Researchers are developing a device that combines electrical brain stimulation with EEG recording, opening potential new paths for treating neurological disorders.
The device, under development at the U.S. Department of Energy’s SLAC National Accelerator Laboratory and Stanford University, could help bring back lost brain function by measuring how the brain responds to therapies that stimulate it with electric current. The approach could selectively switch certain brain activities on and off, according to Anthony Norcia, the Stanford psychology professor who initiated the project.
The impulses sent to the brain through electrodes attached to the scalp are about 1 million times stronger than the brain’s neural response. To detect the much fainter brain response, scientists previously had to monitor brain waves and behavioral response in separate sessions before and after stimulation. The new device measures brain waves at practically the same time that the stimulus is applied, potentially establishing a much better link between the two than when neurostimulation via electrodes are placed on the scalp.
“The device works similar to radar, which sends out electromagnetic waves and passively listens for the weaker reflected waves,” said SLAC senior scientist Christopher Kenney in an agency publication. “Here, we send electrical pulses into the head via the electrodes of an EEG monitoring system, and in the time between those strong pulses we use the same electrodes to pick up the much weaker electrical signals from inside the head.”
Anything that interrupts the network of neurons in the brain, such as abnormal brain development or a stroke, can cause severe disorders, including epilepsy, depression, anxiety, visual impairment, chronic pain and paralysis. Stimulating brain tissue alters the way neurons fire and helps the brain form neural connections.
Norcia’s group develops models that describe how electrical activity from the brain’s visual centers radiates to the scalp, where it can be picked up and measured by an EEG. They also develop models for delivering electrical pulses to specific locations in the brain, where they alter brain function associated with vision. The researchers are applying the method to visual impairment conditions such as amblyopia (lazy eye) and strabismus (crossed eyes), and on better understanding phenomena like binocular rivalry, which describes the fact that when presented with two different images at the same time, we can only be aware of one at a time.
The researchers paired the electronics board of a conventional EEG monitor with one they built that delivers electric stimuli generated with 9-volt batteries and successfully tested the device on themselves. More work needs to be done before studies on a larger group of people can begin. For example, future versions of the device will have more electrodes and will provide more control over the way the pulses are delivered.
“Right now, we can basically switch stimuli on and off and set their intensities and durations,” says SLAC’s Jeff Olsen, an electrical engineer on the project. “In the next generation, we’ll be able to program the device, which will let us choose different types of signal shapes and synchronize electrical signals with other external triggers, such as visual stimulation.”
“In the long run, we would like to develop a device on a chip,” added Kenney. That would make neurostimulation available to patients wherever they go.
Other collaborators involved in this project include Stephen Boyd, chair of Stanford’s Department of Electrical Engineering, and Nolan Williams, clinical assistant professor of psychiatry and behavioral sciences at Stanford.