Hemispheric differences in figurative language processing: Contributions of neuroimaging methods and challenges in reconciling current empirical findings

The following review critically synthesizes the literature on hemispheric differences in idiom and metaphor comprehension. It has long been debated whether figurative language is inherently different from literal language and is processed specifically in the right hemisphere (RH), or rather, whether figurative and literal language form a continuum rather than a dichotomy, and call upon a similar network of brain areas. In this paper, a number of neuropsychological, behavioral and neuroimaging studies are reviewed in the context of major theoretical accounts of metaphor and idiom comprehension. Specifically, the role played by the RH in metaphor and idiom processing is evaluated, and advancements that neuroimaging methods have made to our understanding of figurative language comprehension are assessed. This review also highlights a number of critical methodological discrepancies between studies, and emphasizes how such inconsistencies in operational definitions, stimuli and tasks pose a serious challenge to reconciling the debate on hemispheric differences, and do not allow for a clear-cut conclusion of which neural networks underlie figurative language processing.

► Studies assessing neurocognitive mechanisms of figurative language processing are reviewed.
► Comprehension of idioms/metaphors is compared to comprehension of literal language.
►  Neural networks underlying figurative language processing are discussed.
► Empirical findings on neural basis of metaphor/idiom processing are contradictory.
► Methodological issues with important theoretical implications are highlighted.