Iconic memory contributes to memory as such, providing a coherent presentation of our entire visual perception over a very short period of time. This type of memory helps to take into account phenomena such as changes in the clarity of vision and the continuity of experience. Iconic memory is no longer regarded as a single whole phenomenon. Nowadays, it is already known that it consists of at least two distinctive components. Classical experiments, including experiments on testing the Sperling partial report paradigm, as well as modern methods, confirm the previous conclusion. The development of iconic memory begins in early childhood. In old age, it gets worse. Like any other type of memory.
Theory of Iconic Memory
The emergence of a stable physical image of an object after its displacement from the field of view was observed by many people throughout history. One of the earliest documented reports of this phenomenon was Aristotle, who suggested that these mental phenomena are related to the phenomenon of dreams.
Everyday observation of the light path created by luminous charcoal at the end of a fast-moving stick aroused the interest of researchers in the years 1700 and 1800. The then European researchers were the first to begin empirical studies of this phenomenon, which later became known as apparent persistence. The study of apparent resilience will ultimately lead to the discovery of iconic memory.
In the 1900s, the role of preserving such images in memory attracted considerable attention due to the hypothetical connection of this phenomenon with visual short-term memory (VSTM).
Modern era
In 1960, George Sperling began his classic experiments to confirm the existence of visual sensory memory and some of its characteristics, including power and duration. In 1967, W. Nysser called iconic memory the property of the brain to remember for a very short time the "cast" of the image that had just flashed before our eyes. About 20 years after Sperling's original experiments, the individual components of visual sensory memory began to stand out. That is visual and information resistance. Sperling’s experiments mostly checked information related to the stimulus of this type of memory, while other researchers tested for visual resistance. Iconic memory in psychology is, first of all, the ability to remember fleeting images that are imprinted in the mind for a short time.
Sound connection
In 1978, Di Lollo proposed a model of visual sensory memory with two different states. Although this phenomenon has been known throughout history, the current understanding of iconic memory makes a clear distinction between visual and information resilience, which are tested differently and have fundamentally different properties. It is assumed that information persistence is a key factor in visual short-term memory as a pre-categorical sensory “information store”. First of all, for sounds. The storage time of information in the iconic memory may vary depending on the material.
Structure
The two main components of symbolic memory (another name for the phenomenon under discussion) are visible and information resistance. The first characteristic implies a relatively short (150 ms) precategory visual representation of a physical image created by the sensory system of our brain. This will be a “snapshot” of what the person was looking at for a split second before. The second component is a longer memory drive, which represents an encoded version of a visual image converted into post-categorical information. This will be “raw data” that is received and processed by the brain. A third component, called neural persistence, can also be considered and represents physical activity and recordings of the visual system. Neural persistence is usually determined using neurophysiological methods.
Duration
Various methods were used to determine the duration of visible (visual) resistance. The difference in the duration of the apparent persistence in people is the different duration of the "storage" of visual memory. Phenomenal continuity and the mobile slit method allowed us to determine the average (normal for a person) visible resistance of 300 ms.
Neurophysiological aspect
The main visible persistence is the neural resistance of the visual sensory canal. A long visual presentation begins with the activation of photoreceptors in the retina. It was found that activation in the receptors persists even after the physical displacement of the stimulus, and rod-shaped objects remain in memory longer than, for example, cones. Cells involved in a stable visible image include M and P cells located in the retina. M cells (transient) are active only during the onset of the stimulus and its displacement. P-cells (resistant) show continuous activity during the onset of the stimulus, its duration and displacement. Cortical persistence of the visual image was found in the primary visual cortex (V1) in the occipital lobe of the brain, which is precisely responsible for processing visual information.
Other information resistance features
Consistency of information is information about the stimulus, which is stored after its physical displacement. Sperling's experiments were a test of information resilience. The duration of the stimulus is a key factor affecting the duration of information resistance. As the duration of the stimulus increases, the duration of the visual signal entering the brain also increases. Non-visual components represented by information resistance include the abstract characteristics of the image, as well as its spatial arrangement. Due to the nature of information resistance, in contrast to visible resistance, it is immune to masking effects. The characteristics of this component of sign memory suggest that it plays a key role in presenting a post-categorical storage of memory that the brain can access to analyze information.
The experiments
Although there are not many studies regarding the neural presentation of information resistance compared, new electrophysiological methods have begun to identify areas of the cerebral cortex involved in the formation of iconic memory that no one has previously paid attention to. Unlike visible persistence, information persistence relies on higher-level visual areas outside the visual cortex. It was found that the anterior upper brain region is associated with the recognition of objects and the identification of their identity. The role of iconic memory in detecting changes is associated with the activation of the middle occipital gyrus.
It was found that the activation of this gyrus persists for approximately 2000 ms, which indicates the possibility that the sign memory has a longer duration than previously thought. Iconic memory is also affected by genetics and proteins produced in the brain. The neurotrophin produced by the brain causes the growth of neurons. And contributes to the improvement of all types of memory. It has been proven that individuals with mutations in brain regions producing neurotrophin have much less and less stable information resistance.
The meaning of iconic memory
This memory provides a smooth and gradual flow of visual information into the brain, which can be extracted over a long period of time for consolidation into more stable forms. One of the key roles of symbolic memory is associated with the detection of changes in our visual environment, which helps in the perception of movement.
Iconic memory allows you to integrate visual information during a continuous stream of images, for example, when watching a movie. In the primary visual cortex, new stimuli do not erase information about previous stimuli. Instead, responses to the most recent of them contain approximately the same amount of information about this and the previous stimulus. This one-sided memory can be the main substrate both for integrating sign memory and for recognizing masking effects. The specific result depends on whether the two subsequent images of the component (that is, “icons”, “icons”) are significant only when isolated (masked), or only when superimposed (integrated).