In Vivo Imaging of Therapeutic Electric Current Flow
Condition: Parkinson Disease; Epilepsy; Alzheimer's Disease; Stroke; Autism; Depression; Schizophrenia
MeSH terms: Parkinson Disease; Alzheimer Disease; Epilepsy; Depression; Schizophrenia
Study type: Observational

Summary: 
      The purpose of this research study is to measure current flow inside the head using magnetic
      resonance imaging (MRI). The data from this study will be used to map the current flow caused
      from the electrical stimulation inside the head. The methods develop will be used to map and
      better control delivery of the current for electrical stimulation to modify a psychiatric
      condition such as depression; or other conditions such as epilepsy, Parkinson's disease or
      autism.
    

Detailed description: 
      Transcranial direct current stimulation (tDCS) and deep brain stimulation (DBS) are examples
      of electrical stimulation therapies that are rapidly gaining attention as means of modulating
      motor function, semantic processing, and executive function. Both therapies have attracted
      many clinical and experimental studies. tDCS has been found to have both facilitatory and
      inhibitory effects on the brain depending on stimulation polarity and electrode position. DBS
      has been thoroughly evaluated clinically for treatment of movement disorders, principally
      Parkinson's disease, and is extending its reach to include treatment of disorders such as
      focal dystonia, depression and chronic pain. While still mostly in the experimental stage,
      tDCS applications and acceptance are growing extremely rapidly.

      Although the functional alterations associated with tDCS can be categorized without knowledge
      of the underlying neurophysiology, an understanding of where externally applied current
      actually flows in any electrical stimulation technique is crucial as a basis for
      understanding which brain regions, circuits, or elements are affected by these therapies, and
      how these changes may occur. Such knowledge will lead to a better understanding of the
      mechanisms underlying these therapies, and thus to more focused and effective stimulation
      patterns and locations. Ultimately, this will lead to more efficient and novel clinical
      applications.

      Many studies have simulated the effects of current application in both extra- and
      intracranial modalities using computer simulation. Simulations will always be limited by
      errors in interpreting MRI data during segmentation, differences between assumed and actual
      electrical conductivity values, and mismatches between actual and presumed electrode
      locations and sizes. Thus, better methods to understand and verify current flow distributions
      are badly needed.

      In this study a recently developed MRI-based phase imaging technique to more directly measure
      current densities in vivo. Unlike earlier MRI-based methods of measuring electrical current
      flow, the technique works without requiring subject repositioning. This methods will be
      validated against high-resolution subject-specific models incorporating many tissue
      compartments, including anisotropic white matter. Thus, a new direct measurement method
      against state-of-the-art modeling approaches.
    

Intervention name(s): Transcranial direct current stimulation; MRI
Intervention type(s): Device; Procedure
Intervention description(s): All participants will receive transcranial direct current stimulation. During the MRI images of the head a battery-powered device pulses a small current between a pair of the electrodes which will be immediately followed by more MRI images. The current pulses will be very short and there should be no feeling from the pulses. The entire imaging period will be at most 90 minutes.; All participants will receive an MRI. During the MRI images of the head a battery-powered device pulses a small current between a pair of the electrodes which will be immediately followed by more MRI images. The current pulses will be very short and there should be no feeling from the pulses. The entire imaging period will be at most 90 minutes.
Other intervention name(s): Noninvasive Brain Stimulation; Magnetic Resonance Imaging
Observational model: Cohort
Time perspective: Prospective
Sampling method: Probability Sample
Study population: 
        24 normal adult subjects will be assessed.
      
Keywords: Transcranial direct current stimulation; Noninvasive brain stimulation; Brain; Central Nervous System Diseases; Nervous System Diseases; Parkinson disease; Stroke; Epilepsy; Depression; Schizophrenia; Brain imaging; Electrical impedance tomography; Magnetic resonance electrical impedance tomography; Diffusion tensor imaging; Functional magnetic imaging; Rehabilitation