Melatonin, sometimes called "the hormone of darkness," plays an important role in regulating our daily sleep patterns. This hormone is produced by our bodies and in most organisms melatonin production is higher during the night than during the day.

In addition to their body's own melatonin, many people take melatonin supplements in an attempt to help them sleep, fight jet lag or balance out seasonal affective disorder.

Melatonin And Memories

But a study by a group of scientists at the University of Houston suggests that melatonin might have a negative impact on the ability to form new memories.

The researchers were interested in how the body's internal clock affects the formation of new memories. They found that small striped minnows called zebra fish learned very well during the day but very poorly at night, when melatonin levels are higher.

They wondered if melatonin played a role in learning and memory.

Melatonin And Learning

They treated zebra fish with extra melatonin during the day, boosting the hormone levels to night-time amounts.

They discovered that high melatonin did not affect learning per se, but dramatically reduced the fishes' ability to form new memories, or to remember what they'd learned.

Then the scientists inhibited melatonin activity in the fish. They did this by blocking melatonin receptors with inhibitory drugs. The fishs' melatonin levels were unchanged, but the ability of melatonin to affect the brain was blocked.

Blocking Melatonin

With melatonin activity blocked, the ability of the fish to form new memories was drastically improved, even at night.

This research has potential benefits for humans. For example, the use of melatonin receptor blockers could improve performance of night-time cognitive tasks, helping people such as night-shift workers or students cramming for exams.