Neural Effects of Transcranial Magnetic Stimulation Using Concurrent Functional Magnetic Resonance Imaging

The purpose of this study is to examine the neural mechanisms underlying transcranial magnetic stimulation (TMS) using concurrent functional magnetic resonance imaging (fMRI). Research is conducted in both healthy controls (HCs) and patients with high negative affect symptoms, such as depression. Participants will undergo two visits, the first lasting about two hours and the second, scheduled within one week of the first, also lasting about two hours. Approximately half male and half female participants aged 18-65 will be recruited. The aims are to examine (1) whether the acute/transient effect induced by single-pulse TMS is related to the long-term modulatory effect induced by rTMS, and (2) whether any of these effects predict negative affect symptoms, such as depression.

In the first visit, participants will complete several tests to assess their cognitive abilities and emotional states, specifically measuring depression levels. These tests will help explore the relationship between their cognitive/emotional states and brain activity during TMS-fMRI. After the tests, participants will undergo several brain scans to determine the best locations for TMS during the second visit and to measure the strength of connections between different brain regions. During the second visit, participants will undergo three parts of TMS-fMRI scanning. The first part involves applying single-pulse TMS to the dorsolateral prefrontal cortex (DLPFC) and a control area (the vertex) while taking fMRI scans. This helps elucidate how TMS affects deep brain regions related to mood disorders. By comparing brain responses to TMS between healthy controls and patients, researchers can gain important knowledge of whether the neural pathways between stimulated region and these subcortical brain regions are disrupted in patients. The second part includes theta-burst stimulation (TBS) of TMS to the DLPFC, which is a stimulation protocol approved by Food and Drug Administration (FDA). Finally, in the third part, single-pulse TMS is administered again after TBS to see if the TBS has changed the brain's response. Comparing the after-TBS single-pulse TMS-evoked brain responses with before-TBS responses would allow the investigators to track whether the TBS could change the disrupted neural pathways in patients. Investigators will also examine how participants' cognitive/emotional test results and brain connectivity relate to the TMS-evoked brain responses and the effects of TBS. Any potential relationships found can provide insight into the underlying mechanisms of how individual differences in cognitive/emotional functioning and brain connectivity profile might influence or be influenced by brain stimulation, which could ultimately inform personalized approaches to neuromodulation therapies.