Neuroscience
Where are the Matzoh Balls of Yesterday Year?
How do the smells from Passover meals evoke memories?
Posted April 20, 2008
Where are the Matzoh Balls of Yesterday Years?
This weekend the Jewish holiday of Passover has begun. As Jews around the world sit down to their seder meals, they begin an evening of ritual and the re-telling of the exodus from Egypt. Although there are periodic sips of wine as the story unfolds around the table, there is a long wait before the meal begins. Often the thick salty smell of Matzoh Ball soup pervades the dining room, and while the leader intones the next blessing, memories are stirred in a Proustian flood of images. How does smell memory work and why does it have this compelling emotional power?
Thanks to some of the remarkable detective work of Linda Buck and her colleagues at Harvard University, we now have a much better sense of the intricacy and specificity of our memory for smells. When that matzoh ball is cooking in the other room, it is releasing vaporized molecules (no doubt heavy in sodium!) that waft up our nasal cavity, encountering hair-like olfactory receptors. Some of these receptors react uniquely to particular molecules and in other cases unique molecules activate several different receptors. These receptor messages (which could be considered like the alphabet or letters of smell) travel to the olfactory bulb that sits at about the level of the eyes at the threshold of the brain. Reaching two different receptor areas in the bulb, they combine into distinct patterns (the words of smell), which then travel through a single neural path (the most immediate and direct of all sensory systems) to the smell sensory cortex in the higher brain. Interestingly, and not at all unexpectedly, considering the power of smell to move us, this neuronal connection also finds its way to the limbic system, the older and more emotion-based part of the brain. At same time that our higher order thinking and our emotions are activated, connections to our hippocampus from both these areas have invoked memories linked to the smells. A few vaporized matzoh ball molecules have catapulted into an Armageddon of emotional memory. Proust understood this all when he wrote,
After the people are dead, after the things are broken and scattered...the smell and taste of things remain poised a long time, like souls...bearing resiliently, on tiny and almost impalpable drops of their essence, the immense edifice of memory. (cited from Pines, M., The mystery of smell: The vivid world of odors, retrieved from http://www.geiscollection.com/senses/d110.html, 4/20/08)
So tonight, as you wait patiently for the soup to be served, think of those thousand of receptor cells spelling in a language of smell the seders of the past, filled with the faces of bubbes and zaydes, now long gone, but brought back in this moment when scent, thought, and feeling combine.