Although memory has been scientifically investigated for approximately 130 years, perhaps the most relevant discovery to date is that memory is much more complex than anyone could imagine. Next, we will talk about one of the theories that has gone most unnoticed throughout the history of the study of this brain process and that, however, could be closer to its real functioning: Lewis’s theory of active and inactive memory
Traditional theories, and mostly accepted by the scientific community, postulate that Memory is a basic cognitive process that is divided into two types
A short-term memory, located in the prefrontal cortex, which allows us to manipulate information from the external or internal environment (our mind) and has a limited capacity; and a long-term memory, located in the hippocampus and temporal lobe, which is unlimited and stores information permanently.
On the other hand, these traditional theories also indicate that for the formation of new memories to occur these must go through a period of instability in which they may undergo modifications, but once they reach long-term memory, they remain unchanged.
However, in the late 1960s, several groups of researchers (including Lewis), investigating the phenomenon of amnesia in rats, observed effects that could not be explained by traditional theories of memory.
They saw that memories consolidated in long-term memory could be forgotten if a series of conditions were met Based on this effect, in 1979 Lewis proposed an alternative theory.
The author postulates that there are no types of memory, but that memory is a dynamic process composed of two states: an active state where all memories, both new and consolidated, could be modified and forgotten, and an inactive state where all memories remain stable.
That is to say; active memory would be composed of changing subsets of all the organism’s memories that affect our current behavior, and inactive memory would be made up of all those permanent memories, which have the potential to be activated at some point, that are in a state of relative inactivity and have little or no effect on the present behavior of the organism.
Furthermore, he went one step further, arguing that memory does not have specific locations within the brain, but rather it is a central processor that is subordinate to other basic processes such as perception and attention. An active memory is a unique neural firing pattern. Different activated memories would reflect different patterns of neuronal density and would not have a specific location.
The student example
The following example will allow a greater understanding of this theory:
A university student has just finished a procedural law exam and is remembering the answers he gave based on what he studied (subset of permanent memories and unconsolidated memories that are active at that moment) when he suddenly passes in front of a pastry shop. and a smell of food invades him and makes him remember the menu he is going to make when he gets home (the perception of the smell directed attention to the food, which in turn activated a permanent memory of the menu of the day that until that moment was idle).
As can be seen, and as Lewis stated, “active memory is intuitively apparent to immediate consciousness.” Consciousness is defined as the individual’s ability to recognize the reality that surrounds them relate to it and reflect on it and on yourself.
Recovering this model
However, this theory was quickly rejected at the time due to its highly speculative assumptions and lack of solid empirical contrast. 40 years later, each new discovery in the field of memory could be directly or indirectly related to Lewis’s work. In the year 2000, Nader, Schafe, and Le Doux argued that new memories should be renamed active memories Sara, in the same year, urged the entire scientific community to consider memory as a dynamic process.
In 2015 Ryan, Roy, Pignatelli, Arons and Tonegawa, among others, stated that each memory is a characteristic neuronal firing pattern (currently called cellular engrams). These same authors also conjectured in favor of another of Lewis’s hypotheses, which postulates that amnesia is not a destruction of memory, but an inability to recover it, that is; an inability to activate an inactive memory.
