Visual Memory - Deficits of Visual Memory

Deficits of Visual Memory

Deficits in visual memory are different and not necessarily associated with deficits in visual perception. One common group of people that have this problem 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. 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.