The impact of transparency on hemispheric lateralization of idiom comprehension: An rTMS study

Hazel Zeynep Kurada, Elif Arıca-Akkök, Zerin Özaydın-Aksun, H. Özden Şener, Michal Lavidor

Research output: Contribution to journalArticlepeer-review


Previous neuropsychological data have equivocal suggestions concerning hemispheric involvement during idiom comprehension. The possible contribution of idioms transparency to the lateralization of figurative language comprehension has not been investigated using an interference technique. To analyse the cortical lateralization of idiom transparency processing, we employed inhibitory repetitive transcranial magnetic stimulation (rTMS) to the left and right dorsolateral prefrontal cortex (DLPFC) during the processing of opaque idioms, transparent idioms, and non-idiomatic literal phrases. Based on the Coarse Semantic Coding theory, we predicted a greater right hemisphere involvement when processing opaque than transparent idioms. Eighteen young healthy participants underwent rTMS pulses at 1 Hz frequency, 110% of motor threshold intensity for 15 min (900 pulses) in two sessions at one-week intervals. In a semantic decision task, participants judged the relatedness of an idiom and a target word. The target word was figuratively or literally related to the idiom, or unrelated. The study also included non-idiomatic sentences. We found that left DLPFC functions are more critical for comprehension of opaque rather than transparent idioms when referring to the figurative associations of the idioms. Opaque idioms, in the context of their figurative meaning, rely more heavily on left hemisphere resources. This finding suggests that opaque idioms are seemingly processed as one unit. Taken together, we believe that the transparency of idiomatic expressions may play an important role in modulating hemispheric functions involved in figurative language processing.

Original languageEnglish
Article number108062
StatePublished - 10 Dec 2021

Bibliographical note

Publisher Copyright:
© 2021 Elsevier Ltd


The authors thank Prof. Dr. Özgür Aydın for his enlightening guidance throughout the study, Kelly Swenson and Prof. Susan Curtiss for proofreading the manuscript, Prof. Bülent Cengiz, Adnan Gülaçtı, Semra Koçak, and the staff at the Ankara University Faculty of Medicine Neurology Department for their technical help, as well as all the participants for being a part of this study.

FundersFunder number
Ankara Universitesi


    • DLPFC
    • Idioms
    • Prefrontal cortex
    • Transparency
    • rTMS


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