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

Thinking About Better Speech: Mental Practice for Stroke-Induced Motor Speech Impairments

BACKGROUND: Mental practice (MP) is a mind-body technique in which physical movements are cognitively rehearsed. It has shown efficacy in reducing the severity of a number of neurological impairments. AIMS: In the present review, we highlight recent developments in MP research, and the basis for MP use after stroke-induced motor speech disorders. MAIN CONTRIBUTION: In this review, we: (a) propose a novel conceptual model regarding the development of learned nonuse in people with motor speech impairments; (b) review the rationale and efficacy of MP for reducing the severity of stroke-induced impairments; (c) review evidence demonstrating muscular and neural activations during and following MP use; (d) review evidence showing that MP increases skill acquisition, use, and function in stroke; (e) review literature regarding neuroplasticity after stroke, including MP-induced neuroplasticity and the neural substrates underlying motor and language reacquisition; and (f) based on the above, review the rationale and clinical application of MP for stroke-induced motor speech impairments. CONCLUSIONS: Support for MP use includes decades of MP neurobiological and behavioral efficacy data in a number of populations. Most recently, these data have expanded to the application of MP in neurological populations. Given increasingly demanding managed care environments, efficacious strategies that can be easily administered are needed. We also encounter clinicians who aspire to use MP, but their protocols do not contain several of the elements shown to be fundamental to effective MP implementation. Given shortfalls of some conventional aphasia and motor speech rehabilitative techniques, and uncertainty regarding optimal MP implementation, this paper introduces the neurophysiologic bases for MP, the evidence for MP use in stroke rehabilitation, and discusses its applications and considerations in patients with stroke-induced motor speech impairments.

Changes in maps of language function and the integrity of the arcuate fasciculus after therapy for chronic aphasia

A patient with chronic aphasia secondary to unilateral stroke in the left hemisphere underwent language testing, diffusion tensor imaging (DTI), and functional imaging using magnetoencephalography (MEG) at four time points: 3 weeks prior to, immediately prior to, immediately after, and 3 months after Constraint Induced Language Therapy (CILT). Performance on language tests involving visual naming and repetition of spoken sentences improved between the immediately prior to and immediately after CILT testing sessions, but not between the pre-CILT sessions. MEG activation in putative pre-morbid language areas of the left hemisphere and homotopic areas of the right hemisphere increased immediately after therapy, as did integrity within the arcuate fasciculus bilaterally. These changes were not evident between the two pre-CILT sessions. While some of these functional, neurophysiological and structural changes had regressed 3 months after therapy, all remained at or above baseline levels. Results provide evidence for an association between improvement in functional status and the increased integrity within a white matter tract known to be involved in language function and its contralateral homologue, as well as increased neurophysiological activity in areas that have the potential to subserve language function bilaterally.

Cerebral language reorganization in the chronic stage of recovery: a longitudinal fMRI study

The goal of the present study was to investigate whether spontaneous functional recovery following insult to the language-dominant hemisphere continues in the so-called "chronic stage," and if so, to examine its neuro-functional correlates. We used a longitudinal functional magnetic resonance imaging (fMRI) block design, where each young patient served as his/her own control. Specifically, we examined whether language functions differed significantly in two monitoring sessions conducted years apart, both in the chronic stage, where almost no functional changes are expected. We focused on a unique cohort of young brain damaged patients with aphasiogenic lesions occurring after normal language acquisition, in order to maximize the potential of plasticity for language reorganization following brain damage. The most striking finding was that the linguistic recovery of our patients was significant not just relative to their linguistic scores on initial testing (T1), but also in absolute terms, relative to the respective age-matched normal population. Such improvement, therefore, cannot be simply attributed to the natural process of development. Overall, we found that right hemisphere (RH) activation was associated with better recovery in the chronic stage. Our longitudinal findings may challenge the view of recovery as ending within the first year following onset, suggesting that the RH may provide the substrate for ongoing plasticity in the damaged brain.

Behavioral and neurophysiologic response to therapy for chronic aphasia

Breier JI, Juranek J, Maher LM, Schmadeke S, Men D, Papanicolaou AC. Behavioral and neurophysiologic response to therapy for chronic aphasia.

OBJECTIVE

To characterize the relationship between neurophysiologic changes in the brain and behavioral response to constraint-induced language therapy (CILT) by using magnetoencephalography (MEG).

DESIGN

Case series.

SETTING

Medical school.

PARTICIPANTS

Patients (N=23) with chronic aphasia after first-time unilateral stroke in the left hemisphere.

INTERVENTIONS

Constraint-induced language therapy administered for 3 hours 4 times per week for 3 weeks. Language testing and functional imaging during a language comprehension task using MEG before, immediately after, and 3 months after CILT with a subgroup of patients undergoing additional MEG scanning and language testing 3 weeks before CILT.

MAIN OUTCOME MEASURES

The percent of correct information units and the number of late dipoles normalized to total activation.

RESULTS

Three patterns of behavioral and neurophysiologic response to CILT were identified. Patients with significant improvement in language immediately after CILT who lost these gains at follow-up had greater right hemisphere activation than other patients at all MEG scanning sessions. Patients with significant improvement in language immediately after CILT who maintained these gains at follow-up exhibited an increase in left temporal activation after CILT, whereas patients who did not exhibit significant improvement in language after CILT exhibited comparably greater activation in left parietal areas.

CONCLUSIONS

Results suggest that although the right hemisphere may support recovery of language function in response to therapy, this recovery may not be stable, and some participation of perilesional areas of the left hemisphere may be necessary for a stable behavioral response.

A review of Constraint-Induced Therapy applied to aphasia rehabilitation in stroke patients

Constraint-induced aphasia therapy (CIAT) is an intensive therapy model based on the forced use of verbal oral language as the sole channel of communication, while any alternative communication mode such as writing, gesturing or pointing are prevented.

Objectives

This critical review involved the analysis of studies examining CIAT applied to stroke patients.

Methods and Results

Using keywords, the Medline database was searched for relevant studies published between 2001 and 2008 (Medline 2001-2008). The critical evaluation of the articles was based on the classifications described by the ASNS (Cicerone adaptation). Two studies were categorized as level Ia, two as level II and one study as level IV.

Conclusions

These recommendations should be interpreted with caution, given the small number of studies involved, but serve as a guideline for future studies in aphasia therapy.

Semantic Event-Related Potential Components Reflect Severity of Comprehension Deficits in Aphasia

Background and objectives. Several cognitive event-related potential (ERP) components such as mismatch negativity, P300, N400, and the late positive component (LPC) have been studied in aphasia. The aim of this study was to determine whether a modified semantic incongruity paradigm can serve as a more graded differentiation of ERP changes in patients with mild versus severe comprehension deficits. Methods. A total of 20 aphasic patients with minor and severe comprehension deficits and 20 young and elder healthy controls were examined while reading 4-word sentences ending in a semantically congruent or noncongruent word. Results. In contrast to young controls and to patients with mild comprehension deficits, aphasic patients with severe comprehension deficits exhibit an early positivity in the time window from 200 to 400 milliseconds and no N400 after the presentation of nonrecurrent semantically incongruent words. Patients with mild comprehension deficits were found to have an N400 with prolonged latency in comparison with the controls. An age effect in the control groups was detected as well. Discussion. Semantic access and integration are performed differently in aphasic subjects with severe comprehension deficits. These differences in lexical—semantic processing must be taken into account in rehabilitation approaches that aim to improve comprehension deficits. Moreover, the findings may contribute to the design of therapy studies by employing a physiological measure that can discriminate among patients at baseline and at the end of an intervention.

Memantine and constraint-induced aphasia therapy in chronic poststroke aphasia

OBJECTIVE

We conducted a randomized, double-blind, placebo-controlled, parallel-group study of both memantine and constraint-induced aphasia therapy (CIAT) on chronic poststroke aphasia followed by an open-label extension phase.

METHODS

Patients were randomized to memantine (20 mg/day) or placebo alone during 16 weeks, followed by combined drug treatment with CIAT (weeks 16-18), drug treatment alone (weeks 18-20), and washout (weeks 20-24), and finally, an open-label extension phase of memantine (weeks 24-48). After baseline evaluations, clinical assessments were done at two end points (weeks 16 and 18), and at weeks 20, 24, and 48. Outcome measures were changes in the Western Aphasia Battery-Aphasia Quotient and the Communicative Activity Log.

RESULTS

Twenty-eight patients were included, and 27 completed both treatment phases. The memantine group showed significantly better improvement on Western Aphasia Battery-Aphasia Quotient compared with the placebo group while the drug was taken (week 16, p = 0.002; week 18, p = 0.0001; week 20, p = 0.005) and at the washout assessment (p = 0.041). A significant increase in Communicative Activity Log was found in favor of memantine-CIAT relative to placebo-CIAT (week 18, p = 0.040). CIAT treatment led to significant improvement in both groups (p = 0.001), which was even greater under additional memantine treatment (p = 0.038). Beneficial effects of memantine were maintained in the long-term follow-up evaluation, and patients who switched to memantine from placebo experienced a benefit (p = 0.02).

INTERPRETATION

Both memantine and CIAT alone improved aphasia severity, but best outcomes were achieved combining memantine with CIAT. Beneficial effects of memantine and CIAT persisted on long-term follow-up.

Evidence-based systematic review: effects of intensity of treatment and constraint-induced language therapy for individuals with stroke-induced aphasia

PURPOSE

This systematic review summarizes evidence for intensity of treatment and constraint-induced language therapy (CILT) on measures of language impairment and communication activity/participation in individuals with stroke-induced aphasia.

METHOD

A systematic search of the aphasia literature using 15 electronic databases (e.g., PubMed, CINAHL) identified 10 studies meeting inclusion/exclusion criteria. A review panel evaluated studies for methodological quality. Studies were characterized by research stage (i.e., discovery, efficacy, effectiveness, cost-benefit/public policy research), and effect sizes (ESs) were calculated wherever possible.

RESULTS

In chronic aphasia, studies provided modest evidence for more intensive treatment and the positive effects of CILT. In acute aphasia, 1 study evaluated high-intensity treatment positively; no studies examined CILT. Four studies reported discovery research, with quality scores ranging from 3 to 6 of 8 possible markers. Five treatment efficacy studies had quality scores ranging from 5 to 7 of 9 possible markers. One study of treatment effectiveness received a score of 4 of 8 possible markers.

CONCLUSION

Although modest evidence exists for more intensive treatment and CILT for individuals with stroke-induced aphasia, the results of this review should be considered preliminary and, when making treatment decisions, should be used in conjunction with clinical expertise and the client's individual values.

Neural Mechanisms Underlying Learning following Semantic Mediation Treatment in a case of Phonologic Alexia

Patients with phonologic alexia can be trained to read semantically impoverished words (e.g., functors) by pairing them with phonologically-related semantically rich words (e.g, nouns). What mechanisms underlie success in this cognitive re-training approach? Does the mechanism change if the skill is "overlearned", i.e., practiced beyond criterion? We utilized fMRI pre- and post-treatment, and after overlearning, to assess treatment-related functional reorganization in a patient with phonologic alexia, two years post left temporoparietal stroke. Pre-treatment, there were no statistically significant differences in activation profiles across the sets of words. Post-treatment, accuracy on the two trained sets improved. Compared with untrained words, reading trained words recruited larger and more significant clusters of activation in the right hemisphere, including right inferior frontal and inferior parietal cortex. Post-overlearning, with near normal performance on overlearned words, predominant activation shifted to left hemisphere regions, including perilesional activation in superior parietal lobe, when reading overlearned vs. untrained words.

Aphasia therapy on a neuroscience basis

BACKGROUND: Brain research has documented that the cortical mechanisms for language and action are tightly interwoven and, concurrently, new approaches to language therapy in neurological patients are being developed that implement language training in the context of relevant linguistic and non-linguistic actions, therefore taking advantage of the mutual connections of language and action systems in the brain. A further well-known neuroscience principle is that learning at the neuronal level is driven by correlation; consequently, new approaches to language therapy emphasise massed practice in a short time, thus maximising therapy quantity and frequency and, therefore, correlation at the behavioural and neuronal levels. Learned non-use of unsuccessful actions plays a major role in the chronification of neurological deficits, and behavioural approaches to therapy have therefore employed shaping and other learning techniques to counteract such non-use. AIMS: Advances in theoretical and experimental neuroscience have important implications for clinical practice. We exemplify this in the domain of aphasia rehabilitation. MAIN CONTRIBUTION: Whereas classical wisdom had been that aphasia cannot be significantly improved at a chronic stage, we here review evidence that one type of intensive language-action therapy (ILAT)-constraint-induced aphasia therapy-led to significant improvement of language performance in patients with chronic aphasia. We discuss perspectives for further improving speech-language therapy, including drug treatment that may be particularly fruitful when applied in conjunction with behavioural treatment. In a final section we highlight intensive and rapid therapy studies in chronic aphasia as a unique tool for exploring the cortical reorganisation of language. CONCLUSIONS: We conclude that intensive language action therapy is an efficient tool for improving language functions even at chronic stages of aphasia. Therapy studies using this technique can open new perspectives for research into the plasticity of human language circuits.

Translational research in aphasia: from neuroscience to neurorehabilitation

PURPOSE

In this article, the authors encapsulate discussions of the Language Work Group that took place as part of the Workshop in Plasticity/NeuroRehabilitation Research at the University of Florida in April 2005.

METHOD

In this narrative review, they define neuroplasticity and review studies that demonstrate neural changes associated with aphasia recovery and treatment. The authors then summarize basic science evidence from animals, human cognition, and computational neuroscience that is relevant to aphasia treatment research. They then turn to the aphasia treatment literature in which evidence exists to support several of the neuroscience principles.

CONCLUSION

Despite the extant aphasia treatment literature, many questions remain regarding how neuroscience principles can be manipulated to maximize aphasia recovery and treatment. They propose a framework, incorporating some of these principles, that may serve as a potential roadmap for future investigations of aphasia treatment and recovery. In addition to translational investigations from basic to clinical science, the authors propose several areas in which translation can occur from clinical to basic science to contribute to the fundamental knowledge base of neurorehabilitation. This article is intended to reinvigorate interest in delineating the factors influencing successful recovery from aphasia through basic, translational, and clinical research.

Behavioral, Temporal, and Spatial Targets for Cellular Transplants as Adjuncts to Rehabilitation for Stroke

Stem cell and more differentiated neural cell transplantation strategies are an intriguing approach for neural repair to augment rehabilitation interventions after stroke. In the cortex, exogenous cells could create, augment, or extend in time endogenous peri-infarct and remote molecular signals, such as those for neurogenesis, cell differentiation, axonal and dendritic sprouting, network connectivity, and long-term potentiation, as well as deliver engineered genes and provide replacement cells in a network. If demyelinated axons exist in the periphery of an infarct, they could be targets for remyelination to reestablish conductivity. Much is unknown, however, about the mechanisms by which pluripotent embryonic and multipotent neural stem cells serve as agents of therapeutic plasticity. The robustness of their effects on neuromodulation, reorganization, regeneration, and behavioral recovery is a work in progress. Invasive interventions may have adverse effects not appreciated in preclinical testing. These should initially be offered only to patients with specific profound impairments after it is clinically certain that major disabilities will not improve. If a cellular strategy is very safe, it may be offered to subjects with moderate impairments when they are no longer likely to make further functional gains. Clinical trial designs are suggested that take into account the optimal timing after stroke and specific targets for cellular therapies to foster repair, remapping, and modulation of neural circuits. Cell-mediated rehabilitation would then use task-specific therapies in an optimal dose to maximize training-induced reorganization and learning and, most important, reduce unwanted disability.

Recovery from aphasia as a function of language therapy in an early bilingual patient demonstrated by fMRI

Knowledge about the recovery of language functions in bilingual aphasic patients who suffer from left-hemispheric stroke is scarce. Here, we present the case of an early bilingual patient (German/French) with chronic aphasia. Functional magnetic resonance imaging (fMRI) was used to investigate neural correlates of language performance during an overt picture naming task in German and French (a) 32 months after stroke to assess differential recovery of both languages as a function of the preceding language therapy that was provided exclusively in German and (b) after additional short-term intensive (German) language training. At the first investigation behavioral performance confirmed selective recovery of German naming ability which was associated with increased functional brain activation compared to the French naming condition. Changes in behavioral performance and brain activation pattern as disclosed by fMRI after an additional experimental treatment were confined to the trained (German) language and indicate bilateral neuroplastic reorganization. No generalization to the untrained (French) language was observed. The present case results demonstrate use and/or training-dependent differential recovery of expressive language functions and an enhanced pattern of brain activation as a function of the rehabilitation efforts that were focussed exclusively on the patient's German language abilities.

Effects of classical conditioning on identification and cortical processing of speech syllables

The present study was designed to examine effects of learned motivational significance on processing of speech syllables in adults using a classical conditioning paradigm. Aversive white noise (unconditioned stimulus) was paired with two exemplars of /ba/ (conditioned stimulus, CS+) occurring near the category boundary of a 10-item /ba/-da/ continuum. Two corresponding /da/ syllables served as the CS- and indicated absence of white noise. High-density electroencephalogram (EEG) was recorded while participants passively listened to the stimuli. Prior to the EEG session and after intermittent conditioning, participants were asked to identify the syllables in a categorical perception task. Analysis of time-locked electrocortical data revealed amplitude modulations of the N2 (248-312 ms) component as a function of acquired stimulus properties (CS+ versus CS-). Over right hemisphere regions, negativity was specifically enhanced for the CS+ during intermittent conditioning. During extinction, this conditioning effect was paralleled by findings in the time-frequency domain, showing greater oscillatory activity in the gamma-band (25-40 Hz) range, 80-120 ms following onset of the CS+ compared with CS-. A similar pattern emerged in a later time segment of 400-600 ms (30-45 Hz). Aversive conditioning was not reflected in superior categorical perception performance. Our data indicate that electrocortical correlates of speech syllable perception are susceptible to changes induced by contingencies. Physiological differences were not manifest in behavioral advantage for a specific stimulus, i.e., the CS+, however. We conclude that training speech categorization by merely enhancing motivational relevance is not effective for conveying behavioral improvement.

Mechanisms of recovery in stroke patients with hemiparesis or aphasia: new insights, old questions and the meaning of therapies

PURPOSE OF REVIEW

The mechanisms responsible for recovery after stroke in patients with hemiparesis or aphasia are under intense study, since knowledge of these mechanisms is a prerequisite for choosing which therapy a patient receives and when to apply it.

RECENT FINDINGS

Most of the recent insights are obtained with longitudinal studies using functional imaging and direct cortical stimulation during the process of recovery. They reveal that reorganization is a highly dynamic process, involving the establishment of new communications in the remaining system and showing similarities to learning processes in healthy individuals. Lesion localization is a major determinant for recovery and the pattern of reorganization. Neurobiological hypotheses lead to clinical studies, which in turn are now used to confirm or reject these hypotheses.

SUMMARY

Although our understanding of the mechanisms responsible for recovery is increasing, the application of this knowledge in daily praxis is still limited. A better understanding of the underlying mechanisms, however, can lead to appropriate therapies for individual patients.