Publications by authors named "Kyohei Tanaka"

4 Publications

  • Page 1 of 1

Task-Induced Functional Connectivity of the Syntax-Related Networks for Patients with a Cortical Glioma.

Cereb Cortex Commun 2020 1;1(1):tgaa061. Epub 2020 Sep 1.

Department of Basic Science, Graduate School of Arts and Sciences, The University of Tokyo, Tokyo 153-8902, Japan.

Analysis of the functional connectivity has enabled understanding of the cortical networks. In the present study, we used a picture-sentence matching task to introduce syntactically harder conditions, and clarified 3 major points. First, patients with a glioma in the lateral premotor cortex/inferior frontal gyrus or in other cortical regions showed much weaker activations than controls, especially in the left inferior frontal gyrus. Moreover, the error rates under the harder conditions were much higher for these patients. Secondly, syntactic loads induced selective connectivity with enhancement and suppression, consistently for both patients and controls. More specifically, the local connectivity was enhanced among the 3 syntax-related networks within the left frontal cortex, while the global connectivity of both dorsal and ventral pathways was suppressed. In addition, the exact reproducibility of -values across the control and patient groups was remarkable, since under easier conditions alone, connectivity patterns for the patients were completely unmatched with those for the controls. Thirdly, we found an additional syntax-related network, further confirming the intergroup similarity of task-induced functional connectivity. These results indicate that functional connectivity of agrammatic patients is mostly preserved regardless of a glioma, and that the connectivity can change dynamically and systematically according to syntactic loads.
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http://dx.doi.org/10.1093/texcom/tgaa061DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8152871PMC
September 2020

Differential Effects of a Left Frontal Glioma on the Cortical Thickness and Complexity of Both Hemispheres.

Cereb Cortex Commun 2020 27;1(1):tgaa027. Epub 2020 Jun 27.

Department of Basic Science, Graduate School of Arts and Sciences, The University of Tokyo, Tokyo, 153-8902, Japan.

Glioma is a type of brain tumor that infiltrates and compresses the brain as it grows. Focal gliomas affect functional connectivity both in the local region of the lesion and the global network of the brain. Any anatomical changes associated with a glioma should thus be clarified. We examined the cortical structures of 15 patients with a glioma in the left lateral frontal cortex and compared them with those of 15 healthy controls by surface-based morphometry. Two regional parameters were measured with 3D-MRI: the cortical thickness (CT) and cortical fractal dimension (FD). The FD serves as an index of the topological complexity of a local cortical surface. Our comparative analyses of these parameters revealed that the left frontal gliomas had global effects on the cortical structures of both hemispheres. The structural changes in the hemisphere were mainly characterized by a decrease in CT and mild concomitant decrease in FD, whereas those in the peripheral regions of the glioma ( hemisphere) were mainly characterized by a decrease in FD with relative preservation of CT. These differences were found irrespective of tumor volume, location, or grade. These results elucidate the structural effects of gliomas, which extend to the distant contralateral regions.
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http://dx.doi.org/10.1093/texcom/tgaa027DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8152868PMC
June 2020

Merge-Generability as the Key Concept of Human Language: Evidence From Neuroscience.

Front Psychol 2019 29;10:2673. Epub 2019 Nov 29.

Department of Basic Science, Graduate School of Arts and Sciences, The University of Tokyo, Tokyo, Japan.

Ever since the inception of generative linguistics, various dependency patterns have been widely discussed in the literature, particularly as they pertain to the hierarchy based on "weak generation" - the so-called Chomsky Hierarchy. However, humans can make any possible dependency patterns by using artificial means on a sequence of symbols (e.g., computer programing). The differences between sentences in human language and general symbol sequences have been routinely observed, but the question as to such differences exist has barely been raised. Here, we address this problem and propose a theoretical explanation in terms of a new concept of "Merge-generability," that is, whether the structural basis for a given dependency is provided by the fundamental operation Merge. In our functional magnetic resonance imaging (fMRI) study, we tested the judgments of noun phrase (NP)-predicate (Pred) pairings in sentences of Japanese, an SOV language that allows , unbounded nesting configurations. We further introduced two pseudo-adverbs, which force dependencies that do conform to structures generated by Merge, i.e., non-Merge-generable; these adverbs enable us to manipulate Merge-generability ( or ). By employing this novel paradigm, we obtained the following results. Firstly, the behavioral data clearly showed that an NP-Pred matching task became more demanding under the Artificial conditions than under the Natural conditions, reflecting cognitive loads that could be covaried with the increased number of words. Secondly, localized activation in the left frontal cortex, as well as in the left middle temporal gyrus and angular gyrus, was observed for the [Natural - Artificial] contrast, indicating specialization of these left regions in syntactic processing. Any activation due to task difficulty was completely excluded from activations in these regions, because the Natural conditions were always easier than the Artificial ones. And finally, the [Artificial - Natural] contrast resulted in the dorsal portion of the left frontal cortex, together with wide-spread regions required for general cognitive demands. These results indicate that Merge-generable sentences are processed in these specific regions in contrast to non-Merge-generable sentences, demonstrating that Merge is indeed a fundamental operation, which comes into play especially under the Natural conditions.
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http://dx.doi.org/10.3389/fpsyg.2019.02673DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6895067PMC
November 2019

Activation changes of the left inferior frontal gyrus for the factors of construction and scrambling in a sentence.

Proc Jpn Acad Ser B Phys Biol Sci 2017 ;93(7):511-522

Department of Basic Science, Graduate School of Arts and Sciences, The University of Tokyo.

Our previous functional magnetic resonance imaging (fMRI) studies have indicated that the left dorsal inferior frontal gyrus (L. dF3op/F3t) and left lateral premotor cortex (L. LPMC) are crucial regions for syntactic processing among the syntax-related networks. In the present study, we further examined how activations in these regions were modified by the factors of construction and scrambling (object-initial type). Using various sentence types, we clarified three major points. First, we found that the main effects of construction and scrambling consistently activated the L. dF3op/F3t and L. LPMC. Secondly, the main effects of scrambling clearly localized activation in the L. dF3op/F3t and L. LPMC, indicating the more narrowed down processing of syntax. Thirdly, step-wise percent signal changes were observed in the L. dF3op/F3t, demonstrating synergistic effects of construction and scrambling. These results demonstrate the abstract and intensive nature of syntactic processing carried out by these regions, i.e., the grammar center.
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http://dx.doi.org/10.2183/pjab.93.031DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5713179PMC
March 2018
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