Can Smells Improve Your Memory?


Welcome to Better Brain Fitness, hosted by doctors Josh Turknett and Tommy Wood. In this podcast, we will explore the frontiers of how to keep our brain fit and healthy so that we can perform at our best and do the things we love for as long as possible. Let’s go. Hello, and welcome back to another episode of the Better Brain Fitness podcast. My name is Tommy Wood, and I’m here with my fragrant co-host, doctor Josh Turk. Let’s say hello Josh hello i’m amazed you can smell me all the way across the screen, but I am quite fragrant today. Yeah, I don’t know if that’s a good thing or a bad thing. Thank you there we’ll leave it.

00:43 : Maybe you’re going to tell us. That’s right. We you recently had an addition of your newsletter that talked about fragrances and olfaction or which is a fancy word for smell and the brain. And we had some questions that came straight in about this. So people obviously very interested in it. So we’re going to dive into those questions. I’m going to read two out. So the first comes from Lou in Makanda, Illinois who says the study of essential oil fragrances as cognitive stimulation peaks my interest despite despite prior doubts about aromatherapy.

01:24 : Since this study is about particular odours, I wonder if other odors are stimulating as well. And he lists some options like bacon motor oil at WD forty and fecal matter. So that’s a lots of different smells across the spectrum there. So that’s our first question. And then the second question comes from David McIntyre, who is in Haydenville, Massachusetts. He says, I’m a big fan of the Best Brain Fitness podcast. Thank you very much. And I’m intrigued by the findings about olfactory stimulation that you discussed in the latest Grainger Connection email. Newsletter i find it curious that the particular study you discuss tested the effects of olfactory stimulation during sleep, as most, if not all, of the other activities you recommend for brain health are things you do during the day.

02:12 : The most obvious example is learning a musical instrument, which can clearly be done only be done while we’re awake. I understand, of course, that brain activity while we sleep is an essential part of the process, but for the most part, your brain fitness activities are things you do while you’re conscious, David then says, If I understand correctly, then the rationale for studying this phenomenon at night was simply convenience.

02:32 : My question is whether those of us who typically spend a couple of hours or more in a day, say a Home Office, couldn’t benefit just as much with stimulation during the day rather than at night. Is there any reason to think that olfactory stimulation during a learning activity such as practicing an instrument or studying a foreign language would actually enhance the memory associated with that particular activity? So that’s a nice question because I think there’s some research on that I’m sure you’ll talk about.

02:56 : So a couple of questions. One is that the range of different stimuli, different smells, you know, how might we think about how those might be cognitively stimulating? And then also does this have to happen at night as it was in this paper kind of happened during the day. I’d be particularly interested to know your thoughts on, you know, the idea of stimulation during arrest period when you’re supposedly consolidating and adapting rather than trying to be exposed to new stimuli.

03:27 : So which would happen during sleep. So all of those things rolled into one big question about smell. Off you go. Ok, I’ll do my best to unpack all that without trying, without getting too deep into any one thing. So just to step back the study that I talked about in the newsletter that these questions were related to was they took older adults and had them sleep with certain smells being emitted into their into the air by an essential oil diffuser. So while they were sleeping did they had seven different scents, one for each night of the week and so it just rotated through each cent for seven days and then started back over to the at the beginning after seven days.

04:19 : Did this for six months. Tested them on a range of cognitive tests before and after. There was a control group that was not with that had a diffuser but there was number odors associated with it. And what they found was that the group, the aromatherapy group, the group that did have the actual sense showed significant improvement in a test of working memory and improvement was reported as 226 %. So basically you know having this essential oil diffuser on at night time in six months led to this 200 and twenty two hundred twenty six percent % their performance on this working memory test, which sounds pretty incredible and almost a little bit implausible, right? Seems a little bit like too easy and there were limitations in the test was a fairly small sample size.

05:19 : You know, they did a range of tests, not all show differences and that maybe we’ll talk about why that might be as well. But at any rate, you know, it seems like, you know, how could this really be true? Is this actually even biologically plausible that having you know, something wafting in the air at night could improve your memory and even possibly protect against, you know, cognitive decline, dementia. So is this even plausible? So on the one hand, it is a kind of brain stimulation, right? In this case, we are stimulating our olfactory cortex, you know, in the same way that music stimulates auditory cortex.

06:01 : And ultimately, you know, all of our sensory input is transduced into the firing of neurons. And then subsequent processing is all about finding patterns in those firings, regardless of where they originated, whether it was sound waves or odors or whatnot. And as we talked about in the episode around the kind of music that’s best for cognitive stimulation, you know, the more novel the stimulus, the more likely the brain is to take notice, the more likely it is to, you know, promote an adaptive response of some kind, which is what we’re trying to do with cognitive stimulation. On the other hand, you know, compared to our other senses, smell doesn’t nearly have nearly the same amount of, you know, neural resources dedicated to it, not nearly the amount of brain.

06:50 : So we humans aren’t especially good at old faction, Umm. And we don’t rely nearly as much on it air to make sense of the world as somewhat other animals. For example, dogs have something like 50 times or more receptors that are devoted to smell and our olfactory cortex takes up a fairly small amount of our brain compared to our vision, which is the sense we rely on the most, which takes up about a third of the brain, so it’s way larger. So from the standpoint of sort of providing a whole brain workout, olfactory stimulation is unlikely to do that. However, what it does have going for it is it is right near the hippocampus, which as some of you may know is the part of the brain involved with long term memory storage known to be involved early on in dementia and Alzheimer’s disease.

07:50 : It’s also that proximity is thought to be why smells can so readily elicit memories, including ones that we haven’t revisited for a very long time. And so that proximity also may be the one reason why smell stimulation could be specifically beneficial for memory. And we’ve also talked about previously, there is evidence that a reduction in any of our symptom of any of our senses is associated with an increased risk of dementia and that includes smell. In fact, a reduction in the sense of smell has been well established as a potential early sign of dementia for quite a while, and the question is whether that’s cause or effect.

08:35 : I think it’s likely both. But the good news is that as studies indicate, this is something that can be regained in many cases and improved upon with, you know, smell rehabilitation. And there is also a body of evidence that supports olfactory stimulation being beneficial for memory. So olfactory enrichment of a mouses environment has been shown to improve its memory and lead to the birth of new neurons. Olfactory stimulation, as I mentioned, has been shown to help restore olfactory function in humans.

09:11 : So for people who have had a reduction in sense of smell for a variety of reasons, olfactory stimulation can help to restore it and that has also been shown to lead to an increase in gray matter in the thalamus and in the hippocampus. And then there have also been prior studies showing that olfactory enrichment can improve cognitive function in patients with dementia. This podcast is brought to you by the Brain Jio Academy. The Brain Jio Academy provides brain boosting whole brain stimulation in the form of neuroscience based musical instruction designed for adult brains and with no prior musical experience required.

09:57 : Start your brain boosting musical journey today at Brain Joe dot Academy. So there’s enough to support a claim that olfactory stimulation can enhance memory and protect against cognitive decline and specifically decline in memory. Now the question you know that these that both of the questions we received here are getting at is what kind of protocol, how is what’s the best way to do it to achieve that effect O what kind of odors are best? Does the time of day matter? And in this study, as I think Dave mentioned, you know, that was done at night partly for convenience and I’m sure to ensure consistency in this experimental setting, you want to, you know, as best you can make sure the conditions are held constant across subjects.

10:54 : So, you know, we don’t have the empirical data to answer these questions fully, but I think that the effect is likely a function of how novel it is, how noticeable it is and how long it’s around. So, you know, novel enough and noticeable enough that the brain pays attention and then long enough for it to stimulate some kind of adaptive response. So you know, in that regard, I think maybe an hour or so would be a safe bet and I don’t think whether it’s day or night likely doesn’t matter.

11:29 : It is interesting that you know that stimulus that’s happening while we’re sort of in rest and recovery mode is, you know, exerting this is providing this benefit. But I also think it speaks to the fact that most of our processing is not conscious. And so you know there are likely many different ways that we could take advantage of that fact from a cognitive stimulation standpoint. I mean even when we’re listening to music, right, most of that processing is a non conscious and we’re just sort of receiving the end result of all of it.

12:06 : And that’s happening throughout the day. So you know, if we were to plop into a into a world completely foreign to what ours is right now, just by existing in that world, we would be, you know, providing our brain all sorts of new stimuli that it would start to adapt to that you know, wouldn’t require any conscious effort on our part to get those benefits. And I think this is that’s probably analogous to kind of what’s happening here, you know, for even if just having a new smell in our environment, regardless of whether or not we’re doing anything with that or making any specific effort around, you know, analyzing that smell that it’s having some kind of benefit.

12:46 : Could you enhance that further by doing things to, you know further improve your olfactory discrimination abilities, you know, good study to become a some of yay or whatever. I’m sure, yeah, there are ways to improve it. But the cool thing here is that simply just the novel stimulus alone is enough to be providing some benefits. And All in all, I think, you know, this is just another super easy and essentially 0 risk way to improve brain health and fitness. You know, similar to the benefits of just listening to music. So low hanging fruit in that regard. And as we’ve talked about, one of the central challenges we face as adults is the fact that our perceptual systems for decoding the world we live in have matured.

13:35 : And when we’re young, our brain is building all these neural networks needed to decode all of our perceptual stimuli, which means constant plastic reorganization you know throughout cortex. And I don’t think there’s anything better for promoting brain tissue health than stimulating plastic change. But creating something that is analogous in the perceptual realm as adults, as we encounter less and less novelty in our sensory input day-to-day is a real challenge. And this kind of olfactory stimulation I see is one of the tools we have for overcoming that challenge.

14:12 : The last point was could the could you utilize smells to enhance learning and I think that the main use case there is in consistently associating a particular smell with a particular kind of learning activity. So if you’re going to, you know always you’re going to be, you know, practicing your instrument at a certain time each day, pairing that practice with a particular smell. And you know, provided that the practice itself is high quality, you know you’re paying attention.

14:46 : It’s at a good time of day. You’re motivated, you’re interested, you can begin to condition that particular response to that particular smell. So that can smell can then sort of be enhancing your ability to pay attention or get into kind of the best frame of mind for practice. So that’s one way it could be used. Another way is that if you are studying for a test and you pair while you’re studying, you pair it with some kind of novel olfactory stimulus, then there’s evidence that you know later on you’ll be more likely you’ll be able to recall more your performance will be better in the presence of that stimulus.

15:29 : So that stimulus can act as a cue to sort of how help you pull up those memories or those networks that you created while you were studying. So I think that’s, those were the main points that I wanted to hit on this one. And by the way, I’ll put a link to that issue of the Brain Joe Connection newsletter where I talk about this, but anything else to add there, Tommy? A few random thoughts. That you may have additional thoughts on the 1st. Is that last point about using certain smells to aid in learning and memorization? I think there are a few studies on that, particularly if you’re trying to memorize particular facts or some kind of semantic memory.

16:15 : The other side of that, particularly if we’re thinking about some kind of cognitive performance though is that you don’t want to be reliant on those things because you can create a no sibo effect. You’re like i don’t have my essential oil diffuser so I can’t I can’t remember things and then that will of course lead to work hundred % performance. So that’s just worth bearing in mind. But if you have a very specific use case, right, I need to learn this stuff and I can smell, I can create this smell during the test and then I think there’s good evidence for that, but you don’t want to be reliant on your diffuser for your piano performances, right? Or anything like that.

16:53 : Then that all of this from reminded me of this one paper that came out on those few years ago, seven or eight years ago, where they showed that the distance at which you could smell a tablespoon of peanut butter was associated with your risk of Alzheimer’s disease. I just thought that was that was interesting that was that was the smell that they used to test your like somebody’d olfaction.

17:18 : And then the final thing was maybe more of a question rather than a random comment, which is that there’s a reasonable evidence to suggest that your first particularly say your first night in a new environment is associated with worse sleep because you’re not comfortable, you don’t know what’s going on around you. I imagine that smell is part of that. So I wonder if maybe the first time you have a particular smell that you’re exposing yourself to and you’re doing it at night, as they did in this study may be associated with worse sleep because you’re it’s unfamiliar, which can then affect sleep architecture right then.

17:59 : So maybe like pure novelty, at least the first time we’re just doing it once, may not necessarily be a good thing. But then they had repeated exposures of these of these several scents, right. So eventually it became more familiar, but it was still that’s sort of something relatively new. So I think if people are going to do it during sleep then there may be repeated exposures are going to be useful rather than just like having a different random smell every night because that there’s a hypothetical possibility that it may affect sleep. I just wondered if you had any thoughts on that.

18:32 : That’s a good point. There’s there probably is a balance there you know between like the potential impacts during sleep of it being super novel, right versus the benefits of that you’re accruing from that novelty. I think hopefully you know this the particular protocol that they used here, the fact that the net result was benefit indicate at least that mitigated against any potential downsides from sleep loss. But and then the other thing is too, it’s possible that the cognitive stimulation benefits are tied into the increased amount of attention, right. The fact that you’re attending and you’re disrupting sleep a little bit.

19:07 : So there’s that that’s probably enhancing the stimulation to a degree and I have personally, I do have experience that I do have. So I’ve tried the diffusers at night and when it is something new and novel, I do find that it’s, you know, a little more noticeable and probably has an impact, at least to a degree, on sleep. Not terrible but probably like time to fall asleep at least is a little bit longer but yeah that’s definitely worth considering and I do think too that you know using the same one for a sustained period of time is probably the best idea.

19:44 : And then you know perhaps if you were to do this you say you do the you know do a six month protocol as the study did. You know maybe after six months of rotating to a new a new set of smells you know would be would be wise. Ok well great questions is super interesting topic. Probably a lot more there that we’ll learn and a lot more that could be talked about. And if you guys have any questions about it, about that or about anything else related to brain health and fitness, feel free to send it our way All right. Thank you guys so much and we will see you in the next episode.