Editing Semantic memory (section)

===== Semantic dementia =====
[[Semantic dementia]] is a semantic memory disorder that causes patients to lose the ability to match words or images to their meanings.<ref name=":1">{{Cite web|last=Delacourt|first=Andre|date=October 2009|title=Semantic Dementia|url=https://www.alzheimer-europe.org/Dementia/Other-forms-of-dementia/Neurodegenerative-diseases/Fronto-Temporal-Degeneration/Semantic-Dementia-SD|website=Alzheimer Europe}}</ref> It is fairly rare for patients with semantic dementia to develop category specific impairments, though there have been documented cases of it occurring. Typically, a more generalized semantic impairment results from dimmed semantic representations in the brain.<ref name=":2">{{Cite journal|last=Ralph, Rogers, Lowe|date=2007|title=Neural basis of category-specific semantic deficits for living things: evidence from semantic dementia, HSVE and a neural network model|journal=Brain|volume=130|issue=4|pages=1127–1137|doi=10.1093/brain/awm025|pmid=17438021|doi-access=free|url=https://pure.manchester.ac.uk/ws/files/22806563/POST-PEER-REVIEW-PUBLISHERS.PDF}}</ref>

Alzheimer's disease is a subcategory of semantic dementia which can cause similar symptoms. The main difference between the two is that Alzheimer's is categorized by atrophy to both sides of the brain, while semantic dementia is categorized by loss of brain tissue in the front portion of the left temporal lobe.<ref name=":1" /> With Alzheimer's disease in particular, interactions with semantic memory produce different patterns in deficits between patients and categories over time which is caused by distorted representations in the brain.<ref name=":3">{{Cite journal|last=Devlin, Gonnerman, Andersen, Seidneberg|date=1998|title=Category Specific Semantic Deficits in Focal and Widespread Brain Damage: A Computational Account|journal=Journal of Cognitive Neuroscience|volume=10|issue=1|pages=77–94|doi=10.1162/089892998563798|pmid=9526084|s2cid=8838693}}</ref> For example, in the initial onset of Alzheimer's disease, patients have mild difficulty with the artifacts category. As the disease progresses, the category specific semantic deficits progress as well, and patients see a more concrete deficit with natural categories. In other words, the deficit tends to be worse with living things as opposed to non-living things.<ref name=":3" />