Smell + Sound = SMOUND

Like so many discoveries, the possible link between our senses of smell and sound came to Dr. Daniel Wesson purely by accident.

“I was simply trying to find the way the olfactory tubercle responds to odors,” he explains, referring to a structure at the base of the brain that was implicated in odor detection in 2004. But, when he set down his coffee mug on a laboratory bench one afternoon, he noticed that the activity in the tubercle of the mice he was studying spiked. What followed was new research with surprising implications as to how our senses co-mingle to give our brains the big picture.

According to the February 24 Journal of Neuroscience, Wesson and colleague Donald Wilson of the Nathan S. Kline Institute for Psychiatric Research in Orangeburg, N.Y. began by verifying that the tubercle does indeed respond to smell. They found that 65% of tubercle cells from 23 anesthetized mice were activated by at least one of five odors—an important finding in its own, because no one knew if tubercle cells could detect odors, a process thought to be exclusive to the part of the brain known as the piriform cortex. When the team repeated the experiment, this time presenting a subset of the cells with only a tone, 19% responded.

When Wesson and Wilson sent a mixture of both odors and tones into tubercle cells, responses from 29% became either enhanced or suppressed, depending on the presence or absence of the second stimulus. One cell, for instance, appeared not to care for either smell or sound but reacted enthusiastically to the combination.

The olfactory-auditory link - or “smound” - is not the first connection between seemingly separate sensory input systems (see Olfactory Fact #18: 1-part Taste plus 2000-parts Smell equals Flavor), but the implications are broad nonetheless. It may, for instance, shed light on such baffling disorders as synesthesia, in which the real information of one sense is accompanied by perception in another.