Wednesday , August 17 2022

Rats and humans have a common ability to selectively forget about annoying memories


Our ability to selectively overlook annoying memories is shared with other mammals, suggesting new research from Cambridge University. The discovery that rats and humans have shared active overlooked abilities – and similar brain regions – suggests that forgetting plays an important role in adapting mammal species in their environment, and its development can return to at least our common ancestor.

It is estimated that the human brain includes 86 billion neurons (or nerve cells) and 150 trillion synaptic connections, making it a powerful device for processing and storing memory. We have to select these memories to help us carry out everyday tasks, whether we remember where we left the car in a supermarket car park, or we remember a word that we met on the street. However, the greatest amount of experience that people can keep in mind about our lives poses a risk of being overwhelmed with information. For example, when we come from a supermarket and think about where we left the car, we just have to remember where we were in the car today and not worrying about it every time we arrived to shop.

The previous work by Professor Michael Anderson at the Department of Cognitive and Mental Research at the Medical Research Council of Cambridge University showed that people have the ability to actively overlook annoying memories, and this retrieval plays a crucial role in this process. His group has shown that deliberate recall of previous memory is more than just its repeated recurrence; it actually forces us to overlook other competing experiences that interfere with the recovery of the memory being searched.

"Quite simply, the very act of remembering is the main reason why we forget to build our memory after using it," says Professor Anderson.

"People have thought of oblivion as something of a passport. Our research reveals that people are more involved than they realize by actively shaping what they remember about their lives. The idea that a repeat act can be forgotten is amazing and can tell us more on the ability of people to selective amnesia. "

Although this process improves memory efficiency, it can sometimes cause problems. If the police interview testimony of a crime, for example, their repeated interviewing of the selected details might indicate that the witness will forego information that may prove to be important later.

Although the ability to capture a person actively forgets, it is unclear whether this occurs in other species. Would this ability be unique to our species, or at least to sophisticated mammals such as monkeys and large monkeys?

The study published today in the journal Natural communication, Professor Anderson, along with Pedro Bekinschtein and Noelia Weisstaub of the Universidad Favaloro in Argentina, have shown that the ability to actively overlook is not specific to humans: rats also have selective abandonment of their ability and use of a very similar mechanism of the brain, suggesting this is a certain difference.

To prove this, the researchers invented a wisely simple task based on the innate curiosity of the rat: when inserted into the environment, the rat actively explores to learn more about it. By exploring the environment, the rats create memories of all the new objects they find and explore.

Based on this simple observation, the researchers allowed the rats to discover two previously unobserved objects (A and B) in the open arena – the objects were a bomb, a mug, small toys or soup copper. The rats first needed to explore the object A for five minutes and then were removed from the arena; After 20 minutes they were returned to the arena with object B, which they also studied for five minutes.

In order to see if the rat appeared in the withdrawal caused by forgetting, the same way as humans, the rats subsequently performed a "retrieval practice" in one of the two objects (such as A) to find out how it affected their subsequent memory rival object (B). During this exploratory phase, the researchers repeatedly placed the rats on the arena with the purpose they wanted to remember (for example, A), along with another object that was never visible on the arena. Rats instinctively prefer to explore new objects, and therefore in these "retrieval practice" studies, the rats obviously chose to explore the new objects, indicating that they really remembered A and saw it as "old news".

In order to find out how to retrieve the later memory B of the affected rat, in the final stage, which took 30 minutes later, the researchers placed the rat in the arena with B and a completely new object. Surprisingly, in this final test, the rats studied both B and the new objects equally – selectively remembering their experiences A more and more, rats actively learned to forget about B.

In contrast, under controlled conditions, when researchers released the practice of retrieval and changed it with the same relaxation time in rats in the home cage or alternative non-extraction storage tasks, the rats were a great memory for B.

Professor Anderson's team then identified the area against the brain's brain forward, which controls this active forgetting mechanism. When in the region in front of the rat brain, known as the medial prefrontal choir, was temporarily excluded using drug muskimol, the animal completely lost its ability to selectively overlook competing memories; despite the fact that the same "retrieval practice" task as before is carried out, rats are now recognized B. For people, selective forgetting in this way involves the analogue region in the prefrontal cortex.

"It appears that rats have the same active limbo as humans – they selectively forget memories when these memories draw attention," says Professor Anderson. "And crucially, they use a similar prefrontal control mechanism as we do. This discovery suggests that this ability to actively overlook less useful memories may have evolved far back to the" Tree of Life ", possibly as our common ancestor with a rodent before 100 millions of years. "

Professor Anderson says that now that we know that brain mechanisms are similar to rats and humans in this process, it should be possible to explore this phenomenon of adaptive forgetting in the cell or even at the molecular level. A better understanding of the biological basis of this mechanism can help researchers develop advanced treatments to help people forget about traumatic events.


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