Neuroscientists  report the first results from experimental tests designed to explore the idea that “forgetting” might not be a bad thing, and that it may represent a form of learning – and outline results that support their core idea .

 

Last year the neuroscientists behind the new theory suggested that changes in our ability to access specific memories are based on environmental feedback and predictability. And that rather than being a bug, forgetting may be a functional feature of the brain, allowing it to interact dynamically with a dynamic environment.

 

In a changing world like the one we and many other organisms live in, forgetting some memories would be beneficial, they reasoned, as this can lead to more flexible behaviour and better decision-making. If memories were gained in circumstances that are not wholly relevant to the current environment, forgetting them could be a positive change that improves our wellbeing.

 

In leading international journal Cell Reports, they present the first in a series of new experimental studies where the effect of natural, “every day” forgetting was investigated with respect to how normal forgetting processes affect particular memories in the brain. 

 

The team studied a form of forgetting called retroactive interference, where different experiences occurring closely in time can cause the forgetting of recently formed memories. In their study, mice were asked to associate a specific object with a particular context or room, and then recognise that an object that was displaced from its original context. However, mice forget these associations when competing experiences are allowed to ‘interfere’ with the first memory. 

 

To study the result of this form of forgetting on memory itself, the neuroscientists genetically labelled a contextual “engram” (a group of brain cells that store a specific memory) in the brains of these mice, and followed the activation and functioning of these cells after forgetting had happened. Crucially, using a technique called optogenetics they found that stimulation of the engram cells with light retrieved the apparently lost memories in more than one behavioural situation. Furthermore, when the mice were given new experiences that related to the forgotten  memories, the ‘lost’ engrams could be naturally rejuvenated.