Researchers at University of Southern California at Los Angeles (USC) Viterbi School of Engineering and Wake Forest Baptist Medical Center in Winston-Salem, North Carolina have developed a brain prosthesis designed to help individuals suffering from memory loss associated with Alzheimer’s Disease (AD) and other forms of dementia form new memories, even when the memory center of the brain, called the hippocampus, is damaged.
Worldwide, nearly 44 million people have Alzheimer’s Disease or a related form of dementia, the global cost of which is estimated at $605 billion annually, equivalent to 1 percent of the entire world’s gross domestic product
The scientists report that their prosthesis, which interfaces via a small array of electrodes implanted into the brain, has performed well in laboratory testing in animals and is currently being evaluated in human patients.
Designed originally at USC and tested at Wake Forest Baptist, the device builds on decades of research by Viterbi biomedical engineer Ted Berger, and relies on a new algorithm created by Dong Song, both of the USC Viterbi School of Engineering.
The development also builds on more than a decade of collaboration with Sam Deadwyler and Robert Hampson of the Wake Forest Baptist Department of Physiology & Pharmacology, who have collected the neural data used to construct the models and algorithms.
The implant, which builds on decades of research, has performed well in mice studies and is now being evaluated in human epilepsy patients. The research team from USC and Wake Forest Baptist announced their results on August 27 at the 37th Annual International Conference of the IEEE Engineering in Medicine and Biology Society that was held at MiCo – Milano Conference Center – in Milan, Italy, August 25-29 2015.
For more than three decades, Ted Berger and his colleagues (Vasilis Marmarelis, John Granacki, and Armand Tanguay) have been pursuing an extraordinary vision: silicon chips that can speak to living brain tissue in the brains own electronic language, chips that might someday be used to repair damaged or diseased brain tissue.
Dr. Berger is now within sight of his goal. With a living slice of brain from a rat he has demonstrated systems that are half-silicon, half brain tissue, which respond exactly as brain tissue does. From the point of view of function, there is no way to tell where the brain part ends and the silicon part begins. Dr.Berger, who is also associated with the Biomimetic Microelectronic Systems (BMES), Biomedical Simulations Resource (BMSR), and Center for Neural Engineering (CNE) labs, is confident that within two years his team will have chips implanted into the brains of rats, working as part of these brains to replace lost memory function, and In 10 to 15 years chips based on this technology may be ready for implant in humans.
The device includes a small array of electrodes which can — it is hoped — replicate the function of the hippocampus in memory formation in a damaged or diseased brain. New research using electrodes in people with epilepsy has been able to model the activity of the human hippocampus.
“Although this sounds like the stuff of science fiction stories, the researchers are addressing a major problem for people with Alzheimer’s disease and other forms of dementia – the ability to lay down new memories,” comments Dr. Clare Walton, Research Manager at the U.K. Alzheimer’s Society in a release, “The practical upshot of this is that people may have clear memories of events from their childhood but can’t remember the details of what took place yesterday.”
“The hippocampus is vital for remembering new events, people and places,” Dr. Walton continues, “and it’s one of the first parts of the brain to be damaged in Alzheimer’s disease. In theory this device has the potential to help people to form new memories even when their hippocampus is damaged.
“A prosthetic memory device is a very exciting prospect, but it has taken decades of research to get this far and there are still many unknowns that need to be worked out by the scientists. It’s encouraging to see these cutting edge technologies being applied to help people affected by memory loss, but this isn’t something that people with dementia can expect to be readily available in the next decade.
Dr. Walton observes: “If this device is developed further and successfully tested in humans, it could prove to be an effective treatment for some of the symptoms of dementia, however it will not cure or slow down the progression of the condition.”
When the brain receives the sensory input, it creates a memory in the form of a complex electrical signal that travels through multiple regions of the hippocampus, the brain’s memory center. At each region, the signal is re-encoded until it reaches the final region as a wholly different signal that is sent off for long-term storage.
However, if there’s damage at any region that prevents this translation, there is possibility that long-term memory will not be formed, which is why an individual with hippocampal damage (for example, due to Alzheimer’s disease) can recall events from a long time ago — things that were already translated into long-term memories before the brain damage occurred — but will have difficulty forming new long-term memories.
USC’s Drs. Song and Berger have found a way to accurately mimic how a memory is translated from short-term memory into long-term memory, using data obtained by Wake Forest Baptist’s Drs. Deadwyler and Hampson, first from animals, and then from humans. Their prosthesis is designed to bypass a damaged hippocampal section and provide the next region with the correctly translated memory, despite the fact that there is currently no way of reading a memory just by looking at its electrical signal. “It’s like being able to translate from Spanish to French without being able to understand either language,” Dr. Berger explains.
The prosthesis’s effectiveness was tested by the USC and Wake Forest Baptist teams with the permission of patients who had electrodes implanted in their hippocampi to treat chronic seizures. Drs. Hampson and Deadwyler could read the electrical signals created during memory formation at two regions of the hippocampus, then sent that information to Drs. Song and Berger to construct the model. The team then fed those signals into the model and read how the signals generated from the first region of the hippocampus were translated into signals generated by the second region of the hippocampus. In hundreds of trials conducted with nine patients, the algorithm accurately predicted how the signals would be translated with about 90 percent accuracy.
“Being able to predict neural signals with the USC model suggests that it can be used to design a device to support or replace the function of a damaged part of the brain,” Dr. Hampson observes.
The research team will next attempt to send the translated signal back into the brain of a patient with damage at one of the regions in order to try to bypass the damage and enable the formation of an accurate long-term memory.
University of Southern California at Los Angeles (USC) Viterbi School of Engineering
Wake Forest Baptist Medical Center
U.K. Alzheimer’s Society