The ingredient is six times sweeter than cane sugar and an ingredient found in processed foods with omega-3 fatty acids, which are known to boost memory and learning ability.
They performed experiments on two groups of mice. One consumed enough sugar for six weeks, while the other followed a healthy diet.
At the beginning of the experiment, the results of which are published in the Journal of Physiology, the scientists placed the mice in a maze, marking them to help them find the right path.
Six weeks later they studied their ability to "remember" the route.
One of the study's authors, Professor Fernando Gomez-Pinilla, reported that sugar-fed mice were slower than the rest.
"Eating foods high in fructose can have a long-term effect on the brain's ability to learn and remember information," he said.
Conversely, eating nuts and fish, such as salmon, can have the opposite effect.
"Our study shows that what we eat affects the way we think. "Adding foods with omega-3 fatty acids can reduce the 'destruction' that occurs," he added.