Brain Changes Associated With Learning a Motor Task
Condition: Healthy
Study type: Observational

Summary: 
      This study will determine: 1) whether learning a task with the dominant hand is accompanied
      by changes in the area of the brain that controls hand movement, and 2) how the brain is able
      to make these changes. Previous studies have shown that practicing a motor task can change
      brain excitability, but it is not known how well brain excitabilities are changed during
      motor learning. This study will measure changes in activity of the part of the brain that
      controls hand movement before, during, and after exercising the hand on a response pad.

      Healthy normal volunteers between 18 and 40 years of age may be eligible for this study.
      Candidates who have not been evaluated at NIH within the past year will be screened with a
      brief interview about their current state of health and clinical and neurological
      examinations. Participants will undergo the following procedures:

      Learning a finger movement/reaction time task

      For this procedure, participants sit in front of a computer monitor with the index, middle,
      ring, and little fingers placed flat on four corresponding buttons of a response pad. They
      are asked to press one of the four buttons as fast as they can in response to an asterisk
      displayed on the monitor. The position of the asterisk indicates which button to push.
      Subjects perform nine sets of 120-button pushes with a 15-minute rest between each set.
      During the rest period, subjects undergo transcranial magnetic stimulation (described below),
      which causes twitches in the hand muscles. The electrical activity corresponding to the
      twitches is recorded by attaching electrodes (small metal disks) to the skin over the hand
      muscles.

      Transcranial magnetic stimulation

      For this test, an insulated wire coil is held over the scalp. A brief electrical current
      passes through the coil, creating a magnetic pulse that electrically stimulates the brain.
      The subject hears a click and may feel a pulling sensation on the scalp under the coil. The
      stimulation may also cause twitching in the muscles of the face, arm, or leg. During the
      stimulation, the subject may be asked to tense certain muscles slightly or perform other
      simple actions.

      ...
    

Detailed description: 
      Objective: We aim to show that the development of implicit knowledge of a motor task is
      associated with decrease in intracortical GABA-related inhibition (ICI) in the trained
      muscles (accompanying increasing MEP amplitudes) and increase in ICI in non-trained
      neighboring muscles and that, after the knowledge becomes explicit, ICI modifications become
      less prominent.

      It would be useful to know the role of ICI during learning. As some interventions or drugs
      are known to modify GABA activity, this study may even provide a rationale for using these
      interventions and drugs to enhance plastic changes in patients with impaired motor learning
      capabilities.

      Several studies have shown that learning a motor task with one hand can be transferred to the
      contralateral hand (37, 43, 45, 46, 47). Studies have demonstrated that learning a finger
      sequence task (Serial Reaction Time test, SRTT) with the dominant-hand (trained) can be
      transferred to the contralateral hand (un-trained) (43,49,50). In this additional experiment
      we propose to investigate the effect of disrupting M1 (by using 1 Hz TMS, inhibitory effect)
      on motor learning in the trained hand (dominant) and in the un-trained hand (non-dominant).
      Evidence has shown that there is transcallosal connections between M1 of both hemispheres
      (40). Since M1 is active during implicit learning (41, 42) we expect 1 Hz TMS stimulation
      (inhibitory effect) over M1 will deteriorate implicit learning in the trained hand (dominant)
      as well as in the un-trained hand (non-dominant). This will be evaluated by assessing their
      effect on reaction times and accuracy of motor performance in both hands.

      Study Population: 72 healthy volunteers, aged 18-40 will participate in the study. Subjects
      will be randomly assigned to either the test session or the control session.

      Design: Subjects will complete a unique session. They will perform a serial-reaction-time
      task. The subjects will be instructed to push a button on a 4-button pad in response to a
      visual GO signal (which can appear at 4 different positions) using the appropriate digit and
      the appropriate button. There will be 9 blocks of 120 trials each. In the test group, in
      blocks 1, 4 and 7 the Go signal appears in a random order; in blocks 2-3, 5-6 and 8-9 the
      same 12-trial sequence is repeated 10 times. In the control group Go signals will appear in a
      random order in all blocks. Subjects won't be informed about the sequence but will be asked
      to notify anything they noticed about the task. If they do notice and report about a sequence
      they will be considered as having explicit knowledge. Between each block subjects will
      receive transcranial magnetic stimulations to assess ICI. ICI will be assessed on subjects at
      rest.

      Outcome Measures: Behavioral effect of the motor training will be assessed by measuring the
      mean reaction times (RT) for digits II and V and the percentage of correct responses for each
      block.

      Implicit learning will be assessed by the difference in RTs between block 3 and 4 and between
      block 6 and 7. Time at which explicit learning occurs will be assessed by verbal report and
      the degree of explicit learning by the number of correct items when repeating the sequence.

      Implicit learning will be assessed in the trained hand (dominant) (see above) and in the
      un-trained hand. The un-trained hand will be tested by asking subjects to repeat two random
      blocks (familiarization) and two sequence blocks. One of these sequence blocks is a
      repetition of the same sequence that they learned with the dominant hand. The other sequence
      block is a new sequence containing the same number of characters as the previous sequence.
      Implicit learning on the un-trained hand will be assessed by the difference in RTs, between
      random block and the sequence block. In addition, implicit learning on the un-trained hand
      will be evaluated by testing the difference between the two sequence blocks repeated by the
      un-trained hand. The time at which explicit learning occurs will be assessed by verbal report
      and the degree of explicit learning by the number of correct items when repeating the
      sequence.

      Intracortical inhibitory processes will be assessed by measuring the amount of ICI in trained
      muscles (first dorsal interosseus: FDI and adductor digit minimi: ADM) and a non-trained
      muscle (opponens pollicis brevis: OPB).
    

Keywords: Brain Excitability; Reaction Time; Plasticity; Motor Evoked Potential; Transcranial Magnetic Stimulation; Healthy Volunteer; HV