Editing Visual memory (section)

== Dysfunction of visual memory ==
{{See also|Palinopsia|Hallucinatory palinopsia}}

Hallucinatory palinopsia, which is a dysfunction of visual memory, is caused by [[Visual pathway#Posterior visual pathway|posterior visual pathway]] cortical lesions and [[seizure]]s, 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."<ref name=Gersztenkorn /> Studying the excitability alterations associated with palinopsia in migraineurs could provide insight on mechanisms of encoding visual memory.<ref>{{cite journal|last1=Belcastro|first1=V|last2=Cupini|first2=LM|last3=Corbelli|first3=I|last4=Pieroni|first4=A|last5=D'Amore|first5=C|last6=Caproni|first6=S|last7=Gorgone|first7=G|last8=Ferlazzo|first8=E|last9=Di Palma|first9=F|last10=Sarchielli|first10=P|last11=Calabresi|first11=P|title=Palinopsia in patients with migraine: a case-control study|journal=Cephalalgia: An International Journal of Headache|date=Jul 2011|volume=31|issue=9|pages=999–1004|pmid=21628437|doi=10.1177/0333102411410083|s2cid=41022593}}</ref>

One common group of people that have visual memory problems are children with [[Reading disability|reading disabilities]]. It was often thought that disabilities are caused by failure to perceive the [[Letter (alphabet)|letters]] of a written word in the right order. However, studies show it is more likely that it is caused by a failure to [[Encoding (memory)|encode]] and process the correct order of letters within the word.<ref name="Catts">{{cite book |last1=Catts |first1=Hugh William |last2=Kamhi |first2=Alan G. |title=Language and Reading Disabilities |date=2005 |publisher=Pearson/Allyn and Bacon |isbn=978-0-205-44417-5 |pages=102–106 }}</ref> 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.<ref name="Catts" />  The sustained system is responsible for fine detail such as word and letter recognition and is very important in [[Encoding (memory)|encoding]] words in their correct order. The transient system is responsible for controlling [[Eye movement (sensory)|eye movements]], and processing the larger visual environment around us. When these two processes do not work in [[synchronization]] this can cause [[Reading disability|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 [[Autopsy|postmortem examinations]] of the [[brain]]s of people with reading disabilities that they have fewer [[neuron]]s and connections in the areas representing the transient visual systems.<ref name="Catts" />  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.<ref name="Catts" /> 
 
Deficits in visual memory can also be caused by [[disease]] and/or [[Traumatic brain injury|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.<ref name="Mem">{{cite journal | last1 = Wilson | first1 = B. A. | last2 = Baddeley | first2 = A. D. | last3 = Young | first3 = A. W. | date = 1999 | title = LE, A person who lost her 'mind's eye' | journal = Neurocase | volume = 5 | issue = 2| pages = 119–127 | doi=10.1093/neucas/5.2.119| doi-broken-date = 16 January 2025 }}</ref>  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.