What is melatonin’s role in memory formation?

What is melatonin's role in memory formation?

Exploring the Relationship Between Melatonin and Memory Formation

Sleeping Image credit: Tero Vesalainen/Getty Images

Memory formation has long been a subject of fascination and ongoing research. Scientists have been trying to understand the exact mechanisms in the brain that underpin this complex process. For over a century, the role of sleep in memory retention has been recognized and studied extensively.

Melatonin, a hormone naturally produced in the brain to induce sleep and regulate the circadian cycle, has been found to be associated with improved memory in rodents. Recent research conducted on mice has proposed that melatonin influences memory formation through the regulation of protein phosphorylation in areas of the brain responsible for memory.

The Mystery of Memory Formation

The formation of memories has been a puzzle for researchers for decades, and many questions still remain about the biological mechanisms involved. This lack of understanding has led to a dearth of pharmacological interventions that can be taken to improve memory.

According to Dr. Raj Dasgupta, chief medical advisor for Sleep Advisor, “Currently, there are no drugs specifically approved for improving memory formation. While some prescription medications are used to improve memory in conditions like Alzheimer’s disease, they are not recommended for general memory enhancement in healthy adults.”

Melatonin and Its Role in Sleep Regulation

Melatonin is a hormone naturally produced by the pineal gland in the brain in response to darkness. It helps regulate the circadian clock and sleep patterns. People can also take synthetic forms of melatonin as a supplement to induce sleep.

Research focused on the use of melatonin for treating the symptoms of jet lag and insomnia is ongoing. The National Center for Complementary and Integrative Health highlights the potential benefits of melatonin in sleep regulation and related health issues.

Sleep’s Connection to Memory

The link between sleep and improved memory retention has been recognized for over a century. It is believed that the brain state during sleep is optimized for memory consolidation. However, the exact mechanisms underlying this connection are not fully understood.

To investigate the effects of melatonin and its derivatives on memory, researchers conducted experiments on mice. They found that melatonin promoted long-term memory by affecting protein phosphorylation.

The study, published in NeuroReport, was conducted by researchers at Sophia University in Tokyo, Japan.

Unraveling the Mechanisms of Melatonin and Memory Enhancement

To determine whether the activation of melatonin receptors or the phosphorylation of other memory-associated proteins was responsible for the link between melatonin and improved memory in mice, the researchers carried out a series of experiments.

Male mice were used in the study to avoid the potential impact of the fertility cycle in female mice on the results. The mice were trained to find a ceramic object they hadn’t seen before while exposed to a 12-hour light and 12-hour dark cycle. This training phase allowed the researchers to measure long-term memory formation using the novel object recognition task (NORT).

The mice were then administered either melatonin, a melatonin receptor-binding drug called ramelteon, a metabolic metabolite called AMK, or a control treatment. The efficacy of these treatments on memory performance was evaluated after a day.

The researchers observed that mice administered with melatonin, AMK, and ramelteon showed increased novel object recognition compared to the control group.

The Role of Melatonin in Memory Formation

After conducting the memory tests, the researchers euthanized the mice and examined their brains to analyze the phosphorylation of memory-associated proteins in areas responsible for memory creation, such as the hippocampus and perirhinal cortex.

They discovered that the phosphorylation of these memory-associated proteins increased in the presence of AMK and ramelteon. This finding suggests that melatonin promotes the formation of long-term object recognition memory by modulating the levels of phosphorylation in memory-related proteins.

These proteins are involved in receptor binding-related memory formation pathways as well as pathways not associated with receptor binding.

The Importance of Sleep in Memory Formation

Dr. Alex Dimitriu, a double board-certified psychiatrist and sleep medicine specialist, emphasizes the significance of sleep in memory formation. He states, “Sleep is the holy grail of memory and is behind a lot of the work I do with my patients.”

Dr. Dimitriu explains the memory formation process in humans: “Memories are formed in humans in several discrete steps. The first step is registration — this is the process of paying attention. Memories are next committed to short-term memory, and later with repetition, importance, and especially sleep, memories get converted into long-term storage. A lot of long-term memory formation occurs during slow wave sleep (deep sleep), in the first half of the night.”

Due to the link between sleep and melatonin, researchers have explored the role of melatonin in memory creation. However, it remains unclear whether the activation of melatonin receptors in the brain is solely responsible for improved memory formation or if other mechanisms are involved.

Past research has investigated whether melatonin improves different types of memory in rodents. Dr. Dasgupta highlights two such studies, stating, “A study published in 2021 found that melatonin improves short-term spatial memory in a mouse model of Alzheimer’s disease. Another study published in 2022 found that melatonin improved spatial learning and memory impairment in rats. These studies suggest that melatonin may be a potential treatment for memory problems, such as those associated with Alzheimer’s disease.”

Human Testing and Future Research

It is essential to note that the study was conducted on mice, and its applicability to humans remains uncertain. Further research involving human participants could shed light on the potential benefits of melatonin for memory enhancement.

Dr. Clifford Segil, a neurologist at Providence Saint John’s Health Center, encourages the repetition of animal-based memory improvement experiments in humans. He explains, “If something is shown to have the potential to help animals form better long-term memories and the substance being given to the animals is without health side effects, these studies should be repeated in humans. Testing people to see if melatonin helps with memory would be interesting for me to review.”

Although there is still much to uncover about the relationship between melatonin and memory formation, these findings offer promising insights and potential avenues for further exploration. As researchers continue to investigate the link between sleep, melatonin, and memory enhancement, new discoveries may pave the way for the development of interventions to improve memory formation and retention in the future.