Along with the encoding and storage of memory, retrieving (or: recalling) memory is one of the three major complex brain processes of memory.
By retrieving the stored memory, the human brain ‘replays’ an already established pattern of activity between the neural cells and synapses of the neurons.
This activity has been previously triggered by events that have activated specific areas of the brain in order to process, integrate, consolidate, and store the received information.
How Do Brain Cells Store Memory in the First Place?
The cell is able to store memory by making new neural pathways to the dedicated brain centers which process the information acquired through our five senses. Namely, the sensory stimuli detected by the neural cells (tasting an apple, hearing a sound) are transmitted via an electrical impulse.
At the end of the nerve, this electrical impulse activates the chemical messengers, i.e neurotransmitters which continue to spread the sensory data among the neural cells through their synapses. If that information is intended for immediate use, it will be stored in the short term memory of the brain.
For instance, this could be the information we hear at the supermarket about the sum of money we need to pay, and our brain stores it only until we count the money and pay for our purchased products.
In order to store the information we receive from the sensory stimuli in our long term memory, our brain has to process it, i.e. encode it. During the process of encoding, special areas of the cerebral cortex which serve as primary centers for receiving the sensory stimuli try to define the information. This is how we get the information that an apple is red, crunchy, big, and fresh.
By connecting and sorting this encoded (or defined) data, the brain further links it with the previously stored and related memories, thus creating new neural pathways.
How Can We Retrieve our Memory?
We can retrieve our memory in two basic ways:
- Directly (recalling a memory), and
- Hierarchically (recognition of memory).
Direct Retrieving (Recall) of Memory
With the direct retrieving of memory, the information which is previously stored is retrieved by a direct question or a cue. Such is the case with most of the general information and facts we remember.
The direct retrieving of memory is a process that develops in two stages, referred to as the two-stage theory of memory.
According to the two-stage theory of memory, our recollection of past information stored in a dedicated part of the brain includes both a search thorough memory which allows the brain to reconstruct the needed information, as well as a process of recognition that helps it choose the correct element of the retrieved memory
Hierarchical Retrieving (Recognition) of Memory
When a more specific question is linked with a similar group of information by the means of association or comparison, it creates a sequence of data related to an event which leads to information that is more easily retrievable from our memory.
The hierarchical retrieving (recognition) of memory is a process considered to be the more effective of the two, whereas the recall of the memory is a process consisting of two phases: the reconstruction of information and the reactivation of the neuronal network which has previously conducted the storing of memories.
What Is Schema in Retrieving of Memory?
Schema (pl. schemata) is an organized network, i.e. an organized mental structure of previously determined concepts about the world that surrounds us, which helps us process and translate information received via sensory stimuli. It consists of general facts and notions, as well as of our personal perceptions.
When we try to retrieve a piece of information from our memory, we refer to this network of preconceived concepts in order to depict the details of a past event stored in our memory.
What Are the Patterns in Which We Can Retrieve a Memory?
There are several patterns of retrieving memory:
- Free retrieving of memory
- Cued retrieving of memory
- Serial retrieving of memory
Free Retrieving of Memory
When we randomly retrieve elements of information, we activate the process of free retrieving of memory. This type of memory recall has three different effects:
- Primacy effect – This effect occurs after encountering a longer list of elements. When we try to recall them, we first retrieve the information about the ones which were first on the list.
- Recency effect – This effect also occurs after encountering a longer list of elements. When we try to recall them, we first retrieve the information about the ones which were last (most recent) on the list.
- Contiguity effect – An effect that occurs when we first retrieve elements of information which are close together in time, or are similar/related.
Cued Retrieving of Memory
Cued retrieving of memory is the process when the memory is retrieved after the information is triggered by a cue. Without the cue, the required information would probably be lost among the other memory data.
This process also happens when we retrieve pieces of memory after being exposed to pairs or series of words, pictures, or numbers. The resulting associations between the items trigger, i.e. give cues for the retrieving of the following element.
Serial Retrieving of Memory
The ability to recall events from memory in the order in which they have previously appeared is called serial retrieving of memory.
This is very important when it comes to using language, because this pattern of retrieving information from memory helps us retrieve and arrange sentences in the correct order.
This type of memory retrieving has several rules:
- The more recent events are more easily remembered in order
- As the list of elements recalled increases, the serial retrieving of memory becomes less effective
- In case of errors, there is a tendency to respond with a similar element of memory (for instance, saying ‘bat’ instead of ‘hat’)
Why Do We Forget Things?
The inability to retrieve memory is the most obvious cause that makes us forget things. There are several theories that address the problem of forgetting memorized information over time. Those are:
- Trace decay theory of forgetting
- Interference theory of forgetting
- Cue-dependent theory of forgetting
The Trace Decay Theory of Forgetting
This theory focuses on the time and duration of memory and supports the claim that our memory fades away as time goes by. According to this theory, this is the main reason why we happen to forget things which we have stored in our memory a long time ago.
The process of storing memories leaves traces of that information in our brain which fade away with time. A trace is actually a kind of physical or chemical change in the cerebral cortex.
As time passes, the information from our short term memory becomes less and less available. This is the reason why we can’t remember our fifth birthday, or the details of an event which happened many years ago.
The Interference Theory of Forgetting
The interference theory of forgetting implies that forgetting is influenced not only by the passage of time, but also by previously learned information which may obstruct the retrieving of some particular item from memory.
Interference in Memory Retrieval
There is a phenomenon, referred to as an interference in memory retrieval, which occurs when some elements of memory interfere with other elements of memory. In other words, some pieces of stored information disable our ability to retrieve similar information.
In a way, memories compete with each other to be held longer in our memory, as opposed to forgotten.
Interference in memory retrieval occurs in learning by large, especially when some of the data stored in the long term memory is forgotten, thus becoming unavailable to be retrieved in the short term memory due to memory interference or obstruction.
There are two main types of effects that result from the interference of memory retrieval:
- Proactive memory interference;
- Retroactive memory interference.
Proactive Memory Interference
When old memories interfere with new ones, this is called proactive memory interference.
In real life, it’s the case when we are unable to memorize the new address of our friend because we have referred to their old one during most of our time as friends. In other words, it occurs when the information that is stored in our memory has been learned in a similar context.
Retroactive Memory Interference
When new memories interfere with old ones this is known as retroactive memory interference. This effect occurs when the new information we learn directly triggers the forgetting of previously learned memories.
A good example from our everyday life would be when we learn how to play a new video game. After dedicating our time to the new game, when we go back to the old one, we might have forgotten how to play it, and will need to brush up on our old game skills.
The Cue-dependent Theory of Forgetting
This theory is also referred to as retrieval failure, meaning that sometimes a person is unable to retrieve information from a memory which has previously been encoded.
Countless times we have all been in a situation when we are familiar with a notion of a word, but unable to point out the exact word. This is the so-called tip-of-the-tongue phenomenon, or a failure to retrieve a word from our memory, which occurs when we fail to recall the correct piece of previously memorized information.
What Is the Role of Specific Areas of the Brain in the Retrieving of Memory?
The formation of memory mostly occurs in the limbic system of the human brain. This is because of the fact that the limbic system regulates the most vital cognitive processes: learning, emotions, and memory.
Just like many of the intellectual processes are not controlled by just one area of the cerebral cortex, there isn’t a single region of the brain that processes memory, nor acts as a storage site for all memories.
Short term memories are temporarily stored in the cortex, the place where the brain adds meaning and context to the stimuli received from the five senses (smell, sight, touch, taste, and hearing). The new information is then transmitted from this area of the brain to the hippocampus, where the information is linked and consolidated with the previously stored similar memories.
From the hippocampus, long term memories are further transmitted to areas of the brain which are dedicated to specific types of memory. At this stage, the memories are stored in the synapses of the neurons where they can be reactivated (retrieved) if needed.
Basically, the central part of the prefrontal cortex of the brain plays the most fundamental role in both short-term and working memory.
Which Are the Other Areas of the Brain Associated With Memory?
The following is a list of neural networks associated with various areas of the brain that are involved in memory:
- Temporal lobe – This part of the cerebrum stores sensory memory, as well as language, words, vocabulary, and speech.
- Amygdala – Recalls intensely powerful emotions associated with memorable events, such as fear or joy. It also plays a key role in forming new memories, specifically related to fear.
- Prefrontal cortex – Controls the mental retention of passing situations, such as visual-spatial awareness of current surroundings, and is also involved in remembering semantic tasks.
- Putamen – Stores ‘subconscious’ memories, such as motor skills gained by repetition.
- Cortex – Stores parts of a memory associated with specific senses and motor actions in their relevant areas.
- Cerebellum – Plays a role in processing procedural memories and motor learning, such as how to ride a bike.
What Is the Role of the Hippocampus In Retrieving Memory?
This part of the cerebrum establishes declarative, episodic, and recognition memory, as well as knowledge linked with spatial awareness.
The hippocampus helps transfer immediate thoughts and sensory data into short and long term memories.
When some information from the five organs of sense (smell, touch, taste, sight, and hearing) are processed and translated by the brain as long-term memory data, the hippocampus consolidates and integrates this information in order to create a permanent trace of it in memory.
On the other hand, the information which cannot be processed in this way by the hippocampus, cannot be retrieved at a later point.
Which Factors Can Affect Our Retrieval of Memory?
There is a wide range of neurological conditions, disorders, and diseases that contribute to difficulty in retrieving memory:
- Acquired brain injury – A congenital damage to the brain.
- Agnosia – Loss of the ability to recognize faces, objects, places, and voices.
- Dementia – A medical condition characterized by a decline in memory or complete loss of memory, as well as difficulty in speech.
- Huntington’s Disease – A progressive neurological disorder resulting in loss of cognitive skills.
- Parkinson’s Disease – A neurological disease which can also lead to loss of memory due to a decreased production of dopamine.
- Memory decay – An inability to retrieve the information from the sensory stimuli stored in the short term memory of the brain.
- Amnesia – A loss of memory, pertaining to facts, information, and experiences, that results from injuries of the head and brain, certain drugs, alcohol, traumatic events, or conditions such as Alzheimer’s disease.
- Lack of sleep – Irregular sleeping patterns can lead to brain damage and consequently, the inability of the affected individual to retrieve information stored in the memory.
- Depression – This psychological condition can lead to forgetfulness due to lack of concentration, focus, and clear reasoning.
- Vitamin B12 deficiency – This vitamin aids the health of brain cells. Thus, the lack of Vitamin B12 can cause various problems with the central nervous system, including memory loss.
- Alcohol abuse – Addiction to alcohol can result in damage to the brain structures, which in turn can lead to the loss of memory.
In addition, the following factors can also strongly influence our ability to retrieve memories:
- our personal beliefs
- The psychological state we’re in
- knowledge
- mood
- degree of attention
- personal beliefs
- vigilance
All of the aforementioned can affect and influence what information we actually retrieve from our memory at a given moment.
For instance, when we are sad, the memory of unhappy events can come to us more easily, and vice versa. Sometimes, we even make a conscious effort to forget a traumatic experience.
Motivated Forgetting
Very often, when we are faced with something which reminds us and triggers the retrieving of an unpleasant memory, we tend to redirect our thoughts to something more pleasant and happier.
Every time we try to suppress an unpleasant memory by such continuous practice, we trigger the motivated forgetting, i.e. directed, or intentional forgetting.
This process can be considered as some kind of coping mechanism which we use to protect ourselves from psychological damage and deeper hurt.
As an example, when we suffer violence, an assault, abuse of any kind, as well as a broad range of other emotionally traumatic events, this can all lead to dissociative amnesia.
Though dissociative amnesia is the inability to recall personal information which is not usually lost with the common process of forgetting, it helps the affected individual cope more easily with trauma, as well as temporarily forget the painful details of the event.
To Sum Up
When we try to relieve a past experience, our brain creates a reconstruction of the event by reactivating a previously established neuronal activity in order to trace back and retrieve the required information.
Some specific memories are converted into general knowledge as a part of the process of consolidation of the information we receive through the five senses. This mental process occurs in several different patterns.
We all recollect memories of our summer holiday when it’s cold and snowy outside, trying to think of better places to be at that moment. In this way, our previously-stored memories of a happy event try to override the memories of the cold and, very likely less pleasant day that is trying to find its place in our memory.
Fun Facts
Did you know?
- We don’t always pay full attention to what somebody’s saying to us. However, if we ask that person to repeat what they have just said, it will sound familiar to us, due to the fact that echoing memory has unintentionally stored the information of the heard sound.
- If the hippocampus suffers damage, a person can recall events from long ago, before the damage, but will not be able to remember what happened a few hours previously.
- The temporal lobes play a crucial role in forming and recalling memories in our brains.
- If we forget what we wanted to say or do, walking back to the place where we first got the idea could help us retrieve that memory.
- Memories of events are most often retrieved in the same order they were experienced in in the first place.
- If we feel happy, it’s more likely that it will be easier for us to recall memories of happy events, and vice versa. Namely, the current emotional state of an individual plays a big role in the retrieving of past information stored in our brain.
- If we need to compare the way in which our memories are stored in the brain with actual physical storage, it would be a puzzle, rather than a book-shelf. The information we receive through the five senses is not just put in a dedicated place in the brain, but integrated and consolidated, also.
- The process of recognition is an unconscious process that triggers a sense of familiarity during the retrieving of memory. There’s even a specific area in the cerebral cortex dedicated to face-recognition.
- Sometimes, we may choose to consciously forget certain data. This process occurs in the frontal lobe where the consolidation of memory is blocked during the effort of retrieving the information stored in our brain.
- Repressed memories can be accessed and recovered by specifically designed therapy, which includes guided imagery technique, hypnosis, or age regression.