| This dissertation addressed issues of callosal relay and hemispheric asymmetries in lexical activation and the real-time comprehension of nonliteral language (i.e., metaphors) in neurologically intact populations. Results showed that the cerebral hemispheres process individual lexical items fairly similarly. Left hemisphere and right hand advantages were found for lexical-semantic processing, with a faster transfer of linguistic information from the right hemisphere to the left hemisphere. At the isolated word level, psycholinguistic influences (i.e., concreteness, imageability, frequency of occurrence, length) did not appear to produce any real asymmetries in hemispheric processing, revealing bilateral sensitivities in accuracy and response latencies. Both hemispheres were capable of independently activating lexical items and were able to transfer linguistic information across the corpus callosum.; In the processing of sentential metaphors, however, the hemispheres were observed to work in concert. Both hemispheres were found to play critical roles, with the right hemisphere involved in exhaustively accessing literal and metaphoric interpretations for highly familiar metaphors, and maintaining metaphoric meanings later in the sentence. The left hemisphere, in contrast, showed early activation of metaphoric meanings---suggesting that the left hemisphere is form-driven and may store lexicalized representations for figurative concepts. At the offset of the metaphor, however, the left hemisphere demonstrated dampening of those meanings, only showing activation of literal interpretations---and only for less familiar metaphors. A slow rise in activation was observed for less familiar metaphor interpretations-requiring additional time to transfer semantic features. Additionally, the left hemisphere maintained exhaustive access of literal meanings for both highly familiar and less familiar metaphors.; Exploring interhemispheric transfer revealed that callosal relay served as a motor pathway for the left hemisphere (with similar transmission times across linguistic variables) but was influenced by linguistic complexity in the right hemisphere. Importantly, the hemispheres collaborated and shared information across the corpus callosum, so that similar linguistic information was never active in both hemispheres simultaneously. Such a mechanism aids in the efficiency of the processing system, preventing redundancy during language processing, presenting a complex, but highly integrated and complementary, picture of hemispheric processing and collaboration during the on-line comprehension of metaphoric language. |
