Memory is the capacity to store and retain information, then recall it for use when needed. It is used by most organisms to operate in the most successful manner they possibly can in their unique environment.
There are three main types of memory: sensory, short-term and long-term, although long-term is often split into different types of memory. Sensory memory is a very short-term type of memory, which is evoked through the senses. It lasts for a few seconds at most and is not stored. Short-term memory is a slightly longer-lasting form, sitting at around 20 sees. It’s the recording of memories currently being used – ie, remembering a number to dial in the next 30 seconds. If the information is repeated, however, it causes pathways to form between neurons in the brain and a phrenological loop to be formed, causing a memory to be stored as a long-term memory. Unless this repeated firing of the neurons occurs, forced by repeating of the information, a memory will be lost.
When we cannot remember something, it’s generally not because of suddenly developing a degenerating brain disease like Alzheimer’s – it’s far more likely to be that the correct stimuli have not been presented to prompt retrieval of the memory, or that you did not register or retain the original information properly. For example, if you cannot remember where you put your shoes when you took them off the night before, it may be that you were not paying attention when you put them down and consequently not transferred the memory from short-term to long-term in the first place, rather than having forgotten. As long as you have registered and retained the event, correct stimuli would cause a refiring of the neurons fired when creating the original memory, allowing successful retrieval of the information required. Dependent on its type, a memory is stored in different areas of the brain. This helps people to store related information more easily, as it can be linked to previously stored related material.
Memories are formed in our brains through electronic pulses passing between neurons. As neurons fire more than once, the pathway and link between the neurons strengthens; if the first neuron is triggered in the future, it is more likely that the others will too. Memories are stored in different areas of the brain, depending on what they are and what they are used for.
The stimulus for a memory can be nearly anything. It can be related or unrelated. For example, if you see a letterbox, you may remember you had a letterto post, therefore stimulatinga memory through a related input. However, some people use unrelated stimuli, like a piece of string tied to their finger, which they have formed an unrelated link to something else with.
As a memory is being formed, certain neurons will link together in a circuit to store this memory. It will link related memories and repetition of this circuit firing will strengthen the memory. This is called a phrenological oop.
Repeated firing of the neurons involved in the first memory formation (repetition to remember) will strengthen the memory, as the neuron pathway becomes stronger and the memory can be retrieved and utilised faster.
Types of memory
Sensory memory – This memory is evoked through the senses and is the initial perception of something. This is a fleeting memory, and will not be transferred into short- or long-term unless we focus on remembering the event.
Short-term – This type of memory is stored temporarily for up to 20 seconds. It can, however, be confused with working memory, a separate type of memory that allows an individual to retain information only for long enough to, say, complete a sum. Unless information is repeated several times to establish a pathway between neurons, it will decay and be lost.
Long-term – procedural (implicit) – This kind of long-term memory is how we remember to do things such as ride a bike. It is where we store our ‘body’ memories – our motor skills.
Long-term – declarative (explicit) – This type of memory is how we store facts for retrieval, and consists of things such as names and dates.
Long-term – episodic – This is where we store event-related memories and link them together. For example, if you went to a dinner party you wouldn’t remember every moment, but you would recall a collection of events, smells and sounds which link together when you think of the overall event.