What happens if you cannot recall your memory correctly? You are able to associate and store the name and face of a person, yet you might be unable to remember them when you meet that person. In this example, the recall of the information is temporarily impaired. How such associative memories are “read out” in the brain remains one of the great mysteries of modern neurobiology.
Now, scientists have taken the first step to unravel this mechanism.
Fruit flies have the ability to remember. The brain of these minute animals can store different pieces of information and associations and can recall these for a long time. In comparison to the human brain, which boasts about 100 billion cells, the brain of the fruit fly is, of course, a lot smaller. However, many of the basic principles are the same in both species. Thus, the straightforward structure of the fly brain, with its modest hundred thousand cells, enables the scientists to decode processes at their point of origin: in other words, on the individual cell level.
In their experiments, the neurobiologists conditioned the fruit flies to associate a certain odour with a mild electrical stimulus. After repeating this classical conditioning experiment only once, the flies had already got the message and turned away from the pertaining odor. The key in this experiment was that the scientists could temporarily deactivate specific nerve cells. This was done by a combination of special genetic techniques which allowed certain nerve cells to be deactivated through a change of ambient temperature. In this way, the scientists could show that the behaviour of the flies was not altered, when certain nerve cells were deactivated only while the flies recalled the associated memory. The responsible nerve cells, known as MB-V2 cells, had to be intact in order for the flies to fully retrieve the associative memory. These cells were, however, not important for the flies’ ability to associate odour and electrical stimulus or to stabilize the formed memory. The results thus indicated that MB-V2 cells are involved in a memory ‘read-out’ pathway.
Read the rest of this fascinating article here How memory is read out in the brain