Language Recovery Research Articles

Understanding, facilitating and predicting aphasia recovery after rehabilitation

Purpose: This paper reviews several studies whose aim was to understand the nature of language recovery in chronic aphasia and identify predictors of how people may recover their language functions after a brain injury. Method: Several studies that mostly draw from data collected within the Centre for Neurobiology of Language Recovery were reviewed and categorised in four aspects of language impairment and recovery in aphasia: (a) neural markers for language impairment and recovery, (b) language and cognitive markers for language impairment and recovery, (c) effective treatments and (d) predictive modelling of treatment-induced rehabilitation. Result: Language impairment and recovery in stroke-induced aphasia is multi-factorial, including patient-specific and treatment-specific factors. A combination of these factors may help us predict treatment responsiveness even before treatment begins. Conclusion: Continued work on this topic will lead to a better understanding of the mechanisms that underly language impairment and treatment-induced recovery in aphasia, and, consequently, use this information to predict each person's recovery profile trajectory and provide optimal prescriptions regarding the type and dosage of treatment.

Absence of Perilesional Neuroplastic Recruitment in Chronic Poststroke Aphasia.

Background and ObjectivesA prominent theory proposes that neuroplastic recruitment of perilesional tissue supports aphasia recovery, especially when language-capable cortex is spared by smaller lesions. This theory has rarely been tested directly and findings have been inconclusive. We tested the perilesional plasticity hypothesis using 2 fMRI tasks in 2 groups of patients with previous aphasia diagnosis.MethodsTwo cohorts totaling 82 patients with chronic left-hemisphere stroke with previous aphasia diagnosis and 82 control participants underwent fMRI using either a naming task or a reliable semantic decision task. Individualized perilesional tissue was defined by dilating anatomical lesions and language regions were defined using meta-analyses. Mixed modeling examined differences in activity between groups. Relationships with lesion size and aphasia severity were examined.ResultsPatients exhibited reduced activity in perilesional language tissue relative to controls in both tasks. Although a few cortical regions exhibited greater activity irrespective of distance from the lesion, or only when distant from the lesion, no regions exhibited increased activity only when near the lesion. Larger lesions were associated with reduced language activity irrespective of distance from the lesion. Using the reliable fMRI task, reduced language activity was related to aphasia severity independent of lesion size.DiscussionWe found no evidence for neuroplastic recruitment of perilesional tissue in aphasia beyond its typical role in language. Rather, our findings are consistent with alternative hypotheses that changes in left-hemisphere activation during recovery relate to normalization of language network dysfunction and possibly recruitment of alternate cortical processors. These findings clarify left-hemisphere neuroplastic mechanisms supporting language recovery after stroke.

Genetic and Neurophysiological Biomarkers of Neuroplasticity Inform Post-Stroke Language Recovery

Background There is high variability in post-stroke aphasia severity and predicting recovery remains imprecise. Standard prognostics do not include neurophysiological indicators or genetic biomarkers of neuroplasticity, which may be critical sources of variability. Objective To evaluate whether a common polymorphism (Val66Met) in the gene for brain-derived neurotrophic factor (BDNF) contributes to variability in post-stroke aphasia, and to assess whether BDNF polymorphism interacts with neurophysiological indicators of neuroplasticity (cortical excitability and stimulation-induced neuroplasticity) to improve estimates of aphasia severity. Methods Saliva samples and motor-evoked potentials (MEPs) were collected from participants with chronic aphasia subsequent to left-hemisphere stroke. MEPs were collected prior to continuous theta burst stimulation (cTBS; index for cortical excitability) and 10 minutes following cTBS (index for stimulation-induced neuroplasticity) to the right primary motor cortex. Analyses assessed the extent to which BDNF polymorphism interacted with cortical excitability and stimulation-induced neuroplasticity to predict aphasia severity beyond established predictors. Results Val66Val carriers showed less aphasia severity than Val66Met carriers, after controlling for lesion volume and time post-stroke. Furthermore, Val66Val carriers showed expected effects of age on aphasia severity, and positive associations between severity and both cortical excitability and stimulation-induced neuroplasticity. In contrast, Val66Met carriers showed weaker effects of age and negative associations between cortical excitability, stimulation-induced neuroplasticity and aphasia severity. Conclusions Neurophysiological indicators and genetic biomarkers of neuroplasticity improved aphasia severity predictions. Furthermore, BDNF polymorphism interacted with cortical excitability and stimulation-induced neuroplasticity to improve predictions. These findings provide novel insights into mechanisms of variability in stroke recovery and may improve aphasia prognostics.

Rehabilitating an attrited language in a bilingual person with aphasia

ABSTRACT Language difficulties can arise from reduced exposure to any given language (e.g. attrition) or after brain damage (e.g. aphasia). The manifestations of attrition and aphasia are often similar so differentiating between their effects on language loss and recovery is challenging. We investigated treatment effects for an English-Hebrew bilingual person with stroke-induced aphasia who had minimal contact with his Hebrew for over 14 years. We asked whether his attrited language could be rehabilitated, how effects of attrition and aphasia can be dissociated, and how such dissociation aids our understanding of the mechanisms involved in language recovery in aphasia. We administered a verb-based semantic treatment in Hebrew three times a week for six weeks (totalling 29 hours of therapy) and assessed changes in both Hebrew and English comprehension and production abilities across a variety of language tasks. Quantitative analyses demonstrated improvement in Hebrew production across language tasks, including those involving lexical retrieval processes that were trained during treatment. Improvement to English occurred in these same lexical retrieval tasks only. We interpret these results as indicating that the participant’s attrited language (Hebrew) could be rehabilitated with both specific treatment and general exposure to Hebrew contributing to improvement. Furthermore, treatment effects transferred to the untreated English. Qualitative analyses indicated that an interaction among aphasia, incomplete mastery of Hebrew pre-stroke, and attrition contributed to the participant’s language difficulties post-stroke. We conclude that partially shared underlying mechanisms of attrition and aphasia drive language processing and changes to it with treatment.

The Aftercare Survey: Assessment and intervention practices after brain tumor surgery in Europe.

BackgroundPeople with gliomas need specialized neurosurgical, neuro-oncological, psycho-oncological, and neuropsychological care. The role of language and cognitive recovery and rehabilitation in patients’ well-being and resumption of work is crucial, but there are no clear guidelines for the ideal timing and character of assessments and interventions. The goal of the present work was to describe representative (neuro)psychological practices implemented after brain surgery in Europe.MethodsAn online survey was addressed to professionals working with individuals after brain surgery. We inquired about the assessments and interventions and the involvement of caregivers. Additionally, we asked about recommendations for an ideal assessment and intervention plan.ResultsThirty-eight European centers completed the survey. Thirty of them offered at least one postsurgical (neuro)psychological assessment, mainly for language and cognition, especially during the early recovery stage and at long term. Twenty-eight of the participating centers offered postsurgical therapies. Patients who stand the highest chances of being included in evaluation and therapy postsurgically are those who underwent awake brain surgery, harbored a low-grade glioma, or showed poor recovery. Nearly half of the respondents offer support programs to caregivers, and all teams recommend them. Treatments differed between those offered to individuals with low-grade glioma vs those with high-grade glioma. The figure of caregiver is not yet fully recognized in the recovery phase.ConclusionWe stress the need for more complete rehabilitation plans, including the emotional and health-related aspects of recovery. In respondents’ opinions, assessment and rehabilitation plans should also be individually tailored and goal-directed (eg, professional reinsertion).

Post-stroke enriched auditory environment induces structural connectome plasticity: secondary analysis from a randomized controlled trial

Post-stroke neuroplasticity and cognitive recovery can be enhanced by multimodal stimulation via environmental enrichment. In this vein, recent studies have shown that enriched sound environment (i.e., listening to music) during the subacute post-stroke stage improves cognitive outcomes compared to standard care. The beneficial effects of post-stroke music listening are further pronounced when listening to music containing singing, which enhances language recovery coupled with structural and functional connectivity changes within the language network. However, outside the language network, virtually nothing is known about the effects of enriched sound environment on the structural connectome of the recovering post-stroke brain. Here, we report secondary outcomes from a single-blind randomized controlled trial (NCT01749709) in patients with ischaemic or haemorrhagic stroke (N = 38) who were randomly assigned to listen to vocal music, instrumental music, or audiobooks during the first 3 post-stroke months. Utilizing the longitudinal diffusion-weighted MRI data of the trial, the present study aimed to determine whether the music listening interventions induce changes on structural white matter connectome compared to the control audiobook intervention. Both vocal and instrumental music groups increased quantitative anisotropy longitudinally in multiple left dorsal and ventral tracts as well as in the corpus callosum, and also in the right hemisphere compared to the audiobook group. Audiobook group did not show increased structural connectivity changes compared to both vocal and instrumental music groups. This study shows that listening to music, either vocal or instrumental promotes wide-spread structural connectivity changes in the post-stroke brain, providing a fertile ground for functional restoration.

Effects of CPAP on Language Recovery in Post-Stroke Aphasia: A Review of Recent Literature.

Obstructive sleep apnea is highly prevalent in the post-stroke population, and has been shown to affect cognitive, neurological, and functional status. Continuous positive airway pressure (CPAP) treatment is one of the most effective interventions for obstructive sleep apnea, but compliance is often low due to confounding effects of co-occurring conditions, side effects of treatment titration procedures, and individual patient personality characteristics, perceptions, and social factors. Current research suggests that CPAP treatment for obstructive sleep apnea is not associated with significant risk and can subsequently improve post-stroke motor and neurocognitive function. However, effects of CPAP treatment on post-stroke speech and language recovery remain unclear. Post-stroke communication disorders (e.g., aphasia, dysarthria, and apraxia) are also highly prevalent in this population. Knowledge of the potential positive impact of CPAP on language recovery could contribute to patients’ motivation to comply with CPAP treatment and provide incentive for speech-language pathologists to refer patients to sleep medicine specialists. In this review of the literature, we examine the question of what effect CPAP treatment may have on post-stroke speech and language function and recovery, as well as summarize the current knowledge on cognitive, neurological, and functional effects. While this review of the literature found CPAP to have varying effects on different cognitive domains, there was not sufficient evidence to determine effects on language recovery. Further research is necessary to determine the potential effects of CPAP treatment on speech and language recovery among stroke patients.

Functional Remodeling Associated With Language Recovery After Repetitive Transcranial Magnetic Stimulation in Chronic Aphasic Stroke.

BackgroundRepetitive transcranial magnetic stimulation (rTMS) has shown promising efficacy in improving the language functions in poststroke aphasia. However, randomized controlled trials were lacking to investigate the rTMS-related neuroimaging changes underlying the therapeutic effects on language improvement in chronic aphasia.ObjectiveIn this study, we aimed to evaluate the effects of low-frequency rTMS (LF-rTMS) on chronic poststroke aphasia. We hypothesized that the deactivation of the right pars triangularis could restore the balance of interhemispheric inhibition and, hence, facilitated the functional remodeling of language networks in both the hemispheres. Furthermore, the rTMS-induced functional reorganization should underpin the language recovery after rTMS.MethodsA total of 33 patients (22 males; age: 58.70 ± 13.77 years) with chronic stroke in the left hemisphere and nonfluent aphasia were recruited in this randomized double-blinded study. The ratio of randomization between the rTMS and sham groups is 17:16. All the patients received real 1-Hz rTMS or sham stimulation (placebo coil delivered < 5% of magnetic output with similar audible click-on discharge) at the right posterior pars triangularis for 10 consecutive weekdays (stroke onset to the first stimulation: 10.97 ± 10.35 months). Functional connectivity of language networks measured by resting-state fMRI was calculated and correlated to the scores of the Concise Chinese Aphasia Test by using the stepwise regression analysis.ResultsAfter LF-rTMS intervention, significant improvement in language functions in terms of comprehension and expression abilities was observed compared with the sham group. The rTMS group showed a significant decrease of coupling strength between right pars triangularis and pars opercularis with a strengthened connection between right pars orbitalis and angular gyrus. Furthermore, the LF-rTMS significantly enhanced the coupling strength associated with left Wernicke area. Results of regression analysis showed that the identified functional remodeling involving both the hemispheres could support and predict the language recovery after LF-rTMS treatment.ConclusionWe reported the therapeutic effects of LF-rTMS and corresponding functional remodeling in chronic poststroke aphasia. Our results provided neuroimage evidence reflecting the rebalance of interhemispheric inhibition induced by LF-rTMS, which could facilitate future research in the refinement of rTMS protocol to optimize the neuromodulation efficacy and benefit the clinical management of patients with stroke.

Noninvasive stimulation of the unlesioned hemisphere and phonological treatment in a case of chronic anomia post-stroke

ABSTRACT Chronic lexical anomia after left hemisphere (LH) stroke improves under personalized phonological treatment (PT). Cortical linking between language and hand motor areas (hand_M1) questioned whether PT-related improvement relies on the unlesioned hemisphere (UH) plasticity when LH is dysfunctional. Our 70-yo-woman case study showed that 10 sessions of excitatory stimulation of UH_hand-M1 combined with PT hastened oral picture naming improvement as compared to sham+PT and changes were maintained together with changes of untrained items andcorticomotor excitability increase. This supports a role of stimulation-induced plasticity of UH_hand M1 in language recovery, at least in the improvement of lexical anomia in chronic stroke.

Longitudinal assessment of network reorganizations and language recovery in postoperative patients with glioma.

For patients with glioma located in or adjacent to the linguistic eloquent cortex, awake surgery with an emphasis on the preservation of language function is preferred. However, the brain network basis of postoperative linguistic functional outcomes remains largely unknown. In this work, 34 patients with left cerebral gliomas who underwent awake surgery were assessed for language function and resting-state network properties before and after surgery. We found that there were 28 patients whose language function returned to at least 80% of the baseline scores within 3 months after surgery or to 85% within 6 months after surgery. For these patients, the spontaneous recovery of language function synchronized with changes within the language and cognitive control networks, but not with other networks. Specifically, compared with baseline values, language functions and global network properties were the worst within 1 month after surgery and gradually recovered within 6 months after surgery. The recovery of connections was tumour location dependent and was attributed to both ipsihemispheric and interhemispheric connections. In contrast, for six patients whose language function did not recover well, severe network disruptions were observed before surgery and persisted into the chronic phase. This study suggests the synchronization of functional network normalization and spontaneous language recovery in postoperative patients with glioma.

Best practice guidelines for reporting spoken discourse in aphasia and neurogenic communication disorders

ABSTRACT Background Spoken discourse is a fundamental form of communication, yet often disrupted in persons with aphasia and other neurogenic communication disorders. It follows that discourse analysis is important for understanding language, its impairments, and language recovery in these populations. Being a highly interdisciplinary field, discourse analysis would benefit from a set of guidelines (best practices) that help streamline reporting and discussion of discourse specific to populations with neurogenic communication disorders. This would enhance the overall quality of ongoing research by improving replicability, allowing meta-analysis, and supporting implementation in clinical practice. Aims To establish clear reporting guidelines for studies that use spoken discourse analysis in aphasia. Methods & Procedures An e-Delphi survey methodology was used. We identified aphasia and neurogenic communication disorder experts using Boolean search criteria and author consensus, then invited these individuals to participate in an online, three-round survey. The three rounds took place between November 2020 and June 2021. In each round, participants were asked to rank necessity of items on a scale of 1 (“not at all necessary”) to 5 (“extremely necessary”). Participants were instructed to rate based on whether the item was necessary to inform the creation of a minimum reporting guideline. Only participants who responded in the prior round were invited to participate in subsequent rounds. Items that met predetermined consensus criteria for ratings greater than “necessary” were brought forward to each subsequent round. New items were added to each round based on qualitative information collected from participants. Outcomes & Results Items that were rated by ≥ 70% of the participants as “highly necessary” or “extremely necessary” in Round 3 were those deemed as “necessary” to be reported in research, whereas items rated < 70% in Round 3 were deemed as “recommended” to be reported in research. Following Round 3, 16 items were deemed “necessary” to report in research. A further five items were “recommended”. Conclusions Consensus by leading researchers in the field established that 20 reporting items were “necessary” or “recommended” as the minimum information reported across all spoken discourse studies. These items included information about sampling, transcription, and analysis. Adherence to rigorously developed reporting guidelines is important for improving the overall quality and replicability of research in the field. We have archived the current recommendations on the Open Science Framework, which is where updates to the recommendations will also be located (https://osf.io/y48n9/).

Abstract WP173: Children’s Post-Stroke Expressive Language Outcomes Are Affected By Bilingual Exposure

Introduction: Approximately 2/3 of children face neurological deficits following arterial ischemic stroke (AIS). In neurotypical development, bilingualism is thought to confer certain linguistic and cognitive advantages. However, research on whether this may affect development in bilingual pediatric stroke patients is scarce. Objectives: To evaluate the effects of bilingual vs. monolingual exposure on language and cognitive outcomes in children following arterial ischemic stroke across two studies: (1) large-scale group analysis using the Pediatric Stroke Outcome Measure (PSOM); (2) exploratory case studies using neuropsychological measures. Methods: An institutional stroke registry and chart review were used to gather patient and stroke data, including the Pediatric Stroke Outcome Measure (PSOM) and standardized neuropsychological measures performed at several timepoints post-stroke in children with AIS. In Study 1, growth curve modeling based on PSOM subscales, predicted by age at stroke groups, language groups and their interactions was used. In Study 2, comparative case studies were conducted with a monolingual-bilingual pair, aged 7 and 8 at stroke onset. Results: In Study 1, 237 patients were identified (44%, bilingual patients). Patients were stratified based on age at stroke onset i.e. neonatal (&lt;28 days of life), first-year (28 days-12 months) and childhood (13 months - 18 years). On the PSOM’s language expression subscale, an interaction revealed better post-stroke outcomes among bilingual children aged 1-12 months at stroke (beta = -0.32, t =-2.33, p = 0.02). In Study 2, the bilingual’s performance on neuropsychological assessments corroborated findings of Study 1, favoring a recovery of expressive language. Conclusion: Overall, we found no negative consequences of a bilingual environment on post-stroke outcomes. Additionally, it is possible that bilingualism has a faciliatory effect on expressive language development post-stroke. Further research should evaluate linguistic advantage effects prospectively in bilingual children with stroke and a control group.

Low-Frequency vs. Theta Burst Transcranial Magnetic Stimulation for the Treatment of Chronic Non-fluent Aphasia in Stroke: A Proof-of-Concept Study.

BackgroundAlthough low-frequency repetitive transcranial magnetic stimulation (LF-rTMS) has shown promise in the treatment of poststroke aphasia, the efficacy of high-frequency rTMS (HF-rTMS) has yet to be determined.PurposeWe investigated the efficacy of intermittent theta burst stimulation (iTBS) in ameliorating chronic non-fluent aphasia and compared it with that of LF-rTMS.MethodsWe randomly assigned patients with poststroke non-fluent aphasia to an ipsilesional iTBS (n = 29), contralesional 1-Hz rTMS (n = 27), or sham (n = 29) group. Each group received the rTMS protocol executed in 10 daily sessions over 2 weeks. We evaluated language function before and after the intervention by using the Concise Chinese Aphasia Test (CCAT).ResultsCompared with the sham group, the iTBS group exhibited significant improvements in conversation, description, and expression scores (P = 0.0004–0.031), which characterize verbal production, as well as in auditory comprehension, reading comprehension, and matching scores (P < 0.01), which characterize language perception. The 1-Hz group exhibited superior improvements in expression, reading comprehension, and imitation writing scores compared with the sham group (P < 0.05). The iTBS group had significantly superior results in CCAT total score, matching and auditory comprehension (P < 0.05) relative to the 1-Hz group.ConclusionOur study findings contribute to a growing body of evidence that ipsilesional iTBS enhances the language recovery of patients with non-fluent aphasia after a chronic stroke. Auditory comprehension was more preferentially enhanced by iTBS compared with the 1-Hz protocol. Our findings highlight the importance of ipsilesional modulation through excitatory rTMS for the recovery of non-fluent aphasia in patients with chronic stroke.Clinical Trial Registration:[www.ClinicalTrials.gov], identifier [NCT03059225].

Resting-State Network Changes Following Transcranial Magnetic Stimulation in Patients With Aphasia—A Randomized Controlled Study

BackgroundAlthough repetitive transcranial magnetic stimulation (rTMS) has exhibited promising efficacy in treating stroke-related aphasia, changes in neuroimaging in response to this therapy remain unclear. Materials and MethodsBy using resting-state functional magnetic resonance imaging (rsfMRI), we examined brain activations associated with language recovery in patients with poststroke nonfluent aphasia during an rTMS intervention. Twenty-six stroke patients with nonfluent aphasia were recruited in this randomized double-blinded study. The patients received real (n = 13) or sham (n = 13) 1-Hz inhibitory rTMS to the right pars triangularis (PTr) for ten consecutive weekdays. They underwent rsfMRI and completed the Concise Chinese Aphasia Test (CCAT) before and after the rTMS intervention. ResultThe fractional amplitude of low-frequency fluctuation (fALFF) was calculated to investigate spontaneous neural activity in the brain. After treatment, the language function in the experimental group was higher than that in the sham group in terms of total CCAT score (p = 0.014) and the CCAT subscores of conversation (p = 0.012), description (p = 0.006), and expression (p = 0.003). Postintervention intergroup comparisons revealed that fALFF was significantly increased in the right superior temporal gyrus, right dorsolateral prefrontal gyrus, insular cortex, and caudate nucleus. Clusters in the right thalamus exhibited suppressed fALFF. The enhanced clusters in the frontotemporal region were significantly correlated with CCAT score improvements. ConclusionsOur findings provide empirical evidence for the vital role of the right frontotemporal and subcortical regions in language recovery after rTMS interventions in patients with aphasia. Inhibitory rTMS may improve language expression by promoting involvement of the right frontotemporal region. The results can be further used to refine rTMS protocols and optimize brain stimulation treatments. Clinical Trial RegistrationThe Clinicaltrials.gov registration number for the study is NCT03059225.

Use of Machine Learning in Stroke Rehabilitation: A Narrative Review.

A narrative review was conducted of machine learning applications and research in the field of stroke rehabilitation. The machine learning models commonly used in medical research include random forest, logistic regression, and deep neural networks. Convolutional neural networks (CNNs), a type of deep neural network, are typically used for image analysis. Machine learning has been used in stroke rehabilitation to predict recovery of motor function using a large amount of clinical data as input. Recent studies on predicting motor function have trained CNN models using magnetic resonance images as input data together with clinical data to increase the accuracy of motor function prediction models. Additionally, a model interpreting videofluoroscopic swallowing studies was developed and investigated. In the future, we anticipate that machine learning will be actively used to treat stroke patients, such as predicting the occurrence of depression and the recovery of language, cognitive, and sensory function, as well as prescribing appropriate rehabilitation treatments.

Early white matter connectivity and plasticity in post stroke aphasia recovery

A disruption of white matter connectivity is negatively associated with language (recovery) in patients with aphasia after stroke, and behavioral gains have been shown to coincide with white matter neuroplasticity. However, most brain-behavior studies have been carried out in the chronic phase after stroke, with limited generalizability to earlier phases. Furthermore, few studies have investigated neuroplasticity patterns during spontaneous recovery (i.e., not related to a specific treatment) in the first months after stroke, hindering the investigation of potential early compensatory mechanisms. Finally, the majority of previous research has focused on damaged left hemisphere pathways, while neglecting the potential protective value of their right hemisphere counterparts for language recovery. To address these outstanding issues, we present a longitudinal study of thirty-two patients with aphasia (21 males and 11 females, M = 69.47 years, SD = 10.60 years) who were followed up for a period of 1 year with test moments in the acute (1–2 weeks), subacute (3–6 months) and chronic phase (9–12 months) after stroke. Constrained Spherical Deconvolution-based tractography was performed in the acute and subacute phase to measure Fiber Bundle Capacity (FBC), a quantitative connectivity measure that is valid in crossing fiber regions, in the bilateral dorsal arcuate fasciculus (AF) and the bilateral ventral inferior fronto-occipital fasciculus (IFOF). First, concurrent analyses revealed positive associations between the left AF and phonology, and between the bilateral IFOF and semantics in the acute – but not subacute - phase, supporting the dual-stream language model. Second, neuroplasticity analyses revealed a decrease in connection density of the bilateral AF – but not the IFOF – from the acute to the subacute phase, possibly reflecting post stroke white matter degeneration in areas adjacent to the lesion. Third, predictive analyses revealed no contribution of acute FBC measures to the prediction of later language outcomes over and above the initial language scores, suggesting no added value ofthe diffusion measures for languageprediction. Our study provides new insights on (changes in) connectivity of damaged and undamaged language pathways in patients with aphasia in the first months after stroke, as well as if/how such measures are related to language outcomes at different stages of recovery. Individual results are discussed in the light of current frameworks of language processing and aphasia recovery.

Chapter 9 - Functional MRI evidence for reorganization of language networks after stroke

In this chapter, we review fMRI evidence for language reorganization in individuals with poststroke aphasia. Several studies in the current literature have utilized fMRI as a tool to understand patterns of functional reorganization in poststroke aphasia. Consistent with previous models that have been proposed to explain the trajectory of language recovery, differential patterns of language processing and language recovery have been identified across individuals with poststroke aphasia in different stages of recovery. Overall, a global network breakdown typically occurs in the early stages of aphasia recovery, followed by normalization in "traditional" left hemisphere language networks. Depending on individual characteristics, right hemisphere regions and bilateral domain-general regions may be further recruited. The main takeaway of this chapter is that poststroke aphasia recovery does not depend on individual neural regions, but rather involves a complex interaction among regions in larger networks. Many of the unresolved issues and contrastive findings in the literature warrant further research with larger groups of participants and standard protocols of fMRI implementation.

The role of the hippocampus in statistical learning and language recovery in persons with post stroke aphasia

Although several studies have aimed for accurate predictions of language recovery in post stroke aphasia, individual language outcomes remain hard to predict. Large-scale prediction models are built using data from patients mainly in the chronic phase after stroke, although it is clinically more relevant to consider data from the acute phase. Previous research has mainly focused on deficits, i.e., behavioral deficits or specific brain damage, rather than compensatory mechanisms, i.e., intact cognitive skills or undamaged brain regions. One such unexplored brain region that might support language (re)learning in aphasia is the hippocampus, a region that has commonly been associated with an individual’s learning potential, including statistical learning. This refers to a set of mechanisms upon which we rely heavily in daily life to learn a range of regularities across cognitive domains. Against this background, thirty-three patients with aphasia (22 males and 11 females, M = 69.76 years, SD = 10.57 years) were followed for 1 year in the acute (1–2 weeks), subacute (3–6 months) and chronic phase (9–12 months) post stroke. We evaluated the unique predictive value of early structural hippocampal measures for short-term and long-term language outcomes (measured by the ANELT). In addition, we investigated whether statistical learning abilities were intact in patients with aphasia using three different tasks: an auditory-linguistic and visual task based on the computation of transitional probabilities and a visuomotor serial reaction time task. Finally, we examined the association of individuals’ statistical learning potential with acute measures of hippocampal gray and white matter. Using Bayesian statistics, we found moderate evidence for the contribution of left hippocampal gray matter in the acute phase to the prediction of long-term language outcomes, over and above information on the lesion and the initial language deficit (measured by the ScreeLing). Non-linguistic statistical learning in patients with aphasia, measured in the subacute phase, was intact at the group level compared to 23 healthy older controls (8 males and 15 females, M = 74.09 years, SD = 6.76 years). Visuomotor statistical learning correlated with acute hippocampal gray and white matter. These findings reveal that particularly left hippocampal gray matter in the acute phase is a potential marker of language recovery after stroke, possibly through its statistical learning ability.

Alerting, Orienting, Executive Control and Language Function in Post-stroke Aphasia Patients

Background: Aphasia is frequently observed in post-stroke patients, and this population usually presents attention impairment. Attention is considered to play an important role in the language recovery of patients with Post-Stroke Aphasia (PSA). However, it is no idea whether language function correlates with attention performance. In our study, we investigated the association between attention and language function in PSA patients. Methods: This cross-sectional study was performed from September 2020 to May 2021. A total of 26 PSA patients and 26 healthy people without neurological disorders were recruited in this study. And demographic, language performance, attention performance were recorded. The Aphasia Battery of Chinese (ABC) was applied to assess language performance. Attention network tests were used to measure attention performance. The attention scores were compared between the PSA patients and healthy people. The correlation analysis and stepwise linear regression analysis are used to explore the relationship between attention and language in the PSA group. Results: A total of 26 PSA patients (male/female = 21:5) and 26 healthy people (male/female = 21:5) were enrolled in the study. The mean ages were 50.00 ± 9.01 years, 48.88 ± 7.01, respectively. According to ABC, 14 (53.85%) patients experienced Broca’s aphasia. In accordance with Attention Network Test (ANT), there were significant differences in accuracy and reaction time between the PSA group and the control group (all P<0.05). Orienting RT and alerting inverse efficiency (IE) were significant differences between the two groups. The spearman correlation revealed that executive control was associated with aphasia severity grade, repetition correlated with alerting, auditory comprehension correlated with orienting. And after the stepwise regression analysis, executive control RT alone emerged as a significant predictor of auditory comprehension. Alerting IE and orienting RT are the predictors of repetition. Conclusions: The results suggest that among PSA patients, language items (aphasia severity grade, auditory comprehension, and repetition) are related to three specific attention functions: alerting, orienting, and executive control. Disentangling the mechanism of attention deficits in PSA patients may provide a supplement for the rehabilitation strategies in PSA patients.

Dosage, Intensity, and Frequency of Language Therapy for Aphasia: A Systematic Review-Based, Individual Participant Data Network Meta-Analysis.

Optimizing speech and language therapy (SLT) regimens for maximal aphasia recovery is a clinical research priority. We examined associations between SLT intensity (hours/week), dosage (total hours), frequency (days/week), duration (weeks), delivery (face to face, computer supported, individual tailoring, and home practice), content, and language outcomes for people with aphasia. Databases including MEDLINE and Embase were searched (inception to September 2015). Published, unpublished, and emerging trials including SLT and ≥10 individual participant data on aphasia, language outcomes, and time post-onset were selected. Patient-level data on stroke, language, SLT, and trial risk of bias were independently extracted. Outcome measurement scores were standardized. A statistical inferencing, one-stage, random effects, network meta-analysis approach filtered individual participant data into an optimal model examining SLT regimen for overall language, auditory comprehension, naming, and functional communication pre-post intervention gains, adjusting for a priori-defined covariates (age, sex, time poststroke, and baseline aphasia severity), reporting estimates of mean change scores (95% CI). Data from 959 individual participant data (25 trials) were included. Greatest gains in overall language and comprehension were associated with >20 to 50 hours SLT dosage (18.37 [10.58-26.16] Western Aphasia Battery-Aphasia Quotient; 5.23 [1.51-8.95] Aachen Aphasia Test-Token Test). Greatest clinical overall language, functional communication, and comprehension gains were associated with 2 to 4 and 9+ SLT hours/week. Greatest clinical gains were associated with frequent SLT for overall language, functional communication (3-5+ days/week), and comprehension (4-5 days/week). Evidence of comprehension gains was absent for SLT ≤20 hours, <3 hours/week, and ≤3 days/week. Mixed receptive-expressive therapy, functionally tailored, with prescribed home practice was associated with the greatest overall gains. Relative variance was <30%. Risk of trial bias was low to moderate; low for meta-biases. Greatest language recovery was associated with frequent, functionally tailored, receptive-expressive SLT, with prescribed home practice at a greater intensity and duration than reports of usual clinical services internationally. These exploratory findings suggest critical therapeutic ranges, informing hypothesis-testing trials and tailoring of clinical services. Registration: URL: https://www.crd.york.ac.uk/PROSPERO/; Unique identifier: CRD42018110947.