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The Effect of Word Frequency on the Brain Correlates of Object Naming in Russian
The retrieval of low frequency words is usually slower than that of high frequency words. Neuroimaging research on the role of word frequency in linguistic tasks suggests candidate brain areas for the neural substrates of this effect. The only previous fMRI study of word frequency in Russian (Malutina et al., 2012) used an action naming task and obtained data that were highly inconsistent with results for other languages, findings which were mainly obtained using noun-retrieval tasks. In order to verify whether the reasons for such inconsistency were methodological or cross-linguistic, we examined the fMRI correlates of word frequency in Russian using a covert object naming task. We found that the retrieval of low frequency and high frequency nouns activated the same general pattern of brain areas typical for object naming tasks in many languages. Several brain regions were more activated in the low frequency but not the high frequency condition, including the areas and structures usually associated with linguistic processing (the inferior frontal gyrus bilaterally, the left thalamus, the left insula), visual perception (the fusiform gyrus, the inferior occipital gyrus, the middle occipital gyrus bilaterally) and cognitive and motor control (the supplementary motor area and the right cingulate gyrus). The right cingulate gyrus was the only area that responded only to the low frequency stimuli but not the high frequency items, when compared to the baseline. At the same time, we found no brain areas that responded more to high versus low word frequency. These results are generally consistent with previous fMRI studies in English, German and Chinese and therefore suggest that the inconsistency between the previous research in Russian and other languages was due to the possible interaction of the part of speech (verb or noun) and word frequency in brain mechanisms for word retrieval, rather than cross-linguistic differences.