Core lexicon in aphasia: A longitudinal study

Access to context-specific lexical-semantic information during discourse tasks differentiates speakers with latent aphasia, mild cognitive impairment, and cognitively healthy adults

Purpose

Mild language impairments experienced by adults with neurogenic communication disorders are often difficult to detect due to the lack of sensitive traditional performance-based measures. This is problematic since many adults who have mild language deficits experience daily activity and participation limitations that are undetected and not managed. This study evaluates the potential for variables derived through core lexicon analysis to differentiate two clinical groups (latent aphasia, MCI) from each other, and from a cognitively healthy adult group, across three different discourse tasks (Aim 1). Innovatively, it also contrasts the sensitivity with which each task differentiates the groups based on this metric (Aim 2).

Methods

Transcribed connected speech data from TalkBank were analyzed for three discourse tasks (i.e., Sandwich Procedure, Cat Rescue Picture Description, and Cinderella Story) from three participant groups [Mild Cognitive Impairment (MCI) n = 30, stroke-induced latent aphasia n = 29, and Cognitive Healthy Adults (CHA) n = 56]. Aim 1 used one-way ANOVAs (or non-parametric equivalents) to identify differences in lexical variables (total number of core lexical items; proportion of core lexical items out of all words produced; and rate of core lexical items produced per second) between participant groups. Aim 2 used linear discriminant analysis with cross validation to characterize the sensitivity of discourse task in identifying lexical variables differentiating the participant groups.

Results

Univariate analysis revealed significant differences among the three participant groups. During the Cinderella task, the latent aphasia and MCI groups produced significantly fewer core lexical items than CHAs, while their proportion of core lexical items to total tokens was higher than CHAs. The latent aphasia group produced core lexical items more slowly than the MCI group for all three discourse tasks. Finally, individuals with latent aphasia produced significantly fewer core lexical items during the Sandwich task than either the MCI or CHA groups. Aim 2's sensitivity analysis revealed that number of core lexical items produced during the Cinderella task best differentiated the MCI group from CHAs, number of core lexical items produced during Sandwich best differentiated latent aphasia from CHAs, and core lexical items per second during Cinderella best differentiated latent aphasia from MCI.

Conclusion

Our study suggests that the Cinderella story is more sensitive than a picture description task for demonstrating the subtle lexical-semantic changes in MCI and latent aphasia compared to CHAs. Core lexicon appears to be a sensitive discourse metric to identify linguistic differences between CHAs and individuals with mild cognitive and/or language deficits. These findings further support calls to provide speech/language and cognitive therapy to individuals with MCI and/or latent aphasia.

A preliminary investigation on core lexicon analysis in dementia of the Alzheimer's type

BACKGROUND

Core lexicon (CL) analysis is a time efficient and possibly reliable measure that captures discourse production abilities. For people with aphasia, CL scores have demonstrated correlations with aphasia severity, as well as other discourse and linguistic measures. It was also found to be clinician-friendly and clinically sensitive enough to capture longitudinal changes in aphasia. To our knowledge, CL has never been investigated in individuals with neurologically progressive disease.

AIMS

As a preliminary investigation, we sought to investigate (1) whether CL scores correlate with dementia severity, (2) whether CL scores correlate with measures of discourse quality, and (3) whether CL scores correlate with other measures of lexical/semantic access.

METHODS & PROCEDURES

Twelve participants with a cognitive impairment associated with dementia of the Alzheimer's type (DAT) completed several measures of language and cognitive ability, as well as provide a language sample from the wordless picture book, Picnic.

RESULTS & CONCLUSION

Results are informative, as they provide insight into characteristics of CL and provide support for potential use of CL in individuals with neurologically progressive disease. The results indicated that CL scores do correlate with dementia severity and several measures of language ability, indicating they may provide a useful measure of language abilities in DAT, but more research is needed.

WHAT THIS PAPER ADDS

What is already known on the subject Core lexicon (CL) analysis is an assessment measure of discourse ability, most closely related to informativeness or productivity, used in aphasiology that is easier to use and less time consuming than previous measures of informativeness, such as correct information units or type-token ratio (TTR). For people with aphasia, CL analysis correlates with aphasia severity, measures of informativeness, as well as other measures of discourse quality. It has also been shown to be faster and more reliable between scorers than other informativeness measures. What this study adds Core lexicon analysis is a new simple and online method for assessing the informativeness of a discourse sample without the need to record or transcribe the language sample. CL is receiving a lot of attention in aphasia, correlating with everything from aphasia severity to measures of productivity and lexical access, as well as measures of informativeness. Unfortunately, no one has investigated CL analysis in dementia. The study demonstrates the first evidence that CL analysis may be a useful measure for determining dementia severity and language quality in people with dementia. What are the clinical implications of this work? Core lexicon analysis may provide clinicians and researchers with an easy method for assessing the discourse of people with a cognitive impairment associated with dementia of the Alzheimer's type. This will improve initial assessment, as well as improve ongoing language assessment that may provide clues into their functional ability to communicate effectively.

Written discourse in diagnosis for acquired neurogenic communication disorders: current evidence and future directions

Purpose

We aimed to perform the first review of research focusing on written discourse performance in people with acquired neurogenic communication disorders. In studies from 2000 onward, we specifically sought to determine: (1) the differences between patient populations and control groups, (2) the differences between different patient populations, (3) longitudinal differences between patient populations, and (4) modality differences between spoken and written discourse performance.

Methods

We completed a thorough search on MEDLINE, Embase, Cochrane, APAPsycinfo, Web of Science, and Scopus databases. We identified studies that focus on written discourse performance in people with aphasia, primary progressive aphasia, mild cognitive impairment, and Alzheimer's disease.

Results

Nineteen studies were identified from the review of literature, some of which addressed more than one of our review questions. Fifteen studies included a comparison between clinical populations and controls. Six studies compared different characteristics of patient populations. Three studies reported changes over time in progressive disorders. Six studies targeted different modalities of discourse.

Conclusion

Differences in linguistic features by patient populations are not yet clear due to the limited number of studies and different measures and tasks used across the studies. Nevertheless, there is substantial evidence of numerous linguistic features in acquired neurogenic communication disorders that depart from those of healthy controls. Compared to the controls, people with aphasia tend to produce fewer words, and syntactically simpler utterances compared to the controls. People with Alzheimer's disease produce less information content, and this feature increases over time, as reported in longitudinal studies. Our review imparts additional information that written and spoken discourse provide unique insights into the cognitive and linguistic deficits experienced by people with aphasia, Alzheimer's disease, mild cognitive impairment and primary progressive aphasia and provide targets for treatment to improve written communication in these groups.

Test-Retest Reliability of Microlinguistic Information Derived From Spoken Discourse in Persons With Chronic Aphasia

PURPOSE

The purpose of this study was to characterize test-retest reliability of discourse measures across a battery of common tasks in individuals with aphasia and prospectively matched adults without brain damage.

METHOD

We collected spoken discourse during five monologue tasks at two timepoints (test and retest; within 2 weeks apart) in an aphasia group (n = 23) and a peer group with no brain damage (n = 24). We evaluated test-retest reliability for percentage of correct information units, correct information units per minute, mean length of utterance, verbs per utterance, noun/verb ratio, open/closed class word ratio, tokens, sample duration (seconds), propositional idea density, type-token ratio, and words per minute. We explored reliability's relationship with sample length and aphasia severity.

RESULTS

Rater reliability was excellent. Across tasks, both groups demonstrated discourse measures with poor, moderate, and good reliability, with the aphasia group having measures demonstrating excellent test-retest reliability. When evaluating measures within each task, test-retest reliability again ranged from poor to excellent for both groups. Across groups and task, measures that appeared most reliable appeared to reflect lexical, informativeness, or fluency information. Sample length and aphasia severity impacted reliability, and this differed across and by task.

CONCLUSIONS

We identified several discourse measures that were reliable across and within tasks. Test-retest statistics are intimately linked to the specific sample, emphasizing the importance of multiple baseline studies. Task itself should be considered an important variable, and it should not be assumed that discourse measures found to be reliable across several tasks (averaged) are likewise reliable for a single task.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.23298032.