The finding may explain both why diet products are often viewed as not being as satisfying as their real counterparts and why carbohydrate-loaded drinks seem to immediately perk up athletes - even before their bodies can convert the carbs to energy.
Previous studies have shown that some rodents can distinguish between sugars of different energy densities, while others can still tell carbohydrate and protein solutions apart even when their ability to taste sweetness is lost.
A similar ability has been proposed in humans, with research showing that merely having carbohydrates in your mouth can improve physical performance.
In the new study, to be published in the journal Appetite, researchers asked participants to squeeze a sensor held between their right index finger and thumb when shown a visual cue.
At the same time, the participants' tongues were rinsed with one of three different fluids, Science journal reported.
The first two were artificially sweetened - to identical tastes - but with only one containing carbohydrate; the third, a control, was neither sweet nor carb-loaded.
When the carbohydrate solution was used, the researchers observed a 30 per cent increase in activity for the brain areas that control movement and vision, according to 'The Huffington Post'.
This reaction, researchers propose, is caused by our mouths reporting that additional energy in the form of carbs is coming.