Back in ancient
times, philosophers like Aristotle were already speculating about the origins
of taste, and how the tongue sensed elemental tastes like sweet, bitter, salty
and sour. What researchers discovered just a few years ago is that there are
regions of the brain (regions of the cortex) where particular fields of neurons
represent these different tastes again, so there's a sweet field, a bitter
field, a salty field, etcetera. They found that you can actually taste without
a tongue at all, simply by stimulating the taste part of the brain, the insular
cortex.
They ran the
experiment in mice with a special sort of brain implant, a fiber-optic cable
that turns neurons on with a pulse of laser light. And by switching on the
bitter sensing part of the brain, they were able to make mice pucker up, as if
they tasted something bitter. In another experiment, the researchers fed the
mice a bitter flavouring on their tongues—but then made it more palatable by
switching on the "sweet" zone of the brain. The study suggests that a
lot of our basic judgements about taste (sweet means good, bitter means bad) are
actually hard-wired at the level of the brain.
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