Cross-sectional analysis of Alzheimer disease effects on oral discourse in a picture description task

Using Automatic Assessment of Speech Production to Predict Current and Future Cognitive Function in Older Adults

Neurodegenerative conditions like Alzheimer disease affect millions and have no known cure, making early detection important. In addition to memory impairments, dementia causes substantial changes in speech production, particularly lexical-semantic characteristics. Existing clinical tools for detecting change often require considerable expertise or time, and efficient methods for identifying persons at risk are needed. This study examined whether early stages of cognitive decline can be identified using an automated calculation of lexical-semantic features of participants' spontaneous speech. Unimpaired or mildly impaired older adults (N = 39, mean 81 years old) produced several monologues (picture descriptions and expository descriptions) and completed a neuropsychological battery, including the Modified Mini-Mental State Exam. Most participants (N = 30) returned one year later for follow-up. Lexical-semantic features of participants' speech (particularly lexical frequency) were significantly correlated with cognitive status at the same visit and also with cognitive status one year in the future. Thus, automated analysis of speech production is closely associated with current and future cognitive test performance and could provide a novel, scalable method for longitudinal tracking of cognitive health.

Low Speech Connectedness in Alzheimer's Disease is Associated with Poorer Semantic Memory Performance

Connected speech is an everyday activity. We aimed to investigate whether connected speech can differentiate oral narrative production between adults with Alzheimer's disease (AD; n = 24) and cognitively healthy older adults (n = 48). We used graph attributes analysis to represent connected speech. Participants produced oral narratives and performed semantic, episodic, and working memory tasks. AD patients produced less connected narratives than cognitively healthy older adults. Connectedness was associated with semantic memory in AD and with episodic memory in controls. Word-graphs connectedness represents a practical tool to assess cognitive impairment in AD patients.

Assessing the Utility of Language and Voice Biomarkers to Predict Cognitive Impairment in the Framingham Heart Study Cognitive Aging Cohort Data

BACKGROUND

There is a need for fast, accessible, low-cost, and accurate diagnostic methods for early detection of cognitive decline. Dementia diagnoses are usually made years after symptom onset, missing a window of opportunity for early intervention.

OBJECTIVE

To evaluate the use of recorded voice features as proxies for cognitive function by using neuropsychological test measures and existing dementia diagnoses.

METHODS

This study analyzed 170 audio recordings, transcripts, and paired neuropsychological test results from 135 participants selected from the Framingham Heart Study (FHS), which includes 97 recordings of cognitively normal participants and 73 recordings of cognitively impaired participants. Acoustic and linguistic features of the voice samples were correlated with cognitive performance measures to verify their association.

RESULTS

Language and voice features, when combined with demographic variables, performed with an AUC of 0.942 (95% CI 0.929-0.983) in predicting cognitive status. Features with good predictive power included the acoustic features mean spectral slope in the 500-1500 Hz band, variation in the F2 bandwidth, and variation in the Mel-Frequency Cepstral Coefficient (MFCC) 1; the demographic features employment, education, and age; and the text features of number of words, number of compound words, number of unique nouns, and number of proper names.

CONCLUSION

Several linguistic and acoustic biomarkers show correlations and predictive power with regard to neuropsychological testing results and cognitive impairment diagnoses, including dementia. This initial study paves the way for a follow-up comprehensive study incorporating the entire FHS cohort.

Narrative video scene description task discriminates between levels of cognitive impairment in Alzheimer's disease

The process of interpreting and acting upon the visual environment requires both intact cognitive and visual systems. The narrative description (ND) task, initially developed to detect changes in ecologically relevant visual function in people with impaired vision, is an objective measure of the ability to perceive, understand, and describe a visual scene in a movie clip.

OBJECTIVE

Because the ND task draws heavily on semantic and working memory ability in addition to basic visual perception, we aimed to assess the discriminative performance of this task across levels of cognitive impairment.

METHOD

We recruited 56 participants with cognitive status ranging from normal cognition to mild dementia (median age 82, range 66 to 99 years) to watch 20 30-s video clips and describe the visual content without time constraints. These verbal responses were transcribed and processed to generate ND shared word scores using a "wisdom of the crowd," natural-language processing approach. We compared ND scores across diagnostic groups, and used linear mixed models to examine decrements in task performance.

RESULTS

There was a stepwise decline of ND scores with increasing levels of cognitive impairment. Additional analyses showed that ND performance was highly related to performance on the Montreal Cognitive Assessment (MoCA) and domain-specific neuropsychological tests for semantic fluency and set shifting. Other models demonstrated differences in ND performance related video content between cognitively normal and impaired participants.

CONCLUSION

The ND test was able to detect decrements in task performance between levels of cognitive impairment and was related to other global neuropsychological measures. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

An Interactional Profile to Assist the Differential Diagnosis of Neurodegenerative and Functional Memory Disorders

OBJECTIVE

Specialist services for dementia are seeing an increasing number of patients. We investigated whether interactional and linguistic features in the communication behavior of patients with memory problems could help distinguish between those with problems secondary to neurological disorders (ND) and those with functional memory disorder (FMD).

METHODS

In part 1 of this study, a diagnostic scoring aid (DSA) was developed encouraging linguists to provide quantitative ratings for 14 interactional features. An optimal cut-off differentiating ND and FMD was established by applying the DSA to 30 initial patient-doctor memory clinic encounters. In part 2, the DSA was tested prospectively in 10 additional cases analyzed independently by 2 conversation analysts blinded to medical information.

RESULTS

In part 1, the median score of the DSA was +5 in ND and -5 in FMD (P<0.001). The optimal numeric DSA cut-off (+1) identified patients with ND with a sensitivity of 86.7% and a specificity of 100%. In part 2, DSA scores of rater 1 correctly predicted 10/10 and those of rater 2 predicted 9/10 diagnoses.

CONCLUSIONS

This study indicates that interactional and linguistic features can help distinguish between patients developing dementia and those with FMD and could aid the stratification of patients with memory problems.

Study protocol: Language profile in mild cognitive impairment: A prospective study

Background: The present study will be a longitudinal investigation of language abilities in individuals with mild cognitive impairment (MCI). The research question will include whether there will be an evidence for language impairment in individuals with MCI, and if so, what aspects of language will be the most affected and whether language abilities will be significantly changed over a 12-month period.

Methods: We will diagnose 30 individuals with mild cognitive impairment (MCI), Alzheimer’s disease (AD), and controlled participants using Montreal Cognitive Assessment-Basic (MoCA-B), as a cognitive test, and by asking expert opinions and conducting interviews. Participants will be selected from memory clinics and nursing homes in Tehran during 2018-2019. A comprehensive language test (Barnes Language Assessment (BLA)) will be performed to obtain baseline performance in the elderly. These tests will be repeated after 3, 6, and 12 months. Repeated measures analysis of variance (ANOVA) will be used to determine whether there will be a significant change in participants' language abilities over a 12-month period. In the case of deficient language performance, a discriminant function analysis will be used to identify the language task type that will be highly sensitive to change.

Results and Conclusion: The present study will provide evidence for the nature of language change and will be done in a-year course on individuals with MCI and AD and on healthy elders. Also, in this study, the relative sensitivity of various language components to MCI will be determined, and the relationship between language performance and performance on (MoCA-B) neuropsychological test will be examined.

Connected Speech Features from Picture Description in Alzheimer's Disease: A Systematic Review

The language changes that occur over the course of Alzheimer's disease (AD) can impact communication abilities and have profound functional consequences. Picture description tasks can be used to approximate everyday communication abilities of AD patients. As various methods and variables have been studied over the years, current knowledge about the most affected features of AD discourse in the context of picture descriptions is difficult to summarize. This systematic review aims to provide researchers with an overview of the most common areas of impairment in AD discourse as they appear in picture description tasks. Based on the 44 articles fulfilling inclusion criteria, our findings reflect a multidimensional pattern of changes in the production (speech rate), syntactic (length of utterance), lexical (word-frequency and use of pronouns), fluency (repetitions and word-finding difficulties), semantic (information units), and discourse (efficiency) domains. We discuss our findings in the light of current research and point to potential scientific and clinical uses of picture description tasks in the context of AD.

Language Performance of Individuals at Risk for Mild Cognitive Impairment

Purpose Evidence exists that changes in language performance may be an early indicator of mild cognitive impairment (MCI), often a harbinger of dementing disease. The purpose of this study was the evaluation of language performance in individuals at risk for MCI by virtue of age and self-concern and its relation to performance on tests of memory, visuospatial function, and mental status. Method Eighty-three individuals 55 years or older were administered the Arizona Battery for Communication Disorders of Dementia ( Bayles & Tomoeda, 1993 ), a standardized battery with normative data from 86 healthy older adults (HOAs) and 86 individuals with Alzheimer's dementia, the most common dementing disease. A performance criterion of 1-1.5 SDs below the mean of HOAs defined MCI, as recommended in the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition. We hypothesized that (a) the majority of at-risk participants would score 1 SD or more below the mean of HOAs on 1 or more subtests and (b) language performance tests would present a greater challenge than memory, mental status, and visuospatial construction tests. Results Both hypotheses were confirmed. Sixty-two participants (74.6%) met the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, criteria on at least 1 subtest. Moreover, language subtests were those most likely to elicit a performance 1 SD or more below the mean of HOAs. Conclusions Language performance deficits can appear early before impairment in episodic memory, visuospatial construction ability, or mental status in individuals at risk for MCI. Speech-language pathologists are uniquely qualified to identify subtle changes in language, and standardized language tests with normative data should be used when testing for MCI.

Connected speech and language in mild cognitive impairment and Alzheimer's disease: A review of picture description tasks

INTRODUCTION

The neuropsychological profile of people with mild cognitive impairment (MCI) and Alzheimer's disease (AD) dementia includes a history of decline in memory and other cognitive domains, including language. While language impairments have been well described in AD dementia, language features of MCI are less well understood. Connected speech and language analysis is the study of an individual's spoken discourse, usually elicited by a target stimulus, the results of which can facilitate understanding of how language deficits typical of MCI and AD dementia manifest in everyday communication. Among discourse genres, picture description is a constrained task that relies less on episodic memory and more on semantic knowledge and retrieval, within the cognitive demands of a communication context. Understanding the breadth of evidence across the continuum of cognitive decline will help to elucidate the areas of strength and need in terms of using this method as an evaluative tool for both cognitive changes and everyday functional communication.

METHOD

We performed an extensive literature search of peer-reviewed journal articles that focused on the use of picture description tasks for evaluating language in persons with MCI or AD dementia. We selected articles based on inclusion and exclusion criteria and described the measures assessed, the psychometric properties that were reported, the findings, and the limitations of the included studies.

RESULTS

36 studies were selected and reviewed. Across all 36 studies, there were 1, 127 patients with AD dementia and 274 with MCI or early cognitive decline. Multiple measures were examined, including those describing semantic content, syntactic complexity, speech fluency, vocal parameters, and pragmatic language. Discriminant validity widely reported and distinct differences in language were observable between adults with dementia and controls; fewer studies were able to distinguish language differences between typically aging adults and those with MCI.

DISCUSSION

Our review shows that picture description tasks are useful tools for detecting differences in a wide variety of language and communicative measures. Future research should expand knowledge about subtle changes to language in preclinical AD and Mild Cognitive Impairment (MCI) which may improve the utility of this method as a clinically meaningful screening tool.

Declines in Connected Language Are Associated with Very Early Mild Cognitive Impairment: Results from the Wisconsin Registry for Alzheimer's Prevention

Changes to everyday spoken language ("connected language") are evident in persons with AD dementia, yet little is known about when these changes are first detectable on the continuum of cognitive decline. The aim of this study was to determine if participants with very early, subclinical memory declines were also showing declines in connected language. We analyzed connected language samples obtained from a simple picture description task at two time points in 264 participants from the Wisconsin Registry for Alzheimer's Prevention (WRAP). In parallel, participants were classified as either "Cognitively Healthy" or "Early Mild Cognitive Impairment" based on longitudinal neuropsychological test performance. Linear mixed effects models were used to analyze language parameters that were extracted from the connected language samples using automated feature extraction. Participants with eMCI status declined faster in features of speech fluency and semantic content than those who were cognitively stable. Measures of lexical diversity and grammatical complexity were not associated with eMCI status in this group. These findings provide novel insights about the relationship between cognitive decline and everyday language, using a quick, inexpensive, and performance-based method.

Linguistic Features Identify Alzheimer's Disease in Narrative Speech

BACKGROUND

Although memory impairment is the main symptom of Alzheimer's disease (AD), language impairment can be an important marker. Relatively few studies of language in AD quantify the impairments in connected speech using computational techniques.

OBJECTIVE

We aim to demonstrate state-of-the-art accuracy in automatically identifying Alzheimer's disease from short narrative samples elicited with a picture description task, and to uncover the salient linguistic factors with a statistical factor analysis.

METHODS

Data are derived from the DementiaBank corpus, from which 167 patients diagnosed with "possible" or "probable" AD provide 240 narrative samples, and 97 controls provide an additional 233. We compute a number of linguistic variables from the transcripts, and acoustic variables from the associated audio files, and use these variables to train a machine learning classifier to distinguish between participants with AD and healthy controls. To examine the degree of heterogeneity of linguistic impairments in AD, we follow an exploratory factor analysis on these measures of speech and language with an oblique promax rotation, and provide interpretation for the resulting factors.

RESULTS

We obtain state-of-the-art classification accuracies of over 81% in distinguishing individuals with AD from those without based on short samples of their language on a picture description task. Four clear factors emerge: semantic impairment, acoustic abnormality, syntactic impairment, and information impairment.

CONCLUSION

Modern machine learning and linguistic analysis will be increasingly useful in assessment and clustering of suspected AD.

Compensatory strategies in picture description across severity levels in Alzheimer's disease: A longitudinal study

Communication changes over time were studied in 55-persons with Alzheimer's disease (AD) who completed a picture description task at entry, six, and 12-months. Differences at three levels of AD severity (early, middle, late) were investigated using six discourse measures (total utterances, length of utterance, words, abandoned utterances, information units, and conciseness), and six pragmatic measures (questions, turns, unsure statements, judgments, egocentric comments, and giving names). Across all three groups, subjects were less concise over time, made shorter utterances, asked more questions, and provided fewer information units. Increasing percentages of subjects made unsure statements with time. However, performance varied by severity group, with increasing unsureness occurring only at early AD, and all other observed changes occurring at late AD. Persons with AD appear to strive for communication competence as language declines by increasing certain compensatory pragmatic aspects (questions and unsure statements) at different severity levels of the disorder. This suggests that compensatory pragmatic devices are used with flexibility, and that the desire to communicate is maintained throughout the course of AD.

Microlinguistic processes that contribute to the ability to relay main events: influence of age

The purpose of the current study was to determine the microlinguistic processes that contribute to picture description in healthy adults across the life span. Two-hundred forty healthy adults were separated into three groups, young (n = 80; 20-39), middle (n = 80; 40-69), and older (n = 80; 70-89). Participants provided language samples in response to two single and two sequential pictures analyzed for total number of words, informativeness, lexical diversity, syntactic complexity, and main events. The older group produced a significantly lower proportion of main events for the single and sequential pictures compared to the other groups. Group differences on the microlinguistic measures varied depending on the measure and the stimulus type. Further, regardless of task, total number of words significantly related to main event production for the young and middle aged groups, but not the older group. Results of the current study extend previous findings by researchers who have investigated discourse production in cognitively healthy, older adults. Using a multi-level approach, we found that linguistic processes across different levels interact; however, the relationship is age-dependent. By including a middle-aged group we identify the potential course of documented change and our results indicate that the changes in language processes with age may not be linear.

Auditory and Visual Cues for Topic Maintenance with Persons Who Exhibit Dementia of Alzheimer’s Type

This study compared the effectiveness of auditory and visual redirections in facilitating topic coherence for persons with Dementia of Alzheimer's Type (DAT). Five persons with moderate stage DAT engaged in conversation with the first author. Three topics related to activities of daily living, recreational activities, food, and grooming, were broached. Each topic was presented three times to each participant: once as a baseline condition, once with auditory redirection to topic, and once with visual redirection to topic. Transcripts of the interactions were scored for overall coherence. Condition was a significant factor in that the DAT participants exhibited better topic maintenance under visual and auditory conditions as opposed to baseline. In general, the performance of the participants was not affected by the topic, except for significantly higher overall coherence ratings for the visually redirected interactions dealing with the topic of food.

Doença de alzheimer: cognição e discurso narrativo com apoio em figuras

Objetivo investigar as características discursivas de pessoas com Doença de Alzheimer (DA) nos estágios moderado e moderado-grave por meio de uma tarefa com apoio em figuras; examinar possíveis falhas na expressão do conhecimento e a relação entre o discurso e a cognição. Métodos trata-se de um estudo com delineamento transversal, quantitativo, utilizando-se da análise de comparação de grupos. A amostra do grupo clínico foi constituída por dezoito participantes com DA (oito sujeitos com declínio cognitivo moderado (GDS 4), e dez com declínio cognitivo moderado-grave (GDS 5); o grupo controle foi composto de dezesseis sujeitos sem distúrbios neurológicos ou psiquiátricos. Todos sujeitos foram pareados quanto ao gênero, língua materna, idade e escolaridade e todos submetidos a avaliações de habilidades cognitivas. A tarefa discursiva consistiu na narrativa baseada em uma sequência de figuras do conto “Chapeuzinho Vermelho”. Resultados os sujeitos com DA apresentaram escores de coerência global mais baixos, bem como mais falhas na expressão de conhecimento do que sujeitos sem DA e suas características discursivas correlacionaram-se com suas habilidades cognitivas. Os grupos GDS 4 e GDS 5 diferiram com relação à coerência local. Conclusão o discurso dos participantes com DA caracteriza-se por falhas de coerência e informatividade que apresentam relações estreitas com seus déficits cognitivos.

Connected speech as a marker of disease progression in autopsy-proven Alzheimer's disease

Although an insidious history of episodic memory difficulty is a typical presenting symptom of Alzheimer's disease, detailed neuropsychological profiling frequently demonstrates deficits in other cognitive domains, including language. Previous studies from our group have shown that language changes may be reflected in connected speech production in the earliest stages of typical Alzheimer's disease. The aim of the present study was to identify features of connected speech that could be used to examine longitudinal profiles of impairment in Alzheimer's disease. Samples of connected speech were obtained from 15 former participants in a longitudinal cohort study of ageing and dementia, in whom Alzheimer's disease was diagnosed during life and confirmed at post-mortem. All patients met clinical and neuropsychological criteria for mild cognitive impairment between 6 and 18 months before converting to a status of probable Alzheimer's disease. In a subset of these patients neuropsychological data were available, both at the point of conversion to Alzheimer's disease, and after disease severity had progressed from the mild to moderate stage. Connected speech samples from these patients were examined at later disease stages. Spoken language samples were obtained using the Cookie Theft picture description task. Samples were analysed using measures of syntactic complexity, lexical content, speech production, fluency and semantic content. Individual case analysis revealed that subtle changes in language were evident during the prodromal stages of Alzheimer's disease, with two-thirds of patients with mild cognitive impairment showing significant but heterogeneous changes in connected speech. However, impairments at the mild cognitive impairment stage did not necessarily entail deficits at mild or moderate stages of disease, suggesting non-language influences on some aspects of performance. Subsequent examination of these measures revealed significant linear trends over the three stages of disease in syntactic complexity, semantic and lexical content. The findings suggest, first, that there is a progressive disruption in language integrity, detectable from the prodromal stage in a subset of patients with Alzheimer's disease, and secondly that measures of semantic and lexical content and syntactic complexity best capture the global progression of linguistic impairment through the successive clinical stages of disease. The identification of disease-specific language impairment in prodromal Alzheimer's disease could enhance clinicians' ability to distinguish probable Alzheimer's disease from changes attributable to ageing, while longitudinal assessment could provide a simple approach to disease monitoring in therapeutic trials.

Considering a multi-level approach to understanding maintenance of global coherence in adults with aphasia

BACKGROUND: Discourse is a naturally occurring, dynamic form of communication. Coherence is one aspect of discourse and is a reflection of the listener's ability to interpret the overall meaning conveyed by the speaker. Adults with aphasia may present with impaired maintenance of global coherence, which, in turn, may contribute to their difficulties in overall communicative competence. AIMS: The aim of the study was to determine if microlinguistic processes contribute to maintenance of global coherence in adults with and without aphasia. METHOD AND PROCEDURES: Participants included 15 adults with aphasia (PWA) and 15 healthy controls (HC). Study participants told stories conveyed in wordless picture books. The discourse samples were transcribed and then analyzed for percent of information units produced, lexical diversity, syntactic complexity, and maintenance of global coherence. OUTCOMES AND RESULTS: Several linear regression models were carried out to investigate the relationship among the microlinguistic and macrolinguistic measures. For the control group, percent of information units conveyed was a significant predictor of maintenance of global coherence for stories told. For the aphasia group, percent of information units conveyed and lexical diversity were significant predictors of maintenance of global coherence for stories told. CONCLUSIONS: Results indicated that microlinguistic processes contribute to the maintenance of global coherence in stories told by adults with aphasia. These findings have important clinical implications for using a multi-level discourse model for analyzing discourse ability in adults with aphasia and measuring individual response to treatment.

Descriptive discourse: topic familiarity and disfluencies

This investigation was undertaken to address questions about topic familiarity and disfluencies during oral descriptive discourse of adult speakers. Participants expressed more attributes when the topic was familiar than when it was unfamiliar. Fillers and lexical pauses were the most frequent disfluencies. The mean duration of each hesitation pause was 776 ms. The sum of hesitation pause durations was well correlated with the number of occurrences. Repetitions, hesitation pauses, and prolongations were shown to have the same role, which was distinct from the role of fillers. The type of analysis conducted in this investigation may be useful in distinguishing between normal and disordered speech production.

LEARNING OUTCOMES

The reader will obtain information about the differences between the number of propositions in familiar and unfamiliar oral descriptions. The reader will also become aware of the distribution of disfluencies in discourse categories employed by the participants in this investigation.

Discourse about discourse: What is it and how does it progress in Alzheimer’s disease?

Discourse about discourse or a subject's comments about his/her performance during a discourse task can be defined as modalizing discourse (discours modalisateur; [Nespoulous, 1980]; [Nespoulous et al., 1998]). Since it does not convey the expected content of the discourse task (referential discourse), modalizing discourse has often been considered non-informative, and as such, has received little interest. The present study investigated the modalizing aspect of discourse production and its evolution in Alzheimer's disease (AD). Five AD patients produced a picture-induced narrative across five consecutive assessments. Two measures were derived: the modalizing/referential ratio (M/R ratio) and the percentage of repeated ideas. Results revealed that, compared to a group of 27 normal controls matched for age and education, AD patients: (1) obtained higher M/R ratios that tended to diminish as the number of assessments increased, and (2) produced higher percentages of repeated ideas throughout all assessments. These results suggest that modalizing discourse makes up a large proportion of AD patients' discourse and should be included in further studies to accurately describe their discourse behavior. The implications of modalizing discourse on preserved pragmatic abilities and its inclusion in comprehensive management programs of AD patients are discussed.

Effects of four years of exercise, language, and social interventions on Alzheimer discourse

This article describes a comprehensive cognitive-linguistic intervention program for mild to moderate Alzheimer's disease (AD) patients that provided communication skills practice in the context of health-enhancing and esteem-building community-based activities: physical fitness training and supervised volunteer work. The interventions were administered by undergraduate students who completed academic work, received faculty supervision, and earned three credits for one semester of participation. Effects of the interventions on the discourse of four participants who completed all 4 years of the program are reported in detail. The maintained or improved performance on multiple discourse outcome measures provides powerful rationale for making such interventions more widely available and preliminary support for their effectiveness in preserving communicative function. An additional role for speech-language pathologists (SLPs)--as trainers and supervisors of non-professional rehab partners for persons with dementia--is proposed.

LEARNING OUTCOMES

From this article, participants will be able to (1) list specific language tasks that can be used to assess discourse in individuals with AD; (2) identify several cognitive-linguistic interventions appropriate for use with AD patients; and (3) understand how long-term cognitive-linguistic interventions may affect the language performance of individuals with AD.

Communication abilities of individuals with late-stage Alzheimer disease

The communication abilities of 49 individuals in the late stage of Alzheimer disease were examined in relation to other markers of late-stage Alzheimer disease (e.g., incontinence and ambulatory ability). Two existing tools used to stage severity of dementia, the Global Deterioration Scale and the Functional Assessment Stages, have represented communication abilities in individuals with late-stage Alzheimer disease to be minimal to nonexistent. The individuals in this sample showed greater communication skills and verbal output than would be predicted by these scales.

The rise and fall of frequency and imageability: noun and verb production in semantic dementia

This study examines the impact of progressive degeneration of conceptual knowledge on the content words used in connected speech elicited using the Cookie Theft picture description (Goodglass & Kaplan. 1983). We began with an analysis of control subjects' descriptions with regard to word types and their frequency and imageability. Because the impairment of conceptual knowledge in semantic dementia is graded by concept familiarity, we created a model of a standardized normal Cookie Theft description that was then progressively degraded by the systematic removal of lower bands of word frequency. We drew two main predictions from this model: reduced availability of the lower bands of word frequency should result in (a) an apparent deficit for noun retrieval in relation to verb retrieval and (b) an apparent reverse imageability effect. Results from a longitudinal study. in which three patients with semantic dementia each described the Cookie Theft picture on three occasions during the progression of their disease, confirmed these predictions. An additional cross-sectional analysis, adding narratives from a larger number of cases, demonstrated that the decline in ability to produce suitable words for the picture description is closely related to the extent of semantic impairment as measured in tests of word comprehension and production. Both verbs and nouns are affected by the degradation of semantic memory; the fact that the impairment to noun production is manifested earlier and more catastrophically may be attributed to the relatively lower frequency of these terms.