Do you remember what you had for breakfast yesterday? How did you get to college or work? Who have you been talking to since you woke up? If the answer is yes, it means that your declarative memory is working correctly.
This type of memory without which we could not function, stores all the explicit memories, that is, all the memories of episodes, facts and data in our life. From our eighth birthday to the taste of an orange.
What is declarative memory
Declarative memory, also called explicit memory, it is the ability to voluntarily bring to consciousness episodes or facts of our life. It is thanks to her that we can relive experiences from long ago, recognize the faces of famous people and name them or even what we have eaten throughout the week.
The history of declarative memory is relatively young. Its history dates back to the studies of patient HM in 1957, which shed light on two questions: what components make up memory and where in the brain can we find declarative memory.
Patient HM, who suffered from severe temporal lobe epilepsy, had these lobes severed in both hemispheres. He was able to successfully control his epilepsy, but something unexpected happened: he had lost many memories of eleven years ago and could not remember anything from the past two years, and was unable to create new memories. Thus, his declaratory memory had been affected.
Surprisingly, it has retained the memory that stores motor skills. Riding a bike, using the language, etc., are skills that are stored differently because they are not data or episodes, but “ways of doing”. This memory is called procedural or implicit memory. Thus, the existence of two large memory blocks with different and anatomically independent functions has been demonstrated.
Neurological basis of declarative memory
The first difference between declarative and procedural memory is that they are located in differentiated regions. It follows that at the functional level, they use different neural circuits and have a different way of processing information.
In procedural memory, most of the information is stored as it is received from the senses. Psychologists say it is an ascending process, that is, from the physical to the psychic directly. In contrast, in declarative memory, physical data is reorganized before being stored. As information depends on cognitive elaboration, we are talking about a top-down process. Declarative memory, on the other hand, depends on conceptually controlled or “descendant” processes in which the subject reorganizes the data to store it.
So, the way we remember information is greatly influenced by the way we process it. This is why the internal stimuli that we use to store information can help us remember it spontaneously. Likewise, the contextual stimuli processed with the data can be a source of recovery. Some mnemonic methods exploit this functionality of memory, such as the loci method.
Through the study of animals and humans, Petri and Mishkin propose that implicit and explicit memory follow different neural circuits. The structures that are part of declarative memory are located in the temporal lobe. The most important are the amygdala, which plays a crucial role in the emotional process of memories, the hippocampus, which is responsible for storing or retrieving memories, and the prefrontal cortex, which deals with memory which stores memories. . .
Also included are other structures such as the nuclei of the thalamus, which connect the temporal lobe to the prefrontal, and the brainstem which sends stimuli to the rest of the brain for processing. The neurotransmitter systems most involved in these processes are those of acetylcholine, serotonin and norepinephrine..
Two types of declarative memory
Endel Tulving, through his studies of memory, in 1972 distinguished two subtypes of declarative memory: episodic memory and semantic memory. Let’s take a look at each of them below.
1. Episodic memory
According to Tulving, episodic or autobiographical memory is that which enables a person to recall past personal events or experiences. It allows human beings to remember past personal experiences. Requires three things:
- Subjective sense of time
- Awareness of this subjective time
- A “self” can travel in subjective time
To understand how memory works, Tulving explains it through the metaphor of time travel. According to this metaphor, autobiographical memory is a kind of time machine that allows consciousness to travel back and voluntarily revisit past episodes. It is an ability that requires awareness and is therefore theorized to be unique to our species.
2. Semantic memory
To the knowledge of the world – all that is not autobiographical – Tulving called it semantic memory. This type of declarative memory includes all the knowledge that we can evoke explicitly and that has nothing to do with our own memories. This is our personal encyclopedia, which contains millions of entries on what we know about the world.
It contains information learned in school such as vocabulary, math, Certain aspects of reading and writing, historical figures or dates, knowledge of art and culture, etc.