Every other Friday, the Outside/In team answers one listener question about the natural world.
This week, Amanda asked, "Why do smells have such a powerful connection to memory?”
Outside/In’s Justine Paradis looked into it with host Nate Hegyi.
Transcript
This has been edited for length and clarity.
Justine Paradis: Nate, do you relate to this? Have you ever smelled something that sends you right back to childhood?
Nate Hegyi: Yes, the smell of diesel does. Specifically, diesel in a marina. It always brings me back to my childhood, going out with my uncle, off the coast of Vancouver Island, going fishing. And it’s just a joyful memory.
Justine Paradis: For me it’s that super synthetic coconut-y smell of kids sunscreen.
Nate Hegyi: Right, that’s the amazing thing about smell. It’s just a direct blast, a direct vein right into your memory in a way that I think other senses don’t quite do.
Justine Paradis: So looking at a photo of ourselves as children on the beach—or out fishing with your uncle—that’s probably going be less vivid than smelling the diesel or the sunscreen. And that happens for a reason. Here’s neuroscientist Rachel Herz.
Rachel Herz: When memories are triggered by scent, they are fundamentally, uniquely more emotional and evocative than when that same memory is triggered through any other mechanism.
Justine Paradis: The explanation for that is evolutionary. Our sense of smell is one of our older senses. It’s deeply connected to older parts of the brain, specifically, the hippocampus and the amygdala, the memory and emotional centers of the brain. Neurobiologist Bob Datta said when you see something, that visual information is traveling through 10, maybe 15 or 20 neurons before getting to the hippocampus.
Bob Datta: For smell, that number is two. So, your olfactory system is basically hardwired into your memory and emotion systems directly.
Nate Hegyi: Which is why it feels like such a direct vein into your brain.
Justine Paradis: Direct nerve, it is!
Nate Hegyi: That’s really fascinating. It’s one of those rare moments where how I think about smell and memory is how it works.
Justine Paradis: Yeah, it’s literally a fast, short journey to the memory and emotional centers.
Nate Hegyi: So cool.
Justine Paradis: Bob also told me there’s another significant connection between smell and memory. And that has to do with cognitive disorders. In fact, loss of your sense of smell is one of the first signs of Alzheimer's or Parkinson’s disease—so, if you’re middle-aged and you suddenly lose your sense of smell, Bob says:
Bob Datta: The odds that you will go on to develop Alzheimer's are something like ten times higher than if you had an intact sense of smell.
Nate Hegyi: That’s kind of frightening. Something to be aware of.
Justine Paradis: It’s something to pay attention to. Researchers don’t yet know if this is just a correlation or if there’s some causative thing going on here. Maybe the loss of a sense of smell is just revealing the condition of your nervous system before other symptoms appear. Or maybe the loss of sense of smell is somehow causing or accelerating the disease. We don’t know. But a potential upside to this connection is: your nose offers a direct link to your nervous system, so maybe exercising our sense of smell can help exercise our brains.
Rachel Herz: Deliberate sniffing may be activating stem cells in the nostrils that then help with the regeneration of the sensory neurons, which help in the recovery from the physical end. But having the mental cognitive energy at the same time is helping the brain form those connections again, stimulating the brain in a way that's effortful, which is good for brain function. So it’s always to sort of think, as it were!
Nate Hegyi: So, literally stopping and smelling the roses.
Justine Paradis: Literally stopping and smelling the roses and thinking about it could actually be really good for you.
Nate Hegyi: That’s so cool.
If you’d like to submit a question to the Outside/In team, you can record it as a voice memo on your smartphone and send it to outsidein@nhpr.org. You can also leave a message on our hotline, 1-844-GO-OTTER.
