Do you remember what you had for breakfast yesterday? How have you traveled to university 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 explicit memories, that is, all memories about episodes, events and data of our life. From our eighth birthday to the taste of an orange.
Declarative memory, also called explicit memory, It is the ability to voluntarily bring to consciousness episodes or events of our life It is thanks to it we can relive experiences that happened a long time ago, recognize 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 constitute memory, and where in the brain we can find declarative memory.
Patient HM, who suffered from severe temporal lobe epilepsy, had these lobes sectioned in both hemispheres. He successfully controlled his epilepsy, but something unexpected happened: he had lost many memories from eleven years ago and could not remember anything from the last two years, and was unable to create new memories. Thus, his declarative memory had been affected.
Surprisingly, he did retain the memory that stores motor skills. Riding a bicycle, using 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 blocks of memory with different and anatomically independent functions was evidenced.
Neurological bases of declarative memory
The first difference between declarative and procedural memory is that they are located in different regions From this it follows that, at a functional level, they use different neural circuits and have a different way of processing information.
In procedural memory, most information is stored as it is received from the senses. Psychologists say that it is a bottom-up processing, that is, from the physical directly to the psychological. On the other hand, in declarative memory, physical data is reorganized before being stored. Since information depends on cognitive elaboration, we speak of a top-down process. Declarative memory, on the other hand, depends on conceptually controlled or “top-down” processes, in which the subject reorganizes data to store it.
In this way, the way we remember information is greatly influenced by the way we process it. This is why the internal stimuli that we use when storing information can help us remember them spontaneously. In the same way, the contextual stimuli that are processed with the data can be a source of recovery. Some mnemonic methods exploit this characteristic 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. Those 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 is responsible for the memory that stores the most short-term data..
Other structures are also included such as the nuclei of the thalamus, which connect the temporal lobe with the prefrontal, and the brain stem, which sends stimuli to the rest of the brain for processing. The neurotransmitter systems most involved in these processes are acetylcholine, serotonin and norepinephrine
Two types of declarative memory
Endel Tulving, through his studies on memory, distinguished in 1972 two subtypes of declarative memory: episodic memory and semantic memory. Let’s look at each of them below.
1. Episodic memory
According to Tulving, episodic or autobiographical memory consists of memory that allows a person to remember past events or personal experiences. It allows humans to remember past personal experiences. Requires three elements:
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. This is an ability that requires consciousness and is therefore theorized to be unique to our species.
2. Semantic memory
Tulving called knowledge of the world – everything that is not autobiographical – semantic memory. This type of declarative memory includes all the knowledge that we can explicitly evoke that does not have to do with our own memories. It is our personal encyclopedia, containing millions of entries about what we know about the world.
Contains information learned in school such as vocabulary, mathematics some aspects of reading and writing, historical figures or dates, knowledge about art and culture, etc.
