December 14, 2016
The smell of your childhood bedroom, of the Shore on a summer day, of your favorite pastry baking in the oven -- these are the sensations that, for whatever reason, tend to draw forth all sorts of memories. Why, of course, is anyone's best guess.
Eager to get a firm answer, we reached out to Edmund Pribitkin, a physician with Jefferson Health and an expert in smell.
Why do we associate certain smells with memories? What's the trigger?
Well, I think what happens is, the anatomy of the brain really determines why we do have this trigger memory with [scent]. The basic thing is, the neurons -- the receptors in the nose are actually primary neurons. In other words, a lot of neurons in the body, for different senses, are not primary ...
The sense of smell, it's direct. Those neurons in the nose are directly wired into the brain, unlike other senses. Like sensation, for example, which goes through the spinal cord and then the brain. This is really a direct feed into very important parts of the brain. And that also is implicated not only in memory, but in emotion. Those two parts of the brain are the amygdala and the hippocampus.
The key here is to understand that, for example, your sense of vision doesn't go through the hippocampus or the amygdala; your ability to hear doesn't go through the hippocampus or amygdala. But your sense of smell goes directly through those areas before it gets to higher levels of the brain. And that processing connection probably is why we get emotional when we smell things and also have memories that come back when we smell.
So smells are more all-encompassing than, say, vision or hearing?
Yeah, you know, it's just the way we're put together, basically. When we look at the anatomy of the brain -- when you see something, it goes through the retina to the optic nerve and back to the visual cortex, and then you record it in the visual cortex in the back of your brain. When you smell something, it goes up to the primary area of olfaction, but then it's hard-wired into the amygdala and hippocampus. And those areas are basically the areas that trigger emotions, memories. It is, in a sense, as you put it, more all-encompassing for those real, basic emotions we experience. Because I think it's not just that it brings back a memory, but when I walk into, for example, an old bookstore, that smell of old books triggers an emotional connection. It's really that emotional intensity of memory that I think the sense of smell triggers that nothing else can trigger in the same way.
On the flipside, if you have PTSD ...
Oh my goodness, yeah. That's actually one of the really, really difficult things to cope with. People who have been in fires, in particular, that smell of smoke really can trigger a horrible, horrible series of memories. And if you have a sense of tremendous anxiety -- what we commonly call post-traumatic stress disorder -- visual cues can do the same thing, but there are certain smells people associate with horrible events that bring back that flood of emotion that's just so overpowering. Such a feeling of anxiety and helplessness that it really does cripple them -- they really can't function when they feel that.
Anything you want people to know?
I think that one of the other things that happens is there are lots of studies being done [in which] people are trying to use smells to try and change moods. Positive smells to help people work more efficiently in offices. And the difficulty is that the experience isn't universal for folks -- it's often a very personal experience. It's hard to pump smells into an area and have the same kind of universal response you would hope to get in a laboratory or something. It's interesting how that research is going. There are certainly folks who bring candles to put themselves in a specific mood. The candle doesn't actually give you a visual image, perhaps, but that scent puts you in a mood where you can work and that makes you happy.
The Christmas tree -- people bring it into their homes and that tree smell triggers such a wonderful emotional memory, even more than Christmas music, for example. So, researchers for workplace efficiency look and see 'What are the smells that potentially could help folks be happier at work?' And use those to make folks more efficient and better workers. One of the things that is an issue with smell is smell fatigue. When you go into a room and there's a bad smell, in a minute or two the sense of that smell will disappear -- not as 'bad,' so to speak. So, most of the effect of the sense of smell is temporary. That's one of the things we haven't quite figured out yet -- how that fatigue happens.
We do adjust quickly to smell. Like when friends come over and point out 'that smell,' and you have no idea what they're talking about.
The brain is amazing in that sense. It becomes accustomed to it and it's sort of like when you're driving in a car. You don't pay attention to the million things going on around you; you know how to drive the car. Someone driving the first time says, 'Oh my gosh, did you see that? How hard is this?' Your brain is amazingly adaptable. In the context of memory, it evokes a strong emotion, but then it passes. That's an interesting phenomenon.