Introduction

Imagine yourself getting up in the morning and not remembering where you are, not recognising the people in your home, not knowing where your things are and not knowing what to do??? This is just a small example that entails that how much information and memories are remembered by our brain on daily basis.

Learning, memory & consciousness

The peculiar characteristic of animals and particularly of humans is the ability to adapt on basis of prior learning experience. Learning is acquisition of the information that makes this possible, and memory is the retention and storage of that information. Consciousness is very important for learning, it can be described as our continuing stream of awareness of either our surroundings or of sequential thoughts. Consciousness enables us to deal with difficult environmental conditions (adaptation). Consciousness also helps us to be attentive, to express ourselves and to be aware of our surroundings.

How are memories formed?

In our day to day lives we see, hear and read lot of things and remember only a few. Some people can remember minute details of any incident while some can’t even remember the important facts associated with it. When all of us are genetically engineered the same way and have same physiological processes than why such disparities are there? To understand it we should know how thoughts and memories are formed and how does brain process information.

The kind of memory we have depends on how the memories are encoded, stored and retrieved. There is a constant input of sensory, visual, acoustic, semantic (meaning) and tactile information, our brain does not store all information as such. It is first converted into a form that can be understood by the brain cells, stored and can be retrieved for further use.

Encoding

Encoding is a physiologic process which starts with the perception of bits of information through different senses in conscious or attentive state and these are then decoded in various sensory areas of the brain and then asserted together to form a single experience or memory in hippocampus area of brain . While hippocampus encodes the information it is formed as short term memory from the working memory, which is then converted into long term memory by formation of memory traces. To understand it better we should first of all know what are different types of memory?

• Short-term memory as name implies is a memory which lasts seconds to hours, during which processing in the hippocampus and elsewhere lays down long-term changes in synaptic strength.
• Long-term memory as name suggests is memory which stores memories for years and sometimes for life. During short-term memory, the memory traces are subject to disruption by trauma and various drugs, whereas long-term memory traces are remarkably resistant to disruption.
• Working memory is a form of short-term memory that keeps information available, usually for very short periods, while the individual plans action based on it.

All the inputs we get are encoded in three principle forms visual (picture), acoustic (sound) and semantic (meaning). It is generally believed that formation of short term memory is by acoustic encoding. Let’s take an example when we see a telephone number and then try to recall it if we try to see the image of the digits it is visual encoding but if we remember it by recalling it as we said the number is acoustic encoding whereas formation of long term memory is mostly through semantic encoding.

Consolidation and storage

For short term memory to be converted to long term memory consolidation takes place. Consolidation can be defined as the process of stabilising a memory trace after the initial acquisition. While the encoding process for short-term explicit memory involves the hippocampus, long-term memories are stored in various parts of the neocortex.

Memories that are formed are not stored as such, once you recall a memory it is re-consolidated. Re-consolidation may change the initial memory, when memories are recalled they may become associated with new environmental or emotional conditions and it basically reactivates the memory trace. So it is generally believed and is scientifically proven that to have a better long-term memory you should keep repeating already known facts to have it in your long term memory for years.

Once the memory is encoded it becomes stored by consolidation and reconsolidation firstly into short term or working memory and thereafter consolidating again and again leads to long term memory formation.

There is plenty of information that we are receiving every moment so just to avoid the overload on our brain, habituation occurs i.e same information that is repeated over and over again stops evoking the neural centres but when it is associated with any pain or pleasure, sensitization occurs. It is common knowledge that intensification of the arousal value of stimuli occurs in humans. The mother who sleeps through many kinds of noise but wakes promptly when her baby cries is an example.

Retrieval

The most important thing in memory formation is that we should be able to recall or retrieve the information when required. Commonly we refer it to as remembering. While remembering the events our brain replays the pattern of neural activity or original memory trace. Memories are not stored at location in brain. Hence, memory retrieval is a complex phenomenon which requires revisiting the memory traces that are formed when initial encoding occurs. Recalling causes a long term memory to be converted to working memory where reconsolidation occurs.

According to research by Fergus Craik and Robert Lockhart, recall is also function of depth of mental processing. If we try to recall a memory by visual or sound or fragrance it is relatively a weak memory trace which tends to become weak with time and it is also known as shallow processing, whereas recalling a memory based on semantics and meaning forms a stronger memory trace , it is also called as deep processing .

Hence, we can say that memory retrieval is an automatic process but we can modify the encoding and storage by following some tips and tricks to have a better memory.