TMS of Visual Working Memory

Study Overview
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Brief Summary
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The purpose of this study is to understand how the brain allows individuals to keep information in mind over brief intervals. During the experiment, participants will be asked to maintain fixation while they attend to and remember different visual stimuli (e.g., the location of a dot on the screen, the color of a circle, the orientation of a line, the speed of a group of moving dots) on a computer monitor. Participants will make decisions about these visual stimuli and indicate their decisions by pressing buttons or making eye movements. Through the use of Transcranial Magnetic Stimulation (TMS) investigators hope to understand the contributions of different anatomical areas while subjects perform this task.

Detailed Description
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This study will use a within subject design in which each participant will perform a working memory task combined with Transcranial Magnetic Stimulation. TMS will be applied in three possible procedures, 1) Online TMS, 2) Offline TMS and 3) Sham TMS. All subjects will be given two trials within their one session, one of which will be sham TMS for all subjects and another of which will be randomly assigned to either Online or Offline TMS. Trials order will be randomly counterbalanced across subjects, who will be blind to the treatment of frontal vs. sham TMS (independent variable). Participants will be randomized into either the online or offline groups by computer generated lists to ensure equal numbers of participants in each condition. Half of the subjects will receive online TMS (online group) and half will receive offline TMS (offline group). Subjects will be randomly assigned to one of the two groups. The dependent variables will be performance accuracy and reaction time on the working memory task. By utilizing online and offline TMS, investigators will be able to explore whether frontal cortex is involved transiently in visual working memory or persistently throughout the task.

Official Title
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Transcranial Magnetic Stimulation of Visual Working Memory

Conditions
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Occipital Transcranial Magnetic Stimulation

Intervention / Treatment
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* Device: Sham TMS condition
* Device: OffLine TMS Condition
* Device: Online TMS condition


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Neurologically healthy individuals will be recruited. Exclusion Criteria: Individuals with neurological issues (e.g., history of seizures, neurosurgery, brain trauma) will be excluded. Women of childbearing potential will be told that although there are no known risks of the procedure to the unborn fetus, they should not take part in the study if they are or might be pregnant. Minors and the elderly will be excluded. Individuals who are on medications that heighten the risk of TMS adverse events will be excluded.

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 65 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Treatment
Intervention Model: Single Group Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Working memory task<br>Simple visual stimuli (e.g., dots, colors, lines) will be presented on a computer monitor. The positions of the stimuli must be attended and remembered and decisions about the stimuli and/or their locations must be made. Memory will be probed with a button press or an eye movement towards the remembered locations. | Device: Sham TMS condition<br>* A sham TMS coil will be used to measure baseline performance on the working memory task. The sham coil looks and sounds just like the real coil, but produces a negligible magnetic field. Following the 40 seconds of sham TBS, the subject will perform the working memory task for 45 minutes.<br>Device: OffLine TMS Condition<br>* A total of 200 trains will be delivered successively in 40 s, totaling 600 pulses. The pulses will be delivered at 80% of motor thresholds. A sham TMS coil will be used to measure baseline performance on the working memory task. The sham coil looks and sounds just like the real coil, but produces a negligible magnetic field. Following the 40 seconds of TBS, or sham TBS, the subject will perform the working memory task for 45 minutes.<br>Device: Online TMS condition<br>* A single train of pulses (3 pulses at 50Hz, duration 40ms) will be delivered once during a particular time epoch on each trial, followed by a minimum of 6 seconds of no stimulation. No more than 600 pulses will be applied in a single session. Similar to the offline TMS condition, a sham TMS coil will be used to measure baseline performance on the working memory task. In each session (frontal, sham) subjects will perform the working memory task for 45 minutes.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Performance Accuracy (number of correct button presses) on the working memory task | Simple visual stimuli (e.g., dots, colors, lines) will be presented on a computer monitor. The positions of the stimuli must be attended and remembered and decisions about the stimuli and/or their locations must be made. Memory will be probed with a button press or an eye movement towards the remembered locations. | 1 Hour | 
| Length of reaction time used in answering questions | Simple visual stimuli (e.g., dots, colors, lines) will be presented on a computer monitor. The positions of the stimuli must be attended and remembered and decisions about the stimuli and/or their locations must be made. Memory will be probed with a button press or an eye movement towards the remembered locations. | 1 Hour | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Transcranial Magnetic Stimulation