10/31/2023 0 Comments Define coherence synonym1, 2, 7 Deficits at either level of processing can result in coherence deficits in different patient groups however, the root causes of impaired coherence in post-stroke aphasia remain indeterminate. The mechanisms that support connected speech production can be divided into two sets of interconnected processes: microlinguistic, which focuses on phonological, lexical and syntactic processes and macrolinguistic, which refers to processes that organize and regulate the content and topic of speech. Different discourse tasks can lead to variations in connected speech and discourse features in aphasia, including production quantity, 18–21 lexical and semantic features, 22 and coherence. 6, 10, 15), storytelling narratives (e.g. 7, 10, 11, 14 Second, discourse elicitation tasks vary across investigations and individual studies have typically only utilized a single type of discourse task, such as picture description (e.g. First, the majority of studies tested people with fluent aphasia but not those with less fluent aphasia. 7, 13 This discrepancy in the literature might relate to several factors that have differed across studies. A few studies, in contrast, have reported intact global coherence in people with fluent aphasia. Previous studies that focused on fluent types of aphasia have found impaired global coherence post-stroke in patients with co-existing impaired linguistic processes at the phonological, lexical and syntactic levels 9–12 however, they typically contain small samples. an acquired language disorder that typically presents with deficits in discourse production). The literature is inconsistent with regards to coherence deficits in people with post-stroke aphasia (i.e. This is the focus of the present article. 7 Although impaired coherence might hinder effective communication, the cognitive and neural correlates of coherence in post-stroke aphasia remain uncertain. 1, 2 Producing coherent discourse is often impaired following brain damage or mental disorders, including right hemisphere stroke, 4, 5 schizophrenia, 6 traumatic brain injury 7, 8 and Alzheimer’s disease. 1–3 In this study, we focus specifically on global coherence, which reflects the degree to which each statement of the discourse relates to the current topic of conversation. Coherent discourse involves a series of well-linked utterances that are related to each other and to the specific topic of conversation. Speech that meets these challenges is said to be coherent. To communicate effectively in conversation, speakers must produce statements that are informative and relevant to the topic under discussion. These results make an important contribution to understanding the root causes of disrupted discourse production in post-stroke aphasia. 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). 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 results suggest that impairments in core language components play a role in reducing discourse coherence in post-stroke aphasia. 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. Coherence was then related to fundamental language and cognitive components in aphasia identified using an extensive neuropsychological battery. 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. 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. 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. 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.
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