The Lewis theory of active and inactive memory

Are memory and consciousness the same thing? This theory avoids distinguishing between types of memory.

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 ever imagine. We will now discuss one of the most overlooked theories in the history of the study of this brain process, which, however, may be closer to its actual functioning: Lewis' theory of active and inactive memory..

What is memory?

Traditional theories, and mostly accepted by the scientific community, postulate that memory is a basic cognitive process that is divided in 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 point out that in order for the formation of new memories to occurThese memories have to go through a period of instability in which they may undergo modifications, but once they reach long-term memory, they remain unalterable.

However, at the end of the 1960s, several groups of researchers (including Lewis), investigating the phenomenon of amnesia in rats, observed effects that could not be explained by traditional memory theories.

They saw that the memories consolidated in long-term memory could be forgotten if a number of conditions were met.. Based on this effect, in 1979 Lewis put forward an alternative theory.

Lewis' theory of active and inactive memory.

The author postulates that there are no types of memory, but rather that memory is a dynamic process composed of two statesAn active state where all memories, both new and consolidated, could undergo modifications and be forgotten, and an inactive state where all memories remain stable.

That is; active memory would be composed of changing subsets of all the memories of the organism that affect our present behavior, and inactive memory would consist 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 a step further, arguing that memory has no specific locations within the brainRather, it is a central processor that is subservient to other basic processes such as perception and attention. An active memory is a single neuronal firing pattern. Different activated memories would reflect different patterns of neuronal density and would not have a specific location.

The example of the student

The following example will allow a better understanding of this theory:

A university student has just come out of a procedural law exam and is recalling the answers he gave based on what he studied (subset of permanent memories and unconsolidated memories that is active at that moment) when he suddenly walks past a pastry shop and is overcome by a smell of food and causes him to 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 day's menu that until that moment was inactive).

As can be seen, and as Lewis put it, "active memory is intuitively apparent to immediate consciousness". Consciousness is defined as the individual's capacity to recognize the reality that surrounds him or her, to relate to it, and to reflect on it.and reflect on it and on himself.

Recovering this model

However, this theory was quickly rejected at the time because of its highly speculative assumptions and lack of solid empirical contrast. Forty years later, every new finding in the field of memory could be directly or indirectly related to Lewis' work. In 2000, Nader, Schafe, and Le Doux argued that novel memories should be renamed as 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, asserted that each memory is a characteristic neuronal firing pattern (now called cellular engrams). These same authors also conjectured in favor of another of Lewis' hypotheses, which postulates that amnesia is not a destruction of memory, but an inability to retrieve it, i.e., an inability to activate an inactive memory.

Bibliographical references:

• Lewis, D. J. (1979). Psychobiology of active and inactive memory. Psychological bulletin, 86(5), 1054-1083. doi: 10.1037/0033-2909.86.5.1054.
• Nader, K., Schafe, G. E., & Le Doux, J. E. (2000). Fear memories require protein synthesis in the amygdala for reconsolidation after retrieval. Nature, 406(6797), 722-726. doi: 10.1038/35021052.
• Sara, S. J. (2000). Retrieval and reconsolidation: toward a neurobiology of remembering. Learning & Memory, 7(2), 73-84. doi: 10.1101/lm.7.2.73.
• Ryan, T. J., Roy, D. S., Pignatelli, M., Arons, A., & Tonegawa, S. (2015). Engram cells retain memory under retrograde amnesia. Science, 348(6238), 1007-1013. doi: 10.1126/science.aaa5542