Effects of Prism Adaption and rTMS on Brain Connectivity and Visual Representation
Condition: Normal Physiology; Stroke
MeSH terms: Stroke
Study type: Observational

Summary: 
      Background:

      After a stroke, the balance between the two halves of the brain can be lost. This may cause
      people to lose the ability to perceive a side of space. This is called neglect. Having people
      wear prism glasses (called PA) can reduce neglect symptoms. Researchers want to find out more
      about how PA, and whether it restores the balance in the brain.

      Objective:

      To learn how prism adaption temporarily changes vision and connections in the brain.

      Eligibility:

      People ages 18 75 with brain damage of the right side of the brain from a stroke or other
      cause, leading to neglect.

      Healthy volunteers ages 18 75.

      Design:

      Participants will have 1 3 visits.

      Participants will be screened with a neurological exam. They may also have:

      Tests of thinking and vision

      Tests to see which eye and hand they prefer

      A pregnancy test

      All participants will:

      Answer questions about their personality, style of thinking, and beliefs.

      Do simple tasks on paper or computer

      Have magnetic resonance imaging. They will lie on a table that can slide in and out of a
      cylinder in a strong magnetic field. Participants will lie still or do computer tasks in the
      scanner.

      Participants may also have:

      Transcranial magnetic stimulation. A brief electrical current passes through a wire coil on
      the scalp. This creates a magnetic pulse that affects brain activity. Participants may be
      asked to tense certain muscles or perform simple actions or tasks.

      PA. They will sit in front of a board and point to a dot on it while they wear prism glasses
      that shift vision to the left or right....
    

Detailed description: 
      OBJECTIVES:

      The ability to efficiently select information from the environment relies on a balanced
      interaction between the right and left hemispheres. Hemispatial neglect, most frequently
      following damage to the right hemisphere, has been hypothesized to result from the breakdown
      of this interhemispheric balance. There is evidence from transcranial stimulation studies
      that the breakdown of this interhemispheric balance is reflected in fronto-parietal
      connectivity. The primary goal of this study is to test whether altering the balance between
      the left and right hemispheres, with repetitive transcranial magnetic stimulation (rTMS) or
      prism adaptation (PA), will affect functional connectivity measured with functional magnetic
      resonance imaging (fMRI). We will also explore the relationship between the changes in
      functional connectivity and behavioral performances.

      STUDY POPULATION: Healthy adult volunteers and patients with neglect after a right hemisphere
      damage.

      DESIGN: The study contains three experiments. Experiment 1 is designed to investigate the
      mechanism of the changes induced by PA in both resting state functional connectivity in
      neglect patients and healthy volunteers (a two-arm parallel study). Experiment 2 is designed
      to investigate the mechanism of the changes in resting state functional connectivity induced
      by lPA, rPA, nPA in healthy volunteers with right dominant eyes and lPA in healthy volunteer
      with left dominant eye (a four-arm parallel study). Experiment 3 is designed to see if
      inhibitory rTMS over the right posterior parietal cortex (PPC) can influence functional
      connectivity and visuospatial bias in healthy volunteers (a crossover study).

      OUTCOME MEASURES: For all three experiments the primary outcome measure is the change (or
      difference) in fronto-parietal resting state connectivity between post and pre PA or rTMS
      procedure. The secondary outcome measures are the changes in visual field representation and
      in visuo-motor and cognitive behavior accompanying these manipulations.
    

Observational model: Cohort
Time perspective: Prospective
Sampling method: Probability Sample
Study population: 
        Primary Clinical
      
Keywords: Chronic Stroke; Neglect; Transcranial Magnetic Stimulation; Visual and Motor Integration; Visual Fields; Natural History