Metaphors, and other figurative language, occur frequently in language and can provide a succinct and vivid description of an object, person, or event. Failures in understanding figurative language can have a dramatic impact on language comprehension and production, and can lead to social isolation and decreased self-esteem. Even when brain injuries do not result in aphasia, figurative language processing can be impaired. Despite the importance of figurative language in human communication, most language research focuses on literal language, resulting in a limited understanding of the neural foundation that supports figurative language. Clinical, behavioral, and neuro imaging research support right hemisphere involvement in metaphor processing. However, there is debate over whether it is metaphors per se that engage the right hemisphere or if other factors that co-vary along the figurative-literal dimension elicit right hemisphere engagement. The Graded Salience Hypothesis proposes right hemisphere recruitment when processing language that is low in salience, and left hemisphere recruitment when processing language that is high in salience. Two factors that may influence salience and hemispheric recruitment are semantic relatedness and context. The first goal of this proposal is to use functional magnetic resonance imaging (fMRI) to investigate the influence of semantic relatedness on hemispheric recruitment by manipulating novelty in metaphors and literal sentences. Familiar phrases, by nature of their common occurrence can establish close semantic relationships in the lexicon. In contrast, novel phrases require dynamic integration of concepts. Semantic relatedness will be manipulated by examining familiar and novel metaphors, and sentences containing typical and innovative uses of objects. The second goal of this proposal is to use fMRI to investigate the influence of context on hemispheric recruitment during metaphor and literal language processing. Context can provide a framework which facilitates the processing of subsequent text. Salience will be manipulated by adding related and unrelated sentential context to metaphors and literal sentences.
Public health will benefit from the proposed research by improving our basic knowledge of the neural foundations of metaphor processing and language in general. This research will facilitate our ability to understand and treat children with specific language impairments and adults with acquired language impairments that result from brain damage.
|Diaz, Michele T; Barrett, Kyle T; Hogstrom, Larson J (2011) The influence of sentence novelty and figurativeness on brain activity. Neuropsychologia 49:320-30|
|Diaz, Michele T; Hogstrom, Larson J (2011) The influence of context on hemispheric recruitment during metaphor processing. J Cogn Neurosci 23:3586-97|