By Patience Joseph Mamman
Simply defined, memory is the ability of the brain to store and retrieve information. Physiologically, memories are caused by changes in the sensitivity of synaptic transmission between neurons as a result of previous neural activity. These changes in turn cause new pathways to develop for transmission of signals through the neural circuits of the brain. The new pathways are called Memory Traces. They are important because once the traces are established, they can be activated by the thinking mind to reproduce the memories.
Types of Memory
Memories are classified based on two major characteristics:
- Duration and relevance of the information
- The type of information to be stored.
Based on the first characteristic, there are four basic types of memory formation.
1. Sensory/ Immediate memory.
- This is initiated by sensory signals.
- Signals are stored automatically for seconds
- Forgetting starts immediately after the information is acquired.
- Spontaneous gradual decline or ‘fading’ of information occurs.
2. Primary/ Short Term Memory.
- Last from a few seconds to a few minutes.
- Information enters by verbalization i.e. through written or spoken words.
- Not found in young animals or infants.
- Access to this memory is rapid.
3. Secondary/ Long Term Memory.
- Lasts from several hours to several years.
- Information is introduced into this memory from the sensory and primary mechanism by two means: (i) Stimulation of the ‘reward and punishment’ system (ii) Repeated rehearsal or practice of the exercise.
- Has a large storage capacity.
- Information is stored according to its significance.
- Bits of information of related significance are stored together.
- Forgetting of information in the secondary memory occurs when a new information conflicts with an old stored one. In this case one information cancels the other by repulsion or by replacement. If the old repels the new, the process is called ‘proactive inhibition’ and if the new information replaces the old one, it’s called retroactive inhibition.
4. Permanent / Tertiary Memory.
- The information stored here are never forgotten e.g your name or ability to write.
- Information in this type of memory comes from the secondary memory by years of practice, which strongly consolidates memory.
- The stored memory here remains available for retrieval even if information in other memories are erased by brain damage or disease. This is because information in the tertiary memory occupies large areas of the brain and more than one ‘copy’ of the information are stored in different regions of the brain. Access to information from this memory is very rapid.