Concepts, control, and context: A connectionist account of normal and disordered semantic cognition

Paul Hoffman, James L. McClelland, Matthew A. Lambon Ralph
2018 Psychological review  
Semantic cognition requires conceptual representations shaped by verbal and nonverbal experience and executive control processes that regulate activation of knowledge to meet current situational demands. A complete model must also account for the representation of concrete and abstract words, of taxonomic and associative relationships, and for the role of context in shaping meaning. We present the first major attempt to assimilate all of these elements within a unified, implemented
more » ... framework. Our model combines a hub-and-spoke architecture with a buffer that allows its state to be influenced by prior context. This hybrid structure integrates the view, from cognitive neuroscience, that concepts are grounded in sensory-motor representation with the view, from computational linguistics, that knowledge is shaped by patterns of lexical co-occurrence. The model successfully codes knowledge for abstract and concrete words, associative and taxonomic relationships, and the multiple meanings of homonyms, within a single representational space. Knowledge of abstract words is acquired through (a) their patterns of co-occurrence with other words and (b) acquired embodiment, whereby they become indirectly associated with the perceptual features of co-occurring concrete words. The model accounts for executive influences on semantics by including a controlled retrieval mechanism that provides top-down input to amplify weak semantic relationships. The representational and control elements of the model can be damaged independently, and the consequences of such damage closely replicate effects seen in neuropsychological patients with loss of semantic representation versus control processes. Thus, the model provides a wide-ranging and neurally plausible account of normal and impaired semantic cognition. Our interactions with the world are suffused with meaning. Each of us has acquired a vast collection of semantic knowledgeincluding the meanings of words and the properties of objectswhich is constantly called upon as we interpret sensory inputs and plan speech and action. In addition to storing such conceptual information in a readily accessible form, we must call upon different aspects of knowledge to guide behavior under different circumstances. The knowledge that books are heavy, for example, is irrelevant to most of our interactions with them but becomes important when one is arranging a delivery to a library. These
doi:10.1037/rev0000094 pmid:29733663 pmcid:PMC5937916 fatcat:nbgfx4s5gvfvdkckcdyssdfn6m