Ryohei Nakayama

Ryohei Nakayama

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Research Focus & Metrics

Academic Career Length

23Years (2004-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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1 May 2016 in Journal of Cardiovascular Computed Tomography
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Journal Article
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MIMasaki Ishida
Masaki Ishida
KKKakuya Kitagawa
Kakuya Kitagawa
TITakashi Ichihara
Takashi Ichihara
TNTakahiro Natsume
Takahiro Natsume
RNRyohei Nakayama
Ryohei Nakayama
HSHajime Sakuma
Hajime Sakuma

5 January 2021 in Radiological Physics and Technology
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Journal Article
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YNYuya Nishitani
Yuya Nishitani
RNRyohei Nakayama
Ryohei Nakayama
DHDaisei Hayashi
Daisei Hayashi
AHAkiyoshi Hizukuri
Akiyoshi Hizukuri
KMKan Murata
Kan Murata

18 March 2019 in Journal of Neuroscience
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Journal Article
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RNRyohei Nakayama
Ryohei Nakayama
IMIsamu Motoyoshi
Isamu Motoyoshi
Recent psychophysical studies have demonstrated that periodic attention in the 4–8 Hz range facilitates performance on visual detection. The present study examined the periodicity of feature binding, another major function of attention, in human observers (3 females and 5 males for behavior, with 7 males added for the EEG experiment). In a psychophysical task, observers reported a synchronous pair of brightness (light/dark) and orientation (clockwise/counterclockwise) patterns from two combined brightness–orientation pairs presented in rapid succession. We found that temporal binding performance exhibits periodic oscillations at ∼8 Hz as a function of stimulus onset delay from a self-initiated button press in conditions where brightness–orientation pairs were spatially separated. However, as one would expect from previous studies on pre-attentive binding, significant oscillations were not apparent in conditions where brightness–orientation pairs were spatially superimposed. EEG results, while fully compatible with behavioral oscillations, also revealed a significant dependence of binding performance across trials on prestimulus neural oscillatory phases within the corresponding band. The peak frequency of this dependence was found to be correlated with intertrial phase coherence (ITPC) around the timing of button press in parietal sensors. Moreover, the peak frequency of the ITPC was found to predict behavioral frequency in individual observers. Together, these results suggest that attention operates periodically (at ∼8 Hz) on the perceptual binding of multimodal visual information and is mediated by neural oscillations phase-locked to voluntary action.SIGNIFICANCE STATEMENTRecent studies in neuroscience suggest that the brain's attention network operates rhythmically at 4–8 Hz. The present behavioral task revealed that attentional binding of visual features is performed periodically at ∼8 Hz, and EEG analysis showed a dependence of binding performance on prestimulus neural oscillatory phase. Furthermore, this association between perceptual and neural oscillations is triggered by voluntary action. Periodic processes driven by attention appear to contribute not only to sensory processing but also to the temporal binding of diverse information into a conscious event synchronized with action.

11 March 2004 in Medical Physics
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Journal Article
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RNRyohei Nakayama
Ryohei Nakayama
YUYoshikazu Uchiyama
Yoshikazu Uchiyama
RWRyoji Watanabe
Ryoji Watanabe
SKShigehiko Katsuragawa
Shigehiko Katsuragawa
KNKiyoshi Namba
Kiyoshi Namba
KDKunio Doi
Kunio Doi

21 December 2015 in Journal of Digital Imaging
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Journal Article
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EHEmi Honda
Emi Honda
RNRyohei Nakayama
Ryohei Nakayama
HKHitoshi Koyama
Hitoshi Koyama
AYAkiyoshi Yamashita
Akiyoshi Yamashita

11 August 2022 in Cancers
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FTFumine Tanaka
Fumine Tanaka
MUMaki Umino
Maki Umino
MMMasayuki Maeda
Masayuki Maeda
RNRyohei Nakayama
Ryohei Nakayama
KIKatsuhiro Inoue
Katsuhiro Inoue
HSHajime Sakuma
Hajime Sakuma
As functional magnetic resonance imaging, arterial spin labeling (ASL) techniques have been developed to provide quantitative tissue blood flow measurements, which can improve the performance of lesion diagnosis. ASL does not require contrast agents, thus, it can be applied to a variety of patients regardless of renal impairments and contrast agent allergic reactions. The clinical implementation of head and neck lesions is limited, although, in recent years, ASL has been increasingly utilized in brain lesions. Here, we review the development of the ASL techniques, including pseudocontinuous ASL (pCASL). We compare readout methods between three-dimensional (3D) turbo spin-echo and 2D echo planar pCASL for the clinical applications of pCASL to head and neck lesions. We demonstrate the clinical usefulness of 3D pCASL for diagnosing various entities, including inflammatory lesions, hypervascular lesions, and neoplasms; for evaluating squamous cell carcinoma (SCC) treatment responses, and for predicting SCC prognosis.