Our brain is a complex organic machine made up of many complex parts. Each part of the brain has a different function, ranging from operating the automatic actions we perform each day such as breathing and our heart beat, to allowing us to feel, taste, smell and hear. One of the most complex processes that the brain has is the ability to remember events and information.
Sensory memory is the first type of memory that the brain uses to remember things. However, sensory memory spends the briefest amount of time in our memory banks. Sensory memory works when we see, hear or even feel something. Quickly the sensation is stored in the brain's sensory registers. At this point the memory is an exact picture of what occurred. It has not been processed or changed in any way. Here the brain decides whether or not it is important enough to send to short- or long-term memory banks. If it is not, the memory is replaced with new stimulus and forgotten. If it is important enough, then the memory is sent on to the next areas of memory in the brain. Most sensory memory only remains in the sensory registers for a few seconds.
Short-term memory is different than sensory memory in that it lasts for up to a few minutes, verses a few seconds. Once a memory reaches this area of the brain it has been processed into a more complex idea, rather than an exact picture of what occurred as it was in sensory memory. Short-term memory can come in two forms, regular short-term and working short-term. Regular short-term memories are only in the brain for a short amount of time and are deemed not important enough to be stored long term. At this point they are bumped out by more important thoughts. Working memory is short-term memory that is kept indefinitely by repetition of information. For example, reciting a phone number over and over again keeps the phone number in your short-term memory. However, after you dial it, it can either be forgotten or stored in long term. If the information is important enough to keep indefinitely, the frontal cortex of the brain, in association with the hippocampus, analyzes the information and works to transform the experience into long-term memory.
Long-term memory is where most of the action happens regarding the brain actually remembering things. This starts with encoding. Encoding is where the details of a long-term memory such as smells, colors or information are stored in the hippocampus of the brain. The hippocampus and frontal cortex then take all of this information and turn it into electrical signals that can be distributed to different areas of the brain connected by nerve pathways and synapses. One part of the brain may store the smell involved with the memory, while another part of the brain may remember a color, number, or even emotion.
How strong a memory remains in your brain depends on the strength of the synapse between the nerve cells associated with the memory. The more you practice or think about a piece of information stored in your brain, the more that particular synapse is going to be used. As the synapse is used more frequently, it grows in strength. This allows the memory to be more vivid and clear in your mind. If you do not access the memory often, the synapse begins to weaken. This may cause you to forget, or have a hard time remembering a memory that has not been accessed in some time.