Transcranial Direct Stimulation (tDCS) and Behavioral Intervention in Aphasia
Condition: Aphasia
MeSH terms: Aphasia
Study type: Interventional

Summary: 
      We hypothesize patients who have difficulty with word recall (naming pictures) due to a
      stroke will experience greater benefit in word recall after receiving a combination of
      transcranial direct current stimulation (tDCS) and traditional behavioral treatment. This
      study will investigate the effects of the timing of tDCS in relationship to the behavioral
      treatment to determine the most optimal protocol. Transcranial direct current stimulation
      involves placing two electrodes on your scalp and sending a very small electrical current to
      excite the brain cells of the target site.
    

Detailed description: 
      Specific Aims Aim 1: Identify and quantify the effects of a-tDCS to the left dorsolateral
      prefrontal cortex (DLPFC) in conjunction with intensive behavioral treatment on naming in
      non-fluent aphasia. a-tDCS (2mA for 20 minutes) will be applied over the left DLPFC with
      cathode over the right orbit. Pre and post treatment behavioral measures of naming and
      working memory will be used to quantify and compare differences. Hypothesis 1: a-tDCS will
      result in improvements in naming accuracy, naming response times, and working memory (WM) in
      participants with non-fluent aphasia.

      Aim 2: Compare the effects of a-tDCS applied to the left DLPFC before behavioral treatment to
      during behavioral treatment in non-fluent aphasia. a-tDCS (2mA for 20 minutes) will be
      applied over the left DLPFC with cathode over the right orbit. Pre and post treatment
      behavioral measures of naming and working memory will be used to quantify and compare
      functional differences between conditions. Hypothesis 1: a-tDCS to the DLPFC during treatment
      will result in a greater improvement of naming accuracy, naming response time and WM in
      participants with non-fluent aphasia.

      Significance The findings from the proposed study will lay the foundation for a larger
      clinical trial which will in turn have a significant impact on individuals with aphasia given
      that naming deficits are a common symptom in this population. As the presence of naming
      deficits has a negative relationship to emotional well-being and functional communication
      26-30, treatment that improves naming deficits will positively influence quality of life in
      many of these individuals. The approach taken to remediate naming deficits in aphasia is to
      treat impaired WM systems on the premise that certain cognitive processes underlie linguistic
      functions in aphasia. This approach represents a departure from most behavioral-based naming
      treatment approach, but reflects a growing recognition that WM systems in individuals with
      aphasia impact their linguistic performance 5, 31. The addition of a-tDCS as a
      neuromodulation tool to increase cortical excitability (upregulate) the working memory center
      to target naming is a novel approach. In addition, this study will further elucidate the
      optimal timing of a-tDCS in order to achieve the most beneficial outcomes, which have not yet
      been reported. These findings, along with other related studies, will shape future clinical
      practice guidelines as more studies adopt a concurrent cognitive-linguistic approach to treat
      linguistic deficits in aphasia.

      Design & Methodology Participants. Four individuals with aphasia will be recruited. These
      participants must meet the following inclusionary/exclusionary criteria: a) completion of
      high school or GED; b) normal or corrected-to-normal vision; c) adequate hearing acuity for
      1:1 conversational exchanges; d) use of English as primary language; e) a vascular lesion in
      the dominant left hemisphere verified by an MRI scan within six months of the start of the
      study. These participants must also meet the following exclusionary criteria: a) no previous
      history of neurological- or psychiatric-based illnesses or disease, language or learning
      disabilities, or alcohol/substance abuse; b) no history of seizures; c) no metal implants in
      the head (except dental fillings); d) no lesion in the left DLPFC confirmed by MRI; e) no
      current pregnancy. Pre-Test Behavioral Measures. Participants will be seen between 2-3
      sessions to undergo comprehensive cognitive-linguistic testing prior to initiation of
      treatment. Testing will take place at the University of Minnesota (UMN) Clinical
      Translational Science Institute (CTSI). Behavioral test measures will include the WAB 32 in
      order to obtain the WAB Aphasia Quotient (WAB AQ), Boston Naming Test (BNT) 33 and the
      Apraxia Battery for Adults (ABA-2) 34. The WAB AQ will provide a general classification of
      aphasia subtype, scores from the BNT will provide the level of severity of naming impairment,
      and ABA-2 performance will be used to assess severity of apraxia of speech (AoS). To assess
      the integrity of the phonological store, participants will be tested for the effects of
      phonological similarity using both auditory and visual presentation 35, 36. To assess the
      integrity of subvocal rehearsal processes, participants will be tested for the effects of
      word length on both auditory and visual span 37; the effects of articulatory suppression on
      recall performance 37, 38; and rhyme judgments 39-41. Protocols that have been adapted for
      individuals with aphasia will be followed42-45. These tests will be used to distinguish
      behavioral evidence of deficient subvocal rehearsal processes from deficient phonological
      short-term store. Individuals with a range of moderate to moderately severe nonfluent
      aphasia, a range of moderate to moderately severe anomia, and a range of mild to no AoS will
      be chosen for the study. Baseline probes will also be obtained prior to the initiation of the
      study. Stability of baseline performance, defined as no more than 20% difference between
      scores,will be obtained over three consecutive sessions in order to establish experimental
      control. Post-Test Behavioral Measures. Participants will also be seen for post-treatment
      testing following the implementation of the treatment protocol. Testing will take place in
      the participant's home. Post-treatment behavioral measures will include BNT, the ABA-2, WM
      tasks, and naming treatment and control items. It is anticipated that only one session will
      be needed for post-treatment testing. An adverse events survey will also be provided to
      assess the participant's level of discomfort during use of tDCS. tDCS Protocol. Each
      participant will be seated comfortably in a chair. A swim cap will be placed on the
      participant's head to identify cranial landmarks for accurate electrode placement. The area
      referred to as F3 by the International 10/20 system for electroencephalogram electrode
      placement46 has been established as the optimal location for targeting the left DLPFC25,
      47-49. The F3 region will be located by marking the vertex (the midpoint between left and
      right tragus and midpoint between nasion and inion), measuring the head circumference. When
      these measurements are entered into the Beam F3 Locator Software50, additional values are
      provided to reliably identify the location of F3. Once F3 has been established, two saline
      soaked surface sponge electrodes (352cm) will be prepared and placed. For optimal anodal
      stimulation to the DLPFC, the anode will be placed over F3 and the cathode will be placed
      over the right supraorbital region23, 24, 47, 48. A current of 2mA will be delivered for 20
      minutes 24 by a multichannel transcranial current stimulator (Starstim, Neuroelectrics
      Corporation; Cambridge, MA). a-tDCS will be applied before and during behavioral treatment in
      the design specified below.

      Treatment Design. Two treatment conditions will be presented in a counter-balanced order in a
      cross-over design. The non-prime (NONPRIME) condition will consist of 40 minutes of naming
      treatment only, followed by an additional 20 minutes of concurrent naming treatment with
      a-tDCS. The primed (PRIME) condition will consist of presentation of a-tDCS for 20 minutes
      prior to naming treatment, while the subject sits quietly and comfortably in a chair. After
      the 20-minute priming period, the a-tDCS will be removed and the participant will receive
      naming treatment for 60 minutes. Both conditions will be presented over four consecutive
      days. Two participants will receive NON-PRIME-PRIME sequence, with a one-month washout period
      between the two conditions. Two other participants will receive PRIME-NON-PRIME sequence,
      with a one-month washout period between the two conditions. Naming reaction time will be
      immediately evaluated after each treatment day.
    

Intervention name(s): Transcranial direct current stimulation
Intervention type(s): Device
Intervention description(s): Transcranial direct current stimulation (tDCS) is a non-invasive neuromodulation tool that presents a low current that induces bi-directional polarity-dependent changes in the cortex to facilitate focal, prolonged shifts in cortical excitability at or around the time stimulation is provided. Anodal tDCS (a-tDCS), in which the positively charged electrode is placed over the targeted cortical region, has been shown to increase cortical excitability (upregulation), similar to long-term potentiation (LTP). Combining a-tDCS with behavioral-based approaches has been suggested to enhance the learning process and increase the likelihood of retention.
Allocation: Randomized
Intervention model: Crossover Assignment
Masking: Single (Investigator)
Primary purpose: Treatment
Keywords: Broca's Aphasia; Transcranial Direct Current Stimulation