measure of numerical competence and at the end of their first year of primary school (time 3) on a test of math achievement. Results. Path analysis models revealed the direct influence of working memory and processing speed on predicting numerical competence in pre‐schoolers and the influence of processing speed and verbal IQ on predicting math achievement in first graders. Moreover, this study found a direct link between numerical competence and math achievement. Conclusions. Both domain‐specific and domain‐general factors contribute to determining math achievement at the end of first grade.     

Phonological awareness and language intervention in preschoolers from low socio‐economic backgrounds: A longitudinal investigation

This study examines the literacy outcomes for children from socially disadvantaged backgrounds who had received specific whole‐class phonological awareness (PA) and language intervention in preschool. The participants were 57 children who had been involved in the original intervention study. Their PA skills, letter‐sound knowledge, real word and non‐word spelling and reading comprehension were assessed in Grade 2. The results indicated that children who had received intervention in preschool performed similarly to the children who had not received intervention. The gains made in PA and language skills post intervention had failed to augment further literacy development. A post hoc examination of individual student profiles, however, revealed that a subgroup of children who had received intervention had maintained their enhanced performance and that the intervention cohort had similar scores on tests of PA ability to their age‐matched peers in the population. It was concluded that whole‐class, teacher‐delivered, PA and language intervention, while effective in the short term, does not lead to a generalized improvement in literacy skills in Grade 2. Possible reasons for the failure of the program to produce medium term gains are discussed.     

Job stress and well‐being: An examination from the view of person‐environment fit

The current study investigated the impact of job stressors on well‐being from the perspective of person‐environment fit. Based upon a 288‐case sample from six organizations, we found that the actual and preferred career advancement themselves and their second‐order (curvilinear) combinations jointly predicted job satisfaction, mental well‐being, and turnover intention. Also, the actual and preferred quality of relationships at work and their second‐order (curvilinear) combinations jointly predicted job satisfaction, mental and physical well‐being, and turnover intention. Some possible mechanisms underlying the stressor‐outcome relationship and their implications are discussed.     

Episodic and semantic knowledge in emotional self-report: evidence for two judgment processes

Three studies involving 3 participant samples (Ns = 39, 55, and 53) tested the hypothesis that people retrieve episodic emotion knowledge when reporting on their emotions over short (e.g., last few hours) time frames, but that they retrieve semantic emotion knowledge when reporting on their emotions over long (e.g., last few months) time frames. Support for 2 distinct judgment strategies was based on judgment latencies (Studies 1 and 2) and priming paradigms (Studies 2 and 3). The authors suggest that self-reports of emotion over short versus long time frames assess qualitatively different sources of self-knowledge.     

The variability of country map knowledge in normal and aphasic subjects: Evidence from two new category‐specific screening tests

Two new category‐specific screening tests are described, tapping naming to confrontation and word comprehension at two different levels of frequency. Level I consists of 10 very high‐frequency items from each of the categories of animals, man‐made artefacts, colours, body parts and countries. Level II probes knowledge of 10 marginally lower frequency items from the categories of animals, man‐made artefacts, fruits and vegetables, body parts and countries. A standardization study of 120 healthy older adult subjects is reported. Performance at both levels of frequency in all categories except for countries was at or close to ceiling. A retrospective validation study in the form of a review of 20 cases published during the last 20 years demonstrates the utility of the Level I test for screening for category‐specific deficits in severely aphasic patients who were not able to complete more demanding formal tests of naming and comprehension. The surprising variability of map knowledge observed in the standardization sample is considered in the light of one previous report and one newly presented case (IRQ) of apparent selective impairment of country map naming skills.     

Long‐term memory effects on verbal short‐term memory: A replication study

The influence of lexico‐semantic language representations stored in long‐term memory (LTM) on short‐term memory (STM) performance has been studied extensively in adults. However, there are relatively few data on lexico‐semantic LTM effects on STM in children. On the other hand, the influence of phonological LTM effects on STM has been studied more extensively in children than in adults. In this study, we explored whether these different LTM effects on verbal STM could be replicated in both adults and children by administering immediate serial recall tasks (ISR) for high‐ and lowfrequency words, for high‐ and low‐imageability words, for words and non‐words, and for high and low phonotactic frequency non‐words to 6‐, 8‐, and 10‐year‐old children, to adolescents and to adults. Significant word frequency, lexicality and phonotactic frequency effects were observed in all age groups, as well as a word imageability effect which was, however, weaker than the other three effects. Our data suggest that LTM effects on STM are equivalent in both children and adults.