Why do we forget our dreams?
Rapid eye movement, or REM, sleep is a fascinating period when most of our dreams are made.
Now, in a study of mice, a team of Japanese and US researchers have shown that it may also be a time when the brain actively forgets. Their results suggest that forgetting during sleep may be controlled by neurons found deep inside the brain that were previously known for making an appetite stimulating hormone.
“Ever wonder why we forget many of our dreams?” said study author Dr Thomas Kilduff from the Centre for Neuroscience at SRI International. “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.”
REM is one of several sleep stages the body cycles through every night. It first occurs about 90 minutes after falling asleep and is characterised by darting eyes, raised heart rates, paralysed limbs, awakened brain waves and dreaming.
For more than a century, scientists have explored the role of sleep in storing memories.
While many have shown that sleep helps the brain store new memories, others, including Francis Crick, the co-discoverer of the DNA double helix, have raised the possibility that sleep – in particular REM sleep – may be a time when the brain actively eliminates or forgets excess information.
Moreover, recent studies in mice have shown that during sleep – including REM sleep – the brain selectively prunes synaptic connections made between neurons involved in certain types of learning. However, until this study, no one had shown how this might happen.
“Understanding the role of sleep in forgetting may help researchers better understand a wide range of memory-related diseases like post-traumatic stress disorder and Alzheimer’s,” said Dr Janet He.
“This study provides the most direct evidence that REM sleep may play a role in how the brain decides which memories to store.”
Do you have trouble remembering your dreams? Have you ever taken a notepad to bed so you can write down your dreams?
Do you have trouble remembering your dreams? ... Yep
Have you ever taken a notepad to bed so you can write down your dreams? ... Short answer, no, but ...
I have in the past kept a notebook on the bedside table but not to write down my dreams. I used to enter poetry competitions and would often get a 'good' poetry idea just before falling asleep but it would totally elude me in the morning. The notebook morphed into one of those little battery-operated recorders, which in turn morphed into the recorder on my mobile phone before giving up the comps for the most part.
I have been told by other poets that this is a very common problem, most of our best ideas seem to come just before we fall asleep, or as some say, in the middle of the night and are gone by the morning. I don't want to seem to be downplaying the seriousness of Alzheimer's Disease, but in a very minor way what we are experiencing is a little bit the same, the most recent memories going first.
There might be something in that theory about sleep being the time that cleans out the excess memories, and it's relationship to memory-related disorders like Alzheimer's.
These studies often seem like people are just being paid big money to state the bloomin' obvious, but now and again something comes along that makes us go, uumhh might be something in that. This is one of those times for me.