Amnesia

Amnesia

Some neuropsychological definitions

> The training is the process by which the nervous system acquires new information.

> The memory is the storage and/or the recovery of this information.

> Amnesia comes from the Greek “amnesia” which wants to say lack of memory. Amnesia is the pathological incapacity to learn from new information or to remember already acquired information.

One should not confuse amnesia with:

> The lapse of memory is the process by which stored information is lost with time. If there were not the lapse of memory, our brain would be encumbered of a whole useless heap of information. The lapse of memory thus allows the unballasting of information without interest.

Temporal categories of amnesia

> Retrograde amnesia: incapacity to remind old facts (comes from a Latin root meaning “to go backwards”.

Example: incapacity to remind memories of holidays or places of life of ten years ago.

> Anterograde amnesia: incapacity to remind recent facts (comes from a Latin root meaning “to go forwards”. The subject thus does not manage any more to build new knowledge and trainings.

Example: impossibility to remember name of somebody whom one has just met.

Qualitative categories of amnesia

The man presents at least two qualitative types of information storage: declaratory memory and nondeclaratory memory.

These memories are not located in the same zones of the brain. According to the cerebral area which will be damaged, one will thus have various types of amnesia:

1) Amnesia concerning the declaratory memory (or clarifies)
The declaratory memory relates to the storage and the recovery of data which can emerge with the conscience and be expressed by the language. This memory is located in a cerebral area called “the hippocampus”. The semantic declaratory memory and the episodical declaratory memory are distinguished:

> Semantic memory: generalized memory.
Example: like knowing the direction of a word, the name of the president.

> Episodical memory: autobiographical memory.
Example: to remember the date and the place of the last holidays in family.

Very reached area of the hippocampus in the brain will be able to thus involve a semantic and/or procedural amnesia.

2) Amnesia concerning the nondeclaratory memory (or implicit)
The nondeclaratory memory is not accessible in the details to the conscience. It comprises various types of memory, localized each one in precise places of the brain:

Procedural memory: they are the practices, the acts which we learned and which we make without being aware in the precise way in which they should be carried out. This memory is localized inter alia in a major zone of the brain called the “striatum”.

Example: to roll to bicycle, to play of the piano, to type on a keyboard of computer.

> Starting or priming: unconscious phenomenon which makes that the last stated data are more easily retained.

> The associative training (Pavlovian): a dog whose sound of a bell is associated at the time of the meal goes, at the end of a few days, to salivate with the sound of the bell.

> The nonassociative training (ways reflexes).

Very reached cerebral area implied in one of these four categories of implicit memory will be able to thus involve a particular amnesia relating to the faculties permitted by the type of injured memory.

The causes of amnesias are multiple

Many forms of cerebral attacks can damage the memory and deteriorate new trainings:

> An accident or an physical aggression concerning the brain,

> Diseases: cerebral vascular accident, cerebral tumor, cerebral infection, insufficiency in vitamin B, insanity (example: disease of Alzheimer),

> A neurosurgical operation with ablation of part of the brain.

To retain

Amnesia is the pathological incapacity to learn from new information or to remember already acquired information. It is due to cerebral attacks of various nature. According to the damaged zones, there will be various forms of amnesia because different the type from the human memory have precise cerebral localizations.

In any case, all the aspects of our individuality are learned and memorized. It is thus conceived that deteriorations of our memory can have important consequences on our social life and even on our identity.