About Memory Formation in the Brain

Memory formation is based on the process of neuron transmission, which is activated by environmental stimuli. The information you receive for your environment is processes in a fraction of a second, and then the information is either kept in short term or long term memory. Not all information can be recalled, however; some information is filed in the subconscious mind, where it is not accessible. Other information is stored for life, and certain stimuli can trigger an unintentional memory in response to the stimuli.

Function

Memory is based on several processes, which account for short term, long term and sensory memories. The processes used encode information as it is received, store the information and make it available for retrieval at any later point. The ability to retrieve information depends on where it is stored in your memory, however. The short term memory stores information that is immediately recalled for only half a minute, while memories that are stored in the long term memory bank are stored indefinitely.
Even though memory sounds like an abstract concept, the human brain is able to store each sensory experience almost instantly using neuron transmissions, even though we may not be able to recall those experience later. Memories that are stored in the subconscious part of the brain are not accessible, unlike memories that are stored in short and long term memory.

Type

Short and long term memories are the most important types of memory when you are referring to practical applications. For example, the ability to remember a phone number while you look for a pen to write the number down falls in the short term memory. After you have written the number down, you can "forget" the number until you need it again. If it is a phone number that you use daily, it will be stored in the long term memory after a day or two.
Long term memory works differently than short term memory. Long term memories may be slightly more difficult to access, but they can be retained over the course of a lifetime. Long term memory formation requires meaning and repetition. For example, if you called your mother every day while you were in college, you will remember that number long after she has moved or has a new number.

Features

Each type of memory is stored in a certain part of the brain. Short term memories are stored in the frontal lobe, where they may be transferred to long term memory through the hippocampus, which is located near the back of the brain.
Scientists believe that the formation of long term memory is the result of a transmission of neurons, which work while you sleep. Short term memories are converted to long term memories over time, usually through repetition. Novel experiences can also be committed to long term memory relatively easily, as can information that is meaningful to you personally.
Memories are, to put it simply, activated by certain neural responses to sensory information from the outside world. For instance, the smell of cinnamon may remind you of Christmas. In this example, the smell of cinnamon is the activator which causes an unintentional activation of the neurons that store memories, and therefore remind you of Christmas.

Features

Memory is often one of the primary defenses against hostile environments. Converting short term to long term memory allows you to pass tests, remember the sound of a rattlesnake, and even know where you live and your spouse's phone number. Different types of amino acids, such as Omega-3 fatty acids, are essential to proper brain functioning and memory formation.
Hormones also play a role in memory formation. Although their exact function in memory formation is not known, high levels of estrogen in females improve memory. Other hormones, such as those that are released when you are stressed, negatively effect memory formation in both men and women, making it more difficult to remember even relatively simple new material.

Significance

Memory formation allows humans to develop complex meanings and relationships with the environment and others in that environment. Memory is not just limited to facts and figures, however. You can remember smells, tastes and even the feeling of the things you encounter.
We are also able to have continuous memory formation by attaching meaning to sensory experiences. Memories are built upon each other, using interrelated meaning and significance that form specific memories and opinions of the things in our environment. For instance, our memory categorizes things in terms of similarity and difference, such as apples and oranges. We remember both as a distinct type of food, under the broad categories of food and fruit.
All memory formation is built in this hierarchical manner, based on the importance of the information, the meaning we attach to the information and how often we experience the sensory attributes of the information.

Risk Factors

If one of the areas of the brain that controls memory functions is injured, such as the frontal lobe, then memory formation will be impaired. It is possible to have only short term memory, or to retain only long term information. Conditions such as Alzheimer's disease affect the memory, as well.
In diseases such as Alzheimer's, the entire brain experiences a lapse in the formation and transmission of neural responses related to memory. This degeneration is considered to be irreversible, as are brain injuries that permanently effect memory formation.
Other injuries can cause amnesia, which can be short- or long-term depending on the location of the brain injury and its severity.