Vision and memory are two closely related processes. The mental representation has a high visual component but the image that we build and that we will store in our memory is also related to attention, semantic meaning and emotions, that is, "each one sees their own reality", something that is done evident when checking the differences in the remembered images of the same scene for different observers.

what is memory

“Memory is a way of immortalizing the past” (Emilio Lledó). Memory is based on a set of processes by which information is encoded, consolidated, and retrieved.

That information, the result of experiences that persist over time, is what we call long-term memory. This type of memory can be conscious or unconscious, influencing our thinking and behavior in the present, thus past experiences act in the present but in a non-conscious way.

types of long-term memory

Within long-term memory, we distinguish between declarative and non-declarative modalities.

Declarative long-term memory: Also known as explicit, it refers to the long-term memory of what we can remember consciously and that we can describe or declare to other people (ideas and events). This section includes episodic memory (memory of personal past events) and semantic memory (general knowledge related to objects in the environment and their meaning). Declarative memory, both episodic and semantic, depend on the proper functioning of the medial temporal lobes.

Non-declarative or implicit memory: Refers to non-conscious forms of long-term memory, which manifest as a change in behavior without there being a conscious memory. This type of memory is not made in the temporal lobe, it is made in different regions of the brain (figure).

episodic memory

In the memory of episodes, episodic memory, there is a first question, what determines whether an experience is remembered or forgotten over time? To answer we must review the three basic elements that define memory: encoding, consolidation and recovery.

In the encoding phase, the information is transformed into a mental representation that records some aspects of the current experience. In line with answering the initial question, it is worth looking for what strengthens the coding process. Basically we can cite two factors:

• Degree of attention to information
• Degree to which we delve into its meaning (elaboration).

Processing involves interpreting information, relating it to other information, and reflecting on it. The medial temporal lobes play an important role in episodic encoding. The frontal lobes also play an important role, they contribute to attention and the elaboration of information, elements that favor encoding.

Divided attention

When attention it is split, the encoding is weaker, and subsequent recall attempts are likely to be worse. Neuroimaging studies show that the neural encoding patterns in mindfulness are different from those in divided attention.

Mindfulness

In mindfulness, areas of the left frontal lobe were significantly activated. It has been seen that although the intent to encode may motivate attention, the intent or purpose per se is not absolutely necessary for the encoding to be effective. Encoding is an immediate consequence of attending to a stimulus and then processing it, and what really influences the effectiveness of encoding is how the stimulus is processed, not why the stimulus was performed. prosecution.

To explain this we have the theory of levels of processing (Craik & Tulving, 1975), which is based on the fact that there are various aspects of a given stimulus that can be attended to and processed. Encoding would be a byproduct of stimulus processing. Different aspects of stimulus processing correspond to different levels of analysis ranging from a shallow or superficial level of perceptual analysisat a deep level of semantic analysis (meaning-based), which actively relates afferent information to knowledge already stored in memory. According to this theory, the effectiveness of encoding depends largely on the level of processing to which a stimulus is subjected. The greater the depth, the stronger the representation and the greater the probability that the stimulus will be remembered.

Episodic memory clearly benefits from elaborating the meaning of a stimulus or an event, at the time it is known, at the time the stimulus arrives. We will better remember a person that at the moment of meeting him we not only look at his features, such as the face or way of dressing, but also in aspects such as, he likes our house or has the same political inclination, that is to say with other information that we already we have in memory and we will share with that person (stimulus), during the conversation. It is noteworthy that a "learning" is taking place, not directed or intentional to something in particular, it is an accidental learning that relates new information with what we already had (meaning). This explains why we remember things with a high degree of precision, even in cases where we did not pay much attention to it at the time of the experience and despite this, that information was strongly encoded (we will see how the emotional component plays a role essential in consolidation).

Visual memory with semantic memories

Coding and processing is linked to retrieval, establishing a feedback loop. If retrieval requires retrieving semantic details of a past experience, then processing the encoding of semantic information will be more efficient.

Visual memory with perceptual details

Similarly, if retrieval requires retrieving perceptual details, then perceptual processing in encoding will be more efficient. This principle that processing at encoding is more effective to the extent that such processing overlaps with the processing to be performed at retrieval is known as 'Transfer Appropriate Processing' (Morris 1977). This showed that the level of processing was important, but even more important was the overlap between the features served and processed during encoding and those sought during retrieval.

Our ability to recall a stimulus depends on the similarity between the way the stimulus is processed during encoding and the way it is processed during examination (retrieval).

brain processing

Returning to attention, this is important in the learning and memory process, not per se, but to the extent that it stimulates the elaboration of meaning at a deep level (left frontal lobe). The left frontal lobe supports the encoding of words while the right frontal lobe supports the encoding of non-verbal stimuli, interacting with the medial temporal lobe in the learning process.

Visual memory encoding process

Within the coding process there are two situations that are key to improving efficiency: generation and spacing.

The term generación does not indicate creation but active learning versus passive. Describes the phenomenon that information that one has retrieved or generated oneself (during the study) is more likely to be remembered than information that is simply received and attempted to be memorized thus, we are more likely to remember the 12 cranial nerves with tokens that we have elaborated ourselves than if we studied them directly from a list in a book. We have generated a learning or memorizing mechanism, it is something active, that is to say, it requires elaboration and attention, the two elements that we have previously said that improve the efficiency of encoding. Another point in favor is that the left frontal lobe is activated in the generative process.

El spacing was initially proposed by Ebbinghaus pointing out: "it is undoubtedly more advantageous to use, with a considerable series of repetitions, a convenient distribution of them in a space of time, than to write them down on a single occasion", distributive practices are more effective than massive ones.

Coding and episodic consolidation

We have just seen how encoding in episodic memory involves attention and elaboration, functions that are located in the frontal lobes; however, the lesions in these areas are moderate when compared to when lesions occur in the medial temporal lobes. This means that there is something more than the simple functional anatomical location.

Comprehensive memory representation

The distinctive feature of episodic encoding is to link the various features of a stimulus or event, forming a comprehensive memory representation.

Memory requires disparate elements. When we see a person and memorize them, what we are doing is encoding perceptual aspects of the visual appearance and sound of the voice, the spatial and temporal context, the phonological encoding of names, and the semantics of our conversation. All of this is processed by a different neural network in the brain, not just in the frontal lobes. The problem lies in knowing how this linkage occurs.

Visual memory and the brain

The answer lies in the medial temporal lobe. It has been shown to be a convergence area, where elaborate inputs arrive from many areas of the brain. Information regarding a face, a name, contexts, etc. and which converge especially at the hypocampor, where this information is tied into an integral memory representation. The activity of the frontal lobe, involved in attention and elaboration, modulates encoding favoring the processing of certain features, helping the medial temporal lobe and thus increasing the probability that these features are integrated into an episodic memory representation.

There are experiences that differentiate the side on which the lesion is located. lesions of the hypocampor right produce more alterations in nonverbal episodic memory, while in the hypocampor left, verbal episodic memory is more impaired (Milner 1972).

encoded episodic memory

La encoded episodic memory will follow a process of consolidation or fixation, which makes it resistant to the passage of time. There is a transfer from the medial temporal lobes to lateral cortical regions. This transfer would take place during sleep and during memory.

In the next chapter we will continue with the third phase, the information retrieval, the memory itself, to end long-term non-declarative memory.