Neuromodulation of Mood Switch Circuitry in Bipolar Disorder

This study is exploring a new approach to treating depression in people with bipolar disorder (BD). Investigators are testing whether a non-invasive form of brain stimulation can help us understand depressed-to-euthymic mood shifts and their related brain circuits in BD. Investigators in this study will use a technique called repetitive transcranial magnetic stimulation, or rTMS. It uses non-invasive magnetic pulses delivered to the scalp to stimulate specific areas of the brain. rTMS is already used to treat depression, and investigators are now studying whether it can be made even more effective for people with bipolar disorder by precisely targeting an individualized brain region for each participant. Participants in this study will receive two courses of rTMS, one active and one placebo (called "sham"), in a randomized order so investigators can directly compare the effects. Before treatment, investigators will use brain scans (MRI) to create a personalized map of each participant's brain activity. This lets investigators identify the exact stimulation target most likely to influence the brain circuits involved in BD mood shifts. Investigators will track mood symptoms closely throughout the study to measure what changes. Investigators believe that depression in BD is partly driven by disrupted communication between two brain regions involved in processing what feels important or rewarding. Investigators want to find out whether rTMS can restore that communication and whether doing so leads to measurable improvements in depression.