Transcranial Direct Current Stimulation Investigations of Language Processing in Aphasia
Condition: Aphasia
MeSH terms: Aphasia
Study type: Interventional

Summary: 
      This study proposes to use transcranial direct current stimulation (tDCS) in patients with
      chronic strokes and aphasia in order to characterize and enhance the mechanisms of language
      recovery following injury. Prior to enrollment subjects will undergo six "site-finding'
      sessions involving various placements of positively charged (anodal), negatively charged
      (cathodal), and sham stimulation over the damaged and intact hemispheres of the brain, along
      with standard tests of language. Subjects who are found to experience a transient improvement
      in language ability in this initial experiment will participate in an incomplete cross-over
      design study to determine if 10 sessions of tDCS stimulation lead to prolonged language
      benefit when delivered to the hemisphere and at the polarity shown previously to respond best
      to stimulation.
    

Detailed description: 
      Transcranial Direct Current Stimulation (tDCS) uses a small (typically 1-2 mA) electrical
      current which is passed through the scalp and is delivered for up to 20 minutes. Due to the
      safety and tolerability of tDCS, as well as its demonstrated capacity to temporarily enhance
      cognitive, motor and affective functions of the brain, there has been an explosion of
      interest in the technique since the first reports in 2000. tDCS has been used safely in a
      wide variety of domains including studies of the visual system, working memory, verbal
      fluency and motor function. tDCS has also been used safely to enhance brain function in
      subjects with a variety of brain pathologies including stroke, depression and Alzheimers
      Disease. In this study, the investigators hope to address whether tDCS can be used to enhance
      language function in individuals with post-stroke aphasia.

      This two part experiment will address 1) Can tDCS lead to transient improvement in language
      ability in individuals with stroke and chronic aphasia? and 2) Does repeated tDCS lead to
      prolonged improved language ability in individuals with stroke and chronic aphasia?

      In Experiment 1, which will be referred to as the 'site-finding' portion of this protocol,
      participants will undergo anodal, cathodal, and sham stimulation of the intact or injured
      hemisphere to determine what area of the brain responds best to tDCS. There will be six
      separate sessions which are spaced apart by at least 2 days. Tests of language will be used
      to characterize changes in performance that are induced in each condition.

      In Experiment 2, subjects who had participated in Experiment 1 and were found to experience a
      transient improvement in language ability after receiving tDCS will participate. Subjects
      will be stimulated using the best montage from Experiment 1. This is an incomplete cross-over
      design study to determine if 10 sessions of tDCS stimulation delivered to the brain will lead
      to improvement in language. Improvement will be operationally defined as performance on one
      or more language measures that is significantly better than baseline and sham performance
      (i.e. non-stimulation conditions). Half of our subjects will be randomized to a group
      receiving 10 sessions (divided in to two five-day periods) of real tDCS. The other half of
      our subjects will be randomized to undergo sham stimulation before undergoing optional real
      tDCS stimulation. All subjects will engage in language rehearsal during stimulation. Tests of
      language will be used to characterize changes in performance that are induced by real and
      sham stimulation. Follow-up language testing will be performed at 2 weeks and 2 months after
      stimulation to determine whether tDCS can have prolonged effects on language.
    

Intervention name(s): Transcranial Direct Current Stimulation (tDCS)
Intervention type(s): Device
Intervention description(s): Transcranial direct current stimulation (tDCS) is a form of non-invasive neuromodulation that uses constant, low (1-2mA), direct current delivered via electrodes on the head.
Allocation: Randomized
Intervention model: Crossover Assignment
Intervention model description: This is an incomplete crossover design where subjects randomized to the real tDCS group will end their participation but subjects randomized to the sham tDCS group will crossover into the real tDCS group.
Masking: Single (Participant)
Primary purpose: Treatment
Keywords: stroke; non-invasive brain stimulation; transcranial direct current stimulation (tDCS)