Chronicling the link between scent and memory
Anyone who remembers a vacation to the beach when they breathe in the ocean air or who thinks of their grandmother when they smell homemade cookies is well aware that scent is strongly connected to memories. But what is the mechanism that triggers this trip down memory lane?
A process known as long-term potentiation describes how synapses change in strength following brief periods of activity. It has long been cited to explain how mammals store different types of information—such as specific places, names and events—and has been observed in almost every part of the brain, with one glaring exception: the olfactory bulb, the area that processes the sense of smell.
In the June 2009 issue of Nature Neuroscience, however, Ben W. Strowbridge, PhD, associate professor of neurosciences at Case Western Reserve University School of Medicine, and Yuan Gao, a PhD student, show that olfactory brain circuits actually do change with experience—providing a possible explanation for how animals form memories of particular scents.
"Scientists commonly believe that the brain processes information in a way that is something like climbing a pyramid: Simple sensory information is at the base of the pyramid; more complex concepts, such as recognition of a person's face, are generated in higher areas of the brain," Dr. Strowbridge says. He goes on to explain that he and Gao found that in olfactory learning, higher brain centers may first make a prediction about what a scent could be. They then engage the most appropriate brain circuits to test that prediction against incoming sensory data. "We proved that in olfactory learning there is much more talking back-and-forth from the top of the pyramid to the bottom than we had previously thought."