In this chapter we will deal with long-term memory retrieval, in its episodic and non-declarative forms. We will see its anatomical-physiological basis, how it is produced and how it is altered, the phenomena of interference, competition and forgetfulness, so frequent in our environment and that we often do not know how to explain.
Memory recovery
The phenomenon of "recall" is what produces the subjective experience of consciously remembering the past. Episodic recovery involves a series of processes that basically occur in two anatomical regions of the brain:
- medial temporal lobe: that support the conclusion of models.
- Frontal lobe: that support the mechanisms of strategic recovery.
Temporary or episodic recovery of memory
Episodic retrieval is a powerful cognitive phenomenon that transforms our current state of mind so that the present contacts the past and restores aspects of it.
A first question will be to ask, how does a retrieval key, for example the appearance of a face, act to retrieve details of the past. Episodic memories are encoded by linking the various features of a stimulus or event into a comprehensive representation, a combination of related features. This fact of multi-characteristics explains why, faced with a partial stimulus, one of these characteristics acts as a key that triggers the recovery of the other characteristics that constituted the integral representation. We have access to memory even with a limited amount of information. This is what we call “Model Conclusion” (Nakazawa 2002).
When episodic memory is not yet consolidated, retrieval takes place in the medial temporal lobes. An inverse path to the one followed by the encoding process is produced, it is what is known as “recapitulation".
The keys reach the hypocampand from here they are projected to the cortical areas where the inputs arrived from which an integral memory was generated. in the hippoampor the cue causes the completion of the model and from there it is projected back to the cortical areas and re-enacts the pattern of activation that occurred during encoding. A "copy" of the information that was present during encoding is retrieved, even if it is not an identical copy.
Frontal lobe and memory retrieval
Analyzing patients with selective brain pathology, it was seen that the frontal lobe also played an important role in recovery.
The frontal lobes help by devising a plan for the selection of cues to be used to probe memory. In addition, when trying to remember details of a past experience, the frontal regions of the left hemisphere, associated with semantic elaboration, are activated. In this region, competitive discrimination is also carried out with other memories that can interfere with what we are trying to evoke and that are one of the causes of forgetting. Lastly, the frontal lobes are important for evaluating and monitoring retrieved information, allowing decisions to be made based on the quantity and quality of what has been remembered.
Keys to memory recovery
Retrieval is stimulated by clues and cues from the external and internal environment.
We know that in many cases of forgetfulness it was not due to the fact that the information had been deleted, but that the origin is that the appropriate keys were not given. The context usually provides very solid keys and plays a fundamental role.
Retrieval of memory and context
When we return to the town where we lived as children, any detail we see evokes very rich memories, much stronger than if we are in the room of our current city and try to remember our childhood in the town. This is what is called "context dependent effect” and supports the idea we had that when a representation is encoded, the environment is linked with the action or object that we are fixing in memory, so that if we later come into contact with that environment or similar, any detail can act as key, bringing to our consciousness that memory with many of the details that were encoded at that time.
In the same way, the internal state acts as part of the context, so that in a certain internal state in which certain information was encoded, it is more easily recovered when that same internal state occurs.
Along with forgetting, linked to recovery, a fact that has motivated multiple studies is that of erroneous or distorted memories. Three basic situations have been described to explain it: bias, misattribution and suggestion.
bias errors
bias errors have been related to the cultural base of each person. Their beliefs and knowledge, as well as life habits, condition the information retrieved from memory, tending to modify part of that information with respect to when it was encoded, which is what we call "belief bias".
The false recognition of memory
The false recognition takes place when it reaches us a stimulus that, despite not having prior knowledge of it, is semantically or perceptually similar to previously known stimuli.
If we are asked to remember a list of words for products used in confectionery and are later asked if the word sweet was there, which was not on that list, the majority of respondents said that it was on the list. This is because the word sweet bears semantic resemblance to the other words used in the pastry context. Dulce is a stimulus consistent with the essence of our past experiences and therefore can produce a false memory or a false sense of familiarity. Neuroimaging studies show that in false recognition, medial temporal and hypochondrium areas are activated.ampor but, somewhat differently from how they occur in memory retrieval.
suggestion
The suggestion leads us to false memories of an original event based on false information. Through questions in the recovery process we can induce mistakes in memory.
This is of great importance in criminal investigations, in trials, when a witness is asked to remember something, through our questions we can induce that witness to include in his memory things that were not in the original scene. This can be achieved if falsehoods are included in the interrogation, so that while the interrogated person listens, he fixes them in his representation and encodes them thus, later, they will appear as "true" in the recovery phase, when we return to that scene and ask about those facts.
Admitting misinformation is because when we remember something, we never have a representation that is identical to what was encoded, we know that this is the case and therefore we are not too critical when it comes to incorporating false elements into that representation that fit with the rest of the information. the retrieved representation.
oblivion
In a classic work, Hermann Ebbinhaus observed how the memory of encoded stimuli and events changes as the "retention time" increases, the time that elapses between encoding and retrieval was a determining factor, something that was admitted as such for a long time. time but later it has been seen that it is not exactly like that.
Interference theory
Subsequent studies show that the time between encoding and retrieval, by itself, does not correctly explain forgetting, there must be some process that determines it. One of the hypotheses that have been considered the most is that of competition or “interference theories”, where a key is linked to a series of different representations that would come into competition during retrieval, producing interference and distorting memory or leading to oblivion, to the extent that that key has not been effective enough to retrieve that information we have in our memory file.
retroactive and proactive interference
Examples of interference we have every day. We use an email account for a long time and then we change it for another but, at a certain moment, after a long time, we want to remember the first one and we can no longer. The new account interferes with recall of the first, is what we call "retroactive interference". It can also happen in the opposite direction, something earlier interferes with more recent information, is the “proactive interference”.
memory is associative
Encoding involves the formation of associations between different mental representations, as occurs when linking the concept of a password with a particular sequence of characters.
The recovery supposes a model of conclusion: the presentation of a recovery key, for example, the password request that appears on the computer screen, reactivates the associated representation, the correct sequence of characters of each one.
Given the fundamental principles of binding and the key dependency of model completion, it is clear that interference can lead to forgetting through a number of mechanisms, basically two, blocking and suppression.
memory lock
Forgetting may be due to the "blocking" of a memory representation, that is, to the obstruction that can occur when multiple associations are themselves associated with a key and one of those representations is stronger than the others, which prevents the recovery of the target information. The strongest association between a key and a representation prevents the recovery of weaker associations between that same key and other representations. If what we want to remember is one of those weaker associations, the strongest association always appears, which, in that case, is not what we want to remember. A crash occurs.
To achieve unlocking of a weak representation, a more effective recovery key must be presented, one that is more strongly associated with it.
suppression
Another form of forgetting is what is called “suppression”, in which active retrieval of one memory weakens retrieval of another memory. By memorizing the new email, we are suppressing the previous one, so that it does not compete and interfere with the new one, which is the one that interests us now. In the case of deletion, recovery is more complex than in the case of blocking.
Non-declarative memory retrieval
Non-declarative or implicit memory has no memories, it functions outside of consciousness. The recovery of non-declarative memory is expressed in the behavioral changes that it can induce.
This type of memory is the basis for forms of mechanical learning (habits), such as the ability to ride a bicycle, which are qualitatively distinct from and functionally independent of declarative memory. Non-declarative memory is not involved in the medial temporal lobes, so patients with alterations in these areas of the brain may have declarative memory amnesia but may retain motor skills such as painting or even have the ability to learn to paint. We see this frequently in some phases of Alzheimer's disease.
Priming and skill acquisition
In the study of non-declarative memory, the phenomenon of priming (activation) takes on special importance, which allows us to more easily dispose of stimuli and events that we have previously known.
The presence of a face or hearing a word can cause an unconscious alteration of our subsequent response to that stimulus or another related one. These behavioral changes may include an increase in the speed of the response, the accuracy of that response, or a bias in the nature of the response. A classic example of priming is the one used in the laboratory. A list of words is projected for a very short time, 34 milliseconds, and then the experimental subject is asked to try to identify them. What usually happens is that it remembers a very small number of words, but if before presenting the list a test word is projected into another list, it is very likely that that word will be identified in the second list.
There are various forms of priming, highlighting two categories, perceptual priming and conceptual priming. The first leads to an increased ability to distinguish a stimulus, and the second facilitates the processing of the meaning of a stimulus or increases access to a concept.
perceptual priming
Perceptual priming, like the previous example of the word list, continues to function in patients with lesions in the medial temporal lobes, with failure in declarative memory, this suggests that this type of priming derives from learning that occurs in the regions sensory cortex, such as the occipital in the case of using the visual channel.
concept priming
The conceptual priming is the one that used in skill acquisition.
Three stages have been proposed to acquire a skill (Fitts and Posner 1967). The first phase is
cognitive stage
At Lóleo Eventos, cognitive stage knowledge is represented in a declarative way, frequently according to a verbal code and requiring a high level of attention, as when we learn to ski, we must follow a series of instructions and pay close attention to the movements we make, otherwise we fall .
associative phase
With practice we pass to a second stage, the associative, in which the verbal code is less important and motor stimuli and mnemonic associations count more. Now we are assimilating the sensations of sliding down the track, the supports, the position of the skis, etc.
autonomy phase
Finally we get to the autonomy stage, in which the behavior is executed very quickly, almost automatically, requiring little attention and, if we practice a lot, we can reach the level of the photo.
Skill acquisition and declarative memory
Skill acquisition depends in part on the basal ganglia, cerebellum, and other cortical regions.
The importance of the basal nuclei was revealed with Parkinson's patients in whom these nuclei are altered. In these patients, the priming phenomenon is maintained, but the learning or maintenance of skills related to declarative memory is altered.
Neuroimaging reveals alterations in the activation of the caudate and putamen.
In the next chapter we will deal with the other form of memory, the working memory, which we retain briefly for immediate use.
