The study is investigating working memory brain states by using transcranial magnetic stimulation (TMS) in combination with functional magnetic resonance imaging (fMRI). The study uses a novel, individualized targeting approach for TMS based on each subject's individual multi-modal fMRI data. The individualized target will be stimulated in a TMS/ fMRI imaging session to investigate working memory states and optimal stimulation frequencies.
Prior to any study visits, all subjects will be pre-screened through a REDCap online self-report screening REDCap. The study involves 11 study visits. The first study visit will consist of a consenting and extended screening visit. All participants will have the opportunity to ask questions before signing the electronic consent form. We will complete a semi-structured clinical interview and will demonstrate TMS to ensure the participant is comfortable with all study procedures. This visit will be completed both remote and in-person. The second study visit will involve a 1-hour MRI scan. During the scan, the participant will complete multiple computerized tasks. The MRI scan will include both structural and functional scans, and those scans will be used to localize the stimulation target for the subsequent sessions. The third study visit will be a 2-hour TMS/fMRI session, and the participant will engage in behavioral tasks while interleaved rTMS rounds are delivered at different excitatory frequencies (frequency range: 2Hz-20Hz). This scan will be used to determine the optimal stimulation frequency for the individual participant. The fourth, fifth, and sixth study visits will involve neuromodulation with either the optimized frequency or the frequency least successful in moving a participants brain state, as determined from the third study visit. Each subject will receive \~3000 pulses in each session, including the pulses from the motor threshold determination. We will determine the stimulation amplitude by using the Stokes equation, which accounts for differences in cortical distance from the site relative to motor cortex (where the motor threshold is found). The seventh study visit will involve a 1-hour TMS/fMRI session while the participant is engaging in a behavioral task. This visit is designed to examine brain and behavioral changes after the first round of neuromodulation. The seventh and the eighth visit will be scheduled at least one week apart. The eighth, ninth, and tenth study visits will mirror the fourth, fifth, and sixth study visits and will involve neuromodulation with either the optimized or least-optimized individual frequency. The order of optimized and least-optimized frequencies will be counterbalanced across participants between Visit 4-6 and Visit 8-10 (i.e., half of the participants will receive stimulations of the two frequencies in one order, and the other half will receive stimulations of the two frequencies in the reverse order). The eleventh visit will mirror the seventh visit and will examine brain and behavioral changes after the second round of neuromodulation.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
BASIC_SCIENCE
Masking
SINGLE
Enrollment
27
Participants undergo resting-state and task-based fMRI to identify individualized transcranial magnetic stimulation (TMS) targets and determine optimal and sub-optimal stimulation frequencies. Additional fMRI scans are performed after each neuromodulation phase to assess changes following three days of stimulation at the optimal and sub-optimal frequencies.
Participants first receive multiple rTMS frequencies during an fMRI scan to assess brain responses and determine individualized optimal and sub-optimal stimulation frequencies. They then complete two neuromodulation intervention periods, receiving rTMS at the identified optimal and sub-optimal frequencies. Each frequency is administered over three consecutive days, with the order of conditions randomized and counterbalanced.
University of Pennsylvania
Philadelphia, Pennsylvania, United States
Reaction Time Changes During N-Back Task in Responses to Different TMS Frequencies
During the TMS/fMRI scan, participants perform a working memory task (N-back). To evaluate how different repetitive TMS frequencies (5, 10, and 20 Hz) impact reaction time during N-back task, each rTMS train is followed by a block of the N-back task. A decoder identifies one frequency as optimal frequency and another as suboptimal frequency. Reaction Time during optimal, suboptimal, and no stimulation condition is assessed by taking average of reaction time on accurate trials with faster reaction times indicating better performance.
Time frame: Single visit (~2 hours)
Accuracy Changes During N-Back Task in Responses to Different TMS Frequencies
During the TMS/fMRI scan, participants perform a working memory task (N-back). To evaluate how different repetitive TMS frequencies (5, 10, and 20 Hz) impact accuracy during N-back task, each rTMS train is followed by a block of the N-back task. A decoder identifies one frequency as optimal frequency and another as suboptimal frequency. Accuracy during optimal, suboptimal, and no stimulation condition is assessed by taking average of all the trials with better accuracy indicating better performance.
Time frame: Single visit (~2 hours)
Reaction Time Changes in the Delayed Matching to Sample Task Following Optimal vs. Suboptimal rTMS Stimulation
Each subject completes two 3-day neuromodulation sessions, one using their 'optimal' rTMS frequency, and the other using their 'suboptimal' rTMS frequency, as determined by their TMS/fMRI visit. After each neuromodulation session, subjects complete a working memory task (Delayed Match to Sample). The delay period reflects how long participants can retain the information in working memory. Common delay periods used in research, including our study, are 0 seconds, 4 seconds, and 12 seconds.The outcome measure shows the reaction time for each of these variables.
Time frame: Up to 1 month
Accuracy Changes in the Delayed Matching to Sample Task Following Optimal vs. Suboptimal rTMS Stimulation
Each subject completes two 3-day neuromodulation sessions, one using their 'optimal' rTMS frequency, and the other using their 'suboptimal' rTMS frequency, as determined by their TMS/fMRI visit. After each neuromodulation session, subjects complete a working memory task (Delayed Match to Sample). The delay period reflects how long participants can retain the information in working memory. Common delay periods used in research, including our study, are 0 seconds, 4 seconds, and 12 seconds.The outcome measure shows the accuracy for each of these variables.
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Time frame: Up to 1 month
Reaction Time Changes in the Reaction Time Index Task Following Optimal vs. Suboptimal rTMS Stimulation
Each subject completes two 3-day neuromodulation sessions, one using their 'optimal' rTMS frequency, and the other using their 'suboptimal' rTMS frequency, as determined by their TMS/fMRI visit. After each neuromodulation session, subjects complete a reaction time index task that acted as a control task. The outcome measure shows the reaction time.
Time frame: Up to 1 month
Movement Time Changes in the Reaction Time Index Task Following Optimal vs. Suboptimal rTMS Stimulation
Each subject completes two 3-day neuromodulation sessions, one using their 'optimal' rTMS frequency, and the other using their 'suboptimal' rTMS frequency, as determined by their TMS/fMRI visit. After each neuromodulation session, subjects complete a reaction time index task that acted as a control task. The outcome measure shows the movement time.
Time frame: Up to 1 month