Non-fluent speech following stroke is caused by impaired efference copy

Abstract

Efference copy is a cognitive mechanism argued to be critical for initiating and monitoring speech: however, the extent to which breakdown of efference copy mechanisms impact speech production is unclear. This study examined the best mechanistic predictors of non-fluent speech among 88 stroke survivors. Objective speech fluency measures were subjected to a principal component analysis (PCA). The primary PCA factor was then entered into a multiple stepwise linear regression analysis as the dependent variable, with a set of independent mechanistic variables. Participants’ ability to mimic audio-visual speech (“speech entrainment response”) was the best independent predictor of non-fluent speech. We suggest that this “speech entrainment” factor reflects integrity of internal monitoring (i.e., efference copy) of speech production, which affects speech initiation and maintenance. Results support models of normal speech production and suggest that therapy focused on speech initiation and maintenance may improve speech fluency for individuals with chronic non-fluent aphasia post stroke.

Functional Connectivity and Speech Entrainment Speech Entrainment Improves Connectivity Between Anterior and Posterior Cortical Speech Areas in Non-fluent Aphasia

“…In the context of SE, previous work suggests damage to anterior or posterior language regions, or the connections between the 2, could negatively impact speech motor programming, which relies upon intact feedforward and feedback projections. 3,24 With regard to clinical disorders such as aphasia that result from brain injury, participants with non-fluent aphasia are hypothesized to have an impaired efference copy due to left IFG damage and subsequently, aberrant oscillatory function. To compensate for the absence of an efference copy, the literature suggests that an AV SE model provides an external efference copy by recruiting residual posterior regions (i.e., visual speech units in the pMTG) to induce more fluent speech production.…”

Real-Time EEG Neurofeedback as a Tool to Improve Neural Entrainment to Speech

“…Atypical entrainment to speech has been shown to play a role on various neuropsychological disorders such as dyslexia, stroke, and Broca's aphasia (Goswami, 2011;Molinaro et al, 2016;Feenaughty et al, 2017;Liberto et al, 2018;Thors, 2019;Lizarazu et al, 2021b,c). For example, in terms of developmental dyslexia, Goswami (2011) theorized that atypical speech-brain entrainment could be part of the underlying cause.…”

Speech rehabilitation in post-stroke aphasia using visual illustration of speech articulators: A case report study

“…The focus of the present study is on post-stroke non-fluent aphasia (expressive or Broca's aphasia) that is frequently associated with lesions located within the left inferior frontal gyrus (Ardila et al, 2016;Van Der Meulen et al, 2016). Broca's aphasia is characterized by non-fluent spontaneous speech, apraxia of speech, agrammatism, anomia, effortful speech production, limited vocabulary access and short sentence production, while language comprehension remains relatively intact (Baqué et al, 2015;Cortese et al, 2015;Feenaughty et al, 2017). These deficits often include symptoms such as articulation errors or dysfluencies that are also typical of dysarthria or apraxia of speech.…”

“…These speech and language disturbances may be due to one or several impaired speech production processes, such as selection and planning of speech output, articulatory implementation of selected and planned speech segments, articulatory implementation of speech phonetic parameters and coordination of speech articulators (Kurowski, Hazen, & Blumstein, 2003;Nespoulous, Baqué, Rosas, Marczyk, & Estrada, 2013). Recent studies have shown that less fluent speech may be caused by the inability to create and use an efference copy (internal representation of the speech plan) for speech motor control (Feenaughty et al, 2017;Fridriksson et al, 2012Fridriksson et al, , 2015. For patients with aphasia following stroke, speech and language therapy has been shown to be beneficial in terms of improving language comprehension and production (Brady et al, 2016).…”