Therapy-related reorganization of language in both hemispheres of patients with chronic aphasia

Disentangling neuroplasticity mechanisms in post-stroke language recovery

A major objective in post-stroke aphasia research is to gain a deeper understanding of neuroplastic mechanisms that drive language recovery, with the ultimate goal of enhancing treatment outcomes. Subsequent to recent advances in neuroimaging techniques, we now have the ability to examine more closely how neural activity patterns change after a stroke. However, the way these neural activity changes relate to language impairments and language recovery is still debated. The aim of this review is to provide a theoretical framework to better investigate and interpret neuroplasticity mechanisms underlying language recovery in post-stroke aphasia. We detail two sets of neuroplasticity mechanisms observed at the synaptic level that may explain functional neuroimaging findings in post-stroke aphasia recovery at the network level: feedback-based homeostatic plasticity and associative Hebbian plasticity. In conjunction with these plasticity mechanisms, higher-order cognitive control processes dynamically modulate neural activity in other regions to meet communication demands, despite reduced neural resources. This work provides a network-level neurobiological framework for understanding neural changes observed in post-stroke aphasia and can be used to define guidelines for personalized treatment development.

The Role of the Human Cerebellum for Learning from and Processing of External Feedback in Non-Motor Learning: A Systematic Review

This review aimed to systematically identify and comprehensively review the role of the cerebellum in performance monitoring, focusing on learning from and on processing of external feedback in non-motor learning. While 1078 articles were screened for eligibility, ultimately 36 studies were included in which external feedback was delivered in cognitive tasks and which referenced the cerebellum. These included studies in patient populations with cerebellar damage and studies in healthy subjects applying neuroimaging. Learning performance in patients with different cerebellar diseases was heterogeneous, with only about half of all patients showing alterations. One patient study using EEG demonstrated that damage to the cerebellum was associated with altered neural processing of external feedback. Studies assessing brain activity with task-based fMRI or PET and one resting-state functional imaging study that investigated connectivity changes following feedback-based learning in healthy participants revealed involvement particularly of lateral and posterior cerebellar regions in processing of and learning from external feedback. Cerebellar involvement was found at different stages, e.g., during feedback anticipation and following the onset of the feedback stimuli, substantiating the cerebellum's relevance for different aspects of performance monitoring such as feedback prediction. Future research will need to further elucidate precisely how, where, and when the cerebellum modulates the prediction and processing of external feedback information, which cerebellar subregions are particularly relevant, and to what extent cerebellar diseases alter these processes.

Electrophysiological correlates of basic semantic composition in people with aphasia

The neuroanatomical correlates of basic semantic composition have been investigated in previous neuroimaging and lesion studies, but research on the electrophysiology of the involved processes is scarce. A large literature on sentence-level event-related potentials (ERPs) during semantic processing has identified at least two relevant components - the N400 and the P600. Other studies demonstrated that these components are reduced and/or delayed in people with aphasia (PWA). However, it remains to be shown if these findings generalize beyond the sentence level. Specifically, it is an open question if an alteration in ERP responses in PWA can also be observed during basic semantic composition, providing a potential future diagnostic tool. The present study aimed to elucidate the electrophysiological dynamics of basic semantic composition in a group of post-stroke PWA. We included 20 PWA and 20 age-matched controls (mean age 58 years) and measured ERP responses while they performed a plausibility judgment task on two-word phrases that were either meaningful ("anxious horse"), anomalous ("anxious wood") or had the noun replaced by a pseudoword ("anxious gufel"). The N400 effect for anomalous versus meaningful phrases was similar in both groups. In contrast, unlike the control group, PWA did not show an N400 effect between pseudoword and meaningful phrases. Moreover, both groups exhibited a parietal P600 effect towards pseudoword phrases, while PWA showed an additional P600 over frontal electrodes. Finally, PWA showed an inverse correlation between the magnitude of the N400 and P600 effects: PWA exhibiting no or even reversed N400 effects towards anomalous and pseudoword phrases showed a stronger P600 effect. These results may reflect a compensatory mechanism which allows PWA to arrive at the correct interpretation of the phrase. When compositional processing capacities are impaired in the early N400 time-window, PWA may make use of a more elaborate re-analysis process reflected in the P600.

Electrophysiological Changes in Patients with Post-stroke Aphasia: A Systematic Review

Background Magnetoencephalography (MEG) and electroencephalography (EEG) record two main types of data: continuous measurements at rest or during sleep, and event-related potentials/evoked magnetic fields (ERPs/EMFs) that involve specific and repetitive tasks. In this systematic review, we summarized longitudinal studies on recovery from post-stroke aphasia that used continuous or event-related temporal imaging (EEG or MEG). Methods We searched PubMed and Scopus for English articles published from 1950 to May 31, 2022. Results 34 studies were included in this review: 11 were non-interventional studies and 23 were clinical trials that used specific rehabilitation methods, neuromodulation, or drugs. The results of the non-interventional studies suggested that poor language recovery was associated with slow-wave activity persisting over time. The results of some clinical trials indicated that behavioral improvements were correlated with significant modulation of the N400 component. Discussion Compared with continuous EEG, ERP/EMF may more reliably identify biomarkers of therapy-induced effects. Electrophysiology should be used more often to explore language processes that are impaired after a stroke, as it may highlight treatment challenges for patients with post-stroke aphasia.

Effects of melodic intonation therapy in patients with chronic nonfluent aphasia

Patients with large left-hemisphere lesions and post-stroke aphasia often remain nonfluent. Melodic intonation therapy (MIT) may be an effective alternative to traditional speech therapy for facilitating recovery of fluency in those patients. In an open-label, proof-of-concept study, 14 subjects with nonfluent aphasia with large left-hemisphere lesions (171 ± 76 cc) underwent two speech/language assessments before, one at the midpoint, and two after the end of 75 sessions (1.5 h/session) of MIT. Functional MR imaging was done before and after therapy asking subjects to vocalize the same set of 10 bi-syllabic words. We found significant improvements in speech output after a period of intensive MIT (75 sessions for a total of 112.5 h) compared to two pre-therapy assessments. Therapy-induced gains were maintained 4 weeks post-treatment. Imaging changes were seen in a right-hemisphere network that included the posterior superior temporal and inferior frontal gyri, inferior pre- and postcentral gyri, pre-supplementary motor area, and supramarginal gyrus. Functional changes in the posterior right inferior frontal gyri significantly correlated with changes in a measure of fluency. Intense training of intonation-supported auditory-motor coupling and engaging feedforward/feedback control regions in the unaffected hemisphere improves speech-motor functions in subjects with nonfluent aphasia and large left-hemisphere lesions.

Time course of right-hemisphere recruitment during word production following left-hemisphere damage: A single case of young stroke

Our understanding of post-stroke language function is largely based on older age groups, who show increasing age-related brain pathology and neural reorganisation. To illustrate language outcomes in the young-adult brain, we present the case of J., a 23-year-old woman with chronic aphasia from a left-hemisphere stroke affecting the temporal lobe. Diffusion MRI-based tractography indicated that J.'s language-relevant white-matter structures were severely damaged. Employing magnetoencephalography (MEG), we explored J.'s conceptual preparation and word planning abilities using context-driven and bare picture-naming tasks. These revealed naming deficits, manifesting as word-finding difficulties and semantic paraphasias about half of the time. Naming was however facilitated by semantically constraining lead-in sentences. Altogether, this pattern indicates disrupted lexical-semantic and phonological retrieval abilities. MEG revealed that J.'s conceptual and naming-related neural responses were supported by the right hemisphere, compared to the typical left-lateralised brain response of a matched control. Differential recruitment of right-hemisphere structures (330-440 ms post-picture onset) was found concurrently during successful naming (right mid-to-posterior temporal lobe) and word-finding attempts (right inferior frontal gyrus). Disconnection of the temporal lobes via corpus callosum was not critical for recruitment of the right hemisphere in visually guided naming, possibly due to neural activity right lateralising from the outset. Although J.'s right hemisphere responded in a timely manner during word planning, its lexical and phonological retrieval abilities remained modest.

Understanding Language Reorganization With Neuroimaging: How Language Adapts to Different Focal Lesions and Insights Into Clinical Applications

When the language-dominant hemisphere is damaged by a focal lesion, the brain may reorganize the language network through functional and structural changes known as adaptive plasticity. Adaptive plasticity is documented for triggers including ischemic, tumoral, and epileptic focal lesions, with effects in clinical practice. Many questions remain regarding language plasticity. Different lesions may induce different patterns of reorganization depending on pathologic features, location in the brain, and timing of onset. Neuroimaging provides insights into language plasticity due to its non-invasiveness, ability to image the whole brain, and large-scale implementation. This review provides an overview of language plasticity on MRI with insights for patient care. First, we describe the structural and functional language network as depicted by neuroimaging. Second, we explore language reorganization triggered by stroke, brain tumors, and epileptic lesions and analyze applications in clinical diagnosis and treatment planning. By comparing different focal lesions, we investigate determinants of language plasticity including lesion location and timing of onset, longitudinal evolution of reorganization, and the relationship between structural and functional changes.

Electrophysiologic evidence of reorganization in poststroke aphasia

Electrophysiologic methods have been used to investigate neural changes in individuals with poststroke aphasia. The major types of electrophysiologic measures include the event-related potential (ERP) and spectral power, and aspects of both (including amplitude, topography, and power) have been shown to differ in people with aphasia. Not only that, these measures are sensitive to spontaneous and treatment-induced language change. The purpose of this chapter is to review evidence of poststroke reorganization in the language network that has been identified in the acute and chronic phases of poststroke aphasia. The chapter will begin with a brief introduction to electrophysiologic methods and then focus on evidence from the most commonly studied ERPs and spectral bands in aphasia.

The role and use of event-related potentials in aphasia: A scoping review

Event-related potentials (ERPs) can provide important insights into underlying language processes in both unimpaired and neurologically impaired populations and may be particularly useful in aphasia. This scoping review was conducted to provide a comprehensive summary of how ERPs have been used with people with aphasia (PWA), with the goal of exploring the potential clinical application of ERPs in aphasia assessment and treatment. We identified 117 studies that met inclusionary criteria, reflecting six thematic domains of inquiry that relate to understanding both unimpaired and aphasic language processing and the use of ERPs with PWA. In these studies, a wide variety of ERP components were reported. Inconsistencies in reporting of participant characteristics and study protocols limit our ability to generalize beyond the individual studies and understand implications for clinical applicability. We discuss the potential roles of ERPs in aphasia management and make recommendations for further developing ERPs for clinical utility in PWA.

Increased Recruitment of Domain-General Neural Networks in Language Processing Following Intensive Language-Action Therapy: fMRI Evidence From People With Chronic Aphasia

Purpose This study aimed to provide novel insights into the neural correlates of language improvement following intensive language-action therapy (ILAT; also known as constraint-induced aphasia therapy). Method Sixteen people with chronic aphasia underwent clinical aphasia assessment (Aachen Aphasia Test [AAT]), as well as functional magnetic resonance imaging (fMRI), both administered before (T1) and after ILAT (T2). The fMRI task included passive reading of single written words, with hashmark strings as visual baseline. Results Behavioral results indicated significant improvements of AAT scores across therapy, and fMRI results showed T2-T1 blood oxygenation-level-dependent (BOLD) signal change in the left precuneus to be modulated by the degree of AAT score increase. Subsequent region-of-interest analysis of this precuneus cluster confirmed a positive correlation of T2-T1 BOLD signal change and improvement on the clinical aphasia test. Similarly, the entire default mode network revealed a positive correlation between T2-T1 BOLD signal change and clinical language improvement. Conclusion These results are consistent with a more efficient recruitment of domain-general neural networks in language processing, including those involved in attentional control, following aphasia therapy with ILAT. Supplemental Material https://doi.org/10.23641/asha.12765755.

The sensitivity of event-related potentials/fields to logopedic interventions in patients with stroke-related aphasia

Recovery of stroke-related aphasia can be affected by language therapy in the early and chronic stage. Objectively monitoring therapy-induced neuroplasticity is possible by several measurement techniques including electro- and magneto-encephalography. The obtained event-related potentials (ERPs) and fields (ERFs) provide insights into the neural basis of intact or deficient language processing with milliseconds precision. In this literature review, we highlight the sensitivity of ERPs and ERFs to logopedic interventions by providing an overview of therapy-induced changes in the amplitude, latency and topography of early and mid-to-late components.

Progression of Aphasia Severity in the Chronic Stages of Stroke

Background and Purpose The severity of aphasic impairment in chronic stroke survivors is typically thought to be stable by 6 months postonset. However, a recent study showed that stroke survivors with aphasia experience language improvement or decline in the chronic phase, years beyond onset. Little is known about why some individuals improve whereas others remain stable or decline. Additionally, no study has tracked changes in aphasia from assessments completed at multiple time points across many years. The current study offers a comprehensive analysis of potential predictive demographic and health information to determine which factors predict dynamic changes in aphasia severity in chronic stroke. Methods Individuals in the chronic stage of a single-event, left-hemisphere ischemic stroke were identified from an archival database and included for study ( N = 39). Participants were included if they had undergone 2 or more standardized language assessments acquired at time points at least 6 months apart, with the 1st assessment at least 6 months postinjury. A linear mixed-effects model was used to determine the impact of treatment and a variety of demographic and health factors on language change. Results Over time, half of the participants improved (51%), whereas approximately a quarter (26%) decreased, and a quarter (23%) remained stable. A greater number of aphasia treatment hours significantly predicted language improvement ( p = .03), whereas older stroke age was associated with long-term decline ( p = .04). Two interactions were found to be significant in predicting improvement in individuals with diabetes: Increased exercise and younger age at stroke were significant in predicting outcomes ( p < .05). Conclusions Factors that significantly influence language recovery in chronic aphasia include stroke age and receiving aphasia treatment. For those with diabetes, increased exercise was shown to improve outcomes. Results from this study offer clinicians greater insight into the influence of patient factors on long-term recovery from stroke aphasia while suggesting a potential adjunct to language therapy: exercise. Supplemental Material https://doi.org/10.23641/asha.7849304.

'What's cooking?' A comparison of an activity-oriented and a table-top programme of therapy on the language performance of people with aphasia

BACKGROUND

Many people with aphasia have word-finding difficulties, with some showing particular difficulties with verbs. Picture-naming therapy is often used to improve naming, but gains are usually limited to therapy items and do not transfer to conversation. Therapy where words are produced in sentences and in real-life activities may be more effective.

AIMS

The current pilot study investigated whether an activity-oriented therapy approach would be accepted and viable if implemented in a community setting, and whether communicating whilst cooking was more beneficial than using paper-based activities. If successful, it would be expected that verb production would improve in structured and unstructured tasks in both naming and narrative tasks.

METHODS & PROCEDURES

The study employed a case-series repeated-measures design, with testing of treated and control items. Seven adults with anomia participated, although only five completed the full programme. Participants were divided into two groups and each group completed both treatments, but in different orders. Each treatment was employed for six 2-h sessions over a 3-week period.

OUTCOMES & RESULTS

Naming of both treated and untreated verbs showed a statistically significant improvement following both treatments and this continued into the maintenance phase. There was a numerical but not statistically significant gain in the variety of verbs used in spoken narratives. Participants predominantly chose positive terms to describe their experience of the programme, but did not prefer one therapy over the other.

CONCLUSIONS & IMPLICATIONS

Preliminary findings suggest that an activity-oriented therapy approach, whether it involves carrying out tasks or paper-based activities, can result in clinically meaningful improvements for people with chronic aphasia. Further research using a randomized control trial is required to determine whether cooking therapy alone is effective.

Modulating the interhemispheric balance in healthy participants with transcranial direct current stimulation: No significant effects on word or sentence processing

Patient studies and brain stimulation evidence suggest that language processing can be enhanced by altering the interhemispheric balance: namely, preferentially enhancing left-hemisphere activity while suppressing right-hemisphere activity. To our knowledge, no study has yet compared the effects of such bilateral brain stimulation to both logically necessary control conditions (separate left- and right-hemisphere stimulation). This study did so in a between-group sham-controlled design, applying transcranial direct current stimulation over Broca's area and/or its homologue in 72 healthy participants. The effects were measured not only in a single-word-level task but also in a sentence-level task, rarely tested previously. We did not find either any significant overall effects of stimulation or greater stimulation effects in the bilateral compared to control groups. This null result, obtained in a large sample, contributes to the debate on whether tDCS can modulate language processing in healthy individuals.

Effect of type of language therapy on expressive language skills in patients with post-stroke aphasia

BACKGROUND

Constraint-induced (language) aphasia therapy (CIAT), based on constraint usage of the language channel only, massed practice and shaping through therapeutic language games, has been suggested as a more efficient therapy approach than traditional aphasia therapies.

AIMS

To examine the comparative efficacy of CIAT and a traditional therapy approach on expressive language ability, with the intensity of therapy controlled and matched, in the treatment of post-stroke aphasia.

METHODS & PROCEDURES

Two successive 4-week blocks of intense (1 h, 5 days a week) of aphasia therapy programmes were delivered in a randomized within-subject crossover design: one therapy block consisted of stimulation aphasia therapy (SAT, a common traditional therapy approach), another of CIAT. Twenty consecutive patients, up to 1 year after stroke, were randomly assigned either to have SAT followed by CIAT (S1C2 group) or to have CIAT followed by SAT (C1S2 group). Measurements of naming (Boston Naming Test) and spontaneous sentence production (Cookie Theft Picture description task) were carried at the baseline, following the first therapy block, following the second therapy block and 4 weeks following the last therapy block.

OUTCOMES & RESULTS

Both groups of patients significantly improved in all variables of expressive language skills; the improvement was maintained 1 month post-treatment. However, patients who started with CIAT and continued with SAT (C1S2 group) tended to have higher final improvement than the patients who started with SAT and continued with CIAT (S1C2 group). This was particularly pronounced for naming. Moreover, when CIAT was the first therapy (the C1S2 group) the improvement achieved in naming following CIAT significantly exceeded the improvements achieved following SAT, not only in the same group (when SAT was the second) but also in the S1C2 group (when SAT was the first). In addition, the improvement in naming following CIAT in the C1S2 group exceeded the one in the S1C2 group, too. Similarly, the improvement in the total number of sentences produced following each therapy was quite clear and significant in the C1S2 group (when CIAT was the first), while in the S1C2 group it was much more modest and not significant.

CONCLUSIONS & IMPLICATIONS

Results suggest that the maximization of quantity and frequency of language therapy have a significant impact on the improvement of expressive language ability. Moreover, if practised early in aphasia therapy, the constrained usage of the language modality, as practised in CIAT, confers an additional benefit to massed practice, particularly on naming ability.

Early Recovery of Aphasia through Thrombolysis: The Significance of Spontaneous Speech

BACKGROUND

Aphasia is one of the most devastating stroke-related consequences for social interaction and daily activities. Aphasia recovery in acute stroke depends on the degree of reperfusion after thrombolysis or thrombectomy. As aphasia assessment tests are often time-consuming for patients with acute stroke, physicians have been developing rapid and simple tests. The aim of our study is to evaluate the improvement of language functions in the earliest stage in patients treated with thrombolysis and in nontreated patients using our rapid screening test.

MATERIALS AND METHODS

Our study is a single-center prospective observational study conducted at the Stroke Unit of the University Medical Hospital of Trieste (January-December 2016). Patients treated with thrombolysis and nontreated patients underwent 3 aphasia assessments through our rapid screening test (at baseline, 24 hours, and 72 hours). The screening test assesses spontaneous speech, oral comprehension of words, reading aloud and comprehension of written words, oral comprehension of sentences, naming, repetition of words and a sentence, and writing words.

RESULTS

The study included 40 patients: 18 patients treated with thrombolysis and 22 nontreated patients. Both groups improved over time. Among all language parameters, spontaneous speech was statistically significant between 24 and 72 hours (P value = .012), and between baseline and 72 hours (P value = .017).

CONCLUSIONS

Our study demonstrates that patients treated with thrombolysis experience greater improvement in language than the nontreated patients. The difference between the 2 groups is increasingly evident over time. Moreover, spontaneous speech is the parameter marked by the greatest improvement.

Neuroimaging of stroke recovery from aphasia - Insights into plasticity of the human language network

The role of left and right hemisphere brain regions in language recovery after stroke-induced aphasia remains controversial. Here, we summarize how neuroimaging studies increase the current understanding of functional interactions, reorganization and plasticity in the language network. We first discuss the temporal dynamics across the time course of language recovery, with a main focus on longitudinal studies from the acute to the chronic phase after stroke. These studies show that the functional contribution of perilesional and spared left hemisphere as well as contralesional right hemisphere regions to language recovery changes over time. The second section introduces critical variables and recent advances on early prediction of subsequent outcome. In the third section, we outline how multi-method approaches that combine neuroimaging techniques with non-invasive brain stimulation elucidate mechanisms of plasticity and reorganization in the language network. These approaches provide novel insights into general mechanisms of plasticity in the language network and might ultimately support recovery processes during speech and language therapy. Finally, the neurobiological correlates of therapy-induced plasticity are discussed. We argue that future studies should integrate individualized approaches that might vary the combination of language therapy with specific non-invasive brain stimulation protocols across the time course of recovery. The way forward will include the combination of such approaches with large data sets obtained from multicentre studies.

Constraint-induced aphasia therapy in post-stroke aphasia rehabilitation: A systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Constraint-induced aphasia therapy (CIAT) has been widely used in post-stroke aphasia rehabilitation. An increasing number of clinical controlled trials have investigated the efficacy of the CIAT for the post-stroke aphasia.

PURPOSE

To systematically review the randomized controlled trials (RCTs) concerning the effect of the CIAT in post-stroke patients with aphasia, and to identify the useful components of CIAT in post-stroke aphasia rehabilitation.

METHODS

A computerized database search was performed through five databases (Pubmed, EMbase, Medline, ScienceDirect and Cochrane library). Cochrane handbook domains were used to evaluate the methodological quality of the included RCTs.

RESULTS

Eight RCTs qualified in the inclusion criteria. Inconsistent results were found in comparing the CIAT with conventional therapies without any component from the CIAT based on the results of three RCTs. Five RCTs showed that the CIAT performed equally well as other intensive aphasia therapies, in terms of improving language performance. One RCT showed that therapies embedded with social interaction were likely to enhance the efficacy of the CIAT.

CONCLUSION

CIAT may be useful for improving chronic post-stroke aphasia, however, limited evidence to support its superiority to other aphasia therapies. Massed practice is likely to be a useful component of CIAT, while the role of "constraint" is needed to be further explored. CIAT embedded with social interaction may gain more benefits.

Neuroimaging Correlates of Post-Stroke Aphasia Rehabilitation in a Pilot Randomized Trial of Constraint-Induced Aphasia Therapy

Background

Recovery from post-stroke aphasia is a long and complex process with an uncertain outcome. Various interventions have been proposed to augment the recovery, including constraint-induced aphasia therapy (CIAT). CIAT has been applied to patients suffering from post-stroke aphasia in several unblinded studies to show mild-to-moderate linguistic gains. The aim of the present study was to evaluate the neuroimaging correlates of CIAT in patients with chronic aphasia related to left middle cerebral artery stroke.

Material/Methods

Out of 24 patients recruited in a pilot randomized blinded trial of CIAT, 19 patients received fMRI of language. Eleven of them received CIAT (trained) and eight served as a control group (untrained). Each patient participated in three fMRI sessions (before training, after training, and 3 months later) that included semantic decision and verb generation fMRI tasks, and a battery of language tests. Matching healthy control participants were also included (N=38; matching based on age, handedness, and sex).

Results

Language testing showed significantly improved performance on Boston Naming Test (BNT; p<0.001) in both stroke groups over time and fMRI showed differences in the distribution of the areas involved in language production between groups that were not present at baseline. Further, regression analysis with BNT indicated changes in brain regions correlated with behavioral performance (temporal gyrus, postcentral gyrus, precentral gyrus, thalamus, left middle and superior frontal gyri).

Conclusions

Overall, our results suggest the possibility of language-related cortical plasticity following stroke-induced aphasia with no specific effect from CIAT training.

Language improvement one week after thrombolysis in acute stroke

OBJECTIVES

Language recovery following acute stroke is difficult to predict due to several evaluation factors and time constraints. We aimed to investigate the predictors of aphasia recovery and to identify the National Institute of Health and Stroke Scale (NIHSS) items that best reflect linguistic performance, 1 week after thrombolysis.

MATERIALS AND METHODS

We retrieved data from a prospective registry of patients with aphasia secondary to left middle cerebral artery (MCA) stroke treated with intravenous thrombolysis. Complete recovery at day 7 (D7) was measured in a composite verbal score (CVS) (Σ Language+Questions+Commands NIHSS scores). Lesion size was categorized by the Alberta Stroke Program Early CT score (ASPECTS) and vascular patency by ultrasound. CVS was correlated with standardized aphasia testing if both were performed within a two-day interval.

RESULTS

Of 228 patients included (age average 67.32 years, 131 men), 72% presented some language improvement that was complete in 31%. Total recovery was predicted by ASPECTS (OR=1.65; 95% CI, 1.295-2.108; P < 0.00) and baseline aphasia severity (OR=0.439; 95% CI, 0.242-0.796; P < 0.007). CVS correlated better with standardized aphasia measures (aphasia quotient, severity, comprehension) than NIHSS_Language item.

CONCLUSIONS

Lesion size and initial aphasia severity are the main predictors of aphasia recovery one week after thrombolysis. A NIHSS composite verbal score seems to capture the global linguistic performance better than the language item alone.

Therapy-Induced Neuroplasticity of Language in Chronic Post Stroke Aphasia: A Mismatch Negativity Study of (A)Grammatical and Meaningful/less Mini-Constructions

Clinical language performance and neurophysiological correlates of language processing were measured before and after intensive language therapy in patients with chronic (time post stroke >1 year) post stroke aphasia (PSA). As event-related potential (ERP) measure, the mismatch negativity (MMN) was recorded in a distracted oddball paradigm to short spoken sentences. Critical 'deviant' sentence stimuli where either well-formed and meaningful, or syntactically, or lexico-semantically incorrect. After 4 weeks of speech-language therapy (SLT) delivered with high intensity (10.5 h per week), clinical language assessment with the Aachen Aphasia Test battery demonstrated significant linguistic improvements, which were accompanied by enhanced MMN responses. More specifically, MMN amplitudes to grammatically correct and meaningful mini-constructions and to 'jabberwocky' sentences containing a pseudoword significantly increased after therapy. However, no therapy-related changes in MMN responses to syntactically incorrect strings including agreement violations were observed. While MMN increases to well-formed meaningful strings can be explained both at the word and construction levels, the neuroplastic change seen for 'jabberwocky' sentences suggests an explanation in terms of constructions. The results confirm previous reports that intensive SLT leads to improvements of linguistic skills in chronic aphasia patients and now demonstrate that this clinical improvement is associated with enhanced automatic brain indexes of construction processing, although no comparable change is present for ungrammatical strings. Furthermore, the data confirm that the language-induced MMN is a useful tool to map functional language recovery in PSA.

Magnetoencephalography in Stroke Recovery and Rehabilitation

Magnetoencephalography (MEG) is a non-invasive neurophysiological technique used to study the cerebral cortex. Currently, MEG is mainly used clinically to localize epileptic foci and eloquent brain areas in order to avoid damage during neurosurgery. MEG might, however, also be of help in monitoring stroke recovery and rehabilitation. This review focuses on experimental use of MEG in neurorehabilitation. MEG has been employed to detect early modifications in neuroplasticity and connectivity, but there is insufficient evidence as to whether these methods are sensitive enough to be used as a clinical diagnostic test. MEG has also been exploited to derive the relationship between brain activity and movement kinematics for a motor-based brain–computer interface. In the current body of experimental research, MEG appears to be a powerful tool in neurorehabilitation, but it is necessary to produce new data to confirm its clinical utility.

Choosing words: left hemisphere, right hemisphere, or both? Perspective on the lateralization of word retrieval

Language is considered to be one of the most lateralized human brain functions. Left hemisphere dominance for language has been consistently confirmed in clinical and experimental settings and constitutes one of the main axioms of neurology and neuroscience. However, functional neuroimaging studies are finding that the right hemisphere also plays a role in diverse language functions. Critically, the right hemisphere may also compensate for the loss or degradation of language functions following extensive stroke-induced damage to the left hemisphere. Here, we review studies that focus on our ability to choose words as we speak. Although fluidly performed in individuals with intact language, this process is routinely compromised in aphasic patients. We suggest that parceling word retrieval into its subprocesses-lexical activation and lexical selection-and examining which of these can be compensated for after left hemisphere stroke can advance the understanding of the lateralization of word retrieval in speech production. In particular, the domain-general nature of the brain regions associated with each process may be a helpful indicator of the right hemisphere's propensity for compensation.

What do patients with epilepsy tell us about language dynamics? A review of fMRI studies

The objective of this review is to resume major neuroimaging findings on language organization and plasticity in patients with focal and refractory epilepsy, to discuss the effect of modulatory variables that should be considered alongside patterns of reorganization, and to propose possible models of language reorganization. The focal and refractory epilepsy provides a real opportunity to investigate various types of language reorganization in different conditions. The 'chronic' condition (induced by the epileptogenic zone or EZ) is associated with either recruitment of homologous regions of the opposite hemisphere or recruitment of intrahemispheric, nonlinguistic regions. In the 'acute' condition (neurosurgery and EZ resection), the initial interhemispheric shift (induced by the chronic EZ) could follow a reverse direction, back to the initial hemisphere. These different patterns depend on several modulatory factors and are associated with various levels of language performance. As a neuroimaging tool, functional magnetic resonance imaging enables the detailed investigation of both hemispheres simultaneously and allows for comparison with healthy controls, potentially creating a more comprehensive and more realistic picture of brain-language relations. Importantly, functional neuroimaging approaches demonstrate a good degree of concordance on a theoretical level, but also a considerable degree of individual variability, attesting to the clinical importance with these methods to establish, empirically, language localization in individual patients. Overall, the unique features of epilepsy, combined with ongoing advances in technology, promise further improvement in understanding of language substrate.

Bilateral brain reorganization with memantine and constraint-induced aphasia therapy in chronic post-stroke aphasia: An ERP study

Changes in ERP (P100 and N400) and root mean square (RMS) were obtained during a silent reading task in 28 patients with chronic post-stroke aphasia in a randomized, double-blind, placebo-controlled trial of both memantine and constraint-induced aphasia therapy (CIAT). Participants received memantine/placebo alone (weeks 0-16), followed by drug treatment combined with CIAT (weeks 16-18), and then memantine/placebo alone (weeks 18-20). ERP/RMS values (week 16) decreased more in the memantine group than in the placebo group. During CIAT application (weeks 16-18), improvements in aphasia severity and ERP/RMS values were amplified by memantine and changes remained stable thereafter (weeks 18-20). Changes in ERP/RMS occurred in left and right hemispheres and correlated with gains in language performance. No changes in ERP/RMS were found in a healthy group in two separated evaluations. Our results show that aphasia recovery induced by both memantine alone and in combination with CIAT is indexed by bilateral cortical potentials.

Language specificity of lexical-phonological therapy in bilingual aphasia: A clinical and electrophysiological study

Based on findings for overlapping representations of bilingual people's first (L1) and second (L2) languages, unilingual therapies of bilingual aphasia have been proposed to benefit the untrained language. However, the generalisation patterns of intra- and cross-language and phonological therapy and their neural bases remain unclear. We tested whether the effects of an intensive lexical-phonological training (LPT) in L2 transferred to L1 word production in a Persian-French bilingual stroke patient with Broca's aphasia. Language performance was assessed using the Bilingual Aphasia Test, a 144-item picture naming (PN) task and a word-picture verification (WPV) task. Electroencephalography (EEG) was recorded during PN and WPV in both languages before and after an LPT in French on a wordlist from the PN task. After the therapy, naming improved only for the treated L2 items. The naming performance improved neither in the untrained L2 items nor in the corresponding items in L1. EEG analyses revealed a Language x Session topographic interaction at 540 ms post-stimulus, driven by a modification of the electrophysiological response to the treated L2 but not L1 items. These results indicate that LPT modified the brain networks engaged in the phonological-phonetic processing during naming only in the trained language for the trained items.

Ultra-rapid access to words in chronic aphasia: the effects of intensive language action therapy (ILAT)

Effects of intensive language action therapy (ILAT) on automatic language processing were assessed using Magnetoencephalography (MEG). Auditory magnetic mismatch negativity (MMNm) responses to words and pseudowords were recorded in twelve patients with chronic aphasia before and immediately after two weeks of ILAT. Following therapy, Patients showed significant clinical improvements of auditory comprehension as measured by the Token Test and in word retrieval and naming as measured by the Boston Naming Test. Neuromagnetic responses dissociated between meaningful words and meaningless word-like stimuli ultra-rapidly, approximately 50 ms after acoustic information first allowed for stimulus identification. Over treatment, there was a significant increase in the left-lateralisation of this early word-elicited activation, observed in perilesional fronto-temporal regions. No comparable change was seen for pseudowords. The results may reflect successful, therapy-induced, language restitution in the left hemisphere.

Changes of right-hemispheric activation after constraint-induced, intensive language action therapy in chronic aphasia: fMRI evidence from auditory semantic processing

The role of the two hemispheres in the neurorehabilitation of language is still under dispute. This study explored the changes in language-evoked brain activation over a 2-week treatment interval with intensive constraint induced aphasia therapy (CIAT), which is also called intensive language action therapy (ILAT). Functional magnetic resonance imaging (fMRI) was used to assess brain activation in perilesional left hemispheric and in homotopic right hemispheric areas during passive listening to high and low-ambiguity sentences and non-speech control stimuli in chronic non-fluent aphasia patients. All patients demonstrated significant clinical improvements of language functions after therapy. In an event-related fMRI experiment, a significant increase of BOLD signal was manifest in right inferior frontal and temporal areas. This activation increase was stronger for highly ambiguous sentences than for unambiguous ones. These results suggest that the known language improvements brought about by intensive constraint-induced language action therapy at least in part relies on circuits within the right-hemispheric homologs of left-perisylvian language areas, which are most strongly activated in the processing of semantically complex language.

Rehabilitation of verbal memory by means of preserved nonverbal memory abilities after epilepsy surgery

We present a patient with epilepsy who underwent left anterior temporal cortex resection, sparing the hippocampus, to stop drug-refractory seizures. Given that one year after surgery the patient showed verbal memory difficulties, we proposed a short (twelve weeks) and intensive (two times a week) training based on visual imagery strategies as the nonverbal memory abilities were preserved. Neuropsychological and fMRI assessments were performed before and after rehabilitation to evaluate the cognitive progress and cerebral modifications induced by this rehabilitation program. Our results showed that the rehabilitation program improved both scores for verbal memory and the everyday quality of life. Changes in cerebral activity highlighted by fMRI suggest that the program might have facilitated the development of compensatory strategies, as reflected by the shift of activation from the anterior to the posterior cerebral network during a verbal memory task. One year after the rehabilitation program, the patient reported using mental imagery in everyday life for routine and professional activities. Although supplementary evidence is necessary to increase the robustness of these findings, this case report suggests that an efficient rehabilitation program is feasible and (a) should be based on the individual cognitive profile and on the preserved cognitive abilities, (b) can be short but intensive, (c) can be applied even months after the lesion occurrence, and (d) can induce a positive effect which may be sustainable over time.

Feasibility of event-related potential methodology to evaluate changes in cortical processing after rehabilitation in children with cerebral palsy: a pilot study

This study examined the feasibility of using event-related potentials (ERPs) to measure changes in cortical processing following an established rehabilitative intervention (constraint-induced movement therapy, CIMT) for children with cerebral palsy (CP). Sixteen participants with a diagnosis of hemiparetic CP, with a median age of 6 years, were assessed pre and immediately post CIMT and at 6-month follow-up, using a picture-word match/mismatch discrimination task and standard neurobehavioral measures. Intervention effects were evident in improved performance on behavioral tests of sensory and motor function and the increased mean ERP amplitude of the N400 match/mismatch response on the side ipsilateral to the lesion. These effects were maintained 6 months after the intervention. No such changes were observed on the side contralateral to the lesion. This research suggests that ERPs can measure rehabilitation-induced changes in neural function in children with CP.

Induction of neuroplasticity and recovery in post-stroke aphasia by non-invasive brain stimulation

Stroke victims tend to prioritize speaking, writing, and walking as the three most important rehabilitation goals. Of note is that two of these goals involve communication. This underscores the significance of developing successful approaches to aphasia treatment for the several hundred thousand new aphasia patients each year and over 1 million stroke survivors with chronic aphasia in the U.S. alone. After several years of growth as a research tool, non-invasive brain stimulation (NBS) is gradually entering the arena of clinical aphasiology. In this review, we first examine the current state of knowledge of post-stroke language recovery including the contributions from the dominant and non-dominant hemispheres. Next, we briefly discuss the methods and the physiologic basis of the use of inhibitory and excitatory repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS) as research tools in patients who experience post-stroke aphasia. Finally, we provide a critical review of the most influential evidence behind the potential use of these two brain stimulation methods as clinical rehabilitative tools.

Releasing the constraints on aphasia therapy: the positive impact of gesture and multimodality treatments

PURPOSE

There is a 40-year history of interest in the use of arm and hand gestures in treatments that target the reduction of aphasic linguistic impairment and compensatory methods of communication (Rose, 2006). Arguments for constraining aphasia treatment to the verbal modality have arisen from proponents of constraint-induced aphasia therapy (Pulvermüller et al., 2001). Confusion exists concerning the role of nonverbal treatments in treating people with aphasia. The central argument of this paper is that given the state of the empirical evidence and the strong theoretical accounts of modality interactions in human communication, gesture-based and multimodality aphasia treatments are at least as legitimate an option as constraint-based aphasia treatment.

METHOD

Theoretical accounts of modality interactions in human communication and the gesture production abilities of individuals with aphasia that are harnessed in treatments are reviewed. The negative effects on word retrieval of restricting gesture production are also reviewed, and an overview of the neurological architecture subserving language processing is provided as rationale for multimodality treatments. The evidence for constrained and unconstrained treatments is critically reviewed.

CONCLUSION

Together, these data suggest that constraint treatments and multimodality treatments are equally efficacious, and there is limited support for constraining client responses to the spoken modality.

Changes in N400 topography following intensive speech language therapy for individuals with aphasia

Our goal was to characterize the effects of intensive aphasia therapy on the N400, an electrophysiological index of lexical-semantic processing. Immediately before and after 4 weeks of intensive speech-language therapy, people with aphasia performed a task in which they had to determine whether spoken words were a 'match' or a 'mismatch' to pictures of objects. Pre-therapy, people with aphasia exhibited an N400 mismatch effect that started over right hemisphere electrodes. Post-therapy, gains were seen in clinical measures of language ability, and the onset of the N400 was left-lateralized. No changes in the scalp distribution of the N400 were observed in healthy controls tested twice over the same 4 week interval. Since the distribution of the N400 after aphasia therapy differed from that of healthy controls, we conclude that it reflects the engagement of compensatory neural mechanisms for language processing rather than a return to a "normal" pattern of brain activation.

Sensitive periods for language and recovery from stroke: conceptual and practical parallels

In this review, we consider the literature on sensitive periods for language acquisition from the perspective of the stroke recovery literature treated in this Special Issue. Conceptually, the two areas of study are linked in a number of ways. For example, the fact that learning itself can set the stage for future failures to learn (in second language learning) or to remediate (as described in constraint therapy) is an important insight in both areas, as is the increasing awareness that limits on learning can be overcome by creating the appropriate environmental context. Similar practical issues, such as distinguishing native-like language acquisition or recovery of function from compensatory mechanisms, arise in both areas as well.

Constrained versus unconstrained intensive language therapy in two individuals with chronic, moderate-to-severe aphasia and apraxia of speech: behavioral and fMRI outcomes

PURPOSE

This Phase I study investigated behavioral and functional MRI (fMRI) outcomes of 2 intensive treatment programs to improve naming in 2 participants with chronic moderate-to-severe aphasia with comorbid apraxia of speech (AOS). Constraint-induced aphasia therapy (CIAT; Pulvermüller et al., 2001) has demonstrated positive outcomes in some individuals with chronic aphasia. Whether constraint to the speech modality or treatment intensity is responsible for such gains is still under investigation. Moreover, it remains to be seen whether CIAT is effective in individuals with persistent severe nonfluent speech and/or AOS.

METHOD

A single-subject multiple-baseline approach was used. Both participants were treated simultaneously, first with Promoting Aphasics' Communicative Effectiveness (PACE; Davis & Wilcox, 1985) and then with CIAT. Pre-/posttreatment testing included an overt naming fMRI protocol. Treatment effect sizes were calculated for changes in probe accuracy from baseline to posttreatment phases and maintenance where available.

RESULTS

Both participants made more and faster gains in naming following CIAT. Treatment-induced changes in BOLD activation suggested that better naming was correlated with the recruitment of perilesional tissue.

CONCLUSION

Participants produced more target words accurately following CIAT than following PACE. Behavioral and fMRI results support the notion that the intense and repetitive nature of obligatory speech production in CIAT has a positive effect on word retrieval, even in participants with chronic moderate-to-severe aphasia with comorbid AOS.

Left hemisphere plasticity and aphasia recovery

A recent study by our group revealed a strong relationship between functional brain changes in the left hemisphere and anomia treatment outcome in chronic stroke patients (N=26) with aphasia (Fridriksson, 2010). The current research represents a continuation of this work in which we have refined our methods and added data from four more patients (for a total sample size of 30) to assess where in the left hemisphere treatment-related brain changes occur. Unlike Fridriksson (2010) which only focused on changes in correct naming as a marker of treatment outcome, the current study examined the relationship between changes in left hemisphere activity and changes in correct naming, semantic paraphasias, and phonemic paraphasias following treatment. We also expanded on the work by Fridriksson by examining whether neurophysiological measures taken at baseline (defined henceforth as the time-point before the start of anomia treatment) predict treatment outcome. Our analyses revealed that changes in activation in perilesional areas predicted treatment-related increases in correct naming in individuals with chronic aphasia. This relationship was most easily observed in the left frontal lobe. A decrease in the number of semantic and phonemic paraphasias was predicted by an activation change in the temporal lobe involving cortical areas that were shown to be active during picture naming in 14 normal subjects. In contrast, a far less certain relationship was found between baseline neurophysiological measures and anomia treatment outcome. Our findings suggest that improved naming associated with behavioral anomia treatment in aphasia is associated with modulation of the left frontal lobe whereas a reduction in naming errors is mediated by left posterior regions that classically are thought to be involved in language processing.

First decade of research on constrained-induced treatment approaches for aphasia rehabilitation

Approaches for treating poststroke language impairments (aphasia) based on constraint-induced (CI) principles were first introduced in 2001. CI principles as previously applied to upper extremity and locomotor retraining in stroke survivors were derived from basic neuroscience. They comprise forced-use of the affected modality, a gradual rebuilding of targeted functions using a highly intensive treatment protocol, administered in a behaviorally relevant context. CI-based approaches have stimulated considerable neurorehabilitation research interest in the past decade. The original CI aphasia treatment protocol was tailored to improve functional communication in chronic aphasia (ie, 6-12mo after stroke) and more recently, it has been adapted to treat language impairments in acute stroke survivors as well. Moreover, CI therapy applied to aphasia has been used as a model to assess language network plasticity in response to treatment using functional imaging techniques. In the following article, we review the first 10 years of behavioral and functional brain imaging research on CI-based approaches for aphasia rehabilitation.

Recent Advances and Future Directions in Aphasia Therapy

This article reviews literature in aphasia rehabilitation in the English-speaking world. Although attempts have been made to incorporate literature from other continents, the major bias is toward North America. Four themes are emphasised. They are (1) advances in neuroscience that have already realised influences in language rehabilitation and some that have potential influence for the near future; (2) effects on language rehabilitation that have resulted from the worldwide acknowledgment and acceptance of the International Classification of Functioning, Disability, and Health (ICF); (3) the growing emergence of psychosocial concerns in the management of aphasia; and (4) present and future applications of technology to aphasia rehabilitation. For the sake of manageability, the review is largely limited to the rehabilitation literature of the decade from 1998, and to published or in-press work that is programmatic in the sense that it represents more than a single publication.