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New Implantable Device Can Manipulate and Record Brain Activity

Human tests of an electrode implanted deep into the brain could one day lead to smart, self-regulating implants.

A new brain implant that can record neural activity while it simultaneously delivers electric current has been implanted into a patient for the first time.

The new device from Medtronic, a Minneapolis-based medical device company, can also adjust its electrical output in response to the changing conditions of the brain. This automated control could one day improve deep-brain stimulation treatment and even enable doctors to use the device to treat more conditions, say experts.

More than 100,000 patients have received deep brain stimulation for treating movement problems associated with Parkinson’s and other movement disorders. The treatment is also being explored for use with patients with epilepsy, severe depression, and other brain disorders. The pacemaker-like devices deliver electric shocks to the brain to correct or prevent disruptive neuronal activity associated with symptoms of these conditions. With current devices, the pattern and strength of the electrical pulses must be preset by a specialist and then adjusted to meet a patient’s needs. The new device from Medtronic and others currently in development could change that.

“Everything that is on the market today is a one-way stimulator,” says Joseph Neimat, a neurosurgeon at Vanderbilt University Medical Center who specializes in deep brain stimulation implants. “The devices don’t record or respond to a patient,” he says. “What would be better would be to have a system that could anticipate or read a patient’s state and respond with an appropriate stimulus.”

The patient trials launched on Wednesday will test whether Medtronic’s new device can safely record electrical activity in a patient’s brain while also delivering electric currents. These tests will explore how patients’ brains respond to deep brain stimulation therapy. However, according to lab animal tests, the device is capable of not only sensing the electrical activity of the brain tissue it sits in, but of also changing its output accordingly.

The ultimate goal for the device is to provide responsive therapy by detecting brain signals and tweaking its output accordingly, says Lothar Krinke, general manager of the company’s deep brain stimulation division. Other companies have developed smart stimulators for treating epilepsy patients. NeuroPace, for example, is developing a brain implant that monitors the brain for an oncoming seizure, at which point it delivers shocks to block the attack (see “Zapping Seizures Away”). Medtronic’s new implant could be used to detect brain activity related to Parkinson’s, tremor, obsessive compulsive, and other conditions, in addition to epilepsy.

“This is the start of a new way of doing medicine,” says Robert Fisher, a neurologist who heads the Stanford Epilepsy Center. Instead of implanting a stimulator that changes electrical activity without responding to the current state of the brain, “now we can consider a more sophisticated process where you look at what’s going on in the brain and then stimulate accordingly,” he says. Many neurological diseases are episodic—that is, the symptoms come and go or fluctuate in intensity, says Fisher. If new devices can detect and interpret electrical signals that correlate with symptoms and then respond with electrical pulses to alter brain function, doctors could have a completely new way of treating those disorders, he says.  

The new information that could come from the recording and stimulating implant could help researchers better understand brain disorders. Depression, for example, is a heterogeneous condition. Patients may have deficits in different brain regions or circuits, and for now, there isn’t a really good way to study these differences, says Ron Salomon, a psychiatrist at Vanderbilt University, whose research group studies novel treatments for depression, including deep brain stimulation. “Being able to objectively determine changes in neural activity in different patients may give us some tools for subdividing depression on a neurobiological basis rather than based on symptoms and signs observed from the outside,” he says.

Moreover, a device that can detect disruptive brain activity, interpret it, and use electric shocks to correct it could allow doctors to treat more conditions. “The application has been limited to diseases where a simple stimulation will produce an effect,” Neimat says. Responsive devices “may not only improve the way we currently treat disease but open the door for a whole host of other diseases that can be treated.”