Memory

The role of memory

Memory plays a role in all our activities. It is essential in creating and developing our personality, it is a direct witness of our own past (episodic memory), and also of history and common knowledge (semantic memory). It is therefore one of the most essential cognitive functions in a person’s life.

We tend to consider memory as a whole, for instance by saying we have a good or bad memory. Remembering what we had for lunch yesterday is very different from remembering the fact that Paris is the capital of France. The type of information to be memorized or recalled engages the brain in different ways.

Thus there is no brain area that can be identified as THE place where memories are stored. Whether a neural connection is formed actually depends on the simultaneous activation of neurons in various areas of the brain and also varies depending on the type of information to be memorized.

Main types of memory

Traditional segmentation of memory according to how long information has to be remembered for

• Sensory Memories are the shortest type. They record all new information we experience in the space of a few hundred milliseconds (example of visible persistence).
• Short-term memory (STM) then takes over and retains the information a little longer (for about a minute). This type of memory allows to memorize a verbally received phone number until it has been dialed or written down. It is also necessary when reading and helps momentarily retaining information from a sentence that has just been read, so as to make sense of the next sentence. Short-term memory tends to disappear after a while in order to be replaced by the Working Memory.
• Working Memory (WM) can be considered as a «central administrator » which manages various cognitive mechanisms required to mentally deal with information. It is exactly the same as the “active” part of the Long-Term Memory when carrying out a task requiring us to handle information.
• Long-Term Memory (LTM) intervenes when we wish to memorize a piece of information for a longer period of time (or when we try to retrieve information from the past). This type of memory has an unlimited capacity and preservation time of the information. It contains all lasting knowledge. There are several types of stored information. 
  
  Subsystems of long-term memory:
  • Episodic Memory: Remembering what we did the day before, a dentist appointment or a friend’s birthday party are personal and autobiographic memories for which the memorization context is very important.
  • Semantic Memory: At the same time, knowing grammar rules, names of capitals or objects represents general knowledge that does not depend on the memorization context. Despite the fact that this knowledge has initially been episodic knowledge, it has turned into semantic knowledge since both spatial and temporal context in which it has been memorized have been set aside. This type of knowledge belongs to the semantic memory which allows us to make a list of flower names or to give the word that corresponds to a certain definition.
  • Implicit Memory: As well as these elements of “explicit” memory, which correspond to a conscious and voluntary search for stored information, there is also an “automatic” mode to retrieve data from our knowledge. In this case, these are “implicit” memory mechanisms which group, for instance, our know-how such as: Knowing how to play the piano, riding a bike, driving … These are things we do automatically but that still require us to consider the knowledge we have stored in our procedural memory (knowing that positioning your hands a certain way on the piano will render this or that chord, or that maneuvering your car a certain way will help you make a left turn).

Fatigue, age or stress may interfere with certain aspects of our memory.