Next year, medical researchers will test in patients a one-of-a-kind brain implant that can sense electrical activity in the brain while simultaneously emitting electric pulses, says device developer Medtronic.

Deep-brain stimulators are mainly used to regulate the movement problems associated with Parkinson’s and other diseases, but they are also used in Europe and Canada to treat epilepsy and are being used experimentally to treat severe depression and obsessive-compulsive disorder. But doctors must use trial and error to determine the best parameters for the electrical stimulation programmed into each patient’s chip.

The smarter brain stimulator is an improved version of Medtronic’s existing deep-brain stimulator device, which has already been implanted in more than 80,000 people around the world. Medtronic has added an extra chip so that it can detect electrical activity and respond automatically to changes in the brain.

“If you are in the brain already, you might as well take advantage of the fact that you can listen in,” says Lothar Krinke, who manages the Deep Brain Stimulation division at Medtronic. This means the device could respond automatically when a patient’s symptoms grow stronger, or could turn itself off when the patient is asleep. “We really only want to deliver the electricity when it is needed,” says Krinke. The company has tested the device in lab animals and says that next year outside teams of researchers will test it in patients with diseases such as Parkinson’s and epilepsy.

Although invasive, these sorts of neural implants are vital for patients who otherwise fail to respond to medication, says Dwayne Godwin, a neuroscientist who studies epilepsy at Wake Forest School of Medicine. “Not every patient responds in the same way to treatment,” he says. “As these devices become better established, we will get a better understanding of which are better for certain types of disorders.”

Other brain implants have the ability to sense electrical activity and stimulate the brain, just not at the same time. For example, NeuroPace, a medical-device startup in Mountain View, California, has developed a brain implant that spends most of its time monitoring the brain for an oncoming seizure (see “Zapping Seizures Away”). When an impending seizure is detected, the device, which is currently in clinical trials, delivers imperceptible pacemaker-like shocks that prevent the disruptive activity from spreading and causing a seizure.

A system that can sense and stimulate at the same time could be useful in patients whose disease symptoms fluctuate over time, as is often the case in Parkinson’s patients, says NeuroPace CEO Frank Fischer. “I think it’s a very interesting research tool to be able to look at applications such as movement disorders, where changes may be naturally occurring and a patient could benefit from different levels of stimulation,” he says.

Krinke says adding sensing capability to the deep-brain stimulator could also help determine whether the implant is still functioning properly when a patient’s symptoms worsen, which could either be due to progression of disease or device failure. “The device can self-diagnose whether it is broken,” says Krinke.

Knowing whether a patient’s disease is worsening is more of a challenge, he says, but as researchers continue to use the device to study brain circuits relevant to disease states, eventually the device might become a diagnostic tool. “The future is that we can measure electrical signals that are related to disease progression,” he says.