The purpose of this pilot study is to evaluate safety and efficacy of a novel treatment, low intensity focused ultrasound pulsation (LIFUP) for treatment resistant depression (TRD). The initial visit will involve consent and an MRI scan, followed by two more treatment visits over the course of one week. During the first treatment day, participants will receive either focused ultrasound or sham stimulation. On the second treatment day, all participants will receive focused ultrasound. Response and potential side effects will be monitored pre- and post- each treatment along with one week and one month follow-up assessments.

Currently rTMS for treating depression is delivered without knowing whether the TMS pulses are synchronized with the patient's brain rhythms. We will study healthy and depressed adults with TMS inside of the MRI scanner or outside of the MRI scanner using optics, and test whether it matters precisely timing the TMS pulses with EEG.

Apathy is a common set of symptoms seen in many people following a stroke. Apathy occurs when a person has lost motivation, becomes withdrawn, and stops doing things that used to be important to them. Apathy has a large negative impact on a person's quality of life, and can also have a large impact the people who take care of individuals with apathy. There are currently no FDA-approved treatments to help with apathy, and other services like therapy may be difficult to access for people who have had a stroke. To address this problem, we are conducting a study to find out if a form of treatment called repetitive transcranial magnetic stimulation (rTMS) can be safe and helpful for people struggling with apathy after a stroke. Our study will apply a new form of rTMS which can be delivered quickly to a part of the brain called the medial prefrontal cortex (mPFC). Our study will help establish whether this treatment is safe, comfortable, and effective for people with apathy after a stroke, and will help researchers develop new forms of treatment.

The purpose of this study is to use magnetic resonance imaging (MRI) to take images of a participant's brain, and then apply an investigational way of processing the image, called Individualized Network-based Single-frame Coactivation Pattern Estimation ("INSCAPE") to measure participant's brain activity. This method uses a computer program to understand which parts of the brain communicate with each other and creates a map of the brain areas that are connected.

Participants being recruited in this study will include people planning to receive Transcranial Magnetic Stimulation ("TMS") for Major Depressive Disorder ("MDD"). Healthy participants are also being recruited. Images taken of depressed participants' brains will be compared to images of non-depressed participants' brains. Participation in this study will require three visits in which you will undergo MRI scans. The interval between each visits is about 3 weeks. Depressed participants will also complete mood assessments at several different intervals while they are receiving TMS for depression.

During each visit, MRI scans will require about 30 minutes of time in total. During the MRI scan, participants will need to stay still, relax, and keep eyes open in the scanner.