Can battery-operated brain implants treat bipolar disorder?

Depression treatment is not an exact science. In fact, about 30% of people diagnosed with major depressive disorder discover that their disease is treatment resistant, meaning they experience lingering depression symptoms despite multiple treatment approaches. 

At the University of Minnesota Medical School, a team of researchers is developing a new approach to fighting treatment-resistant depression in patients with severe bipolar disorder. Their novel work involves implanting tiny “paddles” on patients’ brains that can be activated to produce a range of psychological reactions and ultimately to lift symptoms of the disorder. 

The technical term is a mouthful: Personalized and Adaptive Cortical Electrostimulation, or PACE. 

In October 2025, the PACE team, led by Dr. Ziad Nahas at the medical school’s department of psychiatry and behavioral sciences, won a $4.4 million grant to further their work. If successful, the lengthy, complicated project could result in lasting treatment. 

I recently spoke with Dr. Nahas about bipolar disorder and the PACE approach. This interview has been edited for length and clarity.

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MinnPost: How does PACE work? 

Ziad Nahas: There are many ways to stimulate the surface of the brain, or the cortex. We can do it with transcranial magnetic stimulation (TMS) or transcranial direct-current stimulation, and we have been doing it for decades with electroconvulsive therapy. PACE is essentially performing direct cortical stimulation, where through a neurosurgical procedure we implant paddles that sit on the surface of the brain. These paddles are connected to batteries that are implanted typically in the upper chest area, below the collarbone. 

We target very specific regions of the brain that we know are critical for mood regulation. Unlike with TMS, we often see acute psychological responses from this approach — like feeling happy, less anxious in the moment — which tells us that we are indeed modulating relevant brain networks. We proceed by doing a series of “tunings” to select the optimal parameters that seem to work best for a particular patient. We use them to treat the patient over a longer period of time with the expectation that we’ll observe a gradual improvement in depressive symptoms. 

MP: How does the testing work?

ZN: We identify the placement of the paddles based on a functional MRI. 

[Once the paddles are in place], then comes the actual testing where we stimulate the brain and start looking for those psychological responses and underlying brain activity. Each month, patients toggle through different settings at home. Then they come back to the lab and we take their information. We repeat this process for six months and eventually we identify the best parameters that seem to have helped the patient the most. Those are the ones that we would then lock for the following six months to see if they really are going to make a significant dent in the patient’s depression. 

MP: How invasive is the procedure?

ZN: It’s a brain surgery, but we lay the paddles on the surface of the brain rather than taking an electrode through brain tissue and risking damage. 

MP: It sounds very serious. Your patients must be feeling like they are in a desperate situation in order to try PACE. 

ZN: I try not to use the word “desperate” because it feels coercive, but these are clearly patients who have had a long-standing and disabling depression that did not respond to multiple evidence-based antidepressant treatments or psychotherapy.

MP: How many people have participated in PACE so far, and how many participants do you need? 

ZN: At the University of Minnesota, we have implanted three participants and are in the process of considering our fourth.

With the $4.4. million, we anticipate being able to image 25 bipolar patients, out of whom five will actually receive PACE. 

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MP: What have been your results? 

ZN: One patient has been in remission for three years. Previously, he suffered from depression for 30 years with two very serious suicide attempts. The second person is only six to seven months into her treatment and she is roughly 50% improved. The third patient has demonstrated acute psychological responses to our stimulation. The surgery went smoothly, but she’s still too early on in the process to gauge its success. 

The challenge is to scale our research and be able to demonstrate in a large, double-blind placebo study that our approach is clinically meaningful. We are not at that stage yet.

MP: If you had a close friend or relative who struggled with bipolar depression, would you suggest they use PACE?

ZN: I would, but I’d urge them — the same that I would any of my patients — to be cautious, to discuss it with their provider not only for an independent opinion but also to maintain that relationship, learn all about the risks and manage expectations. 

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