Posted on Jan 30, 2005

Ted Berger '72 has found himself in the surprising company of General Tommy Franks and actor Jessica Lange this year, as one of AARP's “2004 Action Heroes” and a recipient of its 2004 Impact Award. To millions of readers, the University of Southern California biomedical engineer is known as “a person who has had the courage to change our world.”

Berger is leading a team of scientists in designing and building a brain implant computer chip that could restore mental function in brains that have been damaged by stroke, epilepsy, or neurodegenerative diseases such as Alzheimer's. His hope is that such chips will perform functions once carried out by neurons that have been damaged or destroyed. Berger, who holds the David Packard Chair at the Viterbi School of Engineering at the University of Southern California, anticipates testing the chip in live rats within the next few years, and in humans in ten to fifteen years.

Berger, who has a Ph.D. in physiological psychology from Harvard, directs the interdisciplinary Center for Neural Engineering and is one of the leaders of the newly established National Science Foundation Engineering Research Center at USC. The NSF center focuses on developing implantable microelectronics that mimic biological functions of the brain (called “biomimetics”) for use as neural prosthetics.

One of the team members is his wife, Roberta Diaz Brinton, professor of molecular pharmacology at the USC School of Pharmacy. She is also one of Berger's greatest boosters: “Ted's work on neural prosthetics has received national and international attention at the frontier of biomedical engineering and neuroscience.” In fact, his work has appeared in The Economist; EE Times; New Scientist; Popular Science; Technology Review; Business 2.0; Der Spiegel and Discover, as well as AARP. The research has also been reported on CNN, 48 Hours, the CBS Evening News, and the Discovery Channel.

Hippocampus a kind of way-station

The cashew-shaped brain tissue that makes up the hippocampus plays a crucial role in learning and memory. The hippocampus is a kind of way-station where experiences are initially processed, assessed, and sorted. After a few days, those experiences that are deemed important move on to long-term memory; the rest are destined for the brain's dump heap. (When the hippocampus is removed-to treat epilepsy, for example-the patient loses the ability to form new long-term memories, but retains memories formed before the surgery.)

Especially intriguing to Ted Berger was the hippocampus' role in generating three-dimensional mental images of spatial positioning. Thus, a rat with a damaged hippocampus can't find its way around a maze. Neurologists believe the 20- to 50-percent loss in hippocampal volume associated with Alzheimer's disease may explain why AD patients are prone to getting lost.

Berger pondered how to mimic what neurons did, even if he didn't fully understand how they did it. A neuron processes inputs into outputs, he reasoned. How much of the “how” did he really need to know? A basketball player, after all, doesn't need to be a rocket scientist to launch the ball on a perfect trajectory through the hoop. So why should a neuroscientist need to understand every nuance of the brain before attempting a slam-dunk?

He and his colleagues bombarded live rat hippocampal neurons with all possible combinations of electrical impulses, and recording the emerging electrical signals. Studying the rat hippocampus made sense: It's essentially the same as a human hippocampus, and cells excised from rat brains retain much of their structure and can be kept alive with nutrients for a day or more.

The researchers traced how one neuron receives a sequence of digital-like pulses from another neuron, and how it transforms that signal into a new pattern of pulses, and sends that along to a third neuron.

Nerve cells communicate with one another using simple pulse signals, whose meaning is determined by the timing, or rhythm, of the pulses. By exposing the experimental cells to every possible set of timings (thousands), the team was able to collect the complete cell “vocabulary.”

Connecting with living brain tissue

The research team's biggest remaining hurdle was figuring out how to connect to living brain tissue-or “wetware,” but they have had a major breakthrough, successfully establishing two-way communication between living nerve cells (in brain tissue culture) and a silicon chip designed to function as the cells do. In other words, the chip can “listen” to brain signals, compute and answer, and then speak to living brain tissue, in brain tissue language, and the brain tissue responds. The demonstration solved three major problems: cracking the code; creating a silicon chip that speaks the code; and getting the chip to speak to living tissue. The next step will involve moving from brain slices in tissue culture to living brains in intact organisms.

In the process of doing this work, Berger has become a vocal advocate for interdisciplinary research. Says Brinton, “There is a grander vision, and to realize that grander vision requires a team of people to work together. Instead of each of us making bricks, we are all building the pyramid together. I expect to see the implant work. We will certainly see the application of this technology within our careers.”

Adds Berger, “We are on the brink of stretching the capabilities of the human race.”

Brains and brawn

Berger, the invited featured speaker at the Founders Day convocation this year, graduated summa cum laude from Union after majoring in math and psychology and taking the Catlin Prize for best scholastic record. He went on to Harvard to study the relationships between brain function and behavior. Soon after arriving, he and another graduate student made a discovery on the brain basis of classical conditioning; their paper was published in Science. By the time he finished graduate school, Berger had already published ten papers and had won the James McKeen Cattell Award from the New York Academy of Sciences for his thesis research.

He holds fond memories of his Union days. Classes he liked best were taught by Bob Sharlet (Political Science), Charles Huntley '34 (Psychology), and Willard Roth (Biology).

How did Union contribute to his success? “The vast majority of Union courses required written exams and reports-you learned how to write. All were very problem oriented: You had to conceptualize a problem, formulate a solution, research your solution, and evaluate it. This was incredibly exciting. Professors were really good at selecting key problems in society and science; they all thought very deeply about their field and were able to distill key problems in that area. And they presented the problems in such a way that you became a partner in finding a solution.”

What did he find most fun about Union? “Everything!” he concludes. “Everyone was very serious about their work and also about having fun. That was key-there was equal investment-we worked hard and played hard. It was balanced-a healthy environment.”

Berger remembers waiting on tables in the cafeteria and at his fraternity, Beta Theta Pi, to pay for meals. “I was a resident adviser one year to cover rooming expenses. I also had the campus concession for The New York Times for two years. I had to get up at 5:30 a.m. seven days a week-rain, sleet, snow, or shine-to deliver the Times to multi-story dorms. This was especially onerous on Sundays, when I had to haul a sack of the Sunday Times which hung around my neck, as I walked up three flights multiple times. Nearly everyone subscribed-which says a lot for the brains at Union-and the brawn that delivered it!”

An ear for crime

Ted Berger's pioneering brain cell research has led directly to a patented system now being rolled out to stem gun violence on the streets.

The new microphone surveillance system uses his insights to recognize-instantly, and with high accuracy-the sound of a gunshot, within a two-block radius. It can then locate, precisely, where the shot was fired; turn an attached camera to center the shooter in the camera viewfinder, and make a 911 call to a central police station. The police can then use the camera to track the shooter and dispatch officers to the scene.

Chicago is installing these devices in high-crime neighborhoods. And Los Angeles is soliciting community involvement in a pilot test.

Algorithms devised by Berger are at the heart of the “SENTRI” system built by Safety Dynamics, a company in which Berger is chief scientist.

SENTRI uses acoustic recognizers, posted on utility poles or other listening posts, which are tuned to certain specific warning sounds.

SENTRI stands for “Smart Sensor Enabled Neural Threat Recognition and Identification.” “Neural” refers to Berger's work, based on analysis of the “language” that nerve cells, or neurons, use to convey information, and specifically on his modeling of the way the brain forms memories of sounds.

Neurons' only way of distinguishing signals is to fire repeatedly in different temporal patterns. “The time difference between pulses carries the information,” Berger says-“a coding completely unlike that used by computers, which are collections of ones and zeros.”

Working with computer specialists, Berger has created neural-like computer systems that can model the neural time coding and make distinctions the way nerves do.

Four years ago, he and a colleague used the technique to demonstrate the first speech recognition system that could pick words out of ambient noise as well as humans can. Continuing work on speech recognition applications is very time consuming because the system has to learn each individual word.

“But for alarm signals,” says Berger, “you start with a relatively small number of sounds-gunshots, or diesel engines for border patrol crossings, or oil pipeline thieves, or chainsaws to listen for outlaw loggers. This vocabulary is quite manageable.”

Machine sounds are the only ones in SENTRI's vocabulary. It cannot eavesdrop on conversations.