Effects of Transcranial Magnetic Stimulation on Object Recognition
Condition: Repetitive TMS (rTMS); Sham rTMS; Bilateral rTMS; Unilateral rTMS
Study type: Interventional

Summary: 
      Background:

      - The brain has natural rhythms called brain waves. An electroencephalogram (EEG) can record
      these rhythms. When people identify the picture of a familiar object shown on a computer
      screen, the communication between certain regions of the brain increases. An EEG can detect
      these communication brain waves. Transcranial magnetic stimulation (TMS) can affect these
      brain waves by slightly changing the brain s rhythms. Researchers want to see if changing
      brain rhythms with TMS interferes with the ability to identify pictures of familiar objects.
      This study will provide more information about how TMS can affect brain waves and behavior.

      Objectives:

      - To see if TMS can interfere with the brain s ability to identify pictures of familiar
      objects.

      Eligibility:

      - Healthy volunteers between 18 and 70 years of age.

      Design:

        -  This study requires two visits to the clinical center. The first visit will last about 2
           hours. The second visit will last about 4 hours.

        -  Participants will be screened with a physical exam and medical history.

        -  At the first visit, participants will have an object recognition test. Participants will
           look at pictures of several objects on a computer screen. They will then have to state
           whether the objects they see on the screen are familiar. The object recognition test
           will be done along with TMS.

        -  At the second visit, participants will have an EEG while taking the object recognition
           test. Brain waves will be monitored during the test. They will then repeat the test
           while having repetitive TMS to study its effect on object recognition. The participants
           will then take the object recognition test alone for a final time. This will make sure
           that TMS effects (if any) on the ability to identify familiar object images are no
           longer present.
    

Detailed description: 
      Inter-hemispheric coherence (IHC) is one of the electroencephalography (EEG) parameters that
      measures synchronization of oscillations originating from brain regions of different
      hemispheres and thereby the functional connectivity between them. We know that object
      discrimination is associated with transient increase in IHC. In this study we will interfere
      with the transient IHC that is associated with midline object discrimination by using
      rhythmic repetitive transcranial magnetic stimulation (rTMS).

      We will study the effects of entrainment by unilateral or bilateral, synchronous or
      asynchronous TMS pulses on behavior. The goal of the study is to determine if entrainment by
      TMS will affect task performance. If the results show that TMS by entrainment influenced
      behavior, then we can expect TMS to be a useful technique to explore the behavioral impact of
      specific neuronal oscillations under physiological as well as pathological conditions.
      Further, TMS could also find applications in rehabilitation or treatment of behavioral
      symptoms in patients with neuropsychiatric diseases.

      STUDY POPULATION:

      We intend to study 11 adult healthy volunteers on an outpatient basis.

      STUDY DESIGN:

      All the subjects will first participate in a screening session where the threshold TMS
      intensity for blocking object discrimination and the optimal coil orientation will be
      determined using single pulse TMS. Later they will attend the main experiment session where
      they will be asked to perform the object discrimination task in four blocks, of which the
      second, third and fourth will be in random order. During the first block, the individual
      coherence frequency will be determined by recording EEG during the task. During the second,
      third and fourth blocks, the subjects will receive either unilateral, bilateral or sham rTMS
      in a random order while EEG is being recorded. Short trains of 7 TMS pulses will be delivered
      during each trial. TMS pulses will be administered over left and/or right LOG at 80% of
      threshold intensity blocking object discrimination or 60% maximum stimulator output whichever
      is smaller.

      OUTCOME MEASURES:

      We expect that short trains of TMS will affect IHC depending on whether the pulses are
      synchronous or asynchronous. By modulating IHC, we expect changes in object discrimination
      task performance. The primary outcome measure in this study includes object discrimination
      task performance. During the study, we will also compute the individual frequency at which
      maximum coherence occurs, the threshold intensity and optimal coil direction for blocking
      object discrimination and the spatio-temporal characteristics of EEG waves during the rTMS
      trains to confirm that entrainment is occurring.
    

Intervention name(s): Sham rTMS; Bilateral rTMS at same frequency and in phase; Bilateral rTMS at different frequencies; Bilateral rTMSat same frequency and out of phase; rTMS over TP8; rTMS over TP7
Intervention type(s): Procedure; Procedure; Procedure; Procedure; Procedure; Procedure
Allocation: Randomized
Intervention model: Single Group Assignment
Primary purpose: Basic Science
Keywords: Repetitive TMS (rTMS)