Editing Semantic memory (section)

== Disorders==
=== Category-specific semantic impairments ===
Category-specific semantic impairments are a neuropsychological occurrence in which an individual ability to identify certain categories of objects is selectively impaired while other categories remain undamaged.<ref name=":0">{{Cite journal|last=Capitani, Laiacona, Mahon, Caramazza|date=May 2003|title=What are the Facts of Semantic Category-Specific Deficits? Article Review of the Clinical Evidence|journal=Cognitive Neuropsychology|volume=20|issue=3|pages=213–261|doi=10.1080/02643290244000266|pmid=20957571|s2cid=6464286}}</ref> This condition can result in brain damage that is widespread, patchy, or localized. Research suggests that the temporal lobe, more specifically the structural description system, might be responsible for category specific impairments of semantic memory disorders.<ref name=":0" />

Theories on category-specific semantic deficits tend to fall into two different groups based on their underlying principles. Theories based on the correlated structure principle, which states that conceptual knowledge organization in the brain is a reflection of how often an object's properties occur, assume that the brain reflects the statistical relation of object properties and how they relate to each other. Theories based on the neural structure principle, which states that the conceptual knowledge organization in the brain is controlled by representational limits imposed by the brain itself, assume that organization is internal. These theories assume that natural selective pressures have caused neural circuits specific to certain domains to be formed, and that these are dedicated to problem-solving and survival. Animals, plants, and tools are all examples of specific circuits that would be formed based on this theory.<ref name=":0" />

==== Impairment categories ====
Category-specific semantic deficits tend to fall into two different categories, each of which can be spared or emphasized depending on the individual's specific deficit. The first category consists of animate objects, with animals being the most common deficit. The second category consists of inanimate objects with two subcategories: fruits and vegetables (biological inanimate objects), and artifacts being the most common deficits. The type of deficit does not indicate a lack of conceptual knowledge associated with that category, as the visual system used to identify and describe the structure of objects functions independently of an individual's conceptual knowledge base.<ref name=":0" />

Most of the time, these two categories are consistent with case-study data. However, there are a few exceptions to the rule. Categories like food, body parts, and musical instruments have been shown to defy the animate/inanimate or biological/non-biological categorical division. In some cases, it has been shown that musical instruments tend to be impaired in patients with damage to the living things category despite the fact that musical instruments fall in the non-biological/inanimate category. However, there are also cases of biological impairment where musical instrument performance is at a normal level. Similarly, food has been shown to be impaired in those with biological category impairments. The category of food specifically can present some irregularities though because it can be natural, but it can also be highly processed, such as in a case study of an individual who had impairments for vegetables and animals, while their category for food remained intact.<ref name=":0" />

=== The role of modality ===
Modality refers to a semantic category of meaning that has to do with necessity and probability expressed through language. In linguistics, certain expressions are said to have modal meanings. A few examples of this include [[Conditional simple|conditionals]], [[Auxiliary verb|auxiliary verbs]], adverbs, and nouns. When looking at category-specific semantic deficits, there is another kind of modality that looks at word relationships which is much more relevant to these disorders and impairments.<ref>{{Cite journal|last=Fintel|first=Kai|date=2006|title=Modality and Language|journal=MIT Department of Linguistics and Philosophy|pages=1–12}}</ref>

For category-specific impairments, there are modality-specific theories that are based on a few general predictions. These theories state that damage to the visual modality will result in a deficit of biological objects, while damage to the functional modality will result in a deficit of non-biological objects (artifacts). Modality-based theories assume that if there is damage to modality-specific knowledge, then all the categories that fall under it will be damaged. In this case, damage to the visual modality would result in a deficit for all biological objects with no deficits restricted to the more specific categories. For example, there would be no category specific semantic deficits for just "animals" or just "fruits and vegetables".<ref name=":0" />

==== Category-specific semantic deficit causes ====

===== 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" />

===== Herpes simplex virus encephalitis  =====
[[Herpes simplex]] virus encephalitis (HSVE) is a neurological disorder which causes inflammation of the brain. Early symptoms include headache, fever, and drowsiness, but over time symptoms including diminished ability to speak, memory loss, and aphasia develop. HSVE can also cause category-specific semantic deficits to occur.<ref>{{Cite web|url=https://rarediseases.org/rare-diseases/encephalitis-herpes-simplex/|title=Encephalitis, Herpes Simplex|date=2009|website=National Organization for Rare Disorders}}</ref> When this happens, patients typically have temporal lobe damage that affects the medial and lateral cortex as well as the frontal lobe. Studies have also shown that patients with HSVE have a much higher incidence of category-specific semantic deficits than those with semantic dementia, though both cause a disruption of flow through the temporal lobe.<ref name=":2" />

==== Brain lesions ====
A [[Brain damage|brain lesion]] refers to any abnormal tissue in or on the brain, most often caused by a trauma or infection. In one case study, a patient underwent surgery to remove an aneurysm, and the surgeon had to clip the anterior communicating artery which resulted in basal forebrain and fornix lesions. Before surgery, this patient was completely independent and had no semantic memory issues. However, after the operation and the lesions developed, the patient reported difficulty with naming and identifying objects, recognition tasks, and comprehension. The patient had a much more significant amount of trouble with objects in the living category which could be seen in the drawings of animals which the patient was asked to do and in the data from the matching and identification tasks. Every lesion is different, but in this case study researchers suggested that the semantic deficits presented themselves as a result of disconnection of the temporal lobe. The findings led to the conclusion that any type of lesion in the temporal lobe, depending on severity and location, has the potential to cause semantic deficits.<ref>{{Cite journal|last=Solca, Di Pietro, Schnider, Leemann|date=December 2013|title=Impairment of Semantic Memory After Basal Forebrain and Fornix Lesion|journal=Neurocase|volume=21|issue=2|pages=198–205|doi=10.1080/13554794.2014.883270|pmid=24498851|s2cid=45152263}}</ref>

==== Semantic differences in gender ====
The following table summarizes conclusions from the ''[[Journal of Clinical and Experimental Neuropsychology]]''.<ref name=":4">{{Cite journal|last=Moreno-Martinez, Quaranta, Gianotti|date=April 2019|title=What a Pooled Data Study Tells Us About the Relationship Between Gender and Knowledge of Semantic Categories|journal=[[Journal of Clinical and Experimental Neuropsychology]]|volume=41 |issue=6|pages=634–643|doi=10.1080/13803395.2019.1602111|pmid=30995891|s2cid=121325008}}</ref>
{| class="wikitable"
|+Semantic Tasks and Familiarity Ratings: Experimental Results
!Males
!Females
|-
|Better with tool names
|Better with fruit names
|-
|Name more animals and artifacts
|Name more fruits and vegetables
|-
|Greater familiarity with vehicles 
|Greater familiarity with flowers and elderly
|}
These results give a baseline for the differences in semantic knowledge across gender for healthy subjects. Experimental data observes that males with category-specific semantic deficits are mainly impaired with fruits and vegetables while women with category specific semantic deficits are mainly impaired with animals and artifacts. It has been concluded that there are significant gender differences when it comes to category-specific semantic deficits, and that the patient will tend to be impaired in categories that had less existing knowledge to begin with.<ref name=":4" />

===Modality-specific impairments===
Semantic memory is also discussed in reference to [[Stimulus modality|modality]]. Different components represent information from different sensorimotor channels. Modality specific impairments are divided into separate subsystems on the basis of input modality. Examples of different input modalities include visual, auditory, and tactile input. Modality-specific impairments are also divided into subsystems based on the type of information. Visual vs. verbal and perceptual vs. functional information are examples of information types.<ref>Valentine, T., Brennen, T. & Bredart, S. (1996). ''The Cognitive psychology of proper names: On the importance of being ernest''. London: Routledge.</ref>

===Semantic memory disorders===
Semantic memory disorders fall into two groups. Semantic refractory access disorders are contrasted with semantic storage disorders according to four factors: temporal factors, response consistency, frequency, and semantic relatedness. A key feature of semantic refractory access disorders is temporal distortions, where decreases in response time to certain stimuli are noted when compared to natural response times. In access disorders there are inconsistencies in comprehending and responding to stimuli that have been presented many times. Temporal factors impact response consistency. In storage disorders, an inconsistent response to specific items is not observed. Stimulus frequency determines performance at all stages of cognition. Extreme word frequency effects are common in semantic storage disorders while in semantic refractory access disorders word frequency effects are minimal. The comparison of close and distant groups tests semantic relatedness. Close groupings have words that are related because they are drawn from the same category, such as a list of clothing types. Distant groupings contain words with broad categorical differences, such as unrelated words. Comparing close and distant groups shows that in access disorders semantic relatedness had a negative effect, which is not observed in semantic storage disorders. Category-specific and modality-specific impairments are important components in access and storage disorders of semantic memory.<ref>{{Cite book |last=McCarthy |first=Rosaleen A. |url=https://books.google.com/books?id=9EeC2-sEeVQC&q=category+impairment |title=Semantic Knowledge and Semantic Representations |date=1995 |publisher=Psychology Press |isbn=978-0-86377-936-7 |language=en}}</ref>