Cerebellar Transcranial Direct Current Stimulation and Aphasia Treatment
Condition: Stroke
MeSH terms: Aphasia
Study type: Interventional

Summary: 
      People with post-stroke aphasia are left with some degree of chronic deficit for which
      current rehabilitative treatments are variably effective. This study investigates the
      behavioral and neural effects of multiple consecutive cerebellar tDCS sessions coupled with
      computerized naming therapy in stroke survivors with aphasia.
    

Detailed description: 
      The investigators will study the effect of right cerebellar transcranial direct current
      stimulation (tDCS) stimulation during language therapy for naming in individuals with chronic
      aphasia (>6 months post stroke). Naming difficulties are a persistent and common symptom in
      aphasia after left-hemisphere (LH) stroke. Although the interventions to improve naming can
      have benefits, a massive number of treatment sessions is usually required to show gains,
      particularly in individuals with chronic, large LH stroke. tDCS is a promising adjunct to
      traditional language therapy. tDCS is a safe, non-invasive, non-painful electrical
      stimulation of the brain which modulates cortical excitability by application of weak
      electrical currents in the form of direct current brain polarization. It is usually
      administered via saline-soaked surface sponge electrodes attached to the scalp and connected
      to a direct current stimulator with low intensities. Prior investigators have mainly focused
      on the role of LH in language recovery, wherein the electrode is placed in the left frontal
      or temporal region. However, in individuals with large lesions involving key language areas
      like the frontal and temporal cortex, it may be difficult to find viable tissue to stimulate
      in the LH. This study uses a novel electrode placement for chronic stroke patients with
      aphasia with large LH lesions. Targeting the intact right cerebellum allows for the
      possibility of identifying a single target that can be used across groups of people with
      aphasia with varying lesion sites and size in the LH. Evidence from functional neuroimaging
      and clinical studies indicate that the right cerebellum is important for both language and
      cognitive functions.

      The investigators will utilize a randomized, double-blind, sham controlled, within-subject
      crossover trial design. A random subset (half) of participants will be assigned to the
      "anode" group (Group Anode) and other half will be assigned to the 'cathode' group (Group
      Cathode). Participants will take part in 2 intervention periods of 15 computerized naming
      training sessions (3-5 sessions per week), with either tDCS + naming therapy or sham+ naming
      therapy, separated by 2 months. Detailed language evaluation will take place before,
      immediately after, 2 weeks and 2 months post-intervention for each condition. The
      investigators will test the hypothesis that anodal tDCS or cathodal tDCS over the cerebellum
      and computerized naming therapy is associated with greater gains in accuracy in naming
      pictures, compared to sham combined with the same computerized naming therapy.
    

Intervention name(s): Anodal or Cathodal tDCS; Sham; Computerized naming therapy
Intervention type(s): Device; Device; Behavioral
Intervention description(s): 2 mA or Anodal or Cathodal tDCS stimulation is induced between 5cm X5 cm saline soaked sponges where one sponge (anode in group anode or cathode in group cathode) is placed on the right cerebellum. The stimulation will be delivered at an intensity of 2 mA in a ramp-like fashion for a maximum of 20 minutes.; 2 mA of Anodal tDCS or Cathodal tDCS is induced between two 5cm X 5cn saline soaked sponges where one sponge (anode in group Anode and cathode in group Cathode) is placed on the right cerebellum. Ramping up of the current to 2 mA occurs over 15-30 seconds to allow participants to habituate to the tingling sensation. Then, the current will be ramped back down to 0 mA in the sham condition. Termination of the stimulation after the ramping up process is generally undetectable, and the brief duration of stimulation yields no functional effects.; Computer delivered naming treatment requires matching (heard and seen being produced by the speaker) with pictures depicting common objects. It is run on a laptop computer with headphones and 2 large response buttons. During treatment, a picture appears on the laptop screen for 2 seconds. Then, a video of the speaker's face below the nose is presented on the screen saying a word that either matches or does not match the picture. The participant is instructed to press a green response button if the word matches the picture and press the red button if the word does not match the picture.
Allocation: Randomized
Intervention model: Crossover Assignment
Masking: Quadruple (Participant, Care Provider, Investigator, Outcomes Assessor)
Primary purpose: Treatment