Targeted transcranial electrotherapy for stroke rehabilitation-Exploratory trial on aphasia "TEASER"

There are over 1 million persons with chronic aphasia in the US, and at least 80,000 new cases of aphasia occur each year, usually following left-hemisphere stroke. Current behavioral treatments for aphasia are inadequate, and new treatments are needed to enhance recovery. The Targeted Transcranial Electrotherapy to Accelerate Stroke Rehabilitation (TEASER) trial aims to enhance the effects of current language treatments using a technique called High Definition – transcranial Direct Current Stimulation (HD-tDCS). HD-tDCS applies a very low level of electrical stimulation to the scalp through several small electrodes. This small amount of electrical current can enhance activity in specific parts of the brain. In TEASER, information from functional MRI scans is used to target the HD-tDCS treatment to unique areas of brain activity for each participant in the study. The hope is that this individualized treatment will give the maximum possible benefit for each person. TEASER is a collaboration between the CRL and investigators at the City College of New York (PI- Lucas Parra), University of North Carolina- Chapel Hill (PI- Adam Jacks), and Soterix Medical, Inc. (New York, NY).  Along with the clinical goals of developing a new HD-tDCS treatment for aphasia, TEASER aims to understand how training-related changes in neural networks occur and how they may be enhanced using brain stimulation.

Inner Speech

Approximately 1 million people in the US have chronic aphasia and word-finding difficulties, called anomia. People with aphasia sometimes voice their frustration by talking about their subjective, internal sense of word-finding, saying for example “I know it, but I can’t say it”. Sometimes, when they are unable to say a word correctly aloud, people with aphasia specifically report being able to say the word correctly in their heads. They say that a word “sounds right in my head” or “I can say it in my head”. Remarkably, although most people with aphasia say they experience this “successful inner speech,” no prior research has tested whether these reports accurately reflect the cognitive processes underlying word-finding, or whether they provide useful clinical information that might guide treatment.  This study uses detailed behavioral testing and MRIs in people with aphasia to determine what subjective reports about inner speech can tell us about word-finding and anomia. Our lab is studying this experience to learn more about the origin of word finding difficulty, aphasia and language in general.

Cerebellar tDCS

The cerebellum is classically thought to be involved only in coordination of movement, but evidence over the past few decades has demonstrated that parts of the cerebellum also contribute to language and cognitive processes, as well as learning. The Cerebellar Enhancement of Language Intervention in Aphasia, or "CELIA" project for short, aims to tests if enhancement of these cognitive areas of the cerebellum using tDCS can improve recovery from post-stroke aphasia. We will examine both behavioral and brain changes after treatment, and conduct other studies in adults without stroke to better understand the role of the cerebellum in language processing.

This research is being conducted in collaboration with Dr. Catherine Stoodley (American University), and is funded by NIH/NIDCD R21 DC014087 to Drs. Stoodley and Turkeltaub (MPI).

Historically, one of the most useful methods for understanding the brain basis of language has been to examine correlations between the brain structures damaged by a stroke and the corresponding behavioral effects of the stroke. Modern neuroimaging techniques allow for very detailed examination of these correspondences in large groups of stroke survivors.

We are using multivariate lesion-symptom mapping and analysis of diffusion tensor imaging data to examine how left hemisphere strokes impact language and cognitive processes. These methods allow for the identification of left hemisphere brain structures that are critical for language and cognition. In addition to gaining insight into the neuroanatomy of language, we are using these methods to predict aphasia severity after stroke.

Understanding the Neuroanatomy of Language through Lesion Analysis

RH Contributions to Aphasia Recovery

Language impairment, or aphasia, is a common problem after left hemisphere stroke, and causes significant long-term disability. Understanding the brain basis of recovery is critical to developing new treatments that can meaningfully improve the lives of people suffering from post-stroke aphasia. This study uses new neuroimaging techniques to examine how the gray matter structure and connections of the right hemisphere contribute to language in left hemisphere stroke survivors compared to people who have never had a stroke.

Speech is an essential component of human life, however the specific mechanisms governing speech perception remain poorly understood. One area of debate is the role of the motor system in speech perception. A number of studies have demonstrated that motor areas primarily devoted to speech production are also active during speech perception, especially when the speech signal is noisy. The neurobiological dual stream model, as well as several other conceptual models, posit that motor speech regions transmit “efference copies” of articulatory motor plans to temporal speech perception regions, and that these motor plans help decode noisy or ambiguous auditory speech input. While evidence supports some level of motor system involvement in speech perception, there is considerable disagreement in the field regarding the degree of motor influence on speech perception and the task contexts in which it occurs. Understanding the mechanisms of speech perception in a more ecologically valid manner than prior studies (i.e. using real words) is a crucial step in furthering our knowledge of language processing in the healthy brain and in developing treatments for individuals with speech perception deficits. Using a novel behavioral task, electroencephalography (EEG) and combined transcranial magnetic stimulation (TMS) and EEG, this project is investigating the role of the motor system in speech perception while addressing several critical gaps in the literature.  

Neural Mechanisms of Speech Perception

Previous Projects

One third of stroke victims suffer an impairment of language ability, called aphasia. In most cases, recovery from aphasia is incomplete, resulting in substantial long-term disability. Approximately 1 million Americans have chronic aphasia, but there are no effective medical treatments to improve recovery. After a stroke causing aphasia, brain networks for language reorganize over time. This dynamic process involves compensatory recruitment of brain tissue in the left hemisphere and recruitment of symmetric right hemisphere areas that may not be optimally suited to support recovery. Thus, one potential avenue for intervention might be to externally enhance left hemisphere activity, while inhibiting the right using transcranial direct current stimulation (tDCS), a new technique that can modulate brain activity non-invasively to potentially improve stroke recovery. To test this hypothesis, we are conducting a randomized double-blind clinical trial of tDCS for people with post-stroke aphasia.

This research is supported by the Doris Duke Charitable Foundation (Grant 2012062) and the National Center for Advancing Translational Sciences via the Georgetown Howard Universities Center for Clinical and Translational Science (KL2TR000102).

Can Enhancing Left Lateralization using tDCS improve recovery from post-stroke aphasia?

The brain combines visual and auditory information to better understand spoken language. We are testing which parts of the brain are important for this multi-sensory integration, how integration is impacted by brain injury, and how it relates to clinical comprehension deficits. This research is supported by an Achievement Rewards for College scientists Metropolitan Washington Chapter Foundation Scholar Award to Laura C. Erickson, the Doris Duke Charitable Foundation (2012062) to Peter E. Turkeltaub, the Vernon Family Fund to Peter E. Turkeltaub, the NIH (KL2TR000102 to Peter E. Turkeltaub, and the NSF PIRE Grant (OISE - 0730255) to Joseph P. Rouschecker.

Audiovisual Integration in Speech Perception

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