Semantic Memory and Language Processing: A Primer

Abstract

Semantic memory refers to our long-term knowledge of word and object meaning. There is increasing evidence that rather than being a passive warehouse of knowledge, semantic memory is a dynamic system whose effectiveness relies on the coordination of multiple components distributed across a large network of cortical regions. Damage to one or more of these components produces distinct profiles of impairment in aphasia and dementia. Furthermore, such differences are associated with different responses to behavioral treatment. That is, effective treatment for semantically based language disorders in aphasia may have very limited success in dementia. We argue that treatment specificity demands a comprehensive understanding of the structure of semantic memory and the nature of its compromise. Here, we review several neuroanatomically informed theories of semantic organization with respect to the effects of semantic impairment on language processing in aphasia and neurodegenerative disease.

Verbal Description of Concrete Objects: A Method for Assessing Semantic Circumlocution in Persons With Aphasia

“…Instances in which the stimulus name was stated during the description were deleted. Consistent with previous work (e.g., Antonucci & Reilly, 2008;De Renzi & Lucchelli, 1994;Hodges et al, 1992Hodges et al, , 1996Lambon Ralph et al, 1999), scoring of accuracy (correct vs. incorrect) was based on the judgment of whether an uninformed listener would be able to name the described item. Evidence of word-finding difficulty (e.g., semantic/ phonemic paraphasic errors) was present in verbal descriptions, but participants were not penalized for word-retrieval difficulty when the description was adequate or intelligible within the context of the description as a whole.…”

“…For example, for the concept dog, semantic features include visual-perceptual (has fur, has wet nose), motor/ action (walks, wags), and functional (guides the blind) information, along with knowledge of superordinate category membership (animal, mammal, canine), encyclopedic information (Lassie was a famous one, cats are afraid of them), and personal associations/opinions (Dogs are my favorite animal.). Accessing such information is an important component of the process of retrieving lexical knowledge for naming, and learning the particular patterns of feature co-occurrence among different concepts allows us to categorize similar concepts using shared features (e.g., dogs, cats, mice: all breathe, eat, grow → are animals), distinguish similar concepts using distinctive features (dogs wag their tails, mice do not wag), and recognize concepts that are semantically unrelated (e.g., pencils are utensils used for writing and erasing, which are not activities frequently engaged in by dogs; e.g., Drew & Thompson, 1999; see also Antonucci & Reilly, 2008).…”

Cortical & Subcortical Dementias: A Psychoneurolinguistic Perspective

“…Results show that aphasic patients may benefit more from semantic treatment than those with dementia (Antonucci & Reilly, 2008;Holland, 2008;Reilly, 2008). In fact, such results cut all doubts that language disorders belong to aphasia per se.…”

Sprachstörungen bei Morbus Parkinson – aphasisch oder dysexekutiv?

“…Semantischen Paraphasien liegen also nicht unbedingt St ö rungen im semantischen Ged ä chtnis selbst zugrunde, sie k ö nnen ebenso durch L ä sionen der Basalganglien oder des Frontallappens verursacht werden. Frontale Regionen sind unter anderem f ü r die Kontrolle des semantischen Abrufs zust ä ndig, f ü r die Selektion und Inhibition konkurrierender lexikalischer Alternativen und f ü r die Aufrechterhaltung selektiver Aufmerksamkeit w ä hrend strategischer Abrufprozesse [47] .…”