Visual memory

In humans, areas specialized for visual object recognition in the ventral stream have a more inferior location in the temporal cortex, whereas areas specialized for the visual-spatial location of objects in the dorsal stream have a more superior location in the parietal cortex. However, these two streams hypothesis, although useful, are a simplification of the visual system because the two streams maintain intercommunication along their entire rostral course. Posterior parietal cortex (light green) is shown at the posterior area of the parietal lobe The posterior parietal cortex is a portion of the parietal lobe, which manipulates mental images, and integrates sensory and motor portions of the brain. A majority of experiments highlights a role of human posterior parietal cortex in visual working memory and attention. We therefore have to establish a clear separation of visual memory and attention from processes related to the planning of goal-directed motor behaviors. We can only hold in mind a minute fraction of the visual scene. These mental representations are stored in visual short-term memory. Activity in the posterior parietal cortex is tightly correlated with the limited amount of scene information that can be stored in visual short-term memory. Ventral stream pathway The ventral stream pathway is mainly involved in object recognition, and is known colloquially as the 'what' pathway. It has connections to the medial temporal lobe (which is involved in the storage of long-term memories), the limbic system (which regulates emotions), and the dorsal stream pathway (which is involved in the visual-spatial locations and motions of objects). Therefore, the ventral stream pathway not only deals with the recognition of objects in the external world, but also the emotional judgement and analysis of these objects. The ventral stream pathway begins with purely visual information in the primary visual cortex (occipital lobe), and then this information is transferred to the temporal lobe. Occipital lobes Located at the back of the brain, the occipital lobes receive and process visual information. The occipital lobes also process colors and shapes. Whereas the right occipital lobe interprets images from the left visual space, the left occipital lobe interprets images from the right visual space. Damage to the occipital lobes can permanently damage visual perception Occipital lobe injury complications Damage to the occipital lobe is characterized by loss of visual capability and the inability to identify colors both important processes in visual memory. Short term visual memory Visual short-term memory (visual working memory) is the capacity for holding a small amount of visual information in mind in an active, readily available state for a short period of time (usually no more than 30 seconds). Although visual short term memory is essential for the execution of a wide array of perceptual and cognitive functions, and is supported by an extensive network of brain regions, its storage capacity is severely limited. == Methods of study ==

Benton visual retention test is presented at the top, after a delay participants are asked to recall the correct target stimulus from the list of design cards. The Benton Visual Retention Test is an assessment of visual perception, and visual memory abilities. More than 50 years of proven clinical use is the staple of the Benton Visual Retention Test. After the time has passed participants are asked to immediately reproduce the designs from each card using their visual memory. Subjects are blindfolded and instructed to lay motionless while simultaneously eliminating any visual imagery present in their mind's eye. As the subject encodes the visual patterns researchers are able to directly view the activation of areas involved in visual memory encoding. During recall subjects again need to have all visual stimuli removed by means of a dark room or blindfolding to avoid interfering activation of other visual areas in the brain. Subjects are asked to recall each image clearly in their mind's eye. While recalling the images researchers are able view the areas activated by the visual memory task. Comparing the control 'baseline' state to the activated areas during the visual memory task allows researchers to view which areas are used during visual memory. == Current theories ==

Visuo-spatial sketch pad The visuo-spatial 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 colour, 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 visuo-spatial 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 and photographic memories 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, for example, 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 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 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, both types of memory are often 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 a 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. == Accuracy ==

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 ==

"We do not store and retrieve words based on visual memory." "Our phonological filing system is the basis for word memory/word recognition." -Dr. Kilpatrick (Equipped for Reading Success). 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 ==

Sleep 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 amount of associations between configurations and target locations that can be learned within a day. 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. With such impairment it is assumed that it must be due to the incorrect interpretation of previously encountered information as being novel. In a study conducted to measure whether visual memory in older adults with 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, vision was found to be correlated with general memory function in older adults and is not modality specific. Performance in regards to spatial configurations deteriorates with aging. 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. 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 correlated of the low level of response to alcohol using functional magnetic resonance imaging during a challenging visual memory task. The results were that young people who report 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." 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 the sustained and transient visual processing systems. 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. == References ==