When we study about memory in organism, we can use different point of view. We can study the memory using the cognitive psychology, cognitive neurology or any other standpoints. From the perspective of cognitive psychology, at least we can group memory in three categories, sensory register, Short-Term Memory (STM) and Long-Term Memory (LTM).

After perceived by one of the senses, a stimulus then passed to the sensory register for the organism to recognize the coming stimulus. The memory created by sensory register is very short in duration hence very easy to decay. One example of this kind of memory is iconic memory, which perceived by visual sense, organism’s eyes.

After passing the sensory register, the next phase is the Short-Term Memory (STM). Many studies done in the past to really understand the importance of Short-Term Memory. One of the studies being done by Allan Baddeley (Baddeley, A. D. (1997). Human Memory: Theory and Practice. 2nd ed. Hove, Sussex: Psychology Press) when he came up with the new term, working memory to describe Short-Term Memory. As its name suggested, this kind of memory is also short in duration, but organisms, especially human do need this kind of memory to comprehend learning process. Take for example, when we want to calculate 58 + 79. Any strategies that you use to calculate the above example will require the working memory. Say you’re using the strategy of calculating 8 + 9 first and then you write down the 7 and memorize the 1 to be calculated later with 5 and 7.

The last kind of memory is Long-Term Memory (LTM). As represented by the name, this kind of memory has the longest duration. Long-term memory can be classified into two groups, declarative and procedural memory. Declarative memory is the kind of memory, which require you to declare, such as fact or information that is really important to the individuals, e.g. names and other personal information. Another type of Long-Term Memory is procedural memory. This kind memory requires individuals to perform the memory in certain procedure. An example of this kind of memory is the skill of riding a bike. Once you able to ride a bike, you will remember for the rest of your life.

Organisms learn by making association between concepts. When an organisms want to learn the new concepts and make them part of Long-Term Memory, the new concepts should be associated with the concepts in the Long-Term Memory. This mechanism is happened through learning.

From the cognitive neurology point of view, we know that in our brain the part that is mostly responsible for learning is neurons. Human brain is composed of million of neurons. Another cells, glial cells that are the white matter in the brain, are nurturing these neurons. These glial cells are a lot bigger in numbers than the neurons. Roughly speaking we can say the ratio between neurons and glial cells is 1: 10.

When information distributed from one part of the brain to another part what actually happen is that one neuron releasing neurotransmitter, a chemical substance that contains specific information through the connection between neuron, synapse. Another neuron in turn receives this neurotransmitter. This transfer of neurotransmitter generate electricity, which can be observed through brain scanning machine such as EEG (Electrode Encephalo Graph). This phenomenon happens because of the connection between neuron what we called as synapse. In our head there are million of synapse that connecting one neuron to another.

At these synapses, new protein being synthesized which is part of creating Long-Term Memory. This phenomenon for the very first time is being able to be observed by Sam Kunes. The synthesis was observed in fruit files and occurred as the files learned to associate an odor with an electric shock. Molecular biologist Sam Kunes said his term "found a new biochemical pathway that determines if and where this protein synthesis happens." Using fluorescent markers, Kunes could see synapses modified after exposure to the odor. The altered synapse meant the difference between remembering something for an hour-a short-term memory a day, which is long-term for a fruit fly.

Because the basic structure of this biochemical pathway is the same in mice and humans, Kunes believes these findings will lead to a better understanding of how memory works in higher animals-and could eventually result in therapies to bolster fading recall, e.g. Alzheimer.