Smells Like Home

California chaparral has a very distinctive smell. It's part warm dirt and part plant life and part air that's close enough to the sea to turn just barely humid. It's a smell that I grew up with, and I associate it with sunscreen and open air and early mornings shooting arrows at paper plate targets. I was biking home the other night, three thousand miles away in a city that hasn't had space to stretch its legs in three hundred years, and I smelled it. It smelled like this:

And this:

And this:

And this: 

It smelled like open space, and oh god, if you think I don't miss this sometimes, you are sorely mistaken. It's funny what a smell will do to you like that. One breath, and I wanted, suddenly and intensely, to be back in California, somewhere where I could see all the way to the horizon and walk more than a hundred feet without seeing something made out of concrete. Visual memories are like old photo albums - kind of faded and familiar, and you can pull them out whenever you want to. Olfactory memories jump out of freaking nowhere and clock you over the head with vivid images and emotions.

It turns out there's a reason for that. The physiology of the olfactory system is such that the primary olfactory cortex, of the brain-bits that process sensation, is physically closest to the hippocampus and the amygdala, which deal with memory and emotion, respectively. Not only that, the olfactory nerve is only a few synapses away from both those structures. Naming odors seems to also have an effect on both the ability to access an olfactory memory as well as our opinion of the odor. For example, someone who smells lavender and can't identify it will probably dislike it, whereas someone who can name the odor will find it pleasant. 

That which we call...lavender.

Science doesn't seem to have a clear reason for why we have olfactory memories. In fact, it's sort of  mysterious - your average olfactory neuron dies after only 60 days. The human sense of smell is sort of the low man on the totem pole - relatively poorly understood in comparison to sight and hearing. Taste and smell are physically and physiologically different than sight and sound. Receptors in your eyes and ears respond to different frequencies of a (light or sound) wave, and your brain translates the frequency into something you perceive as a red, chirping bird. To taste or smell something, your own receptor molecules have to come into physical contact with what you're perceiving. Smell goes one step further: it is the only sense in which receptor neurons interact directly with the environment.

I won't pretend to know the neurological details of why olfactory memories are so strong or so vivid, but everything I've read points to the fact that the olfactory system is a visceral, immediate, and far-reaching one.  Most of our olfactory memories are made in childhood, which may explain why these memories seem so sudden - on smelling boxed birthday cake mix, we don't remember the office party two weeks ago, we remember our sixth birthday party instead. 

Who knows? Maybe after a couple more years in this city, I'll move away and find myself with a new set of olfactory memories to tie me here. I'm not too sure, though. This is an old place, covered in concrete and bricks. I don't know if I want to remember what it smells like.