Tasting the difference between bitter and sweet might guide us around a box of chocolates, but it’s also essential to how we evolved – early mammals survived by choosing energy-packed sweet foods over bitter tasting poisons. Inside this brain, from a young mouse, researchers investigated how brain cells (neurons) react to different tastes. Taste receptors on the tongue send flavour-filled signals to a region of the brain called the gustatory cortex. Its neurons (genetically-engineered here to produce colours) light up differently after bitter (red) or sweet (green) tastes. The team were able to trick the mouse into guzzling down or completely avoiding a drink of water simply by triggering these sweet or bitter brain zones. Like mice, it’s likely that certain tastes are hardwired into our brains at birth – although we can train ourselves to go against these instincts, perhaps developing a fondness for bitter chocolate over sickly-sweet soft centres.
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