Why we struggle to remember every detail of our past experiences.

Many experiences in our lives resemble one another even though they are different. Memories of recent events will be rich in detail but over time we will forget irrelevant minor details which are unique to each experience. But the brain will store general, relevant information across these experiences – like when you go to work every day the common underlying aspects about being at work is retained however you may not remember what you wore to work each day.

Researchers from the University of Toronto, Canada, discovered a reason why we don’t remember minute details of past experiences.

The process by which knowledge is formed is by gradual reorganization of networks in interconnected parts of the brain. One such region which seems to be particularly involved in long term memory is the medial prefrontal cortex (mPFC). The mPFC is important when new goals and behaviours are learnt from knowledge already existing – human imaging data reveals that mPFC is activated when people use existing knowledge to encode new ones.

Memories of recent experiences are rich with minute details which are unique to each experience. But the brain gradually codes and stores important information which is common across past experiences.

Based on this, the researchers predicted that the group of neurons in the mPFC build representations of correlations to multiple experiences over a period of time and that this information has larger representation than the smaller details.

To test this prediction, the scientists examined how two different memories with overlapping associative features are coded by neuron population in the mPFC of rats and how these codes change over time.

The rats were given two experiences – one involved light and tone stimulus and the other a physical stimulus. There was an interval of 20 to 40 seconds between the two experiences. This gave the rats two memories with shared stimulus relationship.

The findings revealed that the group of neurons in the mPFC coded both the unique and shared experiences from the stimuli in a similar way initially, but as a month passed by, the scientists found that the coding becomes more sensitive to shared features and less sensitive to unique features which become lost.

Further experiments also revealed that the brain can adapt general information and knowledge gained from multiple experiences and apply it to new experiences.

This study provides an insight into how the brain works to collect and store useful knowledge of the world and adapt it to apply it to new situations.

This is why we struggle sometimes to remember minute details about our experiences because our brain thinks that these details are irrelevant like what you wore to work last week.

Source: eLife