Tactile Learning in Stroke Patients
Condition: Stroke
MeSH terms: Stroke
Study type: Observational

Summary: 
      This study will determine if stimulation of the stroke-injured side of the brain combined
      with stimulation to the paralyzed hand can temporarily improve the sense of touch in stroke
      patients.

      Healthy normal volunteers and people who have had a single stroke within 3 months of entering
      the study that affected one side of the brain may be eligible for this study. All
      participants must be between 18 and 90 years old and must be right-handed. Candidates are
      screened with a medical history, neurological examination and magnetic resonance imaging
      (MRI) of the brain if one has not been done within 1 year of entering the study.

      Participants undergo the following tests and procedures during four 2-day sessions over about
      6 weeks:

        -  Peripheral high-frequency stimulation: Small loudspeakers are taped to the fingertips
           and simple tactile pulses are passed through the skin. Stimulation may be sham or real.

        -  Transcranial direct current stimulation: Two small rubber electrodes are taped to the
           head - one above the eye and the other on the back of the head. A current is passed
           between the two electrodes. Stimulation may be sham or real.

        -  MRI: The subject lies in the scanner, a metal cylinder surrounded by a magnetic field,
           for about 40 minutes, lying still for up to 40 minutes at a time. An electrical
           stimulation is applied to the fingers of the right and left hand in separate sessions.
           Earplugs are worn to muffle the loud noises during the scanning. Functional MRI measures
           blood flow changes in the brain during the performance of specific tasks.

        -  Behavioral measurements:

             -  Grating orientation task: The subject responds as quickly as possible to a touch
                stimulus to the finger by saying whether the direction of the stimulus is vertical
                or horizontal.

             -  Haptic object recognition task: The subject is given five categories of unfamiliar
                objects in the shape of cubes. During the task, identical objects are hidden in a
                sack. With eyes closed, the subject is asked to identify and find the objects from
                the sack as quickly as possible.

             -  Pegboard test: The subject is asked to place several pegs into a corresponding hole
                of a pegboard as soon as possible.

             -  Tapping task: The subject is asked to tap a metal stick on a metal plate as quickly
                as possible for 1 minute.

        -  Paired-pulse transcranial magnetic stimulation: This test measures changes in brain
           activity. A wire coil is held on the scalp and a brief electrical current is passed
           through the coil, creating a magnetic pulse that stimulates the brain. The subject hears
           a click and may fee a pulling sensation on the skin under the coil, and there may be a
           twitch in the muscles of the face, arm or leg. Subjects may be asked to tense certain
           muscles slightly or perform other simple actions.

        -  Paired-pulse somatosensory evoked potential mapping: This test measures brain activity
           in another brain area. The subject is seated in a chair with eyes closed. One electrode
           is placed above the eye and two others are placed on the back of the head. A short
           electrical stimulus is applied to a nerve in the wrist and brain activity is recorded
           while the stimulus is applied.

        -  Surface electromyography: This test measures the electrical activity of muscles.
           Electrodes are filed with a conductive gel and taped to the skin.

        -  Visual analog and mood scale: Subjects complete questionnaires about their attention,
           fatigue and mood.
    

Detailed description: 
      Chronic stroke is often accompanied by tactile impairments that contribute to long-term
      disability in activities of daily living. While new rehabilitative interventions recently
      became available in the motor domain by using transcranial direct current stimulation (tDCS),
      there is no generally accepted treatment for tactile impairments after chronic stroke.
      Previous studies in healthy volunteers demonstrated that tactile acuity and haptic skills can
      be improved by applying a passive learning protocol to the fingertip (peripheral
      high-frequency stimulation, pHFS). Based on these findings, the purpose of this protocol is
      to enhance the beneficial effect of pHFS on implicit tactile and haptic learning in chronic
      stroke patients by a combined application of pHFS with tDCS (pHFS+tDCS) applied to the
      somatosensory cortex of the affected hemisphere. This approach might identify novel
      strategies to enhance functional recovery after stroke and might provide deeper insight into
      mechanistic information on the neural substrates involved in these behavioral gains. Primary
      outcome measures will be performance in a tactile grating orientation discrimination task
      (GOT) and in a haptic object recognition task. In order to obtain descriptive preliminary
      information on the relation between sensory improvements and motor deficits in chronic stroke
      patients, secondary outcome measures will be fine motor tasks such as a tapping task and a
      pegboard test (PBT) that require manual dexterity, handeye coordination, steadiness, and
      perceptual motor skills. To identify the operating mechanisms underlying hypothesized
      performance improvements after pHFS+tDCS, we will use paired-pulse protocols to evaluate
      changes in cortical excitability as well as fMRI in a subset of patients to identify cortical
      map reorganization in primary (SI) and secondary (SII) somatosensory cortex as well as in
      primary motor cortex (MI). Healthy volunteers will be tested (a) since there are no data
      available on performance of the haptic task in healthy subjects, (b) to obtain descriptive
      information on the influence of our interventions on this task for hypothesis generation
      purposes in our future investigations, and (c) because sensorimotor performance in the
      non-paretic hand of stroke patients is often not normal and therefore a poor sole control for
      performance of the paretic hand. Studies in chronic stroke patients will help address the
      main experimental hypothesis.
    

Keywords: Haptic Skills; Implicit Tactile Learning; Functional Magnetic Resonance Imaging (fMRI); Transcranial Magnetic Stimulation (TMS); Transcranial Direct Current Stimulation (tDCS); Stroke; Healthy Volunteer; HV