Feasibility of Remotely Supervised Transcranial Direct Current Stimulation (RS-tDCS) for People with Stroke-Induced and Progressive Aphasia
Background: Remotely-supervised transcranial direct current stimulation (RS-tDCS) is a telerehabilitation protocol that provides access to tDCS treatment to participants with aphasia in their homes using real-time monitoring via videoconference and overcomes barriers associated with in-person tDCS treatment of neurological disease. Aims: Two feasibility studies for participants with aphasia are presented herein that investigate (1) RS-tDCS procedural implementation, acceptability, and demand, and (2) acceptability of ten repeated consecutive RS-tDCS sessions. Methods & Procedures: Thirteen participants with aphasia were enrolled in Study 1: (1) seven participants with stroke-induced latent aphasia, (2) four participants with stroke-induced clinically diagnosed aphasia, and (3) two participants with logopenic variant primary progressive aphasia (lvPPA). Four supervisors (1 certified speech-language pathologist [SLP], 3 graduate SLPs-in-training) were trained to supervise RS-tDCS and also provided survey responses. All participants participated in RS-tDCS training and a virtual simulation of home delivery. Two participants with stroke-induced aphasia (1 latent aphasia, 1 clinically diagnosed aphasia) were enrolled in 10 consecutive sessions of RS-tDCS alongside computerized treatment in their home for Study 2. Outcomes & Results: This work provides preliminary evidence for the feasibility of RS-tDCS for people with stable and progressive aphasia of varying severity and typology and includes both participant and clinician perspectives. Importantly, no major barriers to use of RS-tDCS were revealed for people with aphasia, though eHelpers were required for two participants. Conclusions: This work confirms that remotely supervised at-home tDCS studies can be used to enable much-needed efficacy trials, with sufficient sample size, power, and dosing considerations, that will determine the clinical efficacy of tDCS as a treatment adjuvant to aphasia treatment.
Response Time Inconsistencies in Object and Action Naming in Anomic Aphasia
Purpose/UNASSIGNED:The effect of repeated naming on both object and action picture naming in individuals with anomic aphasia is explored. We asked whether repeatedly naming the same items leads to improved accuracy and reduced response latency. Method/UNASSIGNED:Ten individuals with anomic aphasia and 6 healthy adults, 3 young and 3 old, named a set of 27 object pictures and a set of 27 action pictures presented 1 at a time on a computer screen. We examined accuracy and response times (RTs) across the 2 blocks of 10 repeated trials. Results/UNASSIGNED:Results demonstrated higher accuracy and faster RTs for object than for action naming for all participants, with lower accuracy rates and slower RTs for the people with aphasia (PWA) compared with the healthy individuals, and diverging patterns of change across trials. Unlike the healthy participants, whose RTs decreased across trials, PWA continued to demonstrate variability in response latencies across the trials. Conclusions/UNASSIGNED:Our preliminary results suggest that measuring RT may be useful in characterizing retrieval difficulty in anomic aphasia and that the retrieval processes in PWA, even in those who experience mild anomia, may be less efficient or different from those processes in neurologically healthy individuals.
Incomplete evidence that increasing current intensity of tDCS boosts outcomes
BACKGROUND:Transcranial direct current stimulation (tDCS) is investigated to modulate neuronal function by applying a fixed low-intensity direct current to scalp. OBJECTIVES/OBJECTIVE:We critically discuss evidence for a monotonic response in effect size with increasing current intensity, with a specific focus on a question if increasing applied current enhance the efficacy of tDCS. METHODS:We analyzed tDCS intensity does-response from different perspectives including biophysical modeling, animal modeling, human neurophysiology, neuroimaging and behavioral/clinical measures. Further, we discuss approaches to design dose-response trials. RESULTS:Physical models predict electric field in the brain increases with applied tDCS intensity. Data from animal studies are lacking since a range of relevant low-intensities is rarely tested. Results from imaging studies are ambiguous while human neurophysiology, including using transcranial magnetic stimulation (TMS) as a probe, suggests a complex state-dependent non-monotonic dose response. The diffusivity of brain current flow produced by conventional tDCS montages complicates this analysis, with relatively few studies on focal High Definition (HD)-tDCS. In behavioral and clinical trials, only a limited range of intensities (1-2â€¯mA), and typically just one intensity, are conventionally tested; moreover, outcomes are subject brain-state dependent. Measurements and models of current flow show that for the same applied current, substantial differences in brain current occur across individuals. Trials are thus subject to inter-individual differences that complicate consideration of population-level dose response. CONCLUSION/CONCLUSIONS:The presence or absence of simple dose response does not impact how efficacious a given tDCS dose is for a given indication. Understanding dose-response in human applications of tDCS is needed for protocol optimization including individualized dose to reduce outcome variability, which requires intelligent design of dose-response studies.
Combining tDCS and evidence-based behavioral treatment in aphasia: A case study [Meeting Abstract]
Despite the growing abundance of studies that combine transcranial direct current stimulation (tDCS) with behavioral treatments, we have much to learn about the neuroplastic effects of tDCS. We present a case with paradoxical findings that leaves room for interpretation and may suggest a delayed treatment effect. We investigated the effect of bihemispheric tDCS (35cm2 electrodes on F5(anode), F6(cathode)) on the language production of a 60-year-old female with nonfluent aphasia when paired with an evidence- based behavioral aphasia treatment . Each of the two treatment blocks (active and sham) included 10 one-hour sessions, separated by a 4 week wash-out period. Active (2mA) or sham stimulation was delivered during the first 20 minutes of each behavioral treatment session. Although a decline in sentence production was observed immediately following active tDCS, at the two-week follow-up point sentence production performance improved relative to baseline, an improvement that was maintained over 2 additional weeks. These results may reflect a cumulative effect of behavioral treatment or an improvement that emerged as a longterm effect of tDCS . We conclude that limiting post-intervention measurement to the immediate effect of tDCS may not be sufficient for observing tDCS-induced behavioral changes and that the after-effects may be delayed and/or cumulative
Use of tDCS in Aphasia Rehabilitation: A Systematic Review of the Behavioral Interventions Implemented With Noninvasive Brain Stimulation for Language Recovery
Purpose: The purpose of this article is to review the behavioral treatments used in aphasia rehabilitation research that have been combined with transcranial direct current stimulation (tDCS). Although tDCS in aphasia treatment has shown promise, the results have not been conclusive, and their interpretation is further compounded by the heterogeneity of study characteristics. Because implementing a behavioral task during brain stimulation has been shown to be pivotal to the adjuvant effects of tDCS, we analyze the behavioral treatments that have been paired with tDCS. Method: A computerized database search (PubMed) was completed to document and review aphasia treatment studies that combine behavioral treatment with noninvasive brain stimulation in the form of tDCS. Two authors reviewed each aphasia tDCS article published between 2008 and 2015 and evaluated (a) the behavioral interventions for aphasia that have been combined with tDCS, and (b) the methodological variables that may have influenced language outcomes in the tDCS aphasia literature. Conclusions: A review of the behavioral treatments implemented in tDCS aphasia rehabilitation studies highlights several methodological considerations for future investigations. Impairment-focused and pragmatic treatments have been implemented in tDCS aphasia research studies. No one behavioral approach stands out as the best treatment to combine with tDCS for the promotion of language recovery.
Use of Computational Modeling to Inform tDCS Electrode Montages for the Promotion of Language Recovery in Post-stroke Aphasia
BACKGROUND: Although pilot trials of transcranial direct current stimulation (tDCS) in aphasia are encouraging, protocol optimization is needed. Notably, it has not yet been clarified which of the varied electrode montages investigated is the most effective in enhancing language recovery. OBJECTIVE: To consider and contrast the predicted brain current flow patterns (electric field distribution) produced by varied 1x1 tDCS (1 anode, 1 cathode, 5 x 7 cm pad electrodes) montages used in aphasia clinical trials. METHODS: A finite element model of the head of a single left frontal stroke patient was developed in order to study the pattern of the cortical EF magnitude and inward/outward radial EF under five different electrode montages: Anodal-tDCS (A-tDCS) over the left Wernicke's area (Montage A) and over the left Broca's area (Montage B); Cathodal tDCS (C-tDCS) over the right homologue of Wernicke's area (Montage C), and of Broca's area (Montage D), where for all montages A-D the "return" electrode was placed over the supraorbital contralateral forehead; bilateral stimulation with A-tDCS over the left Broca's and CtDCS over the right Broca's homologue (Montage E). RESULTS: In all cases, the "return" electrode over the contralesional supraorbital forehead was not inert and influenced the current path through the entire brain. Montage B, although similar to montage D in focusing the current in the perilesional area, exerted the greatest effect over the left perilesional cortex, which was even stronger in montage E. CONCLUSIONS: The position and influence of both electrodes must be considered in the design and interpretation of tDCS clinical trials for aphasia.
Translational treatment of aphasia combining neuromodulation and behavioral intervention for lexical retrieval: implications from a single case study
BACKGROUND: Transcranial direct current stimulation (tDCS), a non-invasive method of brain stimulation, is an adjunctive research-therapy for aphasia. The concept supporting translational application of tDCS is that brain plasticity, facilitated by language intervention, can be enhanced by non-invasive brain stimulation. This study combined tDCS with an ecologically focused behavioral approach that involved training nouns and verbs in sentences. METHOD: PARTICIPANT: A 43-year-old, right-handed male with fluent-anomic aphasia who sustained a single-left-hemisphere-temporal-parietal stroke was recruited. TREATMENT: Instrumentation included the Soterix Medical 1 x 1 Device. Anodal tDCS was applied over Broca's area. Behavioral materials included: sentence production, naming in the sentence context, and implementation of a social-conversational-discourse treatment. DESIGN AND PROCEDURES: The independent variable of this crossover case-study was tDCS, and the dependent variables were language and quality-of-life measures. In each session the subject received language treatment with the first 20 minutes additionally including tDCS. RESULTS: Performance in naming nouns and verbs in single words and sentences were obtained. Verb production in the sentence context increased after active anodal tDCS and speech-language treatment. CONCLUSION: Aphasia treatment that involves naming in the sentence context in conjunction with translational application of tDCS may be a promising approach for language-recovery post stroke.
[New York, N.Y.] : Oxford University Press, 2015
Impairment and Functional Interventions for Aphasia: Having it All
Aphasia, a cognitive-linguistic disorder secondary to stroke, is a frequent and often chronic consequence of stroke with detrimental effects on autonomy and health-related quality of life. Treatment of aphasia can be approached in a number of ways. Impairment-based approaches that focus on training a specific linguistic form can be implemented. Additionally, functionally oriented intervention such as supported conversation and aphasia groups are also frequently utilized when providing a treatment program for an individual with aphasia. Creating a treatment approach that includes both impairment and functional methodologies and considers how these relate to the three domains proposed by the International Classification of Functioning Disability and Health (ICF)-body functions and structure, activity, and participation-can provide an individual with aphasia an optimal treatment program that is person-centered and multi-faceted.
Assessment of neglect dyslexia with functional reading materials
BACKGROUND: Spatial neglect is a neurocognitive disorder that affects perception, representation, and/or motor planning. Neglect dyslexia in spatial neglect after right hemisphere damage may co-occur with, or be dissociated from, other spatial neglect signs. Previous neglect dyslexia research focused on word-level stimuli and reading errors. Using single words for assessment may leave some people with neglect dyslexia undiagnosed, and assessment materials that are closer to texts read in real life may better capture neglect dyslexia. METHOD: The authors tested reading in 67 right hemisphere stroke survivors with 4 types of text materials: words, phrases, an article, and a menu. RESULTS: Accuracy on reading the menu and article texts was significantly poorer than reading the words and phrases. The hypothesis that assessment materials with ecological validity such as reading a menu and reading an article may be more challenging than reading single words and phrases was supported. CONCLUSION: Results suggest that neglect dyslexia assessment after stroke should include text materials comparable to those read in everyday life. Increasing the spatial extent of training materials in future research might also yield better functional generalization after right brain stroke.