Surely many people have been through this: at the right moment the brain refuses to remember a word, date, event or location of an object. After some time, even when it is no longer relevant, the necessary information pops up in memory. In the course of a new study, scientists from Japan and Canada explained why this happens.
The study of forgetfulness is a complex one: in some cases, a person can not remember some information because his brain has not studied it well enough. For example, many can not remember the name of a person presented a few minutes ago. In other cases, people are unable to retrieve information that has long been stored in their brain, a word for example. It is difficult to distinguish between these two cases, and this is one of the main reason why the study of forgetfulness is a complex one.
Researchers at the University of Tokyo identify gene in mice that affects memory performance
To get around this limitation, in the course of a new research work scientists developed a test that takes into account the key difference between not knowing and not recalling. The tests were conducted on adult males and female mice. In the training trial, mice explored a new object for a few minutes.
Later, in the "recall" phase (evoking memories), the researchers observed for how long rodents had been in contact with objects they had previously studied. As expected, mice spent less time interacting with objects they remembered. This data was required for comparison with the next experiment.
Next, researchers tested rodent memory by repositioning the same object next to them at different times of the day. In this part of the experiment, mice were divided into two groups. One was a control group (healthy mice) and mice without BMAL1, a protein which regulates many other gene expressions. The production of BMAL1 tends to fluctuate between low levels just before waking up and high levels before going to sleep.
Mice lacking the BMAL1 protein showed more memory loss shortly before waking up
The results showed that mice that were trained just before they normally woke up and tested just after they normally went to sleep could easily recognize a familiar object. While mice trained at the same time, but tested 24 hours later did not recognize the object at all.
Healthy mice and BMAL1 deficient mice had the same results in the first case, but the BMAL1 deficient mice were even more forgetful just before they normally woke up. Researchers reported the same results when they tested mice on recognizing an object or another mouse.
It follows that at the time of day when mice usually wake up and when BMAL1 protein levels are usually low, the animals are unable to remember what they definitely remember before. Scientists have long suspected that circadian rhythms in the body, which are responsible for regulating sleep and wake-up cycles, affect learning and memory functioning. Now they've been able to prove it on mice.
Possible applications of the findings to human diseases of memory deficit
According to the researchers, the role of BMAL1 in memory retrieval can be traced to a specific area of the brain called the hippocampus. Additionally, the research team linked BMAL1 to activation of dopamine receptors and modification of other signaling molecules in the brain.
Researchers hope the newly obtained data will help identify ways to boost memory retrieval techniques by using BMAL1 pathway. These techniques, in turn, will help create new therapies to help people with memory impairments caused by neurodegenerative disorders such as dementia and Alzheimer's disease.
However, it remains a mystery why the brain evolved with this ability to disrupt memory retrieval at certain times of day. Perhaps it's an evolutionary advantage, the role of which remains to be explained.