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MICHELE NORRIS, host:

Doctors at a Canadian hospital have discovered something new about the human brain. They were trying to treat an obese man with the procedure using electrodes called deep brain stimulation, when something remarkable happened. Professor Andres Lozano was one of the doctors involved.

Dr. ANDRES LOZANO (Neurosurgery, Toronto Western Research Institute): As we were introducing the electrodes in the hypothalamus and as we first started to run some currents through the electrode, he was able to recall an event that had occurred 30 years earlier. And so we new immediately that this was something quite extraordinary.

NORRIS: What exactly do you mean by that? Was it a very vivid memory?

Dr. LOZANO: Well, it was as if we had unlocked a memory of an event that had occurred three decades earlier. He reported that he had a sensation of deja vu, a sensation where he was in a park with his friends. He recognized his girlfriend at that epoch. He saw their clothes. He could see the colors. He could hear certain words that they were saying. He could tell it was a sunny day, and so on. And remarkably, as we increase the current, the richness of the experience increased, it became more vivid.

NORRIS: So you did this a second time?

Dr. LOZANO: Well, we stopped stimulating. We moved along. We went back to the same place. And again, as soon as we turned it on at a certain intensity heat, we provoked exactly the same scene, the same memory. We stimulated in several places, and we found that if there was a memory provoked, it was always the same event, the same scene in the hypothalamus.

NORRIS: How important was that scene to that fellow's life? What was so significant about that memory?

Dr. LOZANO: It wasn't particularly a significant memory. He had no control or he could not, you know, change the channels and change to another scene or another event in his life. It was locked.

NORRIS: That ability to unlock that memory using electrical stimulation, what does this tell you about how our brains work?

Dr. LOZANO: Well, it tells us that, you know, we know very little about the circuitry of memory in humans, and it tells us that these circuits can be accessed. We feel like we're driving the activity or turning up the volume quite high with the current, and this is indeed producing a spontaneous recollection of a past event.

NORRIS: What kind of benefit might that provide to patients who have memory disorders?

Dr. LOZANO: Well, we feel that if we can safely reach these circuits in the brain that regulate memory, and as we've shown in this particular one case, that one can drive the activity of these circuits and we may also be able to access these circuits and increase their activity in patients with memory disorders. What we don't know is whether we'll be able to take someone with disease circuits in the brain, as in Alzheimer's disease, and enhance memory under those circumstances, and that's why we're doing a study.

NORRIS: A technical question. You're talking about electrodes that are implanted in the brain even while the patient is awake. How were you able to do that?

Dr. LOZANO: The patients are operated under local anesthesia. And this procedure that we're doing is exactly the same one that we do for Parkinson's disease. And I should let you know that approximately 40,000 humans with Parkinson's disease already have these electrodes in place.

NORRIS: Boy, this sounds like a remarkable moment of accidental discovery for you when you realize what you had done, you could actually control the vividness of that memory. What was that like for you?

Dr. LOZANO: Well, it, it was a eureka moment for us. We knew it was something extraordinary, something totally unanticipated. My personal philosophy in science is that the best discoveries are always serendipitous. And I think this is an example where we were looking for something and didn't find it, but instead, we found something that was interesting, and we pursued it. And we hope that it may lead to a better understanding of how memory works in the brain and how one day we may use this knowledge to improve memory function.

NORRIS: Congratulations to you. Dr. Lozano, thank you very much.

Dr. LOZANO: You're very welcome.

NORRIS: That's Professor Andres Lozano at the Toronto Western Research Institute.

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