HUMAN MEMORY AND FRUIT FLIES .

 

Learning and memory are two of the most magical capabilities of our mind. Learning is the biological process of acquiring new knowledge about the world, and memory is the process of retaining and reconstructing that knowledge over time.

Most of our knowledge of the world and most of our skills are not innate but learned. Thus, we are who we are in large part because of what we have learned and what we remember and forget. 

Memory is the glue that holds our mental life together. Without its unifying power, both our conscious and unconscious life would be broken into many fragments and our life would be empty and meaningless.

The brain has two types of memory. 1. Explicit (Declarative) memory for facts, events, places, people and objects and 2. Implicit (non declarative memory) for perceptual and motor skills.

Even animals with fewer nerve cells from approximately 20,000 in the central nervous system to 100,000 in Drosophila (fruit flies) have remarkable learning capabilities.  

If one has too much material in the brain, it may make us forget something recent in order to de clutter it. This is an unconscious process and it is the brain that decides what to forget and what to keep.

Only recently neuroscientists have started studying as to how the mind forgets things.  

Surprisingly human brains and fruit fly brains have many things in common. Fruit flies can learn simple tasks, they can form memories, and they can also forget just like us. It is easier to study the brains of fruit flies which also have memories but forget things to clean up their small brain. Fruit flies can be easily grown in the lab environment and their DNA can be changed as easily. So they offer an excellent way to study how the brain forgets.

As fruit flies have an excellent sense of smell for odours, scientists test them for forgetting strong odours coupled with conditioning. When a particular odour is sent on them the scientists give the fruit flies an electric shock. So the electric shock gets paired to the memory and the fruit fly brain remembers that odour brings pain.

Next if those fruit flies are placed in a container and the same odour is given to them, they immediately try to escape from the odour to another chamber connected to the first one where the intensity of that odour becomes less. Normally the flies remember the unpleasantness related to that odour for a few minutes and respond to it. But if the fly is tested for the same after 1 day the effect of the odour is forgotten by the fly.

With the experiment and DNA alteration, scientists have isolated those neurons that control memory and found that important things like source of food are imbedded and not forgotten by the fly while other memories fade with time. They have isolated a gene named Rac in the fruit flies which makes them forget unimportant memories. They also found that when a protein named Scribble protein is removed from the gene of the fruit fly they can remember the odour we mentioned above even after 1 day, which means their long-term learning is enhanced. But they also found that since the Scribbleless flies did not forget, they also found it difficult to make new memories.

Now the Rac and Scribble proteins exist in the human brain as well and therefore this may clearly indicate that more memories in the brain may affect the formation of new memories in the brain.