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Biomedical subjects

Ryuichiro Hashimoto

Publications and source records attributed to Ryuichiro Hashimoto.

3 recordsLinked to original sources

Sentence processing is uniquely human.

In this article, we will focus on three fundamental issues concerning language processing in the human brain, and update recent advances made by functional neuroimaging and magnetic stimulation studies of language. First, we will provide the first experimental evidence that the neural basis of sentence comprehension is indeed specialized. Specifically, our recent functional magnetic resonance imaging (fMRI) study has clarified that the human left prefrontal cortex (PFC) is more specialized in the syntactic processes of sentence comprehension than other domain-general processes such as short-term memory. Second, the distinction between explicit and implicit syntactic processes will be clarified, based on our fMRI studies that elucidate syntactic specialization in the left PFC. Third, we will advance a hypothesis stating that distinct subregions of the left PFC are recruited for the syntactic integration of lexico-semantic information. The current direction of research in the neuroscience of language is beginning to reveal the uniqueness of the human mind.

Animals↗

Specialization in the left prefrontal cortex for sentence comprehension.

Using functional magnetic resonance imaging (fMRI), we examined cortical activation under syntactic decision tasks and a short-term memory task for sentences, focusing on essential properties of syntactic processing. By comparing activation in these tasks with a short-term memory task for word lists, we found that two regions in the left prefrontal cortex showed selective activation for syntactic processing: the dorsal prefrontal cortex (DPFC) and the inferior frontal gyrus (IFG). Moreover, the left DPFC showed more prominent activation under the short-term memory task for sentences than that for word lists, which cannot be explained by general cognitive factors such as task difficulty and verbal short-term memory. These results support the proposal of specialized systems for sentence comprehension in the left prefrontal cortex.

Adolescent↗

From perception to sentence comprehension: the convergence of auditory and visual information of language in the left inferior frontal cortex.

We used functional magnetic resonance imaging (fMRI) to characterize cortical activation associated with sentence processing, thereby elucidating where in the brain auditory and visual inputs of words converge during sentence comprehension. Within one scanning session, subjects performed three types of tasks with different linguistic components from perception to sentence comprehension: nonword (N(AV); auditory and visual), phrase (P; either auditory or visual), and sentence (S; either auditory or visual) tasks. In a comparison of the P and N(AV) tasks, the angular and supramarginal gyri showed bilateral activation, whereas the inferior and middle frontal gyri showed left-lateralized activation. A comparison of the S and P tasks, together with a conjunction analysis, revealed a ventral region of the left inferior frontal gyrus (F3t/F3O), which was sentence-processing selective and modality-independent. These results unequivocally demonstrated that the left F3t/F3O is involved in the selection and integration of semantic information that are separable from lexico-semantic processing.

Adult↗