Can a tiny chip implanted in the brain help control dark or depressive thoughts?
For decades, doctors have been placing small devices in people’s brains to help patients with movement disorders like Parkinson’s disease. But increasingly, physicians have been experimenting with using similar neurological implants in patients with cognitive and emotional disorders like depression or post-traumatic stress disorder.
There is strong interest in using these types of neurological prosthetics in returning soldiers who suffer from mental disorders, particularly those who may feel suicidal. A recent study says that veterans from recent wars exhibit significantly higher suicide risk compared with the general population.
The future of implantable wireless devices that are built to treat neurological diseases is taking shape at Massachusetts General Hospital thanks to a $30 million contract with the federal Defense Advanced Research Projects Agency, or DARPA.
BetaBoston caught up with Emad Eskandar, a neurosurgeon at the hospital’s Center for Nervous System Repair. He is working with Darin Dougherty and Alik Widge, among others, on this research. This is a condensed and edited version of that conversation.
Pacemakers for the heart are commonplace; brain implants less so. Tell us more about them.
Neural prosthetics, or brain implants, are deep brain stimulation (DBS) devices that have been around since the 1980s. These are open loop systems, meaning you put this device in a specific region of the brain, turn it on, and leave it in. Over 100,000 people in the United States have implants for Parkinson’s disease, a movement disorder. They make the tremors go away.
But motor control is the simplest function of the brain. To treat disorders connected with cognition and emotion processing, we need closed-loop systems. Smart implants are responsive DBS devices that will monitor neuronal activity. When they detect unusual patterns, they’ll dampen those signals by stimulating the brain with electrical impulses.
What are some conditions you’d use these smart implants for?
Currently, we are working on a military-funded program called SUBNETS to address neuropsychological conditions our vets are coming home with. These include PTSD, depression, traumatic brain injuries, and substance abuse.
So, what signals will the implants record and modify?
There is no PTSD circuit or depression spot in the brain. Besides, an individual with mental illness usually has a constellation of symptoms. So we look for patterns of neuronal activity across specific regions of the brain and map them to outward expression or behavior. Then, we can therapeutically modify the signals, so they are within a normal range, which makes undesirable symptoms go away.
One year into the program, how far along are you?
Working with the engineers at the Draper Laboratory in Kendall Square, we’ve built a prototype out of standard implant material. It’s about the size of a matchbox, weighs 50 grams or so, and has a hub-and-spoke design. The hub, with the microprocessor and a battery rechargeable through the skin, will sit flush against the scalp. There are five satellites, each with an electrode to access and modulate activity in a specific area of the brain. A base station communicates with the implant telemetrically. Physicians will be able to see data from the device right in their office.
Now that the prototype is ready, what challenges remain?
The decoding, figuring out that tight coupling between the neural signature and behavior, which we are trying to address, is the toughest part. For this, we need lots of data from lots of neurons in human beings in a wakeful state. At Mass General, we have some of the country’s most experienced neurosurgeons and psychiatrists who see multiple cases of interest every month. Trained clinicians collect the volumes of data needed for this research.
Next, we need controls. Groups from MIT, Boston University, and Draper Lab will program the implant. The algorithms have to be extremely efficient. They must fit in this device, which has less power than an iPhone, but they must operate around the clock in a living brain, measuring signals and intervening in real time. As a team, we have to find the right way to make trade-offs between space and function.
When will the implant be ready for clinical trials? Who will get them?
The goal is to have this ready for clinical trial in the next three or four years. It is for those who don’t respond well to conventional treatments like medication and psychotherapy. Most certainly, it will not be the first-line treatment for anyone. Most likely, the first candidate will be a vet before it is rolled to civilians with these target illnesses.
The brain is an electrochemical organ that can respond to both electricity and meds, so instead of prescribing milligrams of a substance, we can now prescribe milliamps for specific regions. The therapy gets right to the target. The downside is, of course, you have to undergo neurosurgery to get the implant.
The implants have the potential to help previously untreatable patients. What are other exciting aspects of this research?
One of the thrilling things is the extent to which many disciplines are coming together to solve the biggest public health problem of the age. We are building assistive tech, something that helps people help themselves. It will enable patients to regulate their own emotions and behavior.
Speaking as a scientist, this implant can give us an understanding of mental illness that has never been possible before. Previously, we could see the brain activity of someone with mental illness as they lay in a scanner — which rumbles like a washing machine — or in a quiet room with no distractions at all. Neither situation is natural. With this innovation, we can record a person’s neuronal signals in their home environment.
We could learn something totally new about how our brains work.