An fMRI investigation of the neural correlates underlying the processing of novel metaphoric expressions.

Theneural networks associated with processing related pairs of words formingliteral, novel, and conventional metaphorical expressions and unrelated pairsof words were studied in a group of 15 normal adults using fMRI. Subjects read the four types of linguisticexpressions and decided which relation exists between the two words(metaphoric, literal, or unrelated). According to the Graded SalienceHypothesis (GSH, Giora, 1997, 2002, 2003), which predicts a selective RHinvolvement in the processing of novel, nonsalient meanings, it is primarilythe degree of meaning salience of a linguistic expression rather thanliterality or nonliterality, which modulates the degree of left hemisphere (LH)and right hemisphere (RH) processing of metaphors. In the present study, novel metaphoricalexpressions represented the nonsalient interpretations, whereas conventionalmetaphors and literal expressions represented the salient interpretations. Adirect comparison of the novel metaphors vs. the conventional metaphorsrevealed signiWcantly stronger activity in right posterior superior temporalgyrus, right inferior frontal gyrus, and left middle frontal gyrus. Theseresults support the GSH and suggest a special role for the RH in processingnovel metaphors. Furthermore, the right PSTS may be selectively involved inverbal creativity.