The human memory is a powerful and mysterious tool. No two people remember exactly the same things in exactly the same manner even if their lives were almost identical. Understanding memory is like tying to understand the inner workings of a complicated machine without being able to take it apart and look inside. Memory seems to be located everywhere, no more so than in the brain. It is believed to function at the level of synapses that are scattered in a web-like pattern throughout the brain. Thus, the brain has unlimited capacity for storing memories. Some experts say that everything we hear, taste, smell, touch, see and experience we remember.

Many scientists believe that the art of memory is a biological phenomenon with its root firmly embedded within the inner reaches of the brain. Researchers believe that there are at least three different types of memory subsystems: sensory, short-term and long-term memory. (Other researchers believe that long-term memory is made up of several different types of remembering). In addition, there are four categories of memory: recognition, recall, redintegration and residual memory. However, as the latest research suggests, all memory begins with perception.

Sensory memory is important to the way you perceive the world. It contains sensory impressions that you will never forget, like the taste of peppermint candy, or the sound of your favorite song. Almost every taste or smell you experience forms a permanent record in your brain. Short term memory, also called the “working memory system” stores information you need only for a brief period of time. This type of memory includes the ability to recall from six to eight different items within a specific category. Long-term memory stores information over a long period of time so you can get it when you need it. While most people think of memory as long-term memory, researchers believe that information must pass though the first two systems (sensory memory and short-term memory) before it can be stored in long-term memory.

The first category of memory is called recognition. This memory means that you are able to recognize someone or something you’ve seen before. Recognition is the most basic kind of memory. It is the type of memory that is inherent within us, as seen in newborn babies that are able to “recognize” the faces of those they see the most often. This kind of memory is used on multiple-choice tests. The second category of memory is called recall. Recall involves the repetition of acquired knowledge or the demonstration of a skill. Recall develops later than recognition because of the use of symbols (words and numbers) to fill things in and recall them from memory. This kind of memory is used in fill-in-the blank tests, short essays and piano recitals. The third category of memory is redintegration. Redintegration involves the ability to bring back a complex memory. This would be used in writing long essays, or in remembering the sights, smells and sounds of something memorable. The final category is residual memory. This type of memory refers to partial retention of memory. For example, you might remember the plane ride to another country when you were little, but not remember anything that happened there.

Memory and perception cannot be split. It is impossible to speak of visual and verbal memory as two separate things. About 60% of Americans primarily have “visual” memory, easily visualizing objects, places, faces and the pages of a newspaper. The others seem better at remembering sounds or words, and the association they think of are often rhymes or puns.

While memory may begin with perception, many researchers believe that it has to do with transmission of electric signals. Nerve cells connect with other cells at junctions called synapses; they transmit electrical signals to each other by firing across this junction, which triggers the release of neurotransmitters that diffuse across the spaces between cells, attaching themselves to receptors on the neighboring nerve cell. The human brain contains about 10 billion of these nerve cells joined together by about 60 trillion synapses.

The backbone of memory could be the parts of the brain cells that receive electric impulses-the dendrites . It is suspected that when an electrical impulse reaches the brain cell, the impulse may compress the dendrite initiating the memory process. When the dendrite spring back up into its elongated shape, the electrical pulse disappears-along with the memory. This, then could be the description of short-term memory.

Most scientists believe that memory occurs as a result of functional changes in these synapses or dendrites caused by the effects of external stimuli, by learned behavior, training or education. Furthermore, while most parts of the brain are involved in the processing of memory, many researchers now believe that specialized information is contained in highly specific areas of the brain.

Researchers and scientists have generally agreed that anything that influences behavior leaves a trace (Engram) somewhere in the nervous system. As long as these memory traces last, they can be restimulated, and the event or experience will be remembered.

While people often think of memory as a single phenomenon, in fact there are two distinct mechanisms corresponding to different mental processes: voluntary and involuntary memory. Involuntary memory may appear with the smell of one’s perfume, when the sensation comes by surprise. The memory may seem to be voluntary if one chooses to search for it.

While most people speak of having “bad memory” or “good memory”, in fact most people are good at remembering certain things and not so good at remembering others. When a person has trouble remembering something, it is generally not the fault of the entire memory system-just an inefficient component of the memory system. Research indicates that older people have trouble with many components of the memory system (recognition, recall, redintegration and residual memory). It is suggested that younger individuals remember recent significant events in great detail. On the other hand, older individuals remember past events and thoughts in greater detail than the events that just occurred. Many factors go into how well a memory is formed, including how familiar the information is and how much attention has been paid. Good health plays a major part in how a person performs intentional memory tasks. When mental and physical conditions are not at the peak, the entire memory system functions at a slower rate.

Memory plays an important role in everything we do. All learning depends on memory and vice versa. Memory is far more than simply recalling a lot of facts, it also involves remembering thinking patterns. The search for how the brain recognizes, acquires and stores memories is one of the most enduring quests among brain researchers.