Melatonin, often called the “sleepiness hormone,” regulates the sleep-wake cycle in mammals, modulates the expression of more than 500 genes, and exerts potent antioxidative and anti-inflammatory properties. A new study in mice suggests that melatonin also influences memory formation. Mice performed better on memory tests after receiving melatonin.

Researchers gave male mice melatonin, ramelteon (a drug that activates melatonin receptors), and AMK (a melatonin metabolite) to assess their effects on memory formation while completing a task involving recognizing new objects. Then, they examined the compounds' effects on the phosphorylation (the addition of phosphate groups to proteins) of five key proteins associated with memory formation. To avoid potential variations in melatonin due to female reproductive cycles, the researchers did not investigate the compounds' effects on female mice.

They found that when the mice received the three compounds immediately after learning, they formed long-lasting memories. However, the compounds exerted variable effects on the memory-related proteins depending on their location in the brain.

These findings suggest that melatonin improves memory by influencing the phosphorylation of memory-related proteins, whether through receptors or other pathways in the brain. They also bring attention to the many ways in which melatonin, memory, and sleep are intricately linked. For example, sleep deprivation markedly impairs memory formation. Learn more in this clip featuring sleep expert Dr. Matthew Walker.

• Read study abstract.