SENSORY MEMORY: CHARACTERISTICS, FUNCTIONS AND TYPES - NEUROPSYCHOLOGY - 2025

The sensory memory is the kind of memory that can retain information impressions senses after the perceived stimulus is gone. It refers to the objects detected by the sensory receptors of the organism (the senses), which are temporarily retained in the sensory registers.

Sensory records contain a high information storage capacity but are only capable of maintaining accurate images of sensory information for a very limited time.

Two main types of sensory memory have been established: iconic memory and echoic memory. The first type is a component of the visual memory system. The second type is a component of short-term memory that is responsible for retaining auditory information.

Sensory memory characteristics

Sensory memory is the persistence of a stimulus over time, beyond its physical presence. That is, it is the memory that allows the effect of a stimulus to continue even if it has disappeared.

For example, if a person visualizes a scene that produces feelings of terror or fear, sensory memory allows them to continue experiencing those sensations when they have stopped seeing it.

Sensory memory is a mnestic capacity that reveals the close relationship between perceptual systems and cognitive processes.

In fact, the operation of one cannot be explained without the other. Perception without cognition would lead to a passive way of connecting with the world, since the mind would not perform any task with the information captured through the senses.

On the other hand, learning and cognitive functioning would be impossible without the capture of new information and knowledge from the outside world through perceptual systems.

Thus, sensations are the starting point of perception, and perception is the first step towards the cognitive process. Without sensation there is no perception and without perception there is no memory.

However, perception and memory have more common elements: perception goes beyond sensations, it is usually defined as the mechanism by which the brain gives meaning to sensations.

Thus, sensory memory processes and stores meaningful information. It also intervenes in the functioning of basic perception processes such as detection, discrimination, recognition or identification.

Historical evolution

The relationship between perception and memory has been a topic of scientific interest for many years. However, the appearance of the term sensory memory is much more recent.

The first investigations about this phenomenon took place in the year 1740 by the hand of Johann Segner. In his study, the German physicist showed that in order for a piece of coal tied to a spinning wheel to be perceived, it needed to make a complete revolution in less than 100 milliseconds.

This first appreciation served to postulate the relationship between the mechanisms of perception and memory.

Later, Broadbent in 1958 proposed the existence of an immediate memory mechanism that would record the information of the proximal stimulus for a short period of time.

Likewise, Neisser in 1967 adopted Broadbent's theory and called it sensory memory. According to the German psychologist, this type of memory consisted of a precategory record of information of limited capacity and short duration.

In parallel, Atkinson and Siffrin proposed the existence of a sensory register for each of the sensory modalities. However, most research on sensory memory focused on the two types initially defined by Neisser (iconic memory and echoic memory).

Finally, it was Sperling in 1960 who was in charge of exploring and specifically delimiting the properties of iconic memory through the use of the tachistocope and the partial report technique.

Features

The main function of sensory memory is to maintain stimulation even though it has disappeared. In this way, they increase the possibilities of being able to process the information, especially in the case of short-duration stimuli.

In this sense, sensory memory acts as an information bridge that allows increasing the duration of the presentation of stimuli.

If the brain could only process information while the stimulus is present and can be registered by the senses, a lot of knowledge would be lost along the way.

The functioning of sensory memory can be exemplified while driving a car. While a person is driving a car, they may perceive multiple signs on the road that indicate traffic regulations, directions on how to get to the destination, etc.

Normally, the visualization of these elements is very brief due to the speed of the car, which allows to capture the stimuli during short periods of time.

However, the stimulation produced by these elements is prolonged at the brain level for a longer period of time than the presentation of the stimulus itself.

This ability is performed by the brain through the performance of sensory memory, which allows the stimulation to be preserved even though the stimulus is no longer being visualized.

Sensory memory types

At present there is a high scientific consensus in establishing two main types of sensory memory: iconic memory and echoic memory.

Iconic memory refers to visual sensory memory, that is, sensory memory processes that are set in motion when stimuli are perceived through sight.

On the other hand, the echoic memory defines the auditory sensory memory and starts when the stimuli are captured through the ear.

Iconic memory

Iconic memory is the record of sensory memory related to the visual domain. It is a component of the visual memory system that includes both visual short-term memory and long-term memory.

Iconic memory is characterized by forming a memory store of very short duration (less than 1000 milliseconds), however, it has a high capacity (it can retain many elements).

The two main components of this type of sensory memory are visual persistence and informational persistence. The first is a brief pre-categorical visual representation of the physical image created by the sensory system. The second forms a memory store with a longer duration that represents an encoded version of the visual image.

The functioning of this type of sensory memory appears to be related to the visual sensory pathway. A prolonged visual representation begins with the activation of photoreceptors in the retina. Rods and cones undergo stimulation after stimulus suppression.

Iconic memory is responsible for providing a flow of visual information to the brain, which can be collected and sustained over time. One of the most important roles of iconic memory is its involvement in detecting changes in the visual environment:

1. Temporal Integration: Iconic memory activates the integration of visual information and provides a constant stream of images in the primary visual cortex of the brain.
2. Blindness to change: several investigations show that the brief representation of iconic memory is especially relevant when it comes to detecting changes in the visual environment.
3. Saccadic eye movements: Newer research suggests that iconic memory is responsible for providing continuity to the experience during saccades.

Echoic memory

Echoic memory is one of the sensory memory records that is responsible for retaining auditory information. It would be a component of short-term memory equivalent to iconic memory for the storage of visual information.

Echoic memory is capable of storing large amounts of auditory information in a period of time between three and four seconds. Sound stimulation remains active in the mind and can be played again during that short period of time.

The first works on this type of memory were carried out by Baddeley on the model of working memory, which is made up of an executive system and two subsystems: the visuospatial agenda related to iconic memory and the phonological loop that processes auditory information (echoica).

According to Baddeley's model (one of the most widely used memory theories today), the phonological loop processes information in two different ways.

The first one consists of a warehouse with the capacity to retain information for three or four seconds. The second is to be a process of sub-vowel repetition that maintains the memory trace through the use of an inner voice.

Currently, the technique that makes it possible to measure echoic memory in a more objective way is the disparity potential task. In this technique, changes in auditory brain activation are recorded using electroencephalography.

References

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