Content Word Production during Discourse in Aphasia: Deficits in Word Quantity, Not Lexical-Semantic Complexity

Connected Speech Fluency in Poststroke and Progressive Aphasia: A Scoping Review of Quantitative Approaches and Features

PURPOSE

Speech fluency has important diagnostic implications for individuals with poststroke aphasia (PSA) as well as primary progressive aphasia (PPA), and quantitative assessment of connected speech has emerged as a widely used approach across both etiologies. The purpose of this review was to provide a clearer picture on the range, nature, and utility of individual quantitative speech/language measures and methods used to assess connected speech fluency in PSA and PPA, and to compare approaches across etiologies.

METHOD

We conducted a scoping review of literature published between 2012 and 2022 following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Extension for Scoping Reviews guidelines. Forty-five studies were included in the review. Literature was charted and summarized by etiology and characteristics of included patient populations and method(s) used for derivation and analysis of speech/language features. For a subset of included articles, we also charted the individual quantitative speech/language features reported and the level of significance of reported results.

RESULTS

Results showed that similar methodological approaches have been used to quantify connected speech fluency in both PSA and PPA. Two hundred nine individual speech-language features were analyzed in total, with low levels of convergence across etiology on specific features but greater agreement on the most salient features. The most useful features for differentiating fluent from nonfluent aphasia in both PSA and PPA were features related to overall speech quantity, speech rate, or grammatical competence.

CONCLUSIONS

Data from this review demonstrate the feasibility and utility of quantitative approaches to index connected speech fluency in PSA and PPA. We identified emergent trends toward automated analysis methods and data-driven approaches, which offer promising avenues for clinical translation of quantitative approaches. There is a further need for improved consensus on which subset of individual features might be most clinically useful for assessment and monitoring of fluency.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.25537237.

The development of a novel, standardized, norm-referenced Arabic Discourse Assessment Tool (ADAT), including an examination of psychometric properties of discourse measures in aphasia

BACKGROUND

People with aphasia (PWA) typically exhibit deficits in spoken discourse. Discourse analysis is the gold standard approach to assess language deficits beyond sentence level. However, the available discourse assessment tools are biased towards English and European languages and Western culture. Additionally, there is a lack of consensus on which discourse measures to use and limited evidence of the psychometric properties of published discourse measurements.

AIMS

(1) To develop a standardized, norm-referenced, culturally and linguistically appropriate Arabic Discourse Assessment Tool (ADAT); and (2) to examine the psychometric properties of content and construct validity and interrater reliability of different discourse measures elicited using three discourse genres (descriptive, narrative and procedural) in neurotypical control adults and matched PWA.

METHODS & PROCEDURES

Discourse samples were collected using three novel discourse stimuli that are sensitive to the Arabic language and culture from 70 neurotypical control adults and a matched group of 50 PWA. Transcription agreement was assessed. A standard approach was used to evaluate construct validity and interrater reliability for 16 discourse measures that assess fluency, language productivity, information content, lexical-semantics, lexical diversity, grammatical category, grammatical structure and syntactic complexity. Strong measures were identified based on their psychometric properties, and normative data were established on these measures. Discourse performance of PWA was then examined using the newly developed tool (ADAT).

OUTCOMES & RESULTS

Transcription agreement was extremely high for all discourse stimuli in both groups. Eight discourse measures were proven to have consistently very high construct validity and consistently very good to excellent reliability across the three stimuli in both neurotypical control and aphasia groups: lexical information units, content information units, words per minute, discourse duration, number of different words, number of complete sentences and proportion of open and closed class words. Norms were established on these measures, and cut-off scores of impairments were determined. Other measures showed low construct validity and variable or poor reliability across the two groups.

CONCLUSIONS & IMPLICATIONS

The newly developed, standardized, and norm-referenced tool (ADAT) consist of three discourse stimuli and eight high-quality discourse measures that assess multiple aspects of spoken discourse and were able to differentiate PWA from neurotypical adults consistently. ADAT also includes normative data and cut-off impairment scores. The tool has great potential to enhance clinical practice and research with Arabic speakers. Evidence was provided that not all discourse measures are of high quality, as some are vulnerable to differences between raters, discourse stimuli and groups. Clinicians and researchers can use ADAT for accurate aphasia assessments, better management plans and to monitor therapy effectiveness. ADAT can be further validated in other clinical populations with language impairments.

WHAT THIS PAPER ADDS

What is already known on the subject Discourse analysis is the gold standard approach to assess language deficits beyond sentence level. However, existing discourse assessment tools are biased towards English and European languages and Western culture. Additionally, there is a lack of consensus on which discourse measures to use in aphasia, and limited evidence of the psychometric properties of published discourse measurements. What this paper adds to existing knowledge A novel, standardized, norm-referenced Arabic Discourse Assessment Tool (ADAT) was developed and validated in this study. ADAT was further validated among PWA. The study provides evidence that not all discourse measures are of high quality and thus should not be used with confidence. Specific measures are vulnerable to the type of stimuli, the rater and/or the tested group. On the other hand, eight discourse measures were identified to be reliable between different raters and across different stimuli for the two groups, and they were able to differentiate the discourse performance of PWA from neurotypical control adults. Normative data derived from neurotypical control adults were established on these strong measures, and the performance of PWA was classified as impaired based on these norms. What are the potential or actual clinical implications of this work? The present study provides a novel, standardized, norm-referenced, validated discourse assessment tool that is culturally and linguistically appropriate for use by Arabic speakers (ADAT). ADAT holds immense potential to enhance clinical practice and research with Arabic speakers. The study also identified strong discourse measures that can be used to assess language productivity, information content, lexical-semantics, lexical diversity, grammatical category, and syntactic complexity for accurate and comprehensive assessments. This will lead to better rehabilitation management by guiding the development of tailored client-centred interventions. ADAT can be utilized in clinical and research settings in PWA and has the potential to be further validated with other clinical populations.

Using predictive validity to compare associations between brain damage and behavior

Lesion-behavior mapping (LBM) provides a statistical map of the association between voxel-wise brain damage and individual differences in behavior. To understand whether two behaviors are mediated by damage to distinct regions, researchers often compare LBM weight outputs by either the Overlap method or the Correlation method. However, these methods lack statistical criteria to determine whether two LBM are distinct versus the same and are disconnected from a major goal of LBMs: predicting behavior from brain damage. Without such criteria, researchers may draw conclusions from numeric differences between LBMs that are irrelevant to predicting behavior. We developed and validated a predictive validity comparison method (PVC) that establishes a statistical criterion for comparing two LBMs using predictive accuracy: two LBMs are distinct if and only if they provide unique predictive power for the behaviors being assessed. We applied PVC to two lesion-behavior stroke data sets, demonstrating its utility for determining when behaviors arise from the same versus different lesion patterns. Using region-of-interest-based simulations derived from proportion damage from a large data set (n = 131), PVC accurately detected when behaviors were mediated by different regions (high sensitivity) versus the same region (high specificity). Both the Overlap method and Correlation method performed poorly on the simulated data. By objectively determining whether two behavioral deficits can be explained by single versus distinct patterns of brain damage, PVC provides a critical advance in establishing the brain bases of behavior. We have developed and released a GUI-driven web app to encourage widespread adoption.

Differences in Connected Speech Outcomes Across Elicitation Methods

Background

Connected speech is often used to assess many aspects of an individual's language abilities after stroke. However, it is unknown the degree to which elicitation methods differ in generating structural and syntactic aspects of connected speech, two critical components of successful communication. Quantifying the degree to which elicitation methods differ in eliciting structurally, syntactically, and lexically complex connected speech at the earliest stage of stroke before reorganization and rehabilitation of function independent of clinical diagnosis of aphasia has not been examined to date. Addressing this gap has implications for early clinical intervention as well as empirical studies of connected speech production.

Aims

We compared two common elicitation methods, picture description and storytelling on lexical, structural, and syntactic measures of connected speech in speakers during the acute stage of left hemisphere stroke.

Methods & Procedures

We measured connected speech using an automated quantitative production analysis approach (Fromm et al., 2021) in 71 native-English speaking participants (27 female; 59 ± 13 years) within an average 3.9 days from left hemisphere stroke onset. We tested the degree of agreement and consistency between elicitation methods for lexical, structural, and syntactic measures of connected speech, as well as the degree of concordance in classifying deficits across individuals.

Outcomes & Results

Storytelling elicited significantly more words and more structurally complex, lexically diverse, and syntactically accurate speech in comparison to picture description. Elicitation methods differed in measuring outcomes across participants for the lexical and syntactic, but not structural complexity aspects of connected speech where storytelling classified more participants with impairments in comparison to picture description.

Conclusions

These differences suggest storytelling provides assessment of connected speech abilities more reflective of real-world abilities where its use is particularly critical for examining individual differences and providing diagnoses of acute stroke language deficits. As a result, using storytelling as a connected speech elicitation method more effectively captures a patient's language capabilities after stroke, consequently informing clinical diagnosis and treatment.

Descriptive discourse in fluent aphasia: The predictive role of attention, phonology, lexical retrieval and semantics

AIMS

To study the relationship between cognitive and linguistic skills (as measured through standardized tasks) over spontaneous speech elicited during a picture description task.

METHODS & PROCEDURES

21 controls and 19 people with fluent aphasia matched by age and sex were evaluated using transcripts made from a picture description task coded using the CHAT format and analyzed using Computerized Language Analysis (CLAN). Indices obtained from the speech samples contained measures of lexical quantity and diversity, morphosyntactic complexity, informativeness, and speech fluency, along with different kinds of speech errors. We studied their correlations with attentional measures from Conners' Continuous Performance Test and with standardized measures of naming, pseudoword repetition and semantic non-verbal association. We further used stepwise linear regression to analyze the predictive value of standardized linguistic and cognitive skills over discursive indices.

OUTCOMES & RESULTS

Contrary to our initial hypothesis, there were no significant correlations between attentional scores and discourse variables in aphasic participants. Moreover, semantic association, along with naming, was the measure more related with discourse performance in people with fluent aphasia, but cognitive and linguistic standardized measures had overall little predictive power on most discourse indices. In the control group, there was a certain association of naming skills and attentional reaction time with discourse variables, but their predictive power was also low.

CONCLUSIONS & IMPLICATIONS

The current results do not support a strong relationship between basic attentional skills and performance in descriptive discourse in fluent aphasia. Although some of the standardized tasks seem to bear some relationship with spontaneous speech, there is a high amount of interindividual variability in discourse that is not captured by classical cognitive tasks routinely used in assessment. Further work on the determinants of discourse performance in aphasia and on the clinical application of discourse analysis is warranted.

Neuroanatomical correlates of macrostructural receptive abilities in narrative discourse in unilateral left hemisphere stroke: A behavioural and voxel-based morphometry study

BACKGROUND

Little is known about story retelling and comprehension abilities in groups with lower levels of education and socio-economic status (SES). A growing body of evidence suggests the role of an extended network supporting narrative comprehension, but few studies have been conducted in clinical populations, even less in developing countries.

AIMS

To extend our knowledge of the impact of a stroke on macrostructural aspects of discourse processes, namely main and complementary information, in individuals with middle-low to low SES and low levels of education. Relationships were tested between the performance in story retell and comprehension and reading and writing habits (RWH). Also, the associations between retelling and comprehension measures and their structural grey matter (GM) correlates were explored.

METHODS & PROCEDURES

A total of 17 adults with unilateral left hemisphere (LH) chronic ischaemic stroke without the presence of significant aphasia and 10 matched (age, education and SES) healthy controls (HC) participated in the study. Retell and comprehension tasks were performed after listening or reading narrative stories. Voxel-based morphometry (VBM) analysis was conducted on a subgroup of nine individuals with LH stroke and the 10 matched controls using structural magnetic resonance imaging (MRI).

OUTCOMES & RESULTS

Retelling and comprehension abilities were not significantly different between LH and HC, nonetheless quantitively lower in LH. Exploratory correlations showed that retelling and comprehension abilities in both written and auditory modalities were correlated with naming abilities. At the neural level, written comprehension positively correlated with GM density of the LH, including areas in the temporal pole, superior and middle temporal gyrus as well as the orbitofrontal cortex, precentral and postcentral gyri. Auditory narrative comprehension was associated with GM density of the lingual gyrus in the right hemisphere.

CONCLUSIONS & IMPLICATIONS

The present results suggest that retelling and comprehension of auditory and written narratives are relatively well-preserved in individuals with a LH stroke without significant aphasia, but poorer than in HC. The findings replicate previous studies conducted in groups with higher levels of education and SES both at the behavioural and neural levels. Considering that naming seems to be associated with narrative retell and comprehension in individuals with lower SES and education, this research provides evidence on the importance of pursuing further studies including larger samples with and without aphasia as well as with various SES and education levels.

WHAT THIS PAPER ADDS

What is already known on this subject Story retell and comprehension of auditory and written discourse have been shown to be affected after stroke, but most studies have been conducted on individuals with middle to high SES and high educational levels. What this paper adds to existing knowledge The study reports on narrative retell and comprehension in both auditory and written modalities in groups of HC and individuals with LH brain damage, with low-to-middle SES and lower levels of education. What are the potential or actual clinical implications of this work? This study highlights the importance of taking into consideration the sociodemographic and RWH of patients when assessing discourse retell and comprehension in both auditory and written modalities. It also underlines the importance of including patients without significant aphasia following LH stroke to look at the effect of both stroke and aphasia on narrative comprehension and story retelling.

The cognitive and neural underpinnings of discourse coherence in post-stroke aphasia

Although impaired discourse production is one of the prominent features of aphasia, only a handful of investigations have addressed the cognitive, linguistic and neural processes that support the production of coherent discourse. In this study, we investigated the cognitive and neural correlates of discourse coherence in a large mixed cohort of patients with post-stroke aphasia, including the first voxel-based lesion-symptom mapping of coherence deficits. Discourse responses using different tasks were collected from 46 patients with post-stroke aphasia, including a wide range of classifications and severity levels, and 20 matched neuro-typical controls. Global coherence, defined as the degree to which utterances related to the expected topic of discourse, was estimated using a previously validated computational linguistic approach. Coherence was then related to fundamental language and cognitive components in aphasia identified using an extensive neuropsychological battery. Relative to neuro-typical controls, patients with aphasia exhibited impaired coherence, and their ability to maintain coherent discourse was related to their performance on other language components: phonological production, fluency and semantic processing, rather than executive functions or motor speech. These results suggest that impairments in core language components play a role in reducing discourse coherence in post-stroke aphasia. Whole-brain voxel-wise lesion-symptom mapping using univariate and multivariate approaches identified the contribution of the left prefrontal cortex, and particularly the inferior frontal gyrus (pars triangularis), to discourse coherence. These findings provide convergent evidence for the role of the inferior frontal gyrus in maintaining discourse coherence, which is consistent with the established role of this region in producing connected speech and semantic control (organizing and selecting appropriate context-relevant concepts). These results make an important contribution to understanding the root causes of disrupted discourse production in post-stroke aphasia.