Essentials: How Smell, Taste & Pheromones Shape Behavior

0:00:02 Welcome to Huberman Lab Essentials,
0:00:04 where we revisit past episodes
0:00:07 for the most potent and actionable science-based tools
0:00:10 for mental health, physical health, and performance.
0:00:12 I’m Andrew Huberman,
0:00:15 and I’m a professor of neurobiology and ophthalmology
0:00:16 at Stanford School of Medicine.
0:00:18 This podcast is separate
0:00:20 from my teaching and research roles at Stanford.
0:00:22 Today, we’re going to talk about chemical sensing.
0:00:25 We’re going to talk about the sense of smell,
0:00:28 our ability to detect odors in our environment.
0:00:31 We’re also going to talk about taste,
0:00:33 our ability to detect chemicals
0:00:37 and make sense of chemicals that are put in our mouth
0:00:39 and into our digestive tract.
0:00:41 And we are going to talk about chemicals
0:00:43 that are made by other human beings
0:00:46 that powerfully modulate the way that we feel,
0:00:48 our hormones, and our health.
0:00:52 Now, that last category are sometimes called pheromones.
0:00:55 However, whether or not pheromones exist in humans
0:00:56 is rather controversial.
0:00:59 There actually hasn’t been a clear example
0:01:02 of a true human pheromonal effect,
0:01:05 but what is absolutely clear, what is undeniable
0:01:09 is that there are chemicals that human beings make
0:01:13 and release in things like tears onto our skin
0:01:18 and sweat and even breath that powerfully modulate
0:01:21 or control the biology of other individuals.
0:01:24 There are things floating around in the environment,
0:01:26 which we call volatile chemicals.
0:01:29 So when you actually smell something,
0:01:34 like let’s say you smell a wonderfully smelling rose or cake,
0:01:38 yes, you are inhaling the particles into your nose.
0:01:41 There are literally little particles of those chemicals
0:01:42 are going up into your nose
0:01:45 and being detected by your brain.
0:01:48 Other ways of getting chemicals into our system
0:01:50 is by putting them in our mouth,
0:01:55 by literally taking foods and chewing them
0:01:57 or sucking on them and breaking them down
0:01:59 into their component parts.
0:02:01 And that’s one way that we sense chemicals
0:02:03 with a thing, our tongue.
0:02:08 So these chemicals, we sometimes bring into our body,
0:02:10 into our biology through deliberate action.
0:02:13 We select a food, we chew that food
0:02:15 and we do it intentionally.
0:02:17 Sometimes they’re coming into our body
0:02:19 through non-deliberate action.
0:02:21 We enter an environment and there’s smoke
0:02:22 and we smell the smoke.
0:02:24 And as a consequence, we take action.
0:02:29 Sometimes, however, other people are actively making chemicals
0:02:30 with their body.
0:02:32 Typically, this would be with their breath,
0:02:36 with their tears, or possibly,
0:02:37 I want to underscore possibly,
0:02:40 by making what are called pheromones,
0:02:42 molecules that they release into the environment,
0:02:43 typically through the breath,
0:02:47 that enter our system through our nose,
0:02:48 our eyes, or our mouth,
0:02:51 that fundamentally change our biology.
0:02:53 I’ll just give an example,
0:02:56 which is a very salient and interesting one
0:02:58 that was published about 10 years ago
0:02:59 in the journal Science,
0:03:01 showing that humans,
0:03:03 men in particular in this study,
0:03:05 have a strong biological response
0:03:07 and hormonal response
0:03:10 to the tears of women.
0:03:13 What they did is they had women,
0:03:14 and in this case,
0:03:16 it was only women for whatever reason,
0:03:17 cry,
0:03:20 and they collected their tears.
0:03:24 then those tears were smelled by male subjects
0:03:28 or male subjects got what was essentially
0:03:30 the control, which was the saline.
0:03:33 Men that smelled these tears
0:03:35 that were evoked by sadness
0:03:39 had a reduction in their testosterone levels
0:03:40 that was significant.
0:03:43 They also had a reduction in brain areas
0:03:45 that were associated with sexual arousal.
0:03:47 They actually recruited subjects
0:03:48 that had a high propensity
0:03:50 for crying at sad movies,
0:03:52 which was not all women.
0:03:52 What they were really trying to do
0:03:54 is just get tears
0:03:56 that were authentically cried
0:03:58 in response to sadness,
0:04:00 as opposed to, you know,
0:04:02 putting some irritant in the eye
0:04:02 and collecting tears
0:04:05 that were evoked by something else,
0:04:07 like just having the eyes irritated.
0:04:08 Nonetheless,
0:04:11 what this study illustrates
0:04:13 is that there are chemicals
0:04:15 in tears
0:04:16 that are evoking
0:04:18 or changing the biology
0:04:19 of other individuals.
0:04:20 Now,
0:04:21 I didn’t select this study
0:04:22 as an example
0:04:23 because I want to focus
0:04:25 on the effects of tears
0:04:26 on hormones per se,
0:04:27 although I do find the results
0:04:28 really interesting.
0:04:30 I chose it because
0:04:32 I wanted to just emphasize
0:04:34 or underscore the fact
0:04:35 that chemicals that are made
0:04:36 by other individuals
0:04:38 are powerfully modulating
0:04:40 our internal state.
0:04:42 And that’s something
0:04:43 that most of us don’t appreciate.
0:04:45 I think most of us
0:04:46 can appreciate the fact
0:04:48 that if we smell something putrid,
0:04:49 we tend to retract
0:04:51 or if we smell something delicious,
0:04:52 we tend to lean into it.
0:04:54 But there are all these ways
0:04:55 in which chemicals
0:04:56 are affecting our biology
0:04:59 and interpersonal communication
0:05:00 using chemicals
0:05:01 is not something
0:05:03 that we hear that often about,
0:05:05 but it’s super interesting.
0:05:06 So let’s talk about smell
0:05:07 and what smell is
0:05:08 and how it works.
0:05:09 I’m going to make this very basic,
0:05:11 but I am going to touch
0:05:12 on some of the core elements
0:05:13 of the neurobiology.
0:05:15 So here’s how smell works.
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0:07:17 Smell starts with sniffing.
0:07:19 Now that might come
0:07:20 as no surprise,
0:07:22 but no volatile chemicals
0:07:23 can enter our nose
0:07:25 unless we inhale them.
0:07:26 if our nose is occluded
0:07:29 or if we’re actively exhaling,
0:07:31 it’s much more difficult
0:07:33 for smells to enter our nose,
0:07:34 which is why people cover their nose
0:07:36 when something smells bad.
0:07:40 Now, the way that these volatile odors
0:07:41 come into the nose
0:07:41 is interesting.
0:07:44 The nose has a mucosal lining,
0:07:45 mucus,
0:07:47 that is designed to trap things,
0:07:48 to actually bring things in
0:07:50 and get stuck there.
0:07:52 At the base of your brain,
0:07:54 so you could actually imagine this
0:07:55 or if you wanted,
0:07:57 you could touch the roof of your mouth
0:07:58 but right above the mouth,
0:08:01 about two centimeters
0:08:02 is your olfactory bulb.
0:08:03 The olfactory bulb
0:08:04 is a collection of neurons
0:08:05 and those neurons
0:08:06 actually extend
0:08:08 out of the skull,
0:08:09 out of your skull,
0:08:10 into your nose,
0:08:12 into the mucosal lining.
0:08:13 So what this means
0:08:14 in kind of a literal sense
0:08:16 is that you have neurons
0:08:19 that extend their little dendrites
0:08:21 and axillary-like things,
0:08:22 their little processes,
0:08:23 as we call them,
0:08:24 out into the mucus
0:08:26 and they respond
0:08:28 to different odorant compounds.
0:08:30 Now, the olfactory neurons
0:08:32 also send a branch
0:08:33 deeper into the brain
0:08:35 and they split off
0:08:38 into three different paths.
0:08:40 So one path
0:08:41 is for what we call
0:08:43 innate odor responses.
0:08:46 So you have some hardwired aspects
0:08:47 to the way
0:08:48 that you smell the world
0:08:49 that were there
0:08:51 from the day you were born
0:08:52 and that will be there
0:08:53 until the day you die.
0:08:56 These are the pathways
0:08:57 and the neurons
0:08:58 that respond to things
0:08:59 like smoke,
0:09:01 which as you can imagine,
0:09:03 there’s a highly adaptive function
0:09:04 to being able to detect
0:09:05 burning things
0:09:07 because burning things
0:09:08 generally means lack of safety
0:09:10 or impending threat
0:09:10 of some kind.
0:09:13 It calls for action
0:09:14 and indeed,
0:09:15 these neurons project
0:09:16 to a central area of the brain
0:09:18 called the amygdala,
0:09:19 which is often discussed
0:09:20 in terms of fear,
0:09:21 but it’s really fear
0:09:22 and threat detection.
0:09:24 You also have neurons
0:09:25 in your nose
0:09:26 that respond to odorants
0:09:28 or combinations of odorants
0:09:30 that evoke a sense
0:09:31 of desire
0:09:32 and what we call
0:09:34 appetitive behaviors,
0:09:35 approach behaviors
0:09:35 that make you want
0:09:37 to move toward something.
0:09:38 So when you smell
0:09:39 a delicious cookie
0:09:42 or some dish
0:09:43 that’s really savory
0:09:44 that you really like,
0:09:45 that’s because of these
0:09:46 innate pathways,
0:09:47 these pathways
0:09:48 that require
0:09:49 no learning whatsoever.
0:09:50 Now,
0:09:51 some of the pathways
0:09:52 from the nose,
0:09:53 these olfactory neurons
0:09:54 into the brain
0:09:55 are involved
0:09:56 in learned associations
0:09:58 with odors.
0:09:59 Many people
0:10:02 have this experience
0:10:04 that they can remember
0:10:05 the smell
0:10:07 of their grandmother’s home
0:10:08 or the smell
0:10:10 of particular items
0:10:10 baking
0:10:13 or on the stove
0:10:15 in a particular environment.
0:10:16 Typically,
0:10:16 these memories
0:10:17 tend to be
0:10:18 of a kind of nurturing sort
0:10:19 of feeling safe
0:10:20 and protected,
0:10:22 but one of the reasons
0:10:24 why olfaction,
0:10:24 smell,
0:10:26 is so closely tied
0:10:26 to memory
0:10:27 is because olfaction
0:10:29 is the most ancient sense
0:10:30 that we have.
0:10:31 So we have pathway
0:10:34 for innate responses
0:10:34 and a pathway
0:10:35 for learned responses.
0:10:37 And then we have
0:10:38 this other pathway
0:10:39 and in humans,
0:10:40 it’s a little bit controversial
0:10:41 as to whether or not
0:10:42 it sits truly separate
0:10:44 from the standard
0:10:45 olfactory system
0:10:46 or whether or not
0:10:47 it’s its own system
0:10:49 embedded in there,
0:10:49 but that they call
0:10:50 the accessory
0:10:52 olfactory pathway.
0:10:54 Accessory olfactory pathway
0:10:56 is what in other animals
0:10:57 is responsible
0:10:59 for true pheromone effects.
0:11:00 For example,
0:11:02 in rodents
0:11:04 and in some primates
0:11:06 including mandrills.
0:11:07 If you’ve ever seen a mandrel,
0:11:07 they have these like
0:11:09 big beak noses things.
0:11:09 You may have seen them
0:11:10 at the zoo.
0:11:10 Look them up
0:11:11 if you haven’t seen them already.
0:11:13 M-A-N-D-R-I-L-S.
0:11:14 Mandrills.
0:11:17 There are strong pheromone effects.
0:11:18 Some of those include
0:11:20 things like
0:11:21 if you take
0:11:23 a pregnant female rodent
0:11:24 or mandrel,
0:11:26 you take away
0:11:26 the father
0:11:28 that created
0:11:30 those fetuses
0:11:31 or fetus
0:11:33 and you introduce
0:11:34 the scent
0:11:35 of the urine
0:11:37 or the fur
0:11:38 of a novel
0:11:39 male,
0:11:41 she will spontaneously
0:11:41 abort
0:11:42 or miscarry
0:11:43 those fetuses.
0:11:45 It’s a very powerful effect.
0:11:46 Another example
0:11:47 of a pheromone effect
0:11:48 is called
0:11:49 the Vandenberg effect
0:11:50 named after
0:11:50 the person
0:11:52 who discovered this effect
0:11:52 where you take
0:11:54 a female
0:11:55 of a given species
0:11:56 that has not
0:11:57 entered puberty,
0:11:59 you expose her
0:12:00 to the scent
0:12:01 or the urine
0:12:03 from a sexually
0:12:04 competent,
0:12:05 meaning post-pubertal
0:12:05 male,
0:12:08 and she spontaneously
0:12:09 goes into
0:12:10 puberty earlier.
0:12:11 So something about
0:12:11 the scent
0:12:12 triggers something
0:12:13 through this
0:12:15 accessory olfactory system.
0:12:15 This is a true
0:12:16 pheromonal effect
0:12:18 and creates
0:12:19 ovulation,
0:12:19 right,
0:12:20 and menstruation
0:12:21 or in rodents,
0:12:22 it’s an estrous cycle,
0:12:23 not a menstrual cycle.
0:12:24 So
0:12:26 this is
0:12:27 not to say
0:12:28 that the exact same
0:12:28 things happen
0:12:29 in humans.
0:12:29 In humans,
0:12:30 as I mentioned earlier,
0:12:32 there are chemical sensing
0:12:33 between individuals
0:12:34 that may be
0:12:34 independent
0:12:35 of the nose,
0:12:37 but those are
0:12:38 basically the three paths
0:12:39 by which smells,
0:12:41 odors impact us.
0:12:42 So I want to talk
0:12:43 about the act
0:12:44 of smelling.
0:12:45 And if
0:12:46 you are not somebody
0:12:47 who’s very interested
0:12:48 in smell,
0:12:49 but you are somebody
0:12:50 who’s interested
0:12:51 interested in making
0:12:52 your brain work better,
0:12:53 learning faster,
0:12:54 remembering more things,
0:12:56 this next little segment
0:12:57 is for you
0:12:58 because it turns out
0:12:59 that how you smell,
0:13:00 meaning the act
0:13:01 of smelling,
0:13:02 not how good
0:13:02 or bad you smell,
0:13:04 but the act
0:13:05 of smelling,
0:13:06 sniffing,
0:13:07 and inhalation
0:13:08 powerfully impacts
0:13:09 how your brain
0:13:10 functions
0:13:11 and what you can learn
0:13:12 and what you can’t learn.
0:13:13 Gnome Sobel’s group
0:13:15 originally at UC Berkeley
0:13:16 and then at the
0:13:17 Weitzman Institute
0:13:19 has published
0:13:20 a number of papers
0:13:21 that I’d like
0:13:22 to discuss today.
0:13:23 One of them,
0:13:25 human non-olfactory
0:13:26 cognition
0:13:27 phase locked
0:13:28 with inhalation.
0:13:28 This was published
0:13:30 in Nature Human Behavior,
0:13:31 an excellent journal.
0:13:33 As we inhale,
0:13:35 what this paper shows
0:13:35 is that
0:13:37 the level of alertness
0:13:39 goes up in the brain.
0:13:40 and this makes sense
0:13:42 because as the most primitive
0:13:44 and primordial sense
0:13:46 by which we interact
0:13:46 with our environment
0:13:47 and bring chemicals
0:13:49 into our system
0:13:51 and detect our environment,
0:13:54 inhaling is a cue
0:13:56 for the rest of the brain
0:13:57 to essentially
0:13:58 to pay attention
0:13:59 to what’s happening,
0:14:01 not just to the odors.
0:14:03 As the name of this paper suggests,
0:14:05 human non-olfactory
0:14:06 cognition,
0:14:07 phase locked
0:14:08 with inhalation.
0:14:09 What that means
0:14:09 is that
0:14:10 the act
0:14:12 of inhaling itself
0:14:13 wakes up the brain.
0:14:14 It’s not about
0:14:15 what you’re perceiving
0:14:16 or what you’re smelling
0:14:18 and indeed
0:14:19 sniffing
0:14:20 as an action,
0:14:21 inhaling
0:14:22 as an action
0:14:23 has a powerful effect
0:14:24 on your ability
0:14:25 to be alert,
0:14:26 your ability
0:14:27 to attend,
0:14:28 to focus,
0:14:29 and your ability
0:14:30 to remember information.
0:14:32 When we exhale,
0:14:34 the brain
0:14:35 goes through
0:14:35 a subtle
0:14:36 but nonetheless
0:14:37 significant dip
0:14:38 in level
0:14:39 of arousal
0:14:40 and ability
0:14:40 to learn.
0:14:41 How should you
0:14:42 use this knowledge?
0:14:43 Well,
0:14:45 you could imagine,
0:14:45 and I think
0:14:46 this would be beneficial
0:14:48 for most people,
0:14:50 to focus on nasal breathing
0:14:51 while doing
0:14:52 any kind of focused work
0:14:53 that doesn’t require
0:14:54 that you speak
0:14:55 or eat
0:14:56 or ingest something.
0:14:58 There is a separate paper
0:14:58 published in
0:15:00 the Journal of Neuroscience
0:15:01 that showed that
0:15:01 indeed,
0:15:02 if subjects,
0:15:03 human subjects,
0:15:03 are restricted
0:15:04 connected to breathing
0:15:05 through their nose,
0:15:07 they learn better
0:15:08 than if they
0:15:09 have the option
0:15:09 of breathing
0:15:10 through their mouth
0:15:12 or a combination
0:15:12 of their nose
0:15:13 and mouth.
0:15:13 Now,
0:15:14 there are other ways
0:15:15 to wake up your brain
0:15:16 more as well.
0:15:17 For instance,
0:15:18 the use of smelling salts.
0:15:19 I’m not recommending
0:15:20 that you do this necessarily,
0:15:22 but there are excellent
0:15:23 peer-reviewed data
0:15:25 showing that indeed,
0:15:27 if you use smelling salts,
0:15:28 which are mostly
0:15:28 of the sort
0:15:31 that include ammonia.
0:15:32 Ammonia is a very
0:15:33 toxic scent,
0:15:35 but it’s toxic
0:15:35 in a way
0:15:36 that triggers
0:15:38 this innate pathway,
0:15:39 the pathway
0:15:39 from the nose
0:15:40 to the amygdala
0:15:41 and wakes up
0:15:41 the brain and body
0:15:42 in a major way.
0:15:43 This is why
0:15:44 they use smelling salts
0:15:45 when people pass out.
0:15:46 They work
0:15:47 because they trigger
0:15:48 the fear
0:15:50 and kind of overall
0:15:51 arousal systems
0:15:51 of the brain.
0:15:52 This is why
0:15:52 I think most people
0:15:53 probably shouldn’t use
0:15:54 ammonia or smelling salts
0:15:55 to try and wake up,
0:15:56 but they really do work.
0:15:58 Now, inhaling through your nose
0:15:59 and doing nasal breathing,
0:16:00 it’s going to be
0:16:01 a more subtle version
0:16:03 of waking up your system,
0:16:05 of alerting your brain overall.
0:16:08 And for those of you
0:16:09 that are interested
0:16:10 in having a richer,
0:16:13 a more deep connection
0:16:13 to the things
0:16:15 that you smell and taste,
0:16:16 practicing or enhancing
0:16:17 your sense of sniffing,
0:16:18 your ability to sniff
0:16:19 might sound like
0:16:20 a kind of ridiculous protocol,
0:16:21 but it’s actually
0:16:22 a kind of fun
0:16:23 and cool experiment
0:16:24 that you can do.
0:16:24 You just do
0:16:25 the simple experiment
0:16:26 of taking,
0:16:26 for instance,
0:16:27 an orange,
0:16:28 you smell it,
0:16:30 do 10 or 15 inhales,
0:16:32 followed by exhales,
0:16:32 of course,
0:16:33 or just through the nose.
0:16:35 I’m not going to do
0:16:35 all 10 or 15
0:16:37 and then smell it again.
0:16:37 And you’ll notice
0:16:38 that your perception
0:16:39 of that smell,
0:16:40 the kind of richness
0:16:41 of that smell
0:16:43 will be significantly increased.
0:16:44 So you can actually
0:16:46 have a heightened experience
0:16:47 of something.
0:16:47 And that of course
0:16:48 will also be true
0:16:49 for the taste system.
0:16:50 I’d like to take
0:16:51 a quick break
0:16:51 and thank one
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0:17:03 but no sugar.
0:17:04 We should all know
0:17:05 that proper hydration
0:17:05 is critical
0:17:06 for optimal brain
0:17:07 and body function.
0:17:08 In fact,
0:17:09 even a slight degree
0:17:09 of dehydration
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0:17:12 and physical performance
0:17:13 to a considerable degree.
0:17:14 It’s also important
0:17:15 that you’re not just hydrated,
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0:17:18 in the right ratios.
0:17:19 Drinking a packet
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0:17:21 in water
0:17:22 makes it very easy
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0:17:23 that you’re getting
0:17:24 adequate amounts
0:17:24 of hydration
0:17:26 and electrolytes.
0:17:26 To make sure
0:17:27 that I’m getting
0:17:28 proper amounts of both,
0:17:29 I dissolve one packet
0:17:29 of Element
0:17:31 in about 16 to 32 ounces
0:17:31 of water
0:17:32 when I wake up
0:17:33 in the morning
0:17:34 and I drink that
0:17:35 basically first thing
0:17:35 in the morning.
0:17:36 I’ll also drink
0:17:37 a packet of Element
0:17:38 dissolved in water
0:17:38 during any kind
0:17:39 of physical exercise
0:17:40 that I’m doing,
0:17:41 especially on hot days
0:17:42 when I’m sweating a lot
0:17:43 and losing water
0:17:44 and electrolytes.
0:17:45 There are a bunch
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0:17:48 I like the watermelon,
0:17:48 I like the raspberry,
0:17:49 I like the citrus,
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0:17:55 slash Huberman
0:17:56 to claim an Element
0:17:57 sample pack
0:17:57 with the purchase
0:17:58 of any Element
0:17:59 drink mix.
0:17:59 Again, that’s
0:18:00 drinkelement
0:18:01 spelled L-M-N-T,
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0:18:07 You also can really
0:18:09 train your sense of smell
0:18:10 to get much, much better.
0:18:12 No other system
0:18:13 that I’m aware of
0:18:14 in our body
0:18:16 is as amenable
0:18:17 to these kinds
0:18:19 of behavioral training shifts
0:18:19 and allow them
0:18:20 to happen so quickly.
0:18:21 In fact,
0:18:22 how well we can smell
0:18:23 and taste things
0:18:24 is actually
0:18:26 a very strong indication
0:18:27 of our brain health.
0:18:29 so our olfactory neurons,
0:18:31 these neurons in our nose
0:18:32 that detect odors
0:18:34 are really unique
0:18:36 among other brain neurons
0:18:39 because they get replenished
0:18:40 throughout life.
0:18:42 They don’t just regenerate,
0:18:44 but they get replenished.
0:18:45 So regeneration
0:18:47 is when something is damaged
0:18:48 and it regrows.
0:18:49 These neurons
0:18:51 are constantly turning over
0:18:52 throughout our lifespan.
0:18:53 They’re constantly
0:18:53 being replenished.
0:18:54 they’re dying off
0:18:55 and they’re being
0:18:56 replaced by new ones.
0:18:58 This is really interesting
0:19:00 because other neurons
0:19:01 in your cortex,
0:19:02 in your retina,
0:19:04 in your cerebellum,
0:19:05 they do not do this.
0:19:06 They are not continually
0:19:07 replenished throughout life.
0:19:08 But these neurons,
0:19:10 these olfactory neurons are,
0:19:11 they are special.
0:19:13 and there are a number
0:19:14 of things
0:19:15 that seem to increase
0:19:16 the amount
0:19:18 of olfactory neuron neurogenesis.
0:19:19 There is evidence
0:19:21 that exercise,
0:19:22 blood flow,
0:19:23 can increase
0:19:24 olfactory neuron neurogenesis.
0:19:25 Although those data
0:19:27 are fewer
0:19:28 in comparison to things
0:19:30 like social interactions
0:19:32 or actually interacting
0:19:34 with odorants
0:19:35 of different kinds.
0:19:36 But what I’d like to do
0:19:36 is empower you
0:19:37 with tools
0:19:38 that will allow you
0:19:39 to keep these systems
0:19:39 tuned up.
0:19:40 Last time we talked
0:19:41 about tuning up
0:19:42 and keeping your visual system
0:19:43 tuned up and healthy
0:19:45 regardless of age.
0:19:46 Here we’re talking about
0:19:47 really enhancing
0:19:50 your olfactory abilities,
0:19:51 your taste abilities
0:19:53 as well by interacting
0:19:55 a lot with odors,
0:19:57 preferably positive odors
0:19:59 and sniffing more,
0:20:00 inhaling more,
0:20:02 which almost sounds crazy.
0:20:03 But now you understand why
0:20:04 even though it might sound crazy,
0:20:05 it’s grounded
0:20:07 in real mechanistic biology
0:20:08 of how the brain wakes up
0:20:10 and responds to these chemicals.
0:20:12 Now, speaking of brain injury,
0:20:13 olfactory dysfunction
0:20:15 is a common theme
0:20:16 in traumatic brain injury
0:20:17 for the following reason.
0:20:18 These olfactory neurons,
0:20:19 as I mentioned,
0:20:20 extend wires
0:20:21 into the mucosa
0:20:23 of the nose,
0:20:25 but they also extend
0:20:26 a wire up into the skull
0:20:27 and they extend
0:20:28 up into the skull
0:20:28 through what’s called
0:20:29 the cribriform plate.
0:20:30 It’s like a Swiss cheese
0:20:31 type plate
0:20:33 where they’re going through
0:20:34 and if you get a head hit,
0:20:36 that bone,
0:20:37 the cribriform plate
0:20:39 shears those little wires off
0:20:41 and those neurons die.
0:20:43 Now, eventually they’ll be replaced,
0:20:45 but there’s a phenomenon
0:20:46 by which concussion
0:20:48 and the severity of concussion
0:20:49 and the recovery
0:20:49 from a head injury
0:20:51 can actually be gauged
0:20:52 in part,
0:20:52 in part,
0:20:53 not in whole,
0:20:54 but in part
0:20:55 by how well
0:20:56 or fully
0:20:57 one recovers
0:20:58 their sense of smell.
0:20:59 So if you’re somebody
0:21:00 that unfortunately
0:21:01 has suffered a concussion,
0:21:02 your sense of smell
0:21:04 is one readout
0:21:05 by which you might evaluate
0:21:06 whether or not
0:21:06 you’re regaining
0:21:08 some of your sensory performance.
0:21:08 Of course,
0:21:09 there will be others
0:21:10 like balance and cognition
0:21:11 and sleep, etc.
0:21:12 But I’d like to refer you
0:21:14 to a really nice paper
0:21:16 which is entitled
0:21:17 Olfactory Dysfunction
0:21:18 in Traumatic Brain Injury,
0:21:20 The Role of Neurogenesis.
0:21:21 The first author
0:21:21 is Marin,
0:21:23 M-A-R-I-N.
0:21:25 The paper was published
0:21:26 in Current Allergy
0:21:27 and Asthma Report.
0:21:28 This is 2020.
0:21:29 I spent some time
0:21:29 with this paper.
0:21:30 It’s quite good.
0:21:31 It’s a review article.
0:21:32 I like reviews
0:21:34 if they’re peer-reviewed reviews.
0:21:36 What they discuss is
0:21:37 and I’ll just read here briefly
0:21:38 because they said it
0:21:38 better than I could.
0:21:40 Olfactory functioning disturbances
0:21:40 are common
0:21:42 following traumatic brain injury,
0:21:42 TBI
0:21:44 and can have a significant impact
0:21:45 on the quality of life
0:21:46 although there’s no standard
0:21:47 treatment for patients
0:21:50 with the loss of smell.
0:21:51 Now I’m paraphrasing
0:21:53 post-injury.
0:21:54 Olfactory training
0:21:56 has shown promise
0:21:58 for beneficial effects
0:22:00 but what does this mean?
0:22:01 This means that
0:22:02 if you’ve had a head injury
0:22:04 or repeated head injuries
0:22:07 that enhancing your sense of smell
0:22:07 is one way
0:22:09 by which you can create
0:22:10 new neurons
0:22:10 and now you know
0:22:11 how to enhance
0:22:12 your sense of smell
0:22:13 by interacting with things
0:22:14 that have an odor
0:22:15 very closely
0:22:17 and by essentially
0:22:18 inhaling more,
0:22:19 focusing on the inhale
0:22:20 to wake up the brain
0:22:21 and to really focus
0:22:22 on some of the nuance
0:22:23 of those smells.
0:22:24 as a last point
0:22:25 about specific
0:22:27 odors and compounds
0:22:28 that can increase
0:22:29 arousal and alertness
0:22:30 and this was simply
0:22:31 through sniffing them
0:22:32 not through ingesting them.
0:22:34 There are data,
0:22:35 believe it or not,
0:22:36 there are good data
0:22:37 on peppermint
0:22:39 and the smell of peppermint.
0:22:41 Minty type scents,
0:22:43 whether you like them or not,
0:22:45 will increase attention
0:22:47 and they can create
0:22:49 the same sort of arousal response
0:22:51 although not as intensely
0:22:52 or as dramatically
0:22:53 as ammonia salts can
0:22:54 for instance.
0:22:55 By the way,
0:22:56 please don’t go sniff
0:22:56 real ammonia.
0:22:57 You could actually damage
0:22:59 your olfactory epithelium
0:22:59 if you do that
0:23:01 too close to the ammonia.
0:23:01 If you’re going to use
0:23:02 smelling salts,
0:23:03 be sure you work with someone
0:23:05 or you know what you’re getting
0:23:06 and how you’re using this.
0:23:07 You can damage
0:23:08 your olfactory pathway
0:23:09 in ways that are pretty severe.
0:23:11 You can also damage your vision.
0:23:12 If you’ve ever teared up
0:23:13 because you inhaled something
0:23:14 that was really noxious,
0:23:17 that is not a good thing
0:23:18 but it means that
0:23:19 you have irritated
0:23:21 the mucosal lining
0:23:23 and possibly even
0:23:24 the surfaces of your eyes
0:23:25 so please be very,
0:23:25 very careful.
0:23:28 Scents like peppermint,
0:23:31 like these ammonia smelling salts,
0:23:32 the reason they wake you up
0:23:33 is because they trigger
0:23:34 specific olfactory neurons
0:23:36 that communicate
0:23:37 with the specific centers
0:23:37 of the brain,
0:23:38 namely the amygdala
0:23:40 and associated neural circuitry
0:23:40 and pathways
0:23:42 that trigger alertness
0:23:43 of the same sort
0:23:44 that a cold shower
0:23:45 or an ice bath
0:23:47 or a sudden surprise
0:23:49 or a stressful text message
0:23:49 would evoke.
0:23:50 Remember,
0:23:52 the systems of your body
0:23:53 that produce arousal
0:23:55 and alertness
0:23:55 and attention
0:23:56 and that cue you
0:23:57 for optimal learning,
0:23:58 aka focus,
0:24:00 those are very general mechanisms.
0:24:01 They involve
0:24:02 very basic molecules
0:24:03 like adrenaline
0:24:03 and epinephrine.
0:24:04 Same thing actually,
0:24:05 adrenaline and epinephrine.
0:24:08 The number of stimuli,
0:24:09 whether it’s peppermint
0:24:10 or ammonia
0:24:12 or a loud blast,
0:24:14 the number of stimuli
0:24:15 that can evoke
0:24:16 that adrenaline response
0:24:18 and that wake-up response
0:24:19 are near infinite
0:24:21 and that’s the beauty
0:24:22 of your nervous system.
0:24:22 It was designed
0:24:24 to take any variety
0:24:25 of different stimuli,
0:24:26 place them into categories
0:24:27 and then evoke
0:24:29 different categories
0:24:31 of very general responses.
0:24:32 Now you know a lot
0:24:33 about olfaction
0:24:33 and how the sense
0:24:34 of smell works.
0:24:35 Let’s talk about taste,
0:24:37 meaning how we sense chemicals
0:24:38 in food
0:24:39 and in drink.
0:24:42 there are essentially five,
0:24:44 but scientists now believe
0:24:45 there may be six
0:24:47 things that we taste
0:24:49 alone or in combination.
0:24:52 They are sweet tastes,
0:24:54 salty tastes,
0:24:55 bitter tastes,
0:24:57 sour tastes,
0:25:00 and umami taste.
0:25:01 Most of you have probably
0:25:03 heard of umami by now.
0:25:05 It’s U-M-A-M-I.
0:25:08 Umami is actually
0:25:09 the name for a particular
0:25:10 receptor that you express
0:25:11 on your tongue
0:25:15 that detects savory tastes.
0:25:17 Each one has a particular
0:25:18 group of neurons
0:25:19 in your mouth,
0:25:21 in your tongue,
0:25:22 believe it or not,
0:25:23 that responds
0:25:25 to particular chemicals
0:25:26 and particular chemical structures.
0:25:29 It is a total myth,
0:25:30 complete fiction
0:25:31 that different parts
0:25:32 of your tongue
0:25:33 harbor
0:25:34 different taste receptors.
0:25:35 You know,
0:25:36 that high school
0:25:37 textbook diagram
0:25:37 that, you know,
0:25:38 sweet is in one part
0:25:39 of the tongue
0:25:40 and sour is in another
0:25:41 and bitter is in another.
0:25:42 They are completely
0:25:43 intermixed
0:25:44 along your tongue.
0:25:45 So all these receptors
0:25:45 in your tongue
0:25:46 make up what
0:25:48 are called
0:25:48 the neurons
0:25:49 that give rise
0:25:50 to a nerve,
0:25:51 a collection
0:25:52 of wires,
0:25:52 nerve bundles
0:25:54 of what’s called
0:25:55 the gustatory nerve.
0:25:56 The gustatory nerve
0:25:57 from the tongue
0:25:58 goes to the nucleus
0:25:59 of the solitary tract
0:26:01 and then to the thalamus
0:26:02 and to insular cortex.
0:26:03 And it is an insular cortex,
0:26:04 this region of our cortex
0:26:05 that we sort out
0:26:07 and make sense of
0:26:07 and perceive
0:26:08 the various tastes.
0:26:10 Now, it’s amazing
0:26:12 because just taking
0:26:13 a little bit of sugar
0:26:14 or something sour,
0:26:15 like a little bit
0:26:15 of lemon juice
0:26:16 and touching it
0:26:17 to the tongue
0:26:19 within 100 milliseconds,
0:26:20 right?
0:26:22 Just 100 milliseconds,
0:26:23 far less than one second,
0:26:25 you can immediately
0:26:25 distinguish,
0:26:26 ah, that’s sour,
0:26:27 that’s sweet,
0:26:28 that’s bitter,
0:26:29 that’s umami.
0:26:31 And that’s
0:26:32 an assessment
0:26:33 that’s made
0:26:34 by the cortex.
0:26:35 Now,
0:26:36 what do these
0:26:38 different five receptors
0:26:39 encode for?
0:26:40 Well, sweet, salty,
0:26:41 bitter, umami, sour,
0:26:41 but what are they
0:26:43 really looking for?
0:26:44 What are they sensing?
0:26:45 Well, sweet stuff
0:26:47 signals the presence
0:26:47 of energy,
0:26:48 of sugars.
0:26:49 And while we’re all
0:26:51 trying or we’re told
0:26:51 that we should eat
0:26:52 less sugar
0:26:54 for a variety
0:26:54 of reasons,
0:26:57 the ability
0:26:57 to sense
0:26:58 whether or not
0:26:58 a food
0:27:00 has rapid
0:27:01 energy source
0:27:02 or could give rise
0:27:02 to glucose
0:27:03 is essential.
0:27:03 So we have
0:27:04 sweet receptors.
0:27:05 The salty
0:27:06 receptors,
0:27:07 these neurons
0:27:08 are trying to sense
0:27:09 whether or not
0:27:10 there are electrolytes
0:27:12 in a given
0:27:13 food or drink.
0:27:14 Electrolytes
0:27:15 are vitally important
0:27:16 for the function
0:27:17 of our nervous system
0:27:17 and for our entire
0:27:18 body.
0:27:18 Bitter receptors
0:27:20 are there
0:27:21 to make sure
0:27:22 we don’t ingest
0:27:23 things that are
0:27:23 poisonous.
0:27:24 The bitter receptors
0:27:26 create a,
0:27:26 what we call
0:27:27 labeled line,
0:27:28 a unique trajectory
0:27:30 to the neurons
0:27:31 of the brainstem
0:27:31 that control
0:27:33 the gag reflex.
0:27:35 If we taste
0:27:36 something very bitter,
0:27:38 it automatically
0:27:39 triggers the gag reflex.
0:27:41 Putrid smells
0:27:42 will also evoke
0:27:43 these same neurons.
0:27:45 The umami receptor
0:27:47 isn’t sensing
0:27:48 savory
0:27:49 because the body
0:27:50 loves savory.
0:27:51 It’s because
0:27:51 savory
0:27:52 is a signal
0:27:53 for the presence
0:27:54 of amino acids.
0:27:55 The presence
0:27:56 of amino acids
0:27:58 in our gut
0:27:58 and in our
0:27:59 digestive system
0:28:00 and the presence
0:28:01 of fatty acids
0:28:02 is essential.
0:28:03 The sour receptor,
0:28:04 why would we have
0:28:05 a sour receptor?
0:28:06 It’s there
0:28:07 and we know
0:28:08 it’s there
0:28:09 to detect
0:28:09 the presence
0:28:10 of spoiled
0:28:11 or fermented
0:28:12 food.
0:28:13 Fermented fruit
0:28:14 can be poisonous,
0:28:14 right?
0:28:15 Alcohols
0:28:16 are poisonous
0:28:17 in many forms
0:28:18 to our system
0:28:19 and
0:28:20 the sour
0:28:21 receptor
0:28:22 bearing neurons
0:28:23 communicate
0:28:24 to an area
0:28:24 of the brainstem
0:28:26 that evokes
0:28:27 the pucker
0:28:27 response,
0:28:29 closing of the eyes
0:28:29 and essentially
0:28:31 shutting of the mouth
0:28:32 and cringing away.
0:28:33 Now,
0:28:34 what’s the sixth
0:28:35 sense
0:28:36 within the taste system?
0:28:37 Not sixth sense
0:28:37 generally,
0:28:38 but within the taste system.
0:28:39 What’s this putative
0:28:40 possible
0:28:41 sixth receptor?
0:28:43 There are now data
0:28:44 to support
0:28:45 the idea,
0:28:46 although there’s still
0:28:47 more work that needs
0:28:47 to be done,
0:28:48 that we also have
0:28:49 receptors on our tongue
0:28:51 that sense fat
0:28:53 and that because fat
0:28:54 is so vital
0:28:56 for the function
0:28:57 of our nervous system
0:28:57 and the other organs
0:28:58 of our body
0:29:00 that we are sensing
0:29:01 the fat content
0:29:01 in food.
0:29:02 I want to talk
0:29:03 about the tongue
0:29:04 and the mouth
0:29:05 as an extension
0:29:07 of your digestive tract.
0:29:08 We are essentially
0:29:09 a series of tubes
0:29:10 and that tube
0:29:11 starts with your mouth
0:29:12 and heads down
0:29:13 into your stomach
0:29:14 and so
0:29:16 that you would sense
0:29:17 so much
0:29:18 of the chemical
0:29:18 constituents
0:29:19 of the stuff
0:29:20 that you might
0:29:21 bring into your body
0:29:22 or that you might
0:29:22 want to expel
0:29:23 and not swallow
0:29:25 or not interact with
0:29:25 by being able
0:29:26 to smell it.
0:29:27 Is it putrid?
0:29:28 Does it smell good?
0:29:30 Does it taste good?
0:29:30 Is this safe?
0:29:31 Is it salty?
0:29:32 Is it so sour
0:29:33 that it’s fermented
0:29:34 and is going to poison me?
0:29:35 Is it so bitter
0:29:36 that it could poison me?
0:29:38 Is it so savory
0:29:40 that yes,
0:29:40 I want more
0:29:41 and more of this?
0:29:42 Well, then you’d
0:29:43 want to trigger dopamine.
0:29:43 That’s all starting
0:29:44 in the mouth.
0:29:47 So you have to understand
0:29:48 that you were equipped
0:29:49 with this amazing
0:29:51 chemical sensing apparatus
0:29:53 we call your mouth
0:29:54 and your tongue
0:29:55 and those little bumps
0:29:56 on your tongue
0:29:56 that they call
0:29:57 the papillae,
0:29:58 those are not
0:29:59 your taste buds.
0:30:00 Surrounding those
0:30:01 little papillae
0:30:03 like little rivers
0:30:04 are these little
0:30:05 dents and indentations
0:30:06 and what dents
0:30:07 and indentations
0:30:08 do in a tissue
0:30:09 is they allow
0:30:10 more surface area.
0:30:10 They allow you
0:30:12 to pack more receptors.
0:30:13 So down in those grooves
0:30:14 are where all
0:30:15 these little neurons
0:30:17 and their little processes
0:30:18 are with these
0:30:19 little receptors
0:30:20 for sweet, salty,
0:30:21 bitter, umami, sour
0:30:22 and maybe fat as well.
0:30:23 Remember,
0:30:25 even though we can enjoy food
0:30:26 and we can evolve
0:30:27 our sense of what’s
0:30:29 tasty or not tasty
0:30:30 depending on life decisions,
0:30:31 environmental changes,
0:30:32 et cetera.
0:30:33 The taste system,
0:30:34 just like the olfactory system
0:30:35 and the visual system
0:30:36 was laid down
0:30:38 for the purpose
0:30:40 of moving towards
0:30:40 things that are good
0:30:41 for us
0:30:41 and moving away
0:30:42 from things
0:30:43 that are bad for us.
0:30:43 That’s the kind of
0:30:44 core function
0:30:45 of the nervous system.
0:30:48 I’d like to take a quick break
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0:32:39 Now I’d like to return
0:32:41 to pheromones.
0:32:42 As I mentioned earlier,
0:32:44 true pheromonal effects
0:32:45 are well-established
0:32:45 in animals
0:32:47 and one of the most
0:32:49 remarkable pheromone effects
0:32:50 that’s ever been described
0:32:51 is one that actually
0:32:51 I’ve mentioned before
0:32:52 on this podcast,
0:32:53 but I’ll mention again
0:32:54 just briefly,
0:32:55 which is the Coolidge effect.
0:32:56 The Coolidge effect
0:32:57 is the effect
0:33:00 of a male
0:33:00 of a given species.
0:33:02 In most cases,
0:33:03 it tended to be a rodent
0:33:04 or a rooster
0:33:06 mating
0:33:08 and at some point
0:33:10 reaching exhaustion
0:33:11 or the inability
0:33:12 to mate again
0:33:13 because they just simply
0:33:14 couldn’t for whatever reason.
0:33:16 The Coolidge effect
0:33:18 establishes that
0:33:20 if you swap out
0:33:21 the hen with a new hen
0:33:23 or the female rat
0:33:24 or mouse with a new one,
0:33:26 then the rat
0:33:27 or the rooster
0:33:29 spontaneously regains
0:33:30 their ability to mate.
0:33:31 Somehow their vigor
0:33:32 is returned.
0:33:33 The refractory period
0:33:34 after mating
0:33:35 that normally occurs
0:33:37 is abolished
0:33:38 and they can mate again.
0:33:39 But it turns out
0:33:41 that females also will,
0:33:43 female rodents
0:33:44 will mate to exhaustion
0:33:45 and at some point,
0:33:46 at some point,
0:33:46 excuse me,
0:33:47 they will refuse
0:33:48 to mate any longer
0:33:50 unless you swap in
0:33:50 a new male.
0:33:52 And then because mating
0:33:53 in rodents
0:33:54 involves the female
0:33:55 being receptive,
0:33:55 there are a certain
0:33:56 number of behaviors
0:33:57 behaviors that mean
0:33:57 that she,
0:33:58 that tell you
0:33:59 that she’s willing
0:34:00 and wanting to mate,
0:34:02 so-called lordosis reflex.
0:34:06 Then if there’s a new male,
0:34:08 she will spontaneously regain
0:34:10 the lordosis reflex
0:34:12 and the desire to mate.
0:34:12 How do we know
0:34:13 it’s a pheromonal effect?
0:34:14 Well,
0:34:15 this recovery
0:34:16 of the desire
0:34:17 and ability to mate
0:34:18 both in males
0:34:20 and in females
0:34:21 can be evoked
0:34:22 completely
0:34:23 by the odor
0:34:23 by the odor
0:34:25 of a new male
0:34:25 or female.
0:34:26 It doesn’t even have
0:34:27 to be the presentation
0:34:28 of the actual animal.
0:34:29 And that’s how you know
0:34:29 that it’s not
0:34:31 some visual interaction
0:34:32 or some other interaction.
0:34:33 It’s a pheromonal interaction.
0:34:34 Now,
0:34:35 as I mentioned earlier,
0:34:36 pheromonal effects,
0:34:39 humans have been debated
0:34:40 for a long period of time.
0:34:40 We are thought
0:34:42 to have a vestigial,
0:34:43 meaning a kind
0:34:44 of shrunken down
0:34:46 miniature
0:34:48 accessory olfactory bulb
0:34:49 called Jacobson’s organ
0:34:51 or the vomeronasal organ.
0:34:53 Some people don’t believe
0:34:54 that Jacobson’s organ exists.
0:34:55 Some people do.
0:34:57 So there’s a little dents
0:34:57 as you go up
0:34:58 through your nasal passages
0:34:59 and there is evidence
0:35:00 of something
0:35:02 that’s vomeronasal-like.
0:35:04 Vomeronasal is the pheromonal organ.
0:35:06 They call it Jacobson’s organ
0:35:07 if it’s present in humans.
0:35:09 Kind of tucked into
0:35:10 some of the divots
0:35:11 in the nasal passage.
0:35:14 Even if that organ,
0:35:15 Jacobson’s organ,
0:35:16 isn’t there
0:35:18 or is not responsible
0:35:19 for the chemical signaling
0:35:20 between individuals,
0:35:22 there is chemical signaling
0:35:23 between human beings.
0:35:24 As I mentioned earlier,
0:35:26 the effect of tears
0:35:28 in suppressing
0:35:29 the areas of the brain
0:35:29 that are involved
0:35:32 in sexual desire
0:35:34 and testosterone of males.
0:35:35 That’s a concrete result.
0:35:37 It’s a very good result
0:35:38 published by an excellent group.
0:35:40 There is also evidence
0:35:43 both for and against
0:35:44 chemical signaling
0:35:46 between females
0:35:47 in terms of synchronization
0:35:48 of menstrual cycles.
0:35:50 Now, the original paper
0:35:51 on this was published
0:35:52 in the 1970s
0:35:54 by McClintock.
0:35:56 And it essentially said
0:35:57 that when women
0:35:58 live together
0:35:59 in group housing,
0:36:00 dormitories,
0:36:01 and similar,
0:36:02 that their menstrual cycles
0:36:03 were synchronized
0:36:04 and that was due to
0:36:04 what was hypothesized
0:36:06 to be pheromonal effects.
0:36:07 over the years
0:36:08 that study
0:36:08 has been challenged
0:36:09 many, many times.
0:36:12 The more recent data
0:36:13 point to the idea
0:36:14 that there is
0:36:15 chemical-chemical signaling
0:36:16 between women
0:36:18 in ways that impact
0:36:18 the timing
0:36:19 of the menstrual cycle.
0:36:21 Is that a pheromonal effect?
0:36:22 Well, by the strict definition
0:36:23 of a pheromone,
0:36:24 a molecule that’s released
0:36:25 from one individual
0:36:26 that impacts the biology
0:36:27 of another individual,
0:36:28 yes.
0:36:28 It’s not clear
0:36:30 what the chemical compound is.
0:36:32 None of this surprises me.
0:36:34 None of this should surprise you.
0:36:35 it’s very clear
0:36:35 that hormones
0:36:36 have a profound effect
0:36:37 on a large number
0:36:39 of systems in our biology
0:36:41 and that smell and taste
0:36:42 and the ability
0:36:43 to sense the chemical states
0:36:44 of others,
0:36:45 either consciously
0:36:45 or subconsciously,
0:36:47 have a profound influence
0:36:47 on whether or not
0:36:49 we might want to spend time
0:36:49 with them,
0:36:49 whether or not
0:36:50 this is somebody
0:36:51 that we’re pair-bonded with,
0:36:52 whether or not
0:36:52 this is somebody
0:36:53 that we just met
0:36:55 and don’t trust yet,
0:36:56 things of this sort.
0:36:58 And given what’s at stake
0:37:00 in terms of reproductive biology,
0:37:02 it makes so much sense
0:37:04 that much of our biology
0:37:06 is wired toward detecting
0:37:07 and sensing whether or not
0:37:08 things and people
0:37:10 are things that we should
0:37:11 approach or avoid.
0:37:13 You and every other human
0:37:14 from the time you’re born
0:37:15 until the time you die
0:37:18 are actively seeking out
0:37:21 and sensing and evaluating
0:37:23 the chemicals that come
0:37:24 from other individuals.
0:37:26 It’s a really nice study
0:37:26 that was done
0:37:29 by the Weitzman Institute,
0:37:29 a group there,
0:37:30 I think it was also
0:37:31 Noam Sobel’s group,
0:37:32 but another group as well,
0:37:32 as I recall,
0:37:35 looking at human-human interactions
0:37:36 when they meet
0:37:36 for the first time.
0:37:38 It’s a remarkable study
0:37:41 because what they found
0:37:43 was people would reach out
0:37:44 and shake hands.
0:37:45 And what they observed
0:37:48 was almost every time
0:37:50 within just a few seconds
0:37:52 of having shaken hands
0:37:53 with this new individual,
0:37:54 people will touch their eyes.
0:37:56 they are taking chemicals
0:37:58 from the skin contact
0:37:59 and they are placing it
0:38:01 on a mucosal membrane
0:38:01 of some sort,
0:38:02 typically not up their nose
0:38:03 or in their mouth,
0:38:04 typically on their eyes.
0:38:05 Believe it or not,
0:38:06 you’re marking other people
0:38:07 when you shake their hand
0:38:09 and they are then
0:38:10 taking your mark
0:38:11 and rubbing it
0:38:13 on themselves subconsciously.
0:38:14 So we all do
0:38:15 these kinds of behaviors
0:38:17 and now that you’re aware of it,
0:38:18 you can watch for it
0:38:18 in your environment,
0:38:20 you can pay attention to people.
0:38:21 We are evaluating
0:38:23 the molecules on people’s breath.
0:38:25 We are evaluating
0:38:26 the molecules on people’s skin
0:38:28 by actively rubbing it
0:38:29 on ourselves.
0:38:31 And we are actively involved
0:38:33 in sensing the chemicals
0:38:34 that they are emitting,
0:38:35 their hormone status,
0:38:36 how they smell.
0:38:38 We’re detecting
0:38:40 the pheromones possibly,
0:38:42 but certainly the odors
0:38:43 in their breath.
0:38:44 So today we talked a lot
0:38:46 about olfaction, taste
0:38:47 and chemical sensing
0:38:48 between individuals.
0:38:49 I like to think
0:38:50 that you now know a lot
0:38:52 about how your smell system works
0:38:53 and why inhaling
0:38:55 is a really good thing to do
0:38:56 in general
0:38:57 for waking up your brain
0:38:59 and for cognitive function
0:39:00 and for enhancing
0:39:00 your sense of smell.
0:39:02 And we talked about
0:39:03 chemical signaling
0:39:03 between individuals
0:39:05 as a way of communicating
0:39:06 some important aspects
0:39:07 about biology.
0:39:08 People are shaping
0:39:09 each other’s biology
0:39:10 all the time
0:39:11 by way of these chemicals
0:39:12 that are being traded
0:39:13 from one body to the next
0:39:14 through air
0:39:16 and skin-to-skin contact
0:39:17 and tears.
0:39:18 Last but not least,
0:39:19 I want to thank you
0:39:20 for your time and attention
0:39:21 and your willingness
0:39:22 to embrace new concepts
0:39:23 and terms
0:39:25 and to learn about science
0:39:25 and biology
0:39:26 and protocols
0:39:28 that hopefully can benefit you
0:39:28 and the people that you know.
0:39:30 And of course,
0:39:31 thank you for your interest
0:39:32 in science.