MEMORY AND DEMENTIA PART-1

                           MEMORY, DEMENTIA, AMNESIA

Hello everyone! And welcome yet again. Today, I am going to discuss about a very important clinical topic which everyone has varied theories about, but still many misconceptions prevail in the society.
Ironically, we don’t realise our memory and thinking capacity before it starts getting degenerated. We don’t even remember in our day to day lives until we remember everything as a part of our daily life but only remember only when one starts forgetting, which helps us realise the value of our memory. Strange isn’t it?
Let us discuss today something about our memory. While in the next blog I will try to cover neurological conditions related to loss of memory.

                                   MEMORY:

As per definition “ THE FACULTY BY WHICH MIND STORES AND REMEMBERS INFORMATIONS” is called memory.
It is rather a complex function of our brains. A layman may consider this to be a small and simple medical issue, however, it is shocking to know that the annual expenditure pertaining to this condition in U.S.A is >$100 billion annually.
 

           PHYSIOLOGICAL BASE OF MEMORY:

                The main structural and functional unit/part of our nervous system and brain is a small cell called neuron. There are billions of neurons in our nervous system, which are in communication with each other and form a network. These neurons contain specific chemical messengers within them which we know today as neurotransmitter. These chemicals have various functions in our nervous system. They are secreted when they get signals from the affected area or site or when they receive informations. These informations or impulses are in the form of electrical impulses. This information is now converted and stored in the brain in the form of memory with the help of neurotransmitters and when required the information can be cited again in the reverse order of the aforesaid events.
                To make things easier we may divide memory into 3 major groups:

1)      Working memory(short term)
2)      Episodic memory and
3)      Long term memory.

There are also subtypes of these memory called semantic memory which further has two subtypes. Declarative memory or explicit memory and procedural or implicit memory.

1)      WORKING MEMORY:  This type of memory is stored in our brain for a very limited period of time. Depending on various factors, after sometimes the bits of information are either discarded and forgotten or converted to long term memory. The prefrontal lobe, a part of our brain responsible for higher intellectual functions and ability is responsible for this type of memory. The positive part of this type of memory is that, though short term information is stored our brain can be trained by intense training of this training and our skills and cognitive function of our brain are shown to be increased. The reason being a well developed prefrontal lobe due to formation of new synapses due to the intense training. However, this type of memory is highly vulnerable to distraction and a continuous concentration is required for its proper utilisation.

2)      EPISODIC MEMORY: As the name suggests, this ,memory helps a person to remember memorable experiences and happenings of the past. Normally a persons lays down multiple episodic memories at once which helps them to carry out various functions in life through new experiences. E.g a birthday of a person or a family picnic or a convocation ceremony. Etc. these experiences form episodic memory. Once the event enters in the brain in the form of episodic memory it undergoes a process called “ information consolidation”. Unlike the working memory, the episodic memory is stored after a cascade of events in the brain through an organ called hippocampus, which is a storehouse of instincts and a basic organ of storing a long term memory or an event. The information is then sent to the cerebral cortex where it is stored in the form of an entire event.

3)      LONG TERM MEMORY: As the name suggests, this is a form of memory which remains permanently or for a very long period of time in our brains. This may include names, faces historical facts etc. as in the episodic memory the cerebral cortex is the most important to store a long term information.

There are also some additional categories of memory:

a.       Semantic memory: The memory responsible for storing unchanging facts of a group of unchangeable phenomenons, like days of the week or months etc.

 b.       Declarative memory(explicit memory): The memory which works by producing or reciting personal events or facts voluntarily. That means those facts that we have to willingly remember or reproduce voluntarily.( similar to episodic memory to which it is a prototype). Like a birthday party of a classmate or a relative, in which we have to put voluntary effort to recollect the past event.

 c.       Procedural memory( implicit memory): As the name suggests, the facts stored in this memory or the specific tasks don’t need voluntary redressal. Eg riding a bicycle or getting dressed up. It goes with the flow of events without a voluntary recall.

                                  STEPS IN MEMORY:

1)      Registration of facts and phenomenons after experiencing them through our senses. This is also called encoding or acquisition, in which the events are aligned in proper sequence before sending to the next stage.

2)      Retention and consolidation: In this stage the information undergoes further processing and now the events are properly sequentially arranged and retained in our memory and gradually converted to memory.

3)      Consolidation and stabilisation: Finally, the information is stored in the brain and ready to comprehend when needed.

4)      Retrieval: The events or facts which were stored can be again retrieved and comprehended.

And finally, there is an EXECUTIVE FUNCTION of the brain which carries out complex and higher intellectual tasks like planning, organising, behaviour etc.