Exploring neural tracking of acoustic and linguistic speech representations in individuals with post-stroke aphasia

Abstract

Aphasia is a communication disorder that affects processing of language at different levels (e.g., acoustic, phonological, semantic). Neural tracking of continuous speech, such as a story, allows to analyze brain responses to acoustic and linguistic properties. Even though neural tracking of speech measured via EEG may be an interesting tool to study aphasia in an ecologically valid way, this method has not yet been investigated in individuals with stroke-induced aphasia. Here, we explored processing of acoustic and linguistic speech representations in individuals with aphasia in the chronic phase after stroke and age-matched healthy controls. We found decreased neural tracking of acoustic and segmentation-related speech representations in individuals with aphasia. In addition, linguistic speech representations at the word-level displayed decreased amplitudes in individuals with aphasia around 200 ms over left-sided frontal electrodes. These results show that there is potential for neural tracking to capture language processing impairments in individuals with aphasia. However, more research is needed to validate these results. Nonetheless, this exploratory study shows that neural tracking of naturalistic, continuous speech presents a powerful tool to study aphasia.

Neural substrates and behavioral relevance of speech envelope tracking: evidence from post-stroke aphasia

“…We describe the behavioral tests of interest below. In previous studies at our research lab, IWA performed worse on these tests compared to healthy controls (Kries et al, 2023a,b; Mehraram et al, 2024).…”

“…The presented sample is a subset of prior studies (Kries et al, 2023a;Mehraram et al, 2024), comprising 39 native Flemish IWA (13 female participants, mean age = 69.6 y/o, sd = 12.4 y/o) in the chronic phase (≥ 6 months) post-stroke. Compared to these prior studies, one participant was excluded as we lacked accessible brain scan data.…”

“…As this task targets the threshold at which differences in rise time can be detected by the participant, higher scores (i.e., higher thresholds) imply worse performance. For more information on this task and visualization of the procedure, we refer to Kries et al (2023a). The task was presented using the software APEX (Francart et al, 2008) and stimuli were presented to the left ear at 70 dB SPL.…”

“…Among various disorders, neural tracking has found application in the study of aphasia, a language disorder commonly caused by a stroke in the language-dominant left hemisphere of the brain (Papathanasiou and Coppens, 2017). In response to narratives, individuals with post-stroke aphasia (IWA) display decreased neural tracking of the envelope and linguistic speech representations (Kries et al, 2023a;De Clercq et al, 2023a, 2024b. Neural tracking measures further predicted aphasia at the individual level (De Clercq et al, 2023b), with prediction accuracy almost entirely driven by envelope tracking rather than linguistic tracking (De Clercq et al, 2024b).…”

Examining cortical tracking of the speech envelope in post-stroke aphasia

“…Recent evidence from primary progressive aphasia (PPA; Dial et al, 2021 ) demonstrated an increased CTenv in theta but not delta compared to neurotypicals, implying that people with PPA may rely more on acoustic properties during continuous speech processing. To date, this is one of the few studies that investigate CTenv in adult neurogenic language disorders (see De Clercq et al, 2023 ; Kries et al, 2023 ). Thus, the association between CTenv and language impairments as measured by aphasia severity is, to our knowledge, yet to be examined.…”