[RADIOLAB INTRO]

JAD ABUMRAD: Hey, I'm Jad Abumrad.

ROBERT KRULWICH: And I'm Robert Krulwich.

JAD: This is Radiolab.

ROBERT: The podcast.

JAD: The podcast. So today on Radiolab, we've got a shorty for you, but it's a—it's a goody.

ROBERT: Yep.

JAD: We're gonna introduce you to two different people.

V.S. RAMACHANDRAN: I am V.S. Ramachandran of the University of California, San Diego. I direct the Center for Brain and Cognition there.

CAROL BERMAN: Okay. My name is Dr. Carol Berman. I'm at NYU Medical Center. I'm a psychiatrist.

JAD: So those are our two folks. And they're gonna tell you two different stories.

ROBERT: But really, it's the same story, just two different versions of it in a way.

JAD: That's right. That's right. And we're gonna start with Carol.

CAROL BERMAN: So my patient, who is this 37-year-old patient, comes back to her house and sits next to this man who's wearing a red plaid shirt and trucking boots.

JAD: And this woman looks at this man, doesn't know quite what to make of him.

CAROL BERMAN: I think the jeans she recognized and the boots. And she takes a look at him and says, "Who are you?" And he says to her, "Well, who are you? Come over here and give me a kiss."

JAD: So she leans in a little tentatively, gives him a kiss. But it feels wrong. Everything about this situation to her feels wrong.

CAROL BERMAN: She was thinking this is some strange man who's sitting here in, you know, her husband's clothing. This did not look like her husband to her. And she was wondering what he was doing in her apartment.

ROBERT: Okay. So that is one story. And now we want you to hear a second story. This one comes from Dr. V.S. Ramachandran.

V.S. RAMACHANDRAN: I saw a patient not long ago, was in coma two weeks, came out of the coma. A student on our campus, intelligent, quite articulate, a little bit slowed down, but overall quite intact. But here's the problem. When he looks at his mother, he says, "Doctor, who is this woman? This woman looks exactly like my mother, but she's an imposter."

ROBERT: An imposter?

V.S. RAMACHANDRAN: "She's an imposter. She is some other woman pretending to be my mother."

ROBERT: Now is this person coming into his room his actual mother?

V.S. RAMACHANDRAN: It is his mother. And of course, this is very alarming to the parents. Sometimes it spill—spills over to the father, okay? It's usually somebody very close to you. And he has nothing else wrong with him.

ROBERT: He just doesn't think that his mother is really his mother. 

V.S. RAMACHANDRAN: Yeah.

CAROL BERMAN: This person looked like her husband, but there was something off.

JAD: Like what?

CAROL BERMAN: There was something about him. Some essence.

JAD: Like the feeling you with—have towards someone when you see them?

CAROL BERMAN: Right. The feeling or the essence of the person, the soul of the person isn't in there.

JAD: So turns out that these two people are suffering from the same delusion.

V.S. RAMACHANDRAN: Capgras delusion.

CAROL BERMAN: Pronounced like "Cahp-grah."

ROBERT: C-A-P ...

V.S. RAMACHANDRAN: G-R-A-S. 

JAD: And these kids of Capgras delusion appear sometimes with brain injuries or certain kinds of dementia. Or sometimes just out of the blue. But the result is almost always that you feel like your loved ones have been replaced by imposters. Now still, no one knows the underlying cause, and there are lots of different ways to explain it.

CAROL BERMAN: We explain it psychologically. There might be some negative aspects of the person that you don't want to recognize. Like, maybe my patient, you know, saw some negative things in her husband that she didn't want to recognize. So when the negative aspects came in, he had to be a completely different person for her to—because she couldn't—you know what I mean?

JAD: So on some level, you think it's a kind of denial?

CAROL BERMAN: Right.

JAD: So it'd be like Robert, if there was something about you that I just couldn't handle.

ROBERT: You couldn't quite—yeah.

JAD: And every time that thing appeared, whatever it is, the only way I could deal with it psychologically was to make a break and to say, "Oh, well that's not the Robert I know."

ROBERT: Therefore it isn't Robert at all. It's some fraud.

JAD: Yeah.

ROBERT: Yeah.

JAD: It's a fake.

JAD: But if you think there's some psychological basis, wouldn't you try and treat that psychological cause, or whatever it is?

CAROL BERMAN: We do, but we don't get too far. [laughs] We tried this stuff, but when a person starts breaking from reality and becomes psychotic, you could take fingerprints, you could show them everything about the person and you can't get anyplace.

V.S. RAMACHANDRAN: I think what's happening is something quite specific. You can explain this in terms of the known circuitry in the brain. The visual centers of the brain funnel in information to the fusiform gyrus where you recognize your mother or a dog or a table or a chair. Is this a stranger? Is it Joe? Is it my mom? Is it a dog? Is it Fifi? Then the message goes to the amygdala, which gauges the emotional significance, emotional relevance of what you're looking at.

ROBERT:  So wait, so, so to cap—to make that into normal English, Mom is a face I recognize as Mom and a set of feelings that I associate with Mom.

V.S. RAMACHANDRAN: Correct. Absolutely. Now what happens is, in this patient, because of the head injury, that wire is cut.

ROBERT: So then no mommy feelings.

V.S. RAMACHANDRAN: No mommy feelings. So you say, "My—my God, if this is my mom? She looks like my mom but why am I—I have no feelings? There's something really weird here. She must be an imposter." Now that's a very far-fetched delusion. Why doesn't she just say, "She doesn't feel like Mom? But of course, she's my mom."

ROBERT: Yeah. Why doesn't he do that?

V.S. RAMACHANDRAN: To be sure, sometimes that happens, but most often he says, "This is not my mom." Because our thought processes are much more dependent on our gut level emotional feelings than we realize.

ROBERT: So absent a feeling, a familiar feeling of Mom, some part of my brain says, "That's your mother." And some part of it says, "No, it can't be." And the deal that the brain works out is a deal that creates this fiction called "It's an imposter."

V.S. RAMACHANDRAN: Yes.

ROBERT: Because that solves the problem.

V.S. RAMACHANDRAN: Yeah. And—and the equation that says it can't be is from your emotions, wins.

ROBERT: But now here's the twist.

V.S. RAMACHANDRAN: Now if she goes to the next room, speaks to him on the phone, he says, "Mom, where are you? How are you? It's wonderful to talk to you!" All the emotions come flooding back and he is not delusional, right? Why would that be? An hour later, she comes to the room. He says, "Who are you? You look just like my mother, but you're not my mother."

ROBERT: Ah. So seeing the face seems to set off this problem.

V.S. RAMACHANDRAN: The reason is there's a separate wire going from the auditory regions in the brain to the amygdala, the emotion centers. That wire was not cut.

ROBERT: So what you hear can be very familiar, but if you see it, then you got a problem.

V.S. RAMACHANDRAN: Now people ask me, how come—what if she just—what if she comes and talks to him, right? What—why doesn't the hearing kick in and say, "Look, she is your mother." The answer is, see our brains, there's a hierarchy of—of priorities. We're highly visual creatures. We pay much more attention to vision, give much more weight to vision than to hearing and to voice.

ROBERT: Huh.

V.S. RAMACHANDRAN: So you say "This is an imposter. She sounds a little bit like my mother, I don't know why, but she's obviously an imposter." Rather than, "She doesn't look like my mother but has my mother's voice."

JAD: And tell me if you don't feel comfortable talking about this, but I understand that you have personal experience with Capgras delusions?

CAROL BERMAN: Yeah. Actually, my husband, he started not recognizing other people first, and then at some points he didn't even think I was his wife. I'm very stressed out with this whole situation because my husband was a charming, intelligent, wonderful person in all ways, and his dementia has been getting worse and worse.

JAD: Yeah. You're a psychiatrist, so does—does your understanding of how that might work in the brain change your experience of it in some way?

CAROL BERMAN: Well, no, it can't really change your feeling because, you know, when I get home and I'd like to—I get home, I kiss my husband and say, "Hi, how are you today?" And I hope he's recognizing me. And if he doesn't, you know, I feel terrible. After a hard day's work, I want to be able to hug him and kiss him and, you know, have a nice, friendly environment when I get back. But you never know what you're gonna get when you get back home.

JAD: Carol Berman is the author of a recent book called Personality Disorders.

ROBERT: And V.S. Ramachandran is the author also of a new book, The Man with the Phantom Twin: Adventures in the Neuroscience of the Human Brain.

[LISTENER: My name is Dusty Taylor, and I'm a Radiolab listener from Pedro, California. The Radiolab podcast is funded in part by the National Science Foundation and the Sloan Foundation.]

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