Prime Time Replay:
Dr. Stuart Firestein
on the Sense of Smell
MsgId: *brain_storm(3)
Date: Fri Dec 13 21:48:10 EST 1996
From: Keith_Harary_with_Stuart_Firestein At: 206.80.164.7
Good evening and welcome to Brainstorms. I'm your host, Dr. Keith Harary, Editor at Large of Omni. Our guest tonight is Columbia University neuroscientist and olfaction expert Dr. Stuart Firestein, discussing those things which he says will give us the answer to the most profound question that people can ask, which is: "How do I smell?"As usual, we'll identify ourselves by our initials: KH for Keith Harary and SF for Stuart Firestein.
KH: Welcome to Brainstorms, Dr. Firestein.
MsgId: *brain_storm(6)
Date: Fri Dec 13 22:00:34 EST 1996
From: Keith_Harary_with_Stuart_Firestein At: 206.80.164.7
SF: Glad to be here.
MsgId: *brain_storm(7)
Date: Fri Dec 13 22:01:13 EST 1996
From: Keith_Harary_with_Stuart_Firestein At: 206.80.164.7
KH: So, Dr. Firestein, how DO we smell?
MsgId: *brain_storm(8)
Date: Fri Dec 13 22:02:08 EST 1996
From: Keith_Harary_with_Stuart_Firestein At: 206.80.164.7
SF: We smell by a remarkable process and organ that allows us to detect and discriminate between from 10,000 different chemicals which we commonly call "odors." This is probably the most sophisticated chemical detector that we know of. Some molecules, especially organic molecules, exist in two forms. We call them stereo-isomers. This means that the molecular structure is exactly the same -- the atoms and their positions are exactly the same. They're simply a mirror image of each other. It's analogous to your left and right hands ,which are exactly the same, except a mirror image of each other. Our olfactory system is capable of discriminating even between stereo-isomers of some molecules. For example, the chemical carvone exists in both a left and right-handed form. The left-handed form smells like caraway. The right handed form smells like spearmint.
MsgId: *brain_storm(11)
Date: Fri Dec 13 22:05:52 EST 1996
From: Keith_Harary_with_Stuart_Firestein At: 206.80.164.7
KH: Is there a big difference between the sense of smell as it exists in human beings as opposed to the way it exists for other animals, such as dogs?
MsgId: *brain_storm(12)
Date: Fri Dec 13 22:07:02 EST 1996
From: Keith_Harary_with_Stuart_Firestein At: 206.80.164.7
SF: The differences are more in quantity than in quality. Certainly some animals -- many animals -- are more sensitive to their odor environment than we are. However, the brain mechanisms used in sensing odors are precisely the same in humans and other animals. In fact, humans actually have quite a good sense of smell. The major difficulty with our sense of smell is that we walk on two feet. Most odor molecules are relatively heavy and the most interesting of these are within 8 or 10 inches of the ground, while we now have our noses five or six feet in the air. You'll note when a dog catches a scent, it immediately puts its nose quite close to the ground.
MsgId: *brain_storm(14)
Date: Fri Dec 13 22:09:48 EST 1996
From: Keith_Harary_with_Stuart_Firestein At: 206.80.164.7
KH: Fascinating. Of course, our noses are not always five or six feet away from one another! So I would imagine that the human sense of smell has a powerful influence on the way we respond to one another as human beings. Is this the case?
MsgId: *brain_storm(15)
Date: Fri Dec 13 22:11:26 EST 1996
From: Keith_Harary_with_Stuart_Firestein At: 206.80.164.7
SF: Indeed, it seems to be so. There are actually two distinct noses in most vertebrates and especially mammals. One is devoted to smelling most of the common odors of food and general surroundings. The other "nose" is a small specialized organ called the vomeronasal organ which we abbreviate as VNO. This organ is specifically involved in detecting chemicals released by other members of the same species. These chemicals are commonly known as pheromones. The word is intended to make one think of a hormone because the action may be very similar in that it appears to be preconscious. That is, pheromones themselves may not have a describable odor that we perceive but nonetheless they will elicit behaviors when they are detected by the VNO. In so called lower animals, these behaviors tend to be sexual. As of this moment, there is no good evidence for the existence of human pheromones and most scientists currently believe that the VNO in humans is lost post-natally. That is, it exists in the embryo but not in the fully developed person.
MsgId: *brain_storm(18)
Date: Fri Dec 13 22:15:06 EST 1996
From: Keith_Harary_with_Stuart_Firestein At: 206.80.164.7
KH: That sounds very surprising, Dr. Firestein, considering the fact that there has been a great deal of hype surrounding the use of pheromones by the fragrance industry. Are you saying that there is no scientific basis for the claim that including these substances in perfumes leads to enhanced sex appeal on the part of those wearing these supposed special fragrances?
MsgId: *brain_storm(19)
Date: Fri Dec 13 22:15:53 EST 1996
From: Keith_Harary_with_Stuart_Firestein At: 206.80.164.7
SF: It greatly pains me to have to say that is the case. God knows, I'd be buying the stuff by the bucket.
MsgId: *brain_storm(20)
Date: Fri Dec 13 22:16:39 EST 1996
From: Keith_Harary_with_Stuart_Firestein At: 206.80.164.7
KH: Well, if you don't mind my saying so, I think that stinks.
MsgId: *brain_storm(21)
Date: Fri Dec 13 22:17:59 EST 1996
From: Keith_Harary_with_Stuart_Firestein At: 206.80.164.7
SF: Indeed, Dr. Harary. Just from an anecdotal point of view, I would say that odors play a more negative rather than a positive role in many of our interactions. For example, you may find yourself attracted to another person who is visually pretty, who has a wonderful personality, who is very bright and sexy, but when you get close to this person, you'll find they have some strange and unappealing odor. You'll find it nearly impossible to overcome this obstacle in spite of all the attractions available.
MsgId: *brain_storm(23)
Date: Fri Dec 13 22:20:16 EST 1996
From: Keith_Harary_with_Stuart_Firestein At: 206.80.164.7
KH: In that case, would you say that perfumes and colognes -- assuming that we like their smell -- might have the opposite effect and lead us to be attracted to people we might find otherwise less sexually appealing? That is, is all the romance and mystery surrounding the fragrance industry justified in your scientific opinion?
MsgId: *brain_storm(24)
Date: Fri Dec 13 22:21:08 EST 1996
From: Keith_Harary_with_Stuart_Firestein At: 206.80.164.7
SF: In this case it seems to be a matter of personal differences. Clearly, some members of the population are more susceptible to odor than to other stimuli, just as other members find certain visual aspects more appealing. This part of it would appear to be cultural.
MsgId: *brain_storm(25)
Date: Fri Dec 13 22:22:38 EST 1996
From: Keith_Harary_with_Stuart_Firestein At: 206.80.164.7
KH: If you'll bear with me, this seems to lead into the myth -- if it is a myth -- surrounding Napoleon and Josephine. We've heard the legend, in any event, that Napoleon would send Josephine a message when he was approaching the neighborhood between epic battles that he was on his way home and therefore that she should NOT bathe! This would suggest that some people might find the raw unfiltered aroma of another human being the most arousing of all. What do you think about that?
MsgId: *brain_storm(26)
Date: Fri Dec 13 22:23:43 EST 1996
From: Keith_Harary_with_Stuart_Firestein At: 206.80.164.7
SF: Well, there's no accounting for taste. This is a man who spends hours a day with his horse, right? In a slightly more serious vein, it's also true that many deodorant and perfume producers use musk as an attractant, an odor that I personally find somewhere between uninteresting and mildly repellant.
MsgId: *brain_storm(28)
Date: Fri Dec 13 22:26:15 EST 1996
From: Keith_Harary_with_Stuart_Firestein At: 206.80.164.7
KH: On another topic, I am sure we've all had the experience of encountering an aroma that we haven't been exposed to for some period of time. It seems that these aromas have the effect of bringing on a flood of memories and even emotions from long ago. For example, when I personally smell roasted peanuts and old wood, I am often reminded of my own childhood experiences walking down the Boardwalk in Atlantic City in front of the old Mr. Peanut Factory. I not only remember the place, but also seem to remember very much the way I felt as a person in the world at that particular point in my life. I'm sure this is not unusual. Do we know very much about the connection between olfaction and memory?
MsgId: *brain_storm(29)
Date: Fri Dec 13 22:27:37 EST 1996
From: Keith_Harary_with_Stuart_Firestein At: 206.80.164.7
SF: Indeed, you've hit upon one of the key elements of this relation between olfaction and memory, and that is that the memories evoked by an olfactory stimulus are almost always of an emotional type. That is, if you study for an exam while eating a chocolate bar, smelling chocolate during the exam will not help you remember what was on the page that you studied. So the memories induced by olfaction always have strong emotional content. Although we don't know the precise reason for this, it may result from the unique connections in the brain made by the olfactory system. In particular, the main fiber pathways from the first relay station for olfactory information in the brain proceed to an area known as the amygdala. The amygdala is known to be a center of emotional regulation in the brain and it sits very close to another structure known as the hippocampus. The hippocampus is believed to play a critical role in the formation of memories. This particular connection is unique among sensory systems.
MsgId: *brain_storm(31)
Date: Fri Dec 13 22:30:41 EST 1996
From: Keith_Harary_with_Stuart_Firestein At: 206.80.164.7
KH: This makes me wonder if there might be some therapeutic use for this effect. Certainly, we've heard a lot of claims about so-called aroma therapy. If different aromas can be used to invoke certain memories, can they also be used to invoke certain feelings as well? Can we use aroma to assist in the therapeutic process, or even to manipulate people into feeling certain emotions so that, for example, they might spend more money in a shopping center because the place has a pleasant or stimulating aroma? In short, Dr. Firestein, is it possible that all of us can just be led around by the nose?
MsgId: *brain_storm(32)
Date: Fri Dec 13 22:31:50 EST 1996
From: Keith_Harary_with_Stuart_Firestein At: 206.80.164.7
SF: It certainly is possible. Most likely, it's probable. Because I'm sure that some advertising or sales type has thought about it and is trying it. I think, however, that we can no more be led around by the nose than by the eyes or the ears, although the use of phenomenally attractive models and canned music attest to the power of those senses as well.
MsgId: *brain_storm(34)
Date: Fri Dec 13 22:34:05 EST 1996
From: Keith_Harary_with_Stuart_Firestein At: 206.80.164.7
KH: Can you tell us something about how our olfactory system manages what seems to be an incredible task of sorting through all of the many, many aromas we are exposed to in our daily lives?
MsgId: *brain_storm(35)
Date: Fri Dec 13 22:34:58 EST 1996
From: Keith_Harary_with_Stuart_Firestein At: 206.80.164.7
SF: Yes. I'll tell you the mechanism briefly first and then point out what's so interesting about it. In order to do this, we have a specialized group of nerve cells in the upper reaches of our nasal cavity. These nerve cells have on their surface small proteins that act as receptors. The idea of a receptor is universal in biology. It is analogous to a lock and key. The receptor is the lock and it can be activated or turned on by a specific key whose shape matches that of the lock. The same is true here except the lock is a protein that has a pocket in it that we call a binding pocket. This pocket has a very specific shape and distribution of charged molecules such that different protein receptors can be matched to different odors and when an odor fits well into a particular protein pocket, that protein turns on processes in the cell which notify the brain that it has detected an odor.
MsgId: *brain_storm(39)
Date: Fri Dec 13 22:40:01 EST 1996
From: Keith_Harary_with_Stuart_Firestein At: 206.80.164.7
KH: It sounds very complicated, but then again, it's probably really very simple in the final analysis. You were going to tell us what you find especially interesting about this mechanism.
MsgId: *brain_storm(40)
Date: Fri Dec 13 22:41:25 EST 1996
From: Keith_Harary_with_Stuart_Firestein At: 206.80.164.7
SF: There are two things that are interesting about it: One is that this system is able to recognize 10,000 different odors. We now know, since 1991, that it does this by having 1,000 different protein receptors. Now, each protein receptor requires one gene to encode it. There are, we believe, between 50,000 and 100,000 genes in the human genome. That is, the entire plan for making a human being is encoded in about 100,000 genes. Of those 100,000 genes, it now turns out, 1,000 of them encode odor receptors. That is, 1% of the entire genome is devoted to smelling odors. That's a remarkably large number.The second interesting thing is that the receptors that we use to smell odors are very closely related to the protein receptors on brain cells -- in our brain, that is -- that recognize neurotransmitters such as serotonin, dopamine, and many others. So brain cells communicate with each other using the same mechanism that we use to detect odors in the environment.
MsgId: *brain_storm(44)
Date: Fri Dec 13 22:45:40 EST 1996
From: Keith_Harary_with_Stuart_Firestein At: 206.80.164.7
KH: So it sounds like understanding our sense of smell will actually help us to learn more about the brain itself.
MsgId: *brain_storm(45)
Date: Fri Dec 13 22:46:41 EST 1996
From: Keith_Harary_with_Stuart_Firestein At: 206.80.164.7
SF: Yes, I agree, and indeed it's one of the reasons we do this work. Let me give you an example that I think many people can relate to: We have all had the experience of walking into a room where there is a very bad smell and after a few minutes in that room we no longer seem to smell it. However, we know the odor is still there because if someone new comes into the room, they say, "Ugh! What stinks in here?" This phenomenon is known as adaptation.
MsgId: *brain_storm(47)
Date: Fri Dec 13 22:49:18 EST 1996
From: Keith_Harary_with_Stuart_Firestein At: 206.80.164.7
KH: I suppose this phenomenon makes it possible for people to work together effectively for long periods on submarines.
MsgId: *brain_storm(48)
Date: Fri Dec 13 22:50:09 EST 1996
From: Keith_Harary_with_Stuart_Firestein At: 206.80.164.7
SF: Certainly true. Not to mention making it possible for people to remain married for many decades. But, seriously, a very similar phenomenon is known clinically as drug tolerance. This situation arises in the treatment of chronic illnesses when a drug can be given that will ameliorate symptoms but after some time in order to be effective the dosage must be increased. Over sufficient time, dosages often have to be increased to the point where side effects become more serious than the illness the drug used to be effective against. Because most drugs act on receptors just like those in olfactory cells, the two phenomena -- olfactory adaptation and drug tolerance -- operate through very similar cellular mechanisms. Therefore, what we learn about olfactory adaptation can be applied to understanding drug tolerance.
MsgId: *brain_storm(52)
Date: Fri Dec 13 22:55:25 EST 1996
From: Keith_Harary_with_Stuart_Firestein At: 206.80.164.7
KH: We're getting close to the end of tonight's show -- just five minutes left. Before we wrap up, however, can you give our viewers some idea of what you're personally working on right now in your own research?
MsgId: *brain_storm(53)
Date: Fri Dec 13 22:56:24 EST 1996
From: Keith_Harary_with_Stuart_Firestein At: 206.80.164.7
SF: Yes. In 1991, the odor receptor protein was cloned by a woman named Linda Buck, then at Columbia, now at Harvard. This led to a thorough understanding of the genetics of olfaction. I am now working on methods to express these receptor genes as proteins in cells that will allow us to monitor their activity when stimulating them with odors. This will permit us to match each of the 1,000 receptors to the odor or odors that fit into their lock. What we hope to do is find a kind of Rosetta Stone that will enable us to understand the olfactory code so that we finally will know how the brain knows what the nose knows.
MsgId: *brain_storm(56)
Date: Fri Dec 13 22:58:42 EST 1996
From: Keith_Harary_with_Stuart_Firestein At: 206.80.164.7
KH: It sounds like fascinating research. You might say that you are a kind of prophet in this field. Shall we call you Nostrildamus?
MsgId: *brain_storm(57)
Date: Fri Dec 13 22:59:14 EST 1996
From: Keith_Harary_with_Stuart_Firestein At: 206.80.164.7
SF: I'd be honored.
MsgId: *brain_storm(58)
Date: Fri Dec 13 22:59:59 EST 1996
From: Keith_Harary_with_Stuart_Firestein At: 206.80.164.7
KH: But seriously, I want to thank you, Dr. Firestein, for a most fascinating and enlightening evening here on Brainstorms. I hope you can come back at some point in the future to answer questions in an open chat directly from our on-line audience.
MsgId: *brain_storm(59)
Date: Fri Dec 13 23:00:27 EST 1996
From: Keith_Harary_with_Stuart_Firestein At: 206.80.164.7
SF: Thank you, and I'd be happy to at any time.
MsgId: *brain_storm(60)
Date: Fri Dec 13 23:01:28 EST 1996
From: Keith_Harary_with_Stuart_Firestein At: 206.80.164.7
KH: Wonderful. Thank you again for sharing your insights on olfaction and the brain, and thank you to our on-line audience here on OMNI Internet. I'm your host, Dr. Keith Harary, inviting our audience to join us again next week here on Brainstorms for another fascinating visit with another leading scientist expanding the boundaries of our understanding of the mind, the brain and human behavior. Good night for Brainstorms.
Home || Prime Time || Live Science || Machine Dreams || Project Open Book || SF-Fantasy-Horror
Continuum || Antimatter || Mind-Brain Lab || Interactive IQ || Gallery || OMNI ToonsQuestions, comments and suggestions can be mailed to the webmaster.
Copyright (C) 1997 by Omni Publications International, Ltd. All Rights Reserved.