HUMAN PERFORMANCES AND LIMITATIONS

The memory represents the mental ability to store, find and gather knowledge with experience. Like all the human functions, the memory varies according to the individuals and situations.

• Information can be stored at the same time in several different places in the memory, which explains why a great number of memories remain intact while some cells are damaged or destroyed because of age or accidents.

• The memory is one of the most significant functions and one of the most interesting properties of the brain. It governs the essence parts of our activities (professional, daily or leisures).

• The memory ensures the link between our past and our present and thus makes our personality. Indeed, it develops as well the identity, the knowledge, the intelligence, the reasoning, the motion ant the affection for each one of us.

• The memory makes it possible to collect, code, preserve and restore stimulations and information which we use. It also stimulates the physical and psychic structures.

1. VARIOUS TYPES OF MEMORY:

Memory is critical to our ability to act consistently and to learn new things. Without memory, we could not capture a ‘stream' of information reaching our senses, or draw on past experience and apply this knowledge when making decisions.

1.1. Training and memory:

Training and memory are two different activities in the brain.

• Training:

  The training is a process of modifying the behavior for a future use. To learn how to eat, make sport or to play a musical instrument are some examples of training. We involuntarily improve our skills. One progresses without knowing why.

  We call training, "the implicit memory ".

• Memory:

  The term memory indicates the capacity to remember past experiences and information learned before. We remember our first ride on a bicycle or our favorite song in childhood. It is known as "the explicit memory ".

  The explicit memory can be categorized in three types, which are:

  • Short-term memory or working memory,

  • Long-term memory or episodic memory,

  • Sensory memory or semantic memory.

1.2. Process of short-term and long-term memory:

The model of the information processing system illustrates the relationships among sensory, short-term, and long-term memory. The four processes by which information is moved from one memory type to another are also considered in the model; the processes are attention, rehearsal, encoding, and retrieval.

Rehearsal involves working or doing something with new information. One must maintain attention through rehearsal in order for information to be stored in short-term memory. The length of time information is held in short-term memory is proportional to the amount that can be stored and the quality of the memory.

Retrieval involves drawing on existing knowledge. It forms the basis for all new knowledge. Retrieval of prior knowledge during learning directly affects the amount of new information that can be processed. At-risk students often have low funds of previous knowledge, hampering retrieval and, therefore, the learning process.

2. SHORT-TERM MEMORY (WORKING MEMORY):

The short-term memory corresponds to the temporary storage of information during analysis. Its function is to allow a temporal storage and to carry out a certain number of analysis at the same time. The short-term memory seems to have a limited storage capacity, but a high storage and reading speed.

• → Rate of change of short-term memory:

Example:

When remembering the words from a list, the performance is better for the last words because they are in short - term memory; if we analyze another task during a few minutes the ability to memorize the last words disappears.

The concept of short-term memory makes it possible to describe many psychological phenomena like the short-term loss of memory, the load and the mental recall.

3. LONG-TERM MEMORY:

3.1. Capacity of long-term memory:

Long-term memory, the last part of our information-processing model, is truly remarkable in what it allows us to recall.

• personal experiences,

• beliefs about people, social norms, values, etc.,

• abilities, such as language comprehension.

• → Capacity to retain information according to the number of recalls:

When we compare long-term memory to short-term memory we find that it is just what its name implies, long term. The information stored in long-term memory is relatively permanent but not always accurate.

3.2. Types of memory storages:

While we often think of memory as a single process, memory storage is actually more than one type of process.

As early as 1911, the French philosopher Henri Bergson stated that our past survives in two fundamentally different forms, conscious and unconscious. Scientists usually characterize these two forms as:

• procedural,

• declarative.

a) Procedural memory:

Procedural memory can be related to the knowledge of rules of action and procedures, which can become quite automatic with repetition.  Practicing a certain task a lot or a little is procedural knowledge. Often a person will learn how to perform a task but will have no awareness of how it was learned.

Procedural memory can be referred to as implicit memory.

Performance of activities or skills is the only method to convey procedural long term memory.

b) Declarative memory:

Information in long-term memory can be divided into two types, semantic and episodic.

• Semantic memory refers to our store of general, factual knowledge about the world, such as concepts, rules, one's own language, etc. It is information that is not tied to where and when the knowledge was originally acquired.

• Episodic memory refers to memory of specific events, such as our past experiences (including people, events and objects). We can usually place these things within a certain context. It is believed that episodic memory is heavily influenced by a person's expectations of what should have happened, thus two people's recollection of the same event can differ.

4. SENSORY MEMORY:

Extremely short, it practically corresponds to the time of perception of a reaction by our sensors. The range of the semantic visual (or iconic) memory is between 300 and 500 milliseconds.

The semantic auditive memory (or echoic) is hardly longer.

With these visual and auditive reactions, the perceptions collected by the other sensors can be added but they seem to play a less significant role. Thus it is the tactile semantic memory.

It is the combination of these various perceptions which allows the identification of information.

5. THE BASE OF MEMORY:

Neurobiologists agree that the hippocampus plays an essential role. Located at the centre of the brain, it ensures the comparison of the information stored in various cerebral areas. It is necessary for the transfer of the short-term memories to the long-term memory.

Today it is known that there is no “memory centre ", but several regions in the brain related to the analysis and to the storage of information.

Thus the memory satisfies the same characteristics as for the other important functions of the brain (motion, the language, perception, intelligence...).

For simplification, it can be specified that:

• the short-term memory uses the front layer of the cerebrum,

• the semantic memory is operated by the neocortex,

• the corrugated bodies and the cerebellum are closely related to the procedural memory,

• the hippocampus is also linked to the episodic memory (at the same time as the thalamus and the front layer of the cerebrum).

6. MEMORY DISEASES:

The disorders of the memory are characterized mainly by amnesias. Less frequent pathologies are observed known as paramnesia and hypermnesia.

6.1. Memory diseases:

• Amnesia:

  According to different cases, the form of amnesia varies. We can distinguish:

  • anterograde amnesia or concentration amnesia. The patient cannot take new data any more, but the old memories are preserved. This type of amnesia happens to chronic alcoholics people (Korsakoff syndrome),

  • the retrograde amnesia prevents the patient from evoking memories former to his disease,

  • the lacunar amnesia is an amnesia referring to defined period of time (period of a loss of conscience, epileptic fit, a psychiatric episode, etc.),

  • the total amnesia which involves the recent as well as the old facts and which can be found in insanities.

• Paramnesia:

  It is the illusion of the already seen or already lived. Insulated and apart from a clinical picture psychotic (schizophrenia), it is about a defect of interpretation of a disorder of perception, sometimes related to tiredness.

• Hyperamnesia:

  It appears in psychiatric disorders where the memories of the patient occupy an obsessing, exaggerated and even incredible place for the patient.

6.2. Alzheimer's disease:

More and more frequent to old people (after 45 years, but especially after 65 years), the Alzheimer's disease affects the brain. It appears by a short-term loss of memory, a mental confusion and, finally, by a total physical and intellectual deterioration.

In spite of intensive search, the precise cause of this disease remains unknown and no cure has been found yet.

Other degenerative diseases, less widespread touch the brain and attack intellectual faculties (Pick syndrome, Chorea Huntington, Steel-Richardson disease, amnesic syndrome).

6.3. Effect of ageing:

We have believed that the progressive loss of the neurons explained the memory difficulties of the old people.

Nowadays, we know that our main neurons is so significant and under employed that even at the end of our life we still have preserved potentials. That undoubtedly explains the quality of the memory performances of some very old persons.

It is however known that with the chronological age, the cerebral capacities slow down; the transmission of information is slower:

Acquisitions of new information are more difficult, the old memories exist but their recall is more complex.

If there are physiological reasons with the decrease in the performances, the ageing of the memory is also explained by a decrease in the psychic, physical and intellectual activities and by an isolation. The memory needs to be used frequently for it to function well: its exercise must continue as far as possible.

6.4. Can we improve our memory?

First of all, let us specify that, according to pharmacologists', until today, it was not proved that an effective drug supposed " to dope " the memory had convincing effects with people having normal or higher memory capacities. Indeed, the products concerned were never the subject of the necessary scientific evaluations. The conclusions states that no chemical substance can be regarded as specific to the memory.

At most, for a limited period of time, we can improve the vigilances, the concentration, decrease the anxiety, and any functions that when altered disturb the memory performances.

But it is necessary to be careful: the best illustration is given to us by the students who, in examination periods, take the stimulative and exciting drugs. If they activate some functions, they harm at the same time the sleep which is very important for the quality of the memory.

Much work was attempted to develop molecules intended to decrease the memory disorders, in particular with old people.

In the case of the people free from pathologies, rather than seeking to stimulate the memory, it is advisable, at any age, to cultivate it.

6.5. What advice is needed?

To cultivate and preserve his memory, it is recommended, on one hand to have a good hygiene in life, and on the other hand to work his memory.

• Hygiene in life:

  The sleep has a particularly beneficial effect on the memorization of acquired information the previous day. As opposed to what we believe still recently, we do not learn while sleeping, but we retain the information better due to a sufficient regular and good quality sleep ( 8 hours at least for an adolescent and a young adult),.

  The use of sleeping pills does not develop a better memory, because they deteriorate one of the important phases of the sleep: the paradoxical phase, during which the process of memorizing is very active.

  Other drugs can have an action on the memory performances.

  Tobacco and alcohol harm the memory. The latter being the cause of lacunar amnesias, exerts a negative action on the neurotransmitter and in the case of chronic alcoholism, it can cause irreversible cerebral lesions.

• To work the memory:

  One of the best methods to work his memory and to preserve his storage capacities is reading. Indeed, it involves the permanently attention, visual perception, and acknowledgement, the construction of mental images, the organization of information etc, and all operations which occur in our memory.

  Other exercises can be recommended which mobilize the attention, where we express interest, where we store the material to be memorized according to an organization, where we use the repetition.

  In case of repeated failures and concern on its memory capacities, it is useful to consultant a general practitioner who will be able to diagnose between anxiety, tiredness, stress or a real memory disorder and thus advise for a consultation at the hospital or in specialized medical centres for the evaluation of the memory.