Though said to be both delicious and an aphrodisiac, oysters often fall down on the texture test. This raises an interesting question – why do so many of us squirm at the thought of shucking a slimy shellfish or slurping on a slippery slice of sashimi? According to a new study in the journal Neuron, the answer may reside in a newly discovered nerve cell in the tongue, which responds to the feel of our food in order to entice or disgust us.
The authors conducted their research using fruit flies, which, like humans, are fairly picky about the texture of their food, and will often refuse to eat things that are too mushy or too hard, regardless of their taste. Using a technique called confocal microscopy, the team discovered a previously unknown type of neuron, which is activated by tiny hairs on the surface of the insect’s tongue.
As these hairs come into contact with food, they register its texture, stimulating the neurons, which then send an impulse to the brain telling it whether or not it fancies eating. The team then used optogenetics to control the activation of these neurons using light. When stimulated with low intensity light, the neurons seemed to generate a signal akin to detecting soft food, thereby causing the flies to eat when presented with a sugary solution.
However, when the researchers gave the flies the same solution but stimulated these neurons with strong light, the impulse generated was similar to that produced when encountering overly tough food, ultimately causing them to reject the syrup.
Upon further examination, the team discovered that the activity of these neurons appears to be controlled by a protein called transmembrane channel-like (TMC) protein. To confirm this, they bred flies to lack this protein, and found that they were then unable to distinguish between different textures, even though they retained the ability to register changes in taste.
This is of particular interest, since the TMS found in fruit flies is very similar a human TMS that controls neuronal signalling in the eardrum. Though taste and hearing obviously have very little to do with one another, it is intriguing that both are examples of machanosensation, meaning the generation of electrical impulses as a result of “feeling” something in the external environment.
The researchers therefore say it’s worth looking for similar mechanisms in the human tongue in order to determine if our disgust for certain textures is caused by the same mechanism. “Because there are eight different types of TMCs in mice and humans, it would be fascinating to learn whether any of them has a role in food texture sensation in mammals,” explained study co-author Craig Montell.