The impact of smell on taste is known to all, but even your sense of taste may influence what you smell.
Vladamir Nabakov could literally see ‘q as browner than k, while s’ was ‘not the light blue of c, but a curious mixture of azure and mother-of-pearl’. He was among the rare breed of individuals we term synesthetics, who can for example see letters or numbers as colours. Such synesthetics number roughly 1 in a 1,000. Many different forms of synesthesia are known, from the taste of sound to the seeing of emotions. There is, however, one kind of synesthesia that is so common we never comment on it, the interplay of smell and taste. As anyone who has tried tasting food with a bad cold can testify, the two senses are closely tied. But while we know a lot about the smell of taste, is there a thing such as the taste of smell? In a study published in Nature Neuroscience, Dan Katz and his colleagues at Brandeis University seem to have shown exactly such an influence in rats. They found that if the taste cortex was inactivated when the rats first smelt a food odour, then the rats would be unable to recognise the odour as the same odour when the taste cortex was activated. “We discovered in this experiment that the sensory systems don’t work in isolation from each other,” said Katz. “One part of the cortex takes direct input from the nose, and one part from the tongue, and while it’s convenient to think that the nose and taste receptors operate independently, they don’t…I am hoping that ultimately this discovery will help drive us to an entirely different approach to brain function,” said Katz. “It doesn’t make sense to probe one system separately from the other. Just like in a chorus, you can’t appreciate the fullness of the music if you hear only the bass or the tenor in isolation.”