The Relationship Between Non-Orthographic Language Abilities and Reading Performance in Chronic Aphasia: An Exploration of the Primary Systems Hypothesis

Dissociating reading and auditory comprehension in persons with aphasia

Language comprehension is often affected in individuals with post-stroke aphasia. However, deficits in auditory comprehension are not fully correlated with deficits in reading comprehension and the mechanisms underlying this dissociation remain unclear. This distinction is important for understanding language mechanisms, predicting long-term impairments and future development of treatment interventions. Using comprehensive auditory and reading measures from a large cohort of individuals with aphasia, we evaluated the relationship between aphasia type and reading comprehension impairments, the relationship between auditory versus reading comprehension deficits and the crucial neuroanatomy supporting the dissociation between post-stroke reading and auditory deficits. Scores from the Western Aphasia Battery-Revised from 70 participants with aphasia after a left-hemisphere stroke were utilized to evaluate both reading and auditory comprehension of linguistically equivalent stimuli. Repeated-measures and univariate ANOVA were used to assess the relationship between auditory comprehension and aphasia types and correlations were employed to test the relationship between reading and auditory comprehension deficits. Lesion-symptom mapping was used to determine the dissociation of crucial brain structures supporting reading comprehension deficits controlling for auditory deficits and vice versa. Participants with Broca's or global aphasia had the worst performance on reading comprehension. Auditory comprehension explained 26% of the variance in reading comprehension for sentence completion and 44% for following sequential commands. Controlling for auditory comprehension, worse reading comprehension performance was independently associated with damage to the inferior temporal gyrus, fusiform gyrus, posterior inferior temporal gyrus, inferior occipital gyrus, lingual gyrus and posterior thalamic radiation. Auditory and reading comprehension are only partly correlated in aphasia. Reading is an integral part of daily life and directly associated with quality of life and functional outcomes. This study demonstrated that reading performance is directly related to lesioned areas in the boundaries between visual association regions and ventral stream language areas. This behavioural and neuroanatomical dissociation provides information about the neurobiology of language and mechanisms for potential future treatment interventions.

Reading for Meaning: The Influence of Reader Characteristics on Paragraph Understanding in Aphasia

PURPOSE

The study improves our understanding of the reading comprehension difficulties seen in people with aphasia. It investigates the influence of reader characteristics, including personal demographic variables, and linguistic and wider cognitive skills, on text comprehension.

METHOD

Seventy-five people with aphasia and 87 neurologically typical readers completed a test of paragraph comprehension. People with aphasia also completed background tests of language, attention, recognition memory, and executive functions. The influence of demographic variables (age, gender, and level of education) was analyzed separately in the group of people with aphasia and the typical readers using analyses of variance. In the people with aphasia, the relationship between paragraph comprehension and the language and cognitive tests was explored using correlational analyses.

RESULTS

In the typical readers, there was a significant effect of gender and level of education and a significant three-way interaction. For the people with aphasia, there were no significant effects of demographic variables. Significant positive correlations were found between performance on paragraph comprehension and each of the language tests and with tests of auditory attention, executive functions, and recognition memory for words.

CONCLUSIONS

In people with aphasia, the effects of demographic variables were overshadowed by the effect of their language difficulties. The association seen across language measures reflects the shared semantic representations across single-word, sentence, and text levels, across modalities. The study emphasizes the importance of attention, executive functions, and short-term memory in the comprehension of and memory for what we read. The contribution of both language difficulties and wider cognitive skills needs to be considered when planning intervention.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.24695451.

Common predictors of spoken and written language performance in aphasia, alexia, and agraphia

Language performance requires support from central cognitive/linguistic abilities as well as the more peripheral sensorimotor skills to plan and implement spoken and written communication. Both output modalities are vulnerable to impairment following damage to the language-dominant hemisphere, but much of the research to date has focused exclusively on spoken language. In this study we aimed to examine an integrated model of language processing that includes the common cognitive processes that support spoken and written language, as well as modality-specific skills. To do so, we evaluated spoken and written language performance from 87 individuals with acquired language impairment resulting from damage to left perisylvian cortical regions that collectively constitute the dorsal language pathway. Comprehensive behavioral assessment served to characterize the status of central and peripheral components of language processing in relation to neurotypical controls (n = 38). Performance data entered into principal components analyses (with or without control scores) consistently yielded a strong five-factor solution. In line with a primary systems framework, three central cognitive factors emerged: semantics, phonology, and orthography that were distinguished from peripheral processes supporting speech production and allographic skill for handwriting. The central phonology construct reflected performance on phonological awareness and manipulation tasks and showed the greatest deficit of all the derived factors. Importantly, this phonological construct was orthogonal to the speech production factor that reflected repetition of words/non-words. When entered into regression analyses, semantics and phonological skill were common predictors of language performance across spoken and written modalities. The speech production factor was also a strong, distinct predictor of spoken naming and oral reading, in contrast to allographic skills which only predicted written output. As expected, visual orthographic processing contributed more to written than spoken language tasks and reading/spelling performance was strongly reliant on phonological and semantic abilities. Despite the heterogeneity of this cohort regarding aphasia type and severity, the marked impairment of phonological skill was a unifying feature. These findings prompt greater attention to clinical assessment and potential treatment of underlying phonological skill in individuals with left perisylvian damage.