Modulating the Hippocampal and Striatal Memory Networks With rTMS
Condition: Normal Behavioral Patterns
Study type: Interventional

Summary: 
      Background:

      People have 2 memory systems. One helps them learn skills and the other helps them learn
      facts. Repetitive transcranial magnetic stimulation (rTMS) uses electric currents to activate
      brain cells. This can make small changes in how brain systems operate. Researchers will use
      rTMS to change how memory systems work and to see if changing one system causes the other to
      change too. This could help find ways to improve learning and memory in people with memory
      disorders.

      Objective:

      To learn how different memory systems work with each other.

      Eligibility:

      Healthy adults ages 18-40 who are not pregnant

      Design:

      Potential participants will be screened with a neurological exam if they have not had one
      from NINDS in the past 2 years. They may have urine tests.

      Eligible participants will have 5-10 visits at NIH. Each visit will last 1-6 hours. Visits
      1-4 will each take place 1 day apart.

      At visit 1, participants will have an MRI and take memory tests. For MRI, they will lie on a
      table that slides in and out of a cylinder that takes pictures of their brain. They will also
      have rTMS. For rTMS, a metal coil is held on their scalp. Brief electrical currents pass
      through the coil.

      At visits 2 and 3, participants will have rTMS.

      At visit 4, participants will have an MRI and do memory tests.

      About a week later, participants will have visit 5. They will have an MRI and do memory
      tests. Participants may be asked to have more visits if any technical problems occur.
      Participant involvement will last 2 weeks.

      ...
    

Detailed description: 
      Objective

      The Behavioral Neurology Unit studies the human brain systems underlying learning and
      adaptation with the ultimate goal of finding interventions to make these processes more
      efficient. We are interested in whether repetitive transcranial magnetic stimulation (rTMS)
      can alter functional connectivity (FC) and behavioral efficiency in two memory networks in
      the brain: the hippocampal network, which supports the storage and retrieval of recallable
      facts, concepts, and events, and the striatal network, which supports the storage and
      retrieval of skills and habits. Additionally, because these networks interact behaviorally
      and can interfere with each other, an important question is whether neuromodulation of one
      network changes connectivity and efficiency in the other network. Pilot data from our group
      suggest that exogenous stimulation of one network causes it to expand its range of FC and
      co-opt resources from the other, which is a potential mechanism for the observed behavioral
      interaction. This study is designed to test a) whether rTMS- modulates within-network FC and
      memory supported by that network, and b) whether this also causes FC and behavioral changes
      in the other network.

      Study population: Healthy Volunteers

      Design

      This study contains four between-subjects experiments and is a mixed inter/intra subject
      design. Experiment 1 will use nominally excitatory stimulation targeting the hippocampal
      network to increase FC within the hippocampal network. We also expect to increase FC between
      the hippocampal and striatal networks, increased declarative memory, and a possible decrease
      in procedural, learning. Experiment 2 will use excitatory stimulation targeted to the
      striatal network. We expect this to cause stronger within- network FC in the striatal
      network, increased FC between the hippocampus and the striatal network and concomitant
      behavioral effects. Experiments 3 and 4 will be similar except that we will target nominally
      inhibitory stimulation to these networks and look for the inverse results. FC will be
      measured under resting and task-activated conditions and active rTMS will be compared to
      vertex sham.

      Outcome measures

      The primary outcome measure is the change in FC produced by rTMS within the targeted network.
      Between-network FC changes and corresponding memory changes will be secondary outcomes.
      Exploratory measures will include correlations between individual cognitive differences
      (questionnaires and NIH Toolbox scores), and our primary and secondary outcome measures.
    

Intervention name(s): RTMS
Intervention type(s): Other
Intervention description(s): Altering the connectivity of trans-synaptic pathways
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Single (Participant)
Primary purpose: Basic Science
Keywords: Memory Systems; Repetitive Transcranial Magnetic Stimulation; Behavioral Efficiency; Hippocampal and Striatal Memory Networks