Therapy-Induced Neuroplasticity in Chronic Aphasia After Phonological Component Analysis: A Matter of Intensity

A Speech Neuroprosthesis in the Frontal Lobe and Hippocampus: Decoding High-Frequency Activity into Phonemes

BACKGROUND AND OBJECTIVES

Loss of speech due to injury or disease is devastating. Here, we report a novel speech neuroprosthesis that artificially articulates building blocks of speech based on high-frequency activity in brain areas never harnessed for a neuroprosthesis before: anterior cingulate and orbitofrontal cortices, and hippocampus.

METHODS

A 37-year-old male neurosurgical epilepsy patient with intact speech, implanted with depth electrodes for clinical reasons only, silently controlled the neuroprosthesis almost immediately and in a natural way to voluntarily produce 2 vowel sounds.

RESULTS

During the first set of trials, the participant made the neuroprosthesis produce the different vowel sounds artificially with 85% accuracy. In the following trials, performance improved consistently, which may be attributed to neuroplasticity. We show that a neuroprosthesis trained on overt speech data may be controlled silently.

CONCLUSION

This may open the way for a novel strategy of neuroprosthesis implantation at earlier disease stages (eg, amyotrophic lateral sclerosis), while speech is intact, for improved training that still allows silent control at later stages. The results demonstrate clinical feasibility of direct decoding of high-frequency activity that includes spiking activity in the aforementioned areas for silent production of phonemes that may serve as a part of a neuroprosthesis for replacing lost speech control pathways.

Focusing on the locus of the breakdown for treatment of anomia: a pilot study

The primary goal of this study was to evaluate the treatment effects of semantic feature analysis (SFA) and phonological components analysis (PCA) on word retrieval processing in persons with aphasia (PWAs). After identifying the locus of the breakdown in lexical retrieval processing, 15 monolingual native Persian speakers with aphasia were divided into two groups. After three naming trials, participants with dominant semantic deficits received SFA, and participants with primary phonological deficits were provided with PCA three times a week for eight weeks. Both approaches improved participants' naming and performance on language tests, including spontaneous speech, repetition, comprehension, and semantic processing. However, the correct naming of treated and untreated items was higher in mild-to-moderate participants, with mostly circumlocution and semantic paraphasias in the SFA group. The same holds for mild-to-moderate participants with mostly phonemic paraphasia who received PCA therapy. Moreover, the results showed that participants' baseline naming performance and semantic abilities could be associated with the treatment outcomes. Although limited by a lack of a control group, this study provided evidence supporting the possible benefits of focusing on the locus of the breakdown for treating anomia through SFA and PCA approaches, specifically in participants with mild to moderate aphasia. However, for those with severe aphasia, the treatment choice may not be as straightforward because several variables are likely to contribute to this population's word-finding difficulties. Replication with larger, well-stratified samples, use of a within-subjects alternating treatment design and consideration of treatments' long-term effects are required to better ascertain the effects of focusing on the locus of breakdown for treatment of anomia.

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.

Mechanisms of brain activation following naming therapy in aphasia: A systematic review on task-based fMRI studies

The pattern of brain neuroplasticity after naming therapies in patients with aphasia can be evaluated using task-based fMRI. This article aims to review studies investigating brain reorganization after semantic and phonological-based anomia therapy that used picture-naming fMRI tasks. We searched for those articles that compared the activation of brain areas before and after aphasia therapies in the PubMed and the EMBASE databases from 1993 up to April 2020. All studies (single-cases or group designs) on anomia treatment in individuals with acquired aphasia were reviewed. Data were synthesized descriptively through tables to allow the facilitated comparison of the studies. A total of 14 studies were selected and reviewed. The results of the reviewed studies demonstrated that the naming improvement is associated with changes in the activation of cortical and subcortical brain areas. This review highlights the need for a more systematic investigation of the association between decreased and increased activation of brain areas related to anomia therapy. Also, more detailed information about factors influencing brain reorganization is required to elucidate the neural mechanisms of anomia therapy. Overall, regarding the theoretical and clinical aspects, the number of studies that used intensive protocol is growing, and based on the positive potential of these treatments, they could be suitable for the rehabilitation of people with aphasia.

Treatment-induced neuroplasticity after anomia therapy in post-stroke aphasia: A systematic review of neuroimaging studies

We systematically reviewed the literature on neural changes following anomia treatment post-stroke. We conducted electronic searches of CINAHL, Cochrane Trials, Embase, Ovid MEDLINE, MEDLINE-in-Process and PsycINFO databases; two independent raters assessed all abstracts and full texts. Accepted studies reported original data on adults with post-stroke aphasia, who received behavioural treatment for anomia, and magnetic resonance brain imaging (MRI) pre- and post-treatment. Search results yielded 2481 citations; 33 studies were accepted. Most studies employed functional MRI and the quality of reporting neuroimaging methodology was variable, particularly for pre-processing steps and statistical analyses. The most methodologically robust data were synthesized, focusing on pre- versus post-treatment contrasts. Studies more commonly reported increases (versus decreases) in activation following naming therapy, primarily in the left supramarginal gyrus, and left/bilateral precunei. Our findings highlight the methodological heterogeneity across MRI studies, and the paucity of robust evidence demonstrating direct links between brain and behaviour in anomia rehabilitation.

French Phonological Component Analysis and aphasia recovery: A bilingual perspective on behavioral and structural data

Studies show bilingualism entails an advantage in cognitive control tasks. There is evidence of a bilingual advantage in the context of aphasia, resulting in better cognitive outcomes and recovery in bilingual persons with aphasia compared to monolingual peers. This bilingual advantage also results in structural changes in the right hemisphere gray matter. Very few studies have examined the so-called bilingual advantage by reference to specific anomia therapy efficacy. This study aims to compare the effect of French-Phonological Component Analysis (Fr-PCA) in monolinguals and bilingual persons with aphasia, both at the linguistic and cognitive control level, and to examine the structural impact of left hemisphere lesion location and right hemisphere structural data. Eight participants with chronic aphasia received Fr-PCA for a total of 15 h over 5 weeks. The results showed improved accuracy for treated words and generalization to untreated items and discourse in both groups, and improved Flanker task performance for some participants. Bilingual participants improved more than monolinguals for picture-naming tasks and narrative discourse. Damage to the left postcentral gyrus and the middle frontal gyrus was associated with less therapy-induced improvement. Additionally, left hemisphere damage to the inferior parietal gyrus and postcentral gyrus was associated with reduced cognitive control pre-therapy. Undamaged right hemisphere cortical thicknesses were significantly different between groups; the inferior frontal gyrus and the middle frontal gyrus were greater for the bilingual participants and correlated with cognitive control skills. These results suggest a bilingual advantage in anomia recovery following Fr-PCA, potentially resulting from enhanced cognitive control abilities that could be supported by right hemisphere neural reserve.

Lesion location may attenuate response to strategy training in acute stroke

BACKGROUND

Strategy training, a rehabilitation intervention, reduces disability and improves functional skills associated with goal-directed behavior. Stroke lesions impacting selected ventromedial regions of interest associated with initiation of goal-directed behavior may attenuate intervention response. If so, strategy training may not be optimal for people with stroke lesions in these regions.

OBJECTIVE

To examine whether ventromedial regions of interest attenuate changes in disability status attributed to strategy training.

DESIGN

Secondary analysis of data from two randomized controlled clinical trials.

SETTING

Inpatient stroke rehabilitation.

PARTICIPANTS

People with acute stroke diagnosis and available diagnostic studies enrolled in inpatient rehabilitation randomized controlled studies between 2009 and 2017.

INTERVENTION

Participants were randomized to strategy training or a control condition in addition to the usual care during inpatient rehabilitation.

MAIN OUTCOME MEASURES

Diagnostic magnetic resonance imaging studies were retrieved from electronic medical records, and stroke lesion location was characterized by a neuroradiologist. Intervention response was defined by Functional Independence Measure change scores of 22 points or greater.

RESULTS

Only 186 of 275 participants had diagnostic studies available; 13 patients showed no apparent lesion on their diagnostic study. Among 173 cases, 156 had complete data at discharge (strategy training n = 71, control n = 85). Twenty-five cases had a lesion within a region of interest (strategy training n = 14, control n = 11). Intervention response was attenuated in the strategy training group for those with lesions in regions of interest [χ² (1, n = 71) = 4.60, P = .03], but not for those in the control group [Fisher exact test, n = 85, P = .19).

CONCLUSIONS

Lesions in the ventromedial regions of interest may attenuate response to strategy training.

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.

Behavioral interventions for poststroke aphasia

There is a long history of behavioral interventions for poststroke aphasia with hundreds of studies supporting the benefits of aphasia treatment. However, interventions for aphasia are complex with many interacting components, and no one treatment is appropriate for all persons with aphasia. We present a novel, simple framework for classifying aphasia interventions. The framework is incorporated within the overarching International Classification of Functioning, Disability, and Health (ICF) model and is consistent with the commonly-held definition that aphasia is a multimodality disorder that impairs, in varying degrees, the understanding and expression of both oral and written language modalities. Furthermore, within the language impairment level, it distinguishes between the linguistic areas of phonology, semantics, and syntax that may be impaired individually or in combination. We define the terminology of the proposed framework and then categorize some common examples of behavioral interventions for post-stroke aphasia. We describe some of these interventions in greater detail to illustrate the extensive toolbox of evidence-based treatments for aphasia. We address some key issues that clinicians, usually speech-language pathologists, consider when selecting interventions for their specific patients with aphasia, including dose. Finally, we address various models of service delivery for persons with aphasia such as Intensive Comprehensive Aphasia Programs (ICAPs) and Aphasia Centers.

Repetition Priming in Treatment of Anomia

PURPOSE

Repetition priming has been suggested as a method for targeting implicit processes in anomia treatment. Prior studies have used masked priming for this purpose. This study extends that work with visible primes, a more clinically feasible approach.

METHOD

This study used a single-subject design across three participants with aphasia. Treatment involved repeated exposure to identity primes (trained condition) or sham primes (untrained condition) paired with pictures. Analyses assessed acquisition effects for trained items and untrained items that were seen during the training period, generalization to untrained items that had not been seen, and generalization to broader language skills, immediately and 3 months post-treatment.

RESULTS

All participants improved in naming trained items immediately after treatment, with greater improvements for trained than for untrained items. All participants maintained some degree of improvement on trained items 3 months post-treatment, although the degree differed across participants. Inconsistent generalization occurred to unexposed items. Improvements were noted in some areas of broader language ability, although these varied.

CONCLUSIONS

These data suggest a repetition priming treatment paradigm may increase naming accuracy for individuals with anomia and may benefit other aspects of language. Participant factors may have influenced response to treatment. Directions for future investigation are discussed.

Resting-State Functional Connectivity following Phonological Component Analysis: The Combined Action of Phonology and Visual Orthographic Cues

Anomia is the most frequent and pervasive symptom for people with aphasia (PWA). Phonological component analysis (PCA) is a therapy incorporating phonological cues to treat anomia. Investigations of neural correlates supporting improvements following PCA remain scarce. Resting-state functional connectivity (rsFC) as a marker of therapy-induced neuroplasticity has been reported by our team. The present study explores the efficacy of PCA in French and associated therapy-induced neuroplasticity using whole-brain rsFC analysis. Ten PWA participated in a pre-/post-PCA fMRI study with cognitive linguistic assessments. PCA was delivered in French following the standard procedure. PCA led to significant improvement with trained and untrained items. PCA also led to changes in rsFC between distributed ROIs in the semantic network, visual network, and sub-cortical areas. Changes in rsFC can be interpreted within the frame of the visual and phonological nature of PCA. Behavioral and rsFC data changes associated with PCA in French highlight its efficacy and point to the importance of phonological and orthographic cues to consolidate the word-retrieval strategy, contributing to generalization to untrained words.

The effects of intensity on a phonological treatment for anomia in post-stroke aphasia

INTRODUCTION

The evidence regarding optimal treatment intensity is mixed, and differing definitions have further confounded existing findings. The primary objective of this study was to compare the efficacy of Phonological Components Analysis (PCA) treatment for anomia delivered at intense and non-intense schedules, using a well-controlled design. The number of teaching episodes and active ingredients of therapy are important considerations when defining intensity. We hypothesized that an active ingredient of PCA is the self-generation of phonological components during therapy sessions. Our secondary aim was to examine whether component generation predicted treatment outcome.

METHODS

Sixteen adults (M = 52.63 years old, SD = 11.40) with chronic post-stroke aphasia (M = 4.52 years post-onset, SD = 5.55) were randomly assigned to intensive (IT) or standard (ST) PCA treatment conditions. Cumulative treatment intensity in both conditions was equivalent: ST participants received PCA 1 hour/day, 3 days/week for 10 weeks, whereas IT participants received PCA 3 hours/day, 4 days/week for 2.5 weeks. The primary outcome was naming accuracy on a set of treated and (matched) untreated words, measured pre- and post-treatment, and at four- and eight-week follow-ups.

RESULTS

IT and ST conditions were similarly efficacious. However, secondary analyses suggest an advantage for the IT condition in naming of the treated words immediately post-treatment, but not at follow-ups. The self-generation of phonological components emerged as a significant positive predictor of naming accuracy for both the treated and untreated words. However, this relationship did not reach significance once baseline anomia severity was accounted for.

CONCLUSIONS

Although replication in a larger sample is warranted, results suggest that PCA treatment is similarly efficacious when delivered at different intensities. Other factors related to the quality of treatment (i.e., active ingredients such as cue-generation) may play an important role in determining treatment efficacy and must also be considered when comparing treatment intensities.

A systematic review of maintenance following intensive therapy programs in chronic post-stroke aphasia: importance of individual response analysis

PURPOSE

Recent evidence supports the benefit of intensive aphasia intervention programs for people with chronic aphasia, yet it is unclear if all participants can expect positive outcomes and for how long therapeutic gains last.

METHODS

We systematically searched for studies investigating intensive interventions in chronic aphasia. To explore individual response rates and maintenance of therapeutic gains we carried out meta-synthesis by calculating and analysing the Standard Error of Measurement and Minimal Detectable Change metrics of six common outcome measures.

RESULTS

Forty-four studies comprising 24 experimental (13 group, 11 single-subject) and 20 non-experimental studies met our inclusion criteria (n = 670). Whereas most group studies reported statistically significant post-therapy improvement and maintenance, analysis of individual participant data (IPD, n = 393) from these studies revealed that only about a third of participants were classified as "immediate responders," of which more than a third had lost their initial immediate gains at follow-up. This pattern did not change when IPD from single-subject studies (n = 49) was added to the analysis. Thus, only 22% of all IPD receiving an intensive intervention improved significantly and maintained their therapy gains.

CONCLUSIONS

Intensive aphasia therapy is effective when measured at the group-level, but many individuals do not respond significantly to the intervention, and even fewer individuals preserve their initial gains. Group study results do not allow prediction of an individual's response to the intervention. Future research should elucidate which factors mediate positive treatment response and maintenance for an individual.Implications for rehabilitationOnly a small proportion (about one fifth in this review) of intensive aphasia treatment program participants respond and maintain their therapy gains, a fact that is obscured by traditional p-value group analysis.A simple clinical decision-making method is presented for evaluating individual therapy gains and their maintenance.For some immediate treatment responders (about one third in this review), gains from intensive therapy programs are unlikely to be maintained in the long-term without additional, ongoing practice.Clinicians should consider the possibility of individual clients losing some of their therapy gains and take proactive steps to support long-term maintenance.

Mechanisms underlying anomia treatment outcomes

Treatments for anomia have demonstrated short- and long-term efficacy. However, individual outcomes can be variable, and evidence for treatment generalization is limited. We investigated whether treatment-related measures of access to- and learning of language, namely, a) responsiveness to cues, and b) during-treatment improvements in naming, are good predictors of treatment outcomes. In addition, we investigated mechanisms underlying treatment generalization. Ten adults with chronic, post-stroke aphasia received a phonological treatment for anomia three times a week for five weeks. Naming accuracy of treated and untreated words was assessed pre- and post-treatment and at four- and eight-week follow-ups. Generalization to an untrained naming task, which involved analyses of naming accuracy and speech errors, was also assessed; speech errors were analyzed according to the Interactive Activation (IA) model of word retrieval. Group analyses indicate significant improvements in naming treated compared to untreated words, at all timepoints after therapy. Additional analyses showed significant long-term improvements in naming untreated words. Initial responsiveness to cueing and early improvement emerged as significant predictors of overall pre- to post-treatment improvements in naming treated words; naming improvements made early-on in treatment were also predictive of improvements in naming of the untreated words at follow-up. Furthermore, our study is the first to demonstrate that generalization after a phonological treatment for anomia may be driven by a strengthening of lexical-phonological connections. This study provides novel insights regarding mechanisms driving anomia treatment outcomes. Understanding such mechanisms is critical to improving existing assessment practices, optimizing treatment selection and building treatment protocols that are more likely to generalize.

A Review on Treatment-Related Brain Changes in Aphasia

Numerous studies have investigated brain changes associated with interventions targeting a range of language problems in patients with aphasia. We strive to integrate the results of these studies to examine (1) whether the focus of the intervention (i.e., phonology, semantics, orthography, syntax, or rhythmic-melodic) determines in which brain regions changes occur; and (2a) whether the most consistent changes occur within the language network or outside, and (2b) whether these are related to individual differences in language outcomes. The results of 32 studies with 204 unique patients were considered. Concerning (1), the location of treatment-related changes does not clearly depend on the type of language processing targeted. However, there is some support that rhythmic-melodic training has more impact on the right hemisphere than linguistic training. Concerning (2), we observed that language recovery is not only associated with changes in traditional language-related structures in the left hemisphere and homolog regions in the right hemisphere, but also with more medial and subcortical changes (e.g., precuneus and basal ganglia). Although it is difficult to draw strong conclusions, because there is a lack of systematic large-scale studies on this topic, this review highlights the need for an integrated approach to investigate how language interventions impact on the brain. Future studies need to focus on larger samples preserving subject-specific information (e.g., lesion effects) to cope with the inherent heterogeneity of stroke-induced aphasia. In addition, recovery-related changes in whole-brain connectivity patterns need more investigation to provide a comprehensive neural account of treatment-related brain plasticity and language recovery.

Treatment dose in post-stroke aphasia: A systematic scoping review

Little is known about how the amount of treatment a person with aphasia receives impacts aphasia recovery following stroke, yet this information is vital to ensure effective treatments are delivered efficiently. Furthermore, there is no standard dose terminology in the stroke rehabilitation or aphasia literature. This scoping review aims to systematically map the evidence regarding dose in treatments for post-stroke aphasia and to explore how treatment dose is conceptualized, measured and reported in the literature. A comprehensive search was undertaken in June 2019. One hundred and twelve intervention studies were reviewed. Treatment dose (amount of treatment) has been conceptualized as both a measure of time and a count of discrete therapeutic elements. Doses ranged from one to 100 hours, while some studies reported session doses of up to 420 therapeutic inputs per session. Studies employ a wide variety of treatment schedules (i.e., session dose, session frequency, and intervention duration) and the interaction of dose parameters may impact the dose-response relationship. High dose interventions delivered over short periods may improve treatment efficiency while maintaining efficacy. Person- and treatment-level factors that mediate tolerance of high dose interventions require further investigation. Systematic exploration of dose-response relationships in post-stroke aphasia treatment is required.

Comparing higher and lower weekly treatment intensity for chronic aphasia: A systematic review and meta-analysis

Optimizing intensity for aphasia treatment is a high priority research issue for people with aphasia, their families and clinicians, and could result in healthcare cost savings. An important aspect of intensity is the frequency of intervention, or how regularly treatment should be provided each week. While principles of neuroplasticity endorse massed practice, cognitive psychology has established superiority of distributed practice within normal learning. Neither concept has been conclusively tested in aphasia. There have been many literature reviews of intensity in aphasia intervention, but most have not investigated treatment intensity whilst also ensuring that therapy dose and treatment type are identical between study groups. Some have also combined studies across acute, subacute and chronic aphasia. We searched systematically for studies directly comparing higher and lower weekly treatment frequency in chronic aphasia. Eight studies were retrieved and rated for methodological quality. Meta-analysis was completed for group and single case experimental designs. Results showed that there are few studies investigating treatment frequency in chronic aphasia and their quality is low-moderate. Meta-analyses were inconclusive due to limited data, but there was no indication of either schedule being superior. Further research directly comparing treatment schedules is needed.

The role of executive control in post-stroke aphasia treatment

Executive control (EC) ability is increasingly emerging as an important predictor of post-stroke aphasia recovery. This study examined whether EC predicted immediate treatment gains, treatment maintenance and generalization after naming therapy in ten adults with mild to severe chronic post-stroke aphasia. Performance on multiple EC tasks allowed for the creation of composite scores for common EC, and the EC processes of shifting, inhibition and working memory (WM) updating. Participants were treated three times a week for five weeks with a phonological naming therapy; difference scores in naming accuracy of treated and untreated words (assessed pre, post, four- and eight-weeks after therapy) served as the primary outcome measures. Results from simple and multiple linear regressions indicate that individuals with better shifting and WM updating abilities demonstrated better maintenance of treated words at four-week follow-up, and those with better common EC demonstrated better maintenance of treated words at both four- and eight-week follow-ups. Better shifting ability also predicted better generalization to untreated words post-therapy. Measures of EC were not indicative of improvements on treated words immediately post-treatment, nor of generalization to untreated words at follow-up. Findings suggest that immediate treatment gains, maintenance and generalization may be supported by different underlying mechanisms.

Efficacy of a self-administered treatment using a smart tablet to improve functional vocabulary in post-stroke aphasia: a case-series study

BACKGROUND

Aphasia is an acquired language disorder that occurs secondary to brain injury, such as stroke. It causes communication difficulties that have a significant impact on quality of life and social relationships. Although the efficacy of speech-language therapy has been clearly demonstrated in this population, long-term services are currently limited due to logistical and financial constraints. In this context, the potential contribution of technology, such as smart tablets, is worth exploring, especially to improve vocabulary that is relevant in daily life.

AIMS

The main aim was to investigate the efficacy of a self-administered treatment using a smart tablet to improve naming of functional words in post-stroke anomia.

METHODS & PROCEDURES

Four adults with post-stroke aphasia took part in the study. An ABA design with multiple baselines was used to compare naming performances for four equivalent lists: (1) trained with functional words chosen with the participant; (2) trained with words randomly chosen from a picture database; (3) exposed but not trained; and (4) not exposed (control).

OUTCOMES & RESULTS

For all participants, the treatment self-administered at home (four times/week for 4 weeks) resulted in a significant improvement for both sets of trained words that was maintained 2 months after the end of treatment. Moreover, in two participants, evidence of generalization to conversation was found.

CONCLUSIONS & IMPLICATIONS

This study confirms the efficacy of using smart tablets to improve naming in post-stroke aphasia. Although more studies are needed, the use of new technologies is unquestionably a promising approach to improve communication skills in people with aphasia, especially by targeting vocabulary that is relevant to them in their daily lives.