Memory Loss What is Memory Loss ? ( मेमोरी लॉस क्या है )

Amnesia ( मेमोरी लॉस )

Amnesia refers to loss or impairment of memory. It may be

caused by organic disorders, such as injury or loss of blood

supply to the limbic system, or by nervous disorders such

hysteria. Amnesia could also be total, with complete loss of recall;

or partial, occurring only immediately before or after

traumatic event; or systematic, relating to a particular type a

group of experiences. Amnesia is a symptom rather than a

disease and treatment is aimed at determining and removing

the basic cause.

Short-term and long-term memory

We tend to talk of memory as though it were a distinct

physical entity contained somewhere in our heads-a kind

of scrapbook of mental pictures, or a videotape to be played

back at will on a slightly quirky recorder. Memory

nowhere near as tangible. It is a fundamental function built

into the living brain.

Brain tissue has the ability to change as messages pass

within it. Its modification whether for long or short periods

gives it the power of remembering and gives us the ability

to profit from past events. Without this ability we should he

mindless, unable to learn, to read, to write, to talk or even

to think. Lacking a memory we could comprehend nothing

and communicate nothing.

Every fraction of every second, information is entering

the brain and memory is at work, whether we are aware of

it or not. The point of our attention when reading a book,

for example, is the meanings of the words on a page. But

behind this the information that the print is black and the

paper white is also being recorded, repeatedly, with each

successive word we read. Otherwise we would not notice if

a specially important word were printed in red. Whether

transiently or for long periods the information from all our

senses modifies the brain's activity in some way so that

events are 'remembered' in its complex circuits.

Experiments indicate that there are quite distinct stages

in the process of acquiring and storing information. During

the phase of acquisition there is first an extremely brief stage

which is called sensory storage. The sensory circuits involved

remain activated for a very short time and a fleeting mental

image is formed only to die away. By far the greater part of

the information stored in the image is simply forgotten.

Anything that does survive for a particular reason passes to

the state of short-term memory. Long-term memory, or the

storage of information for considerable periods, may or may

not follow.

A person might be asked, for example, to describe what

he saw after being allowed to glimpse a photograph of 12

familiar objects for just a few hundredths of a second. It is

likely that only four or so objects would be recalled, despite

the fact that all 12 were perceived. The retention of the image

in the sensory store is so transient that by the time four

objects have been named, the image has disappeared and,

no longer being available for inspection, the others have

been forgotten.

The very act of naming the four objects has, for a while,

saved them from being forgotten. The information from the

sensory circuits has been encoded into a verbal form and

reinforcement of the visual image is now given by hearing

the names of the objects. They have entered short-term

memory and can be recalled for a time.

Short-term memory retains information and passes it

into long-term memory only if the information is 'rehearsed',

that is, thought about again and again by making a conscious effort.

Otherwise the information disappears in probably less than half a minute.

An example of rehearsal is repeating a telephone number to oneself after looking it up, in order to dial. Without rehearsal, a seven-digit number is forgotten in seconds. Given sufficient rehearsal, however, it may pass into long-term memory and be remembered for days or even years. 

How information is retained in long-term memory is still a mystery. It may be through the occurrence of chemical changes in the neurons, or the establishment of new connections at their synapses so that impulses travel more readily through certain circuits or both. The passage of nerve impulses influences the production of ribonucleic acid (RNA) during the acquisition of memory with consequent formation of new proteins in the nerve cells. The process of learning is disrupted in animals given drugs that hinder the production of RNA. 

Memory 'has a third component besides acquisition. registration and retention. This is recall. We are not sure how the process works, or how out of all the memories we store up in our lives, we can select some at will quite readily, while others seem to remain temporarily inaccessible and yet others seem to disappear forever.