Health researchers from Japan have discovered neurons in our brain’s hypothalamus region, whose inhibition during rapid eye movement (REM) sleep is connected to removing the “unnecessary” memories from the brain, as per a new study published in the journal Science.

The results provide information about mechanisms behind the regulation of memory during our sleep, The Indian Express reported.

When we sleep, our brain continues to work and it processes all the information that we gather during the day and classifies and consolidates them into memories, the study said.

However, not all the day’s experiences are worth remembering so it is necessary to forget for our memory regulation. The process of removing unwanted memories is termed as synaptic renormalization which only occurs during our sleep.

A group of researchers headed by Shuntaro Izawa from Japan’s Nagoya University analysed and studied the role of a specific set of nerve cells that are called the Melanin-concentrating hormone (MCH).

These MCH neurons are found only in the brain’s hypothalamus and play a role in the regulation of sleep and wakefulness, and the time spent in the REM sleep, the report said.

The research team found that inhibition of the MCH neurons increased the memory in mice, while the activation of MCH neurons impaired memory.

Hence, the results from the study suggested that the REM sleep neural pathway plays a key role in our active forgetting. The researchers mentioned that MCH pathways could be used as a target for memory modulation.

Akihiro Yamanaka, professor of neurophysiology at Nagoya University, told The Mainichi, “We tend to forget our dreams, which might be caused by MCH neurons that become active during REM sleep. Our finding may lead to the development of a treatment method for eliminating memories causing post-traumatic stress disorder.”

“Ever wonder why we forget many of our dreams?” said Thomas Kilduff, Ph.D., director of the Center for Neuroscience at SRI International, Menlo Park, Calif., and a senior author of the study team, who was quoted in the National Institute of Health. “Our results suggest that the firing of a particular group of neurons during REM sleep controls whether the brain remembers new information after a good night’s sleep.”

“These results suggest that MCH neurons help the brain actively forget new, possibly, unimportant information,” said Dr. Kilduff. “Since dreams are thought to primarily occur during REM sleep, the sleep stage when the MCH cells turn on, activation of these cells may prevent the content of a dream from being stored in the hippocampus — consequently, the dream is quickly forgotten.”

In the future, the researchers plan to explore whether this new circuit plays a role in sleep and memory disorders.