Forgetfulness is considered an irksome flaw of the mind, but it seems such loss of memory is a necessary part of a well-functioning brain. A new study has recently shown that the brain might have a specialized set of neurons whose function is to actively make us forget, in a bid to weed out the unnecessary information we collect all day long.
Researchers revealed their discovery, in a report published in the journal Science, that people forget during a particular phase of sleep called rapid eye movement i.e. REM via a specific set of neurons positioned deep inside the brain.
These neuron cells are known as melanin-concentrating hormone neurons viz. MCH for short. Previously, these brain cells were recognized for producing an appetite-stimulating hormone, but now they are also believed to control the active destruction of memories during REM sleep, the exclusive phase of sleep in mammals and birds that are linked with vivid dreams.
By observing the brains of mice, the team noted that a majority of more than 52% of MCH cells fired when mice experienced REM sleep, compared with 35% when the mice were awake. Paired with this, they exposed that the MCH cells sent inhibitory messages to the hippocampus considered as the brain’s memory headquarters.
With some genetic alteration, the scientists created mice that could have their MCH neurons either turned on or off. They found that the mice with activated MCH neurons actually had reduced memory during a series of memory tests. To their surprise, the researchers discovered that activating the cells reduced the time mice spent sniffing around new objects compared to familiar ones while turning off the MCH cells produced the opposite effect.
Thomas Kilduff, Ph.D., director of the Center for Neuroscience at SRI International, said in a statement, “Ever wonder why we forget many of our dreams? 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”.
Dr. Kilduff added, “These results suggest that MCH neurons help the brain actively forget new, possibly, unimportant information. 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.”
The complete mechanism of sleep and memory, whether it’s forgetting and recollecting memories, is yet not fully understood. But, it’s hoped that this study could lead to research that advances our understanding of memory-related conditions like Alzheimer’s disease.