Visual memory describes the relationship between perceptual processing and the encoding, storage, and retrieval of the resulting neural representations.
Visual memory occurs over a broad time range spanning from eye movements to years in order to visually navigate to a previously visited location.
Visual memory is a form of memory which preserves some characteristics of our senses pertaining to the visual experience. We are able to place in memory visual information which resembles objects, places, animals or people in a mental image.
The experience of visual memory is also referred to as the mind’s eye through which we can retrieve from our memory a mental image of original objects, places, animals or people.
Visual memory is one of several cognitive systems, which are all interconnected parts that combine to form the human memory.
Types of palinopsia, the persistence or recurrence of a visual image after the stimulus has been removed, is a dysfunction of visual memory.
Visuospatial sketch pad
The visuospatial sketchpad is part of Baddeley and Hitch’s model of working memory. It is responsible for temporarily storing visual and spatial information, which is currently being used or encoded.
It is thought of as a three-dimensional cognitive map, which contains spatial features about where the person is and visual images of the area, or an object being concentrated on.
It is used in tasks such as mental image manipulation where a person imagines how a real object would look if it were changed in some way (rotated, flipped, moved, change of color, etc.).
It is also responsible for representing how vivid an image is. A vivid image is one which you have a high potential for retrieving its sensory details.
The visuospatial sketchpad is responsible for holding onto the visual and spatial qualities of a vivid image in your working memory, and the degree of vividness is directly affected by the limits of the sketchpad.
Eidetic or ‘photographic memory’
Eidetic memory is an ability to recall images, sounds, or objects in memory with high precision for a few minutes without using mnemonics. It occurs in a small number of children and generally is not found in adults.
The popular culture concept of “photographic memory,” where (e.g.) someone can briefly look at a page of text and then recite it perfectly from memory, is not the same as seeing eidetic images, and photographic memory has never been demonstrated to exist.
Iconic memory is the visual part of the sensory memory system. Iconic memory is responsible for visual priming because it works very quickly and unconsciously. Iconic memory decays very quickly but contains a very vivid image of the surrounding stimuli.
Spatial memory is a person’s knowledge of the space around them, and their whereabouts in it. It also encompasses all memories of areas and places, and how to get to and from them.
Spatial memory is distinct from object memory and involves different parts of the brain. Spatial memory involves the dorsal parts of the brain and more specifically the hippocampus.
However many times both types of memory are used together, such as when trying to remember where you put a lost object.
A classic test of spatial memory is the Corsi block-tapping task, where an instructor taps a series of blocks in random order and the participant attempts to imitate them.
The number of blocks they can tap before performance breaks down on average is called their Corsi span. Spatial memory is always being used whenever a person is moving any part of their body; therefore it is generally more vulnerable to decay than object memory is.
Object memory involves processing features of an object or material such as texture, , size, and orientation. It is processed mainly in the ventral regions of the brain.
A few studies have shown that on average most people can recall up to four items each with a set of four different visual qualities. It is a separate system from spatial memory and is not affected by interference from spatial tasks.
Visual memory is not always accurate and can be misled by outside conditions. This can be seen in studies carried out by Elizabeth Loftus and Gary Wells.
In one study by Wells, individuals were exposed to misleading information after witnessing an event; they were then tested on their ability to remember details from this event.
Their findings included: when given misinformation that contradicts the witnessed event they were less able to recall those details; and whether misinformation was given before or after the witnessed event did not seem to matter. Furthermore, visual memory can be subjected to various memory errors which will affect accuracy.
Visual memory in education
Visual memory, in an academic environment, entails work with pictures, symbols, numbers, letters, and especially words.
Students must be able to look at a word, form an image of that word in their minds and be able to recall the appearance of the word later. When teachers introduce a new vocabulary word, generally they write it on the chalkboard, have the children spell it, read it and then use it in a sentence.
The word is then erased from the chalkboard. Students with good visual memory will recognize that same word later in their readers or other texts and will be able to recall the appearance of the word to spell it.
Children who have not developed their visual memory skills cannot readily reproduce a sequence of visual stimuli. They frequently experience difficulty in remembering the overall visual appearance of words or the letter sequence of words for reading and spelling.
Factors affecting visual memory
Findings surrounding sleep and visual memory have been mixed. Studies have reported performance increases after a bout of sleep compared with the same period of waking.
The implications of this are that there is a slow, offline process during sleep that strengthens and enhances the memory trace.
Further studies have found that quiet rest has shown the same learning benefits as sleep. Replay has been found to occur during post-training quiet wakefulness as well as sleep.
In a recent study where a visual search task was administered quiet rest or sleep is found to be necessary for increasing the number of associations between configurations and target locations that can be learned within a day.
Reactivation in sleep was only observed after extensive training of rodents on familiar tasks. It rapidly dissipates; it also makes up a small proportion of total recorded activity in sleep. It has also been found that there are gender differences between males and females in regards to visual memory and sleep.
In a study done testing sleep and memory for pictures it was found that daytime sleep contributed to the retention of source memory rather than item memory in females, females did not have recollection or familiarity influenced by daytime sleep, whereas males undergoing daytime sleep had a trend towards increased familiarity.
The reasons for this may be linked to different memory traces resulting from different encoding strategies, as well as with different electrophysiological changes during daytime sleep.
Brain damage is another factor that has been found to have an effect on visual memory. Memory impairment affects both novel and familiar experiences.
Poor memory after damage to the brain is usually considered to result from information being lost or rendered inaccessible. With such impairment, it is assumed that it must be due to the incorrect interpretation of previously encountered information as being novel.
In experiments testing rats’ object recognition memory, it was found that memory impairment can be the opposite, that there was a tendency to treat novel experiences as familiar. A possible solution for this impairment could be the use of a visual-restriction procedure that reduces interference.
Studies have shown that with aging, in terms of short-term visual memory, viewing time and task complexity affect performance.
When there is a delay or when the task is complex recall declines. In a study conducted to measure whether visual memory in older adults with the age-related visual decline was caused by memory performance or visual functioning, the following were examined: relationships among age, visual activity, and visual and verbal memory in 89 community-dwelling volunteers aged 60–87 years. The findings were that the effect of vision was not specific to visual memory.
Therefore, the vision was found to be correlated with general memory function in older adults and is not modality-specific. As we age performance in regards to spatial configurations deteriorates. In a task to store and combine two different spatial configurations to form a novel, one young people out-performed the elderly.
Vision also has an effect on performance. Sighted participants outperformed the visually impaired regardless of testing modality. This suggests that vision tends to shape the general supramodal mechanisms of memory.
Studies have shown that there is an effect of alcohol on visual memory. In a recent study, visual working memory and its neural correlates were assessed in university students who partake in binge drinking, the intermittent consumption of large amounts of alcohol.
The findings revealed that there may be binge-drinking related functional alteration in recognition working memory processes.
This suggests that impaired prefrontal cortex function may occur at an early age in binge drinkers. Another study conducted in 2004 examined the level of response to alcohol and brain response during visual working memory.
This study looked at the neural correlates of the low level of response to alcohol using functional magnetic resonance imaging during a challenging visual memory task.
The results were that young person who reports having needed more alcohol to feel the effects showed higher levels of brain response during visual working memory, this suggests that the individual’s capacity to adjust to cognitive processing decreases, they are less able to adjust cognitive processing to contextual demands.
Dysfunction of visual memory
Hallucinatory palinopsia, which is a dysfunction of visual memory, is caused by posterior visual pathway cortical lesions and seizures, most commonly in the non-dominant parietal lobe.
Focal hyperactivity causes persistent activation of a visual cortex-hippocampal neuronal circuit which encodes an object or scene that is already in visual memory.
“All of the hallucinatory palinopsia symptoms occur concomitantly in a patient with one lesion, which supports current evidence that objects, features, and scenes are all units of visual memory, perhaps at different levels of processing. This alludes to neuroanatomical integration in visual memory creation and storage.”
Studying the excitability alterations associated with palinopsia in migraineurs could provide insight on mechanisms of encoding visual memory.
One common group of people that have visual memory problems are children with reading disabilities. It was often thought that disabilities are caused by failure to perceive the letters of a written word in the right order.
However, studies show it is more likely that it is caused by a failure to encode and process the correct order of letters within the word.
This means that the child perceives the word just as anyone else would, however, their brains do not appear to hold onto the visual characteristics of the word. Although initially it was found that children with reading disabilities had comparable visual memory to those without difficulty, a more specific part of the visual memory system has been found to cause reading disabilities.
These parts are sustained and transient visual processing systems. The sustained system is responsible for fine detail such as word and letter recognition and is very important in encoding words in their correct order.
The transient system is responsible for controlling eye movements, and processing the larger visual environment around us. When these two processes do not work in synchronization this can cause reading disabilities. This has been tested by having children with and without reading disabilities perform on tasks related to the transient systems, where the children with reading disabilities did very poorly.
It has also been found in postmortem examinations of the brains of people with reading disabilities that they have fewer neurons and connections in the areas representing the transient visual systems.
However, there is debate over whether this is the only reason for reading disabilities, scotopic sensitivity syndrome, deficits in verbal memory and orthographic knowledge are other proposed factors.
Deficits in visual memory can also be caused by disease and/or trauma to the brain. These can lead to the patient losing their spatial memory, and/or their visual memory for specific things.
For example, a patient “L.E.” suffered brain damage and her ability to draw from memory was severely diminished, whilst her spatial memory remained normal. Other patients represent the opposite, where memory for colors and shapes is unaffected but spatial memory for previously known places is greatly impaired.
These case studies show that these two types of visual memory are located in different parts of the brain and are somewhat unrelated in terms of functioning in daily life.
*This article was originally published at en.wikipedia.org.