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Semantic memory

Dr. Simon Moss

Overview

Semantic memory comprises all our knowledge and understanding about the meaning of words, objects, people, concepts, and events (for reviews, see Caramazza & Mahon, 2006& Patterson, Nestor, & Rogers, 2007& Rogers, Lambon Ralph, Garrard, Bozeat, McClelland, Hodges, 2004). In particular, semantic memory, together with episodic memory, constitutes declarative memory-that is, memories that we can declare or describe explicitly. However, in contrast to episodic memory, semantic memory represents knowledge of objects or events that transcend particular places, times, or contexts. Episodic memory, however, represents memories of specific events and experiences (Tulving, 1972).

Models of semantic memory

Network models

Collins and Quillian (1969) proposed that semantic knowledge is underpinned by a set of nodes, each representing a specific feature or concept, which are all connected to one another. Nodes that related in some way, such as often coincident in time, are more strongly connected.

For example, in the model developed by Collins and Quillian (1969), each node represents a specific word, such as "bird". Each node is stored together with a set of properties, such as "has wings" or "can fly. Furthermore, in this model, connections link categories to exemplars, representing a hierarchical arrangement. For example, "bird" is connected to "chicken". Features, such as "can fly" are stored only at the category level, such as "bird", in which they represent key properties.

To retrieve this knowledge, some cue or stimulus activates one set of nodes, which then activate other related nodes, called spreading activation. To illustrate, in response to the question "Is a chicken a bird", the time to answer this question depends on the number of connections that intervene between the node that represents chicken and the node that represents "bird".

Collins and Loftus (1975) then refined this model. They weighted the connections to explain the typicality effect-the finding that typical instantiations of a category are recognized more rapidly. Nevertheless, this model cannot explain a finding, observed by Glass, Holyoak, and Kiger (1979), that individuals can readily respond to questions that are patently false, like "Is a chicken a meteor". In this instance, the nodes are far apart, but the responses are rapid.

Later, more sophisticated network models were developed (for an example, see Cravo & Martins, 1993). These models are similar to the propositions proposed by Collins and Loftus (1975). However, each node might represent some other element, like a concept or feature, rather than merely a word. Furthermore, the links or connections can represent a variety of relationships, not just hierarchy.

Feature models

According to feature models, such as the propositions developed by Smith, Shoben, and Rips (1974), semantic memory is assumed to comprise lists of features for each concept. Hence, according to the perspective, the connections between concepts do not represent the relationships between concepts. Instead, to uncover these relationships, individuals must compare the sets of features between two concepts (see also Meyer, 1970& Rips, 1975).

Associative models

Raaijmakers and Schiffrin (1981) proposed one of the seminal examples of an associative model to characterize episodic and semantic memory, called the Search of Associative Memory model. According to this model, when two items occupy working memory concurrently, the strength of their association increases. Over time, items, such as stimuli or features, that often coincide are connected by strong links.

Ongoing controversies

Unitary versus multifaceted systems

Some scholars assume the semantic knowledge is represented as a single system (see Caramazza, Hillis, Rapp, & Romani, 1990& Lambon Ralph, Patterson, & Hodges, 1997). In contrast, other researchers argue that semantic knowledge might be represented in multiple systems. Each system, for example, might correspond to one modality. Alternatively, each system might correspond to one category of concepts (see Farah, Hammond, Mehta, & Ratcliff, 1989& Humphreys & Forde, 2001& McCarthy & Warrington, 1988).

The proposition that semantic memory might constitute multiple systems emerged from case studies, in which individuals demonstrated selective impairments in specific modalities or categories (Warrington & Shallice, 1984& see also Lambon Ralph, Patterson, & Hodges, 1997). That is, as a consequence of lesions, often following stroke or herpes simplex encephalitis, some participants demonstrated impairments in only one modality. They might, for example, not be able to describe an object that is presented visually. Nevertheless, they might be able to describe this object if the stimulus was defined verbally. Alternatively, participants demonstrated impairments in a subset of categories. They could, for example, describe living organisms but not inanimate objects or vice versa (Lambon Ralph, Lowe, & Rogers, 2007).

Nevertheless, some scholars can reconcile these findings, and other observations, to the perspective that semantic memory corresponds to one system (Caramazza, Hillis, Rapp, & Romani, 1990& Caramazza & Mahon, 2006). According to proponents of this perspective, semantic knowledge is represented as a single, central system, whereas perceptual knowledge is represented in stores that are specific to one modality (e.g., Riddoch, Humphreys, Coltheart, & Funnell, 1988).

Indeed, some research findings challenge the proposition that semantic memory might constitute multiple systems. In patients with Alzheimer's Disease, for example, semantic deficits in one modality tend to coincide with similar semantic deficits in other modalities (Hodges, Patterson, Graham, & Dawson, 1996).

Relationship between perceptual and semantic representations of objects

Some scholars assume that perceptual and semantic representations of objects correspond to separate systems (e.g., Biederman, 1987& Riddoch, Humphreys, Coltheart, & Funnel, 1988). According to these conceptualizations, one system represents only the perceptual features of objects, such as their shape, color, weight, and intensity. This system is used to identify the object-that is, to ascertain which features of a stimulus match one of the objects in this store.

When the stimulus is recognized, a separate representation of this object in semantic memory is activated. This representation comprises all the semantic features of this object, such as its utility, consequences, problems, and so forth,

Other scholars, however, argue the perceptual and semantic representations of objects are represented in the same system (e.g., Rogers, Hodges, Lambon Ralph, & Patterson, 2003). According to this conceptualization, the physical representations of objects in different modalities-such as the appearance, sound, smell, or size of these stimuli-and the interactions and associations across these features integrate to generate semantic knowledge. In other words, semantic knowledge is derived from the relationships between perceptual features.

Relationship between semantic and episodic memory

Tulving (1972, 1985) argued that semantic memory is merely a specialized form-a subset-of procedural memory, which stores skills and sequences of actions. Furthermore, according to Tulving (1972, 1985), episodic memory represents a subset, or specialized form, of semantic memory. Consistent with this proposition, several studies, such as research conducted by Dalla Barba and Goldblum (1996) and Goldblum, Gomez, Dalla Barba, Boller, Deweer, Hahn et al. (1998) for example, imply that episodic memory depends on the integrity of semantic memory.

Nevertheless, some studies have uncovered some findings that contradict this perspective. Dudas, Clague, Thompson, Graham, and Hodges (2005), for example, conducted a study with older participants who showed mild cognitive impairment, which is often regarded as a potential precursor of Alzheimer's Disease. These participants completed a task that involved recognizing an object, representing episodic memory, and naming this object, representing semantic memory. Performance on these two facets of the task were uncorrelated with one another, challenging the perspective that deficits in semantic memory should degrade episodic memory. Furthermore, patients with semantic dementia do show deficits in semantic, but not episodic, memory-at least during the early stages of this disease (Graham, Simons, Pratt, Patterson, & Hodges, 2000& Hodges & Patterson, 2007).

In the olfactory modality, however, semantic memory seems to be related to episodic memory. For example, the semantic encoding of odors facilitates subsequent recognition of these smells (Jehl, Royet, & Holley, 1997& Lehrner, Gluck, & Laska, 1999).

Neuroanatomical underpinnings of semantic memory

Some studies, often conducted with patients who exhibit various forms of dementia, indicate that semantic memory is underpinned by circuits primarily located in the right, rather than left hemisphere. Giffard, Laisney, Mezenge, de la Sayette, Eustache, and Desgranges (2008), for example, conducted an FDG-PET study. They discovered that hypometabolism in the superior temporal lobe, especially in the right hemisphere, related to performance on a semantic priming task.

In contrast, some studies imply that semantic memory is primarily underpinned by circuits primarily located in the left hemisphere. Zahn, Juengling, Bubrowski, Jost and Dykierek et al. (2004), for example, also conducted an FDG-PET study. They showed that hypometabolism in the left anterior temporal, posterior inferior temporal, inferior parietal and medial occipital lobes were related to performance-in both verbal and nonverbal semantic tasks.

In addition to hemisphere, whether semantic memory is primarily represented in posterior or anterior regions is unclear. Some studies show that hypometabolism in posterior association regions, including the temporoparietal and temporo-occipital areas, is associated with deficits on semantic tasks (Meguro, LeMestric, Landeau, Desgranges, Eustache, & Baron, 2001& Mosconi, Pupi, De Cristofaro, Fayyaz, Sorbi, & Herholz, 2004). Research on patients with semantic dementia, for example, indicate that both anterior temporal lobes, including the perirhinal cortex, are involved in semantic processing (Chan Fox, Scahill, Crum, Whitwell, Leschziner, 2001& Davies, Graham, Xuereb, Williams, & Hodges, 2004& Patterson, Nestor, & Rogers 2007),

According to Patterson, Nestor and Rogers (2007), the anterior temporal lobes might function as a nucleus in the distributed semantic network. That is, semantic knowledge might be distributed across cortical association areas-some of which assimilate information from multiple modalities. The anterior temporal lobes, as corroborated by their connections with all other sensory systems, might integrate this information.

References

Biederman, I. (1987). Recognition-by-Components: A theory of human image understanding. Psychological Review, 94, 115-147.

Burianova, H., & Grady, C. L. (2007). Common and unique neural activations in autobiographical, episodic, and semantic retrieval. Journal of Cognitive Neuroscience, 19, 1520-1534.

Caramazza, A., Hillis, A. E., Rapp, B. C., & Romani, C. (1990). The multiple semantics hypothesis: Multiple confusions? Cognitive Neuropsychology, 7, 161-189.

Caramazza, A., & Mahon, B. Z. (2006). The organisation of conceptual knowledge in the brain: The future's past and some future directions. Cognitive Neuropsychology, 23, 13-38.

Chan, D., Fox, N. C., Scahill, R. I., Crum, W. R., Whitwell, J. L., Leschziner, G., et al. (2001). Patterns of temporal lobe atrophy in semantic dementia and Alzheimer's disease. Annals of Neurology, 49, 433-442.

Collins, A. M., & Loftus, E. F. (1975). A spreading activation of semantic processing. Psychological Review, 82, 407-428.

Collins, A. M., & Quillian. (1969). Retrieval time from semantic memory. Journal of Verbal Learning and Verbal Behavior, 8, 240-247.

Collins, A. M. & Quillian, M. R. (1972). How to make a language user. In E. Tulving & W. Donaldson (Eds.), Organization of memory (pp. 309-351). New York: Academic Press.

Cravo, M. R. & Martins, J. P. (1993). SNePSwD: A newcomer to the SNePS family. Journal of Experimental & Theoretical Artificial Intelligence, 5, 135-148.

Dalla Barba, G., & Goldblum, M. C. (1996). The influence of semantic encoding on recognition memory in Alzheimer's disease. Neuropsychologia, 34, 1181-1186.

Davies, R. R., Graham, K. S., Xuereb, J. H., Williams, G. B., & Hodges, J. R. (2004). The human perirhinal cortex and semantic memory. European Journal of Neuroscience, 20, 2441-2446.

Dudas, R. B., Clague, F., Thompson, S. A., Graham, K. S., & Hodges, J. R. (2005). Episodic and semantic memory in mild cognitive impairment. Neuropsychologia, 43, 1266-1276.

Farah, M. J., Hammond, K. M., Mehta, Z., & Ratcliff, G. (1989). Category-specificity and modality-specificity in semantic memory. Neuropsychologia, 27, 193-200.

Giffard, B., Laisney, M., Mezenge, F., de la Sayette, V., Eustache, F., & Desgranges, B. (2008). The neural substrates of semantic memory deficits in early Alzheimer's disease: Clues from semantic priming effects and FDG-PET. Neuropsychologia, 46,1657-1666.

Glass, A. L., Holyoak, K. J. & Kiger, J. I. (1979). Role of antonymy relations in semantic judgments. Journal of Experimental Psychology: Human Learning & Memory, 5, 598-606.

Graham, K. S., Simons, J. S., Pratt, K. H., Patterson, K., & Hodges, J. R. (2000). Insights from semantic dementia on the relationship between episodic and semantic memory. Neuropsychologia, 38, 313-324.

Goldblum, M. C., Gomez, C. M., Dalla Barba, G., Boller, F., Deweer, B., Hahn, V., et al. (1998). The influence of semantic and perceptual encoding on recognition memory in Alzheimer's disease. Neuropsychologia, 36, 717-729.

Hodges, J. R., & Patterson, K. (2007). Semantic dementia: a unique clinicopathological syndrome. Lancet Neurology, 6, 1004-1014.

Hodges, J. R., Patterson, K., Graham, N., & Dawson, K. (1996). Naming and knowing in dementia of Alzheimer's Type. Brain and Language, 54, 302-325.

Humphreys, G. W., & Forde, E. M. (2001). Hierarchies, similarity, and interactivity in object recognition: "category-specific" neuropsychological deficits. Behavioral and Brain Sciences, 24, 453-476& discussion 476-509.

Jehl, C., Royet, J. P., & Holley, A. (1997). Role of verbal encoding in short- and long-term odor recognition. Perception & Psychophysics, 59, 100-110.

Lambon Ralph, M., Lowe, C. & Rogers, T.T. (2007). Neural basis of category-specific semantic deficits for living things: Evidence from semantic dementia, HSVE and a neural network model. Brain: Journal of Neurology, 130(Pt 4):1127-37.

Lambon Ralph, M. A., Patterson, K., & Hodges, J. R. (1997). The relationship between naming and semantic knowledge for different categories in dementia of Alzheimer's type. Neuropsychologia, 35, 1251-1260.

Lehrner, J. P., Gluck, J., & Laska, M. (1999). Odor identification, consistency of label use, olfactory threshold and their relationships to odor memory over the human lifespan. Chemical Senses, 24, 337-346.

McCarthy, R. (1995). Semantic knowledge and semantic representations. Erlbaum: Psychology Press.

McCarthy, R. A., & Warrington, E. K. (1988). Evidence for modality-specific meaning systems in the brain. Nature, 334(6181), 428-430.

Meguro, K., LeMestric, C., Landeau, B., Desgranges, B., Eustache, F., & Baron, J. C. (2001). Relations between hypometabolism in the posterior association neocortex and hippocampal atrophy in Alzheimer's disease: A PET/MRI correlative study. Journal of Neurology, Neurosurgery and Psychiatry, 71, 315-324.

Meyer, D. E. (1970). On the representation and retrieval of stored semantic information. Cognitive Psychology, 1, 242-299

Mosconi, L., Pupi, A., De Cristofaro, M. T., Fayyaz, M., Sorbi, S., & Herholz, K. (2004). Functional interactions of the entorhinal cortex: An 18F-FDG PET study on normal aging and Alzheimer's disease. Journal of Nuclear Medicine, 45, 382-392.

Patterson, K., Nestor, P. J., & Rogers, T. T. (2007). Where do you know what you know? The representation of semantic knowledge in the human brain. Nature Reviews Neuroscience, 8, 976-987.

Patterson, K., Nestor, P. Rogers, S. L., & Friedman, R. B. (2008). The underlying mechanisms of semantic memory loss in Alzheimer's disease and semantic dementia. Neuropsychologia, 46(1), 12-21.

Raaijmakers, J. G. W. & Schiffrin, R. M. (1981). Search of associative memory. Psychological Review, 8, 98-134.

Rajah, M.N. & McIntosh, A.R. (2005). Overlap in the functional neural systems involved in semantic and episodic memory retrieval. Journal of Cognitive Neuroscience, 17, 470-482.

Riddoch, M. J., Humphreys, G. W., Coltheart, M., & Funnel, E. (1988). Semantic systems or system? Neuropsychological evidence re-examined. Cognitive Neuropsychology, 5, 3-25.

Rips, L. J., Shoben, E. J. & Smith, F. E. (1973). Semantic distance and the verification of semantic relations. Journal of Verbal Learning and Verbal Behavior, 14, 665-681.

Rogers, S. L., & Friedman, R. B. (2008). The underlying mechanisms of semantic memory loss in Alzheimer's disease and semantic dementia. Neuropsychologia, 46, 12-21.

Rogers, T. T., Hodges, J. R., Lambon Ralph, M. A., & Patterson, K. (2003). Object recognition under semantic impairment: The effects of conceptual regularities on perceptual decisions. Language and Cognitive Processes, 18, 625-662.

Rogers, T. T., Ivanoiu, A., Patterson, K., & Hodges, J. R. (2006). Semantic memory in Alzheimer's disease and the frontotemporal dementias: a longitudinal study of 236 patients. Neuropsychology, 20, 319-335.

Rogers, T. T., Lambon Ralph, M. A., Garrard, P., Bozeat, S., McClelland, J. L., Hodges, J. R., et al. (2004). Structure and deterioration of semantic memory: a neuropsychological and computational investigation. Psychological Review, 111, 205-235.

Smith, E. E., Shoben, E. J. & Rips, L. J. (1974). Structure and process in semantic memory: A featural model for semantic decisions. Psychological Review, 1, 214-241.

Thompson-Schill, S.L., 2003. Neuroimaging studies of semantic memory: Inferring "how" from "where". Neuropsychologia, 41, 280-122.

Tulving, E. (1972). Episodic and Semantic Memory. In E. Tulving & W. Donaldson (Eds.), Academic Press. New-York.

Tulving, E. (1985). How many memory systems are there? . American Psychologist, 44, 385-398.

Warrington, E. K. & Shallice, T. (1984). Category specific semantic impairments. Brain, 107, 829-853.

Wilson, D. A., & Stevenson, R. J. (2003). The fundamental role of memory in olfactory perception. Trends in Neuroscience, 26, 243-247.

Zahn, R., Juengling, F., Bubrowski, P., Jost, E., Dykierek, P., Talazko, J., et al. (2004). Hemispheric asymmetries of hypometabolism associated with semantic memory impairment in Alzheimer's disease: a study using positron emission tomography with fluorodeoxyglucose-F18. Psychiatry Research, 132, 159-172.








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Last Update: 6/19/2016