Melatonin, a hormone available in supplement form and often sold as a sleep aid, may boost long-term memory and help protect from cognitive decline over time, according to a new study out of Japan. The potential benefits were linked to melatonin and two metabolites that result from it called N1-acetyl-N2-formyl-5-methoxykynuramine (AFMK) and N1-acetyl-5-methoxykynuramine (AMK).

The new study comes from the Tokyo Medical and Dental University; it involved lab mice, not humans, but the researchers say the findings may also apply to people. The research involved mice faced with novel object recognition, which refers to presenting mice with new and familiar items and observing how they interact with them.

Mice are naturally curious and will spend more time exploring new objects than the ones they’ve seen before. This makes it possible to study memory in the mice — if they’re presented with an object they’ve seen before, but they examine it as if it’s new, the researchers can assume the mice have developed memory issues that mean they forgot they’ve seen the item before.

When it comes to melatonin, the body breaks down the hormone into molecules called metabolites.

The researchers studied the effects of these metabolites, which are present in the brain, and whether they have an effect on cognition. Using mice to evaluate this, mice were presented with objects to get them familiar with the items, then given melatonin and its two metabolites an hour later.

The next day, the mice were presented with the same objects and the researchers observed memory improvements in the rodents. A single dose of the metabolite AMK given 15 minutes after exposing older, memory-impaired mice to objects enabled them to remember those items up to four days after the test.

When blocking the formation of the AMK metabolite from melatonin in the brain, the researchers also found that it wasn’t possible to get the same long-term memory enhancement. All ages of mice benefited from melatonin. Additional research is necessary to determine whether melatonin can have the same effect in humans.