Chapters > Cognition > Memory and learning

Memory and learning

Category: Cognition• Published on: April 18, 2012• Hits: 16331•

Memory plays a decisive role in our lives [3]. In fact, without memory, life would have no meaning. Memory is the means by which we locate ourselves in time; it is the fabric that shapes each individual's history.

Definitions :

Memory is defined as the capacity to capture, encode, store, and retrieve information [4].

Memory is often confused with learning. Even though these two processes are closely linked, it is worth mentioning that learning [1] primarily applies to the phase of acquisition and storing of memories.

Recall involves the active retrieval of information, while recognition requires only deciding whether an item among others has been previously encountered [119].

Classifications :

The concept of memory, while in common usage, is actually more complex than it appears. In fact, a distinction is made between several types of memory [38, 135]:

Based on duration :

Sensory memory :

This is of extremely short duration; it is nothing other than our perception of things and events. It is the echo and internal resonance of sensory information that persists for a few fractions of a second within our consciousness [145].

Short-term memory :

Also called working memory [163], this constitutes a level of selective filtering for information gathered by our senses, lasting for up to one minute [164]. It allows us to retain a few items - on average, seven pieces of data, such as a phone number [42] - data with which we work (hence its name). Depending on their importance, these items may or may not move to a longer-term level storage [161].

Long-term memory :

Long-term memory [165] ensures the preservation of memories over a long period: months, years, or even a lifetime.

Based on the type of information stored:

Depending on the type of data to be memorized [39], it may be:

Explicit memory :

Also known as declarative memory [167], this concerns data that can be expressed in words. A distinction is made between [165]:

Semantic memory [164], which involves the memorization of specific objects and facts.

Episodic memory [145], which concerns events clearly situated in time.

Implicit memory [166] :

Also called procedural memory [165], this is an essentially motor memory that concerns "know-how." It consists of sensorimotor automatisms so well integrated that we are unaware of them. For example, someone who knows how to perform sutures would find it difficult to explain the method using only words. Many of our emotional responses and conditioned reflexes are also part of implicit memory.

Memory efficiency :

Nature of memory :

Our memory is associative [119], meaning it is more effective when we link the data to be memorized with items already stored in our memory; one thing reminds us of another, which reminds us of yet another, and so on.

Memory is the result of a reconstruction of different elements. We do not store entire scenes in our brains. Furthermore, no memory is truly identical to its origin, like a photograph; that would require too much to memorize, and our skull is, unfortunately, non-expandable. We retain only a few pieces of the puzzle - a few breadcrumbs that later help us reconstruct and retrieve memories from various key elements.

Factors influencing memory :

Several factors influence memory efficiency [168]:

  • The degree of vigilance, arousal, attention, and concentration at the time of memorization.
  • Interest, motivation, need, or the necessity of the items to be remembered.
  • Repetition.
  • Location, lighting, smell, noise... in short, the entire context present during memorization is recorded along with the data.
  • The effort of memorization, hence the term working memory. Developing one's memory means giving meaning to the elements to be memorized and making logical connections with what has already been acquired. The more a memory is encoded, elaborated, organized, and structured, the easier it will be to retrieve.

Mechanisms of memory :

Several neural structures play a vital role in memory:

The hippocampus [54] plays a key role in episodic memory. It constantly gathers data from different sensory areas (visual, auditory, somatosensory, etc.), selects the most significant ones, links them into a single episode of events rather than a collection of separate memories, and redistributes them to the appropriate areas.

Individuals who have undergone the removal of both hippocampi can no longer store new memories in their long-term memory [167], but they retain the ability to recall old memories from before the surgery.

Certain highly intense personal memories involve what is called emotional memory [169]. In addition to the hippocampus, this involves another structure of the limbic system: the amygdala [39], a region known for managing our fear responses. Several other limbic system structures contribute to encoding our memories in a lasting way.

The path of information to be stored in long-term memory follows the Papez circuit [38, 50], which connects the hippocampus, fornix, mammillary bodies, anterior thalamus, and cingulate gyrus.

Procedural memory does not involve the hippocampus at all. It is instead associated with changes in the cerebellum [1], the basal ganglia, and the motor cortex.

The prefrontal cortex plays a vital role in working memory [1]. It acts as the brain's "mental scratchpad" holding information in our minds while we actively use it.

No single neuron contains within itself the information necessary to retrieve a memory. The brain retains data through the formation of new networks. These networks are modifiable through the formation of new synapses or the strengthening of existing ones. These may have existed before, but their functioning was previously ineffective.

Long-term potentiation (LTP) [3, 38, 39], which is the primary mechanism of neurological plasticity, plays an essential role in the formation and efficiency of these synapses.