The role of the right hemisphere in processing nonsalient metaphorical meanings: Application of Principal Components Analysis to

Some researches indicatethat the right hemisphere (RH) has a unique role in comprehending thefigurative meaning of metaphors whereas the results of other studies do notsupport the notion of a selective role for the RH in accessing metaphoricalmeanings. The present research used fMRI technology to test a theoreticalexplanation of the above conflicting findings. This theoretical account is derivedfrom the Graded Salience Hypothesis (GSH) [Giora, R. (1997). Understandingfigurative and literal language: The Graded Salience Hypothesis. CognitiveLinguistics, 7, 183–206; Giora, R. (2003). On our mind: Salience, context andfigurative language. New York: Oxford University Press],according to which the degree of meaning salience, rather than literality ornonliterality primarily affects differences between the LH and RH in linguisticprocessing. Thus, the GSH predicts a selective RH involvement in comprehensionof novel, nonsalient metaphoric meanings and LH involvement in thecomprehension of conventional, salient metaphoric meanings. Fifteen normaladults participated in a block designed fMRI experiment that compared thepatterns of brain activation induced by processing the meanings of literal,conventional metaphoric, novel metaphoric and unrelated word pairs. Thesubjects performed a semantic judgment task. We applied the PrincipalComponents Analysis (PCA) technique in order to find different functionalnetworks corresponding to the different stimuli. Our results, obtained from PCAof the fMRI data indicate that the right homologue of Wernicke’s area has aspecial role in processing novel metaphors. We suggest that a unique network,consisting of the right homologue ofWernicke’s area, right and left premotorareas, right and left insula and Broca’s area, is recruited for the processingof novel metaphors but not for the processing of conventional metaphors.