Effects of Transcranial Direct Current Stimulation (tDCS) on Language

This study will investigate the effects of mild electrical stimulation in conjunction with speech therapy for people with post-stroke aphasia to enhance language recovery.

Aphasia is a disturbance of language, primarily caused by brain injury to the left cerebral hemisphere. Aphasia treatments include speech and language therapy and pharmacologic therapy, but several studies have found that these treatments are not completely effective for patients with aphasia, leaving them with residual deficits that significantly add to the cost of stroke-related care. Additionally, the amount and frequency of speech and language therapy delivered may have a critical effect on recovery. Therefore, there is a need for new treatments or adjuncts to existing treatments, such as brain stimulation interventions, that have the potential to show greater improvements in patients with aphasia. One such new approach for non-invasive brain stimulation is transcranial direct current stimulation (tDCS). This study will examine the effects of tDCS during speech therapy to further examine which method or methods is best for patient recovery. Patients enrolled in the study will undergo language testing that covers a broad range of language functions. Functional Magnetic Resonance Imaging (fMRI) will be completed before and after speech therapy intervention arms to investigate the neural processes affected by tDCS and speech therapy. Study design: Patients will be randomly assigned to one of 2 speech therapy groups in a double-blind, partial crossover design. Patients will receive one of two different speech therapy treatment interventions to focus on specific processing deficits. Participants will undergo neuropsychological evaluation and fMRI assessment before receiving targeted or active-control anodal-tDCS for 10 therapy sessions. Participants will then be re-tested using the behavioral assessment measure and fMRI before crossing over to either receive the tDCS intervention they did not already receive, within the same speech therapy arm. They will complete a behavioral assessment and fMRI at 3 months post Treatment 2 and a final behavioral assessment at 6 months post Treatment 2.

Partial crossover design. Participants will maintain one of two speech therapy modalities throughout the study, but will crossover from targeted to active control stimulation (or vice versa).

Participants will receive phonologic-focused speech therapy with targeted anodal-tDCS for 10 therapy sessions before.

Participants will receive phonologic-focused speech therapy with active control tDCS for 10 therapy sessions.

Participants will receive semantic-focused speech therapy with targeted anodal-tDCS for 10 therapy sessions.

Participants will receive semantic-focused speech therapy with active control tDCS for 10 therapy sessions.

High-Definition-tDCS will be delivered via a battery-driven constant direct current stimulator (Soterix) using a 4x1 montage (1 central anodal electrode and 4 cathodal electrodes) arranged in a HD-cap. The current is turned on and increased in a ramplike fashion over approximately 30 seconds until reaching a strength of no more than 2mA, with a current density equal to 0.08mA/cm2. Stimulation will be maintained no longer than 20 minutes, and stimulation will be applied to the targeted region.

High-Definition-tDCS will be delivered via a battery-driven constant direct current stimulator (Soterix) using a 4x1 montage (1 central anodal electrode and 4 cathodal electrodes) arranged in a HD-cap. The current is turned on and increased in a ramplike fashion over approximately 30 seconds until reaching a strength of no more than 2mA, with a current density equal to 0.08mA/cm2. Stimulation will be maintained no longer than 20 minutes, and stimulation will be applied to the active control region.

Participants are asked to generate or choose from a list phonologic information about a target picture.

Participants who have difficulty retrieving an object name are given hierarchical clues or asked questions about the objects function as a way of activating the semantic network for that object, leading to eventual retrieval of the target word.

Improvement on trained, untrained and untested items used during therapy. Items will consist of words and pictures that participants will name. Percent improvement on lists after each therapy cycle will be the primary behavioral outcome measure.

Rs-fMRI functional connectivity changes between time points at the site of stimulation will be assessed. Rs-FMRI functional connectivity changes between time points with the semantic network and between semantic network and perilesional phonological areas. Cortical activation patterns and ROI lateralization will be measured using an adaptive language mapping task-fMRI procedure. Activation patterns will be assessed for each task contrast within a set of ROIs thought to reflect the semantic and phonological network in healthy controls. Laterality indexes will be created using the same ROIs and their right-sided homologues to assess whether lateralization changes as a result of therapy.

A full language battery assessing different language processes (phonology, semantics, orthography, comprehension, executive functioning, etc) will be repeated three times (Time 1, Time 2, Time 3), and change scores between times will be used to create behavioral variables for comparison of treatment effects. Change in functional rating between assessment times will be used to examine functional improvement as a result of intervention.

Inclusion Criteria: Patients with a language deficit from focal neurologic damage (e.g. stroke, tumor). Patients must be adults and have English-language fluency. Patients must be eligible to undergo MRI. Exclusion Criteria: Advanced neurodegenerative disease (i.e. Stage 3 Alzheimer's disease) or neurologic disorder (e.g. idiopathic epilepsy, Parkinson's disease, ALS) Severe psychopathology (e.g. schizophrenia, bipolar disorder, acute major depressive episode) No suspected or diagnosed uncorrectable hearing or vision difficulties, or developmental disabilities (i.e. intellectual disability or learning disability). Contraindications to MRI such as claustrophobia, implanted electronic devices, MRI-incompatible metal in the body, extreme obesity, pregnancy, inability to lie flat, and inability to see or hear stimulus materials

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