Brain targets identified for regulating heartbeat and treating depression

New research from researchers at Brigham and Women's Hospital suggests a common network in the brain linked to slow heart rate and depression. After analyzing data from 14 people without symptoms of depression, the team found that stimulating certain parts of the brain associated with depression using transcranial magnetic stimulation (TMS) also affected heart rate. This suggests that doctors will be able to target these areas without the use of brain scans, which are not always available. The study results were published in Nature Mental Health.

"Our goal was to find a way to use TMS therapy more effectively, correctly calculating the dosage, slowing the heart rate and determining the best place for stimulation on the brain," said senior author of the study, Dr. Shan Siddiqui from the Department of Psychiatry and Brigham Brain Circuit Therapeutic Research Center. Siddiqui said the idea arose during a conference in Croatia, where researchers from the Netherlands were presenting data on the relationship between the heart and brain.

"They showed that not only can TMS temporarily lower heart rate, but that the location of stimulation matters," Siddiqui added, noting that the most exciting part of the study for him is the potential to make this highly targeted depression therapy available to the rest of the world. "We have a lot of technology available here in Boston that can help people manage their symptoms," he said. "But some of these technologies have been difficult to bring to the rest of the world before."

Siddiqui worked with his colleagues at the Brigham and Women's Center for Therapeutic Brain Circuit Research and lead author Eva Dijkstra, MSc, to complete the study. Dijkstra, a PhD candidate, came to the Brigham from the Netherlands to combine their work on heart-brain connectivity with the CBCT team’s work on brain circuits.

The researchers looked at functional MRI scans of 14 people and identified areas in their brains that were thought to be optimal targets for depression treatment based on previous research on connectivity and depression. Each participant was assigned 10 brain areas, both optimal (“connected areas”) and suboptimal for depression treatment. The researchers then looked at what happened to the heart rate when each area was stimulated.

“We wanted to see if there was heart-brain connectivity in the connected areas,” Dijkstra said. "For 12 out of 14 usable datasets, we found that we could pinpoint the region associated with depression with high accuracy simply by measuring heart rate during brain stimulation."

Dijkstra noted that this discovery could help both individualize TMS therapy for depression by choosing a personalized location on the brain for stimulation, and make it more accessible since it would not require an MRI scan beforehand.

Siddiqi added that the results of this study could also be used to develop treatments that could be useful to cardiologists and emergency room physicians in the future.

One limitation of the study is that it was conducted on a small number of people, and the researchers did not stimulate every possible region of the brain.

The team's next goal is to map out the brain regions to stimulate, making heart rate changes more consistent.

Dijkstra's team in the Netherlands is now working on a larger study involving 150 people with major depressive disorders, many of whom have treatment-resistant depression. The data from the study will be analyzed later this year, potentially moving the research closer to clinical use.