Production of time reference in Turkish Broca's aphasia: The effect of morphological complexity.

In PWA (people with aphasia) difficulties with sentences that refer to the past compared to non-past time reference have been shown for many languages, including Turkish. However, the impact of morphological complexity on past time reference ability in production has not yet been reported for Turkish-speaking PWA. Turkish, where verb forms have complex inflectional paradigms and exhibit overt and non-overt morphology, facilitates the examination of the effects of morphological complexity. The current study has two objectives: 1) to investigate whether the morphological complexity of the verb form affects time reference production of Turkish-speaking PWA and 2) to provide analysis for the error patterns discovered. Seventeen Turkish individuals with Broca's aphasia who were matched in age with a control group of 17 neurologically intact Turkish individuals were tested with a picture sentence completion task. Test conditions were present progressive, simple past, past perfect, past progressive, and future tense. The task required the participants to complete each sentence frame with a verb. Our findings show that Turkish-speaking PWA were more successful in producing verb forms referring to non-past than verb forms referring to the past time reference. The current study supports previous findings that past is more difficult than non-past time reference for Turkish-speaking PWA. In terms of morphological complexity, we find that PWA were more impaired when producing morphologically complex verb forms rather than morphologically simple forms. We argue that these impairments lie in the realization of overt morphology.

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

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.