Hiroaki Shigemasu

Dr. Hiroaki Shigemasu

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Research Focus & Metrics

Academic Career Length

26Years (2001-Present)

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

Representative Publications

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1 June 2020 in Cerebral Cortex
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RORyu Ohata
Ryu Ohata
TATomohisa Asai
Tomohisa Asai
HKHiroshi Kadota
Hiroshi Kadota
HSHiroaki Shigemasu
Hiroaki Shigemasu
KOKenji Ogawa
Kenji Ogawa
HIHiroshi Imamizu
Hiroshi Imamizu
The sense of agency is defined as the subjective experience that “I” am the one who is causing the action. Theoretical studies postulate that this subjective experience is developed through multistep processes extending from the sensorimotor to the cognitive level. However, it remains unclear how the brain processes such different levels of information and constitutes the neural substrates for the sense of agency. To answer this question, we combined two strategies: an experimental paradigm, in which self-agency gradually evolves according to sensorimotor experience, and a multivoxel pattern analysis. The combined strategies revealed that the sensorimotor, posterior parietal, anterior insula, and higher visual cortices contained information on self-other attribution during movement. In addition, we investigated whether the found regions showed a preference for self-other attribution or for sensorimotor information. As a result, the right supramarginal gyrus, a portion of the inferior parietal lobe (IPL), was found to be the most sensitive to self-other attribution among the found regions, while the bilateral precentral gyri and left IPL dominantly reflected sensorimotor information. Our results demonstrate that multiple brain regions are involved in the development of the sense of agency and that these show specific preferences for different levels of information.

4 June 2016
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CSChaklam Silpasuwanchai
Chaklam Silpasuwanchai
XMXiaojuan Ma
Xiaojuan Ma
HSHiroaki Shigemasu
Hiroaki Shigemasu
XRXiangshi Ren
Xiangshi Ren

1 January 2012 in Frontiers in Psychology
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TTTakeshi Tamura
Takeshi Tamura
AGAtsuko Gunji
Atsuko Gunji
HTHiroshige Takeichi
Hiroshige Takeichi
HSHiroaki Shigemasu
Hiroaki Shigemasu
MIMasumi Inagaki
Masumi Inagaki
MKMichiteru Kitazaki
Michiteru Kitazaki
Understanding the neural mechanisms underlying speech production has a number of potential practical applications. Speech production involves multiple feedback loops. An audio-vocal monitoring system plays an important role in speech production, based on auditory feedback about the speaker’s own voice. Here we investigated the mu-rhythm activity associated with speech production by examining event-related desynchronization and synchronization in conditions of delayed auditory feedback (DAF) and noise feedback (Lombard). In Experiment 1, we confirmed that the mu-rhythms were detectable for a conventional finger-tapping task, and vocalization. In Experiment 2, we examined the mu-rhythms for imagined speech production. We tested whether the same motor-related mu-rhythm activity was exhibited while participants listened to their own voice, and while reading. The mu-rhythms were observed for overt vocalization and covert reading, while listening to simulated auditory feedback of the participants’ own voice reading text. In addition, we found that the mu-rhythm associated with listening was boosted and attenuated under the DAF and Lombard conditions, respectively. This is consistent with the notion that auditory feedback is important for the audio-vocal monitoring system in speech production. This paradigm may help clarify the way in which auditory feedback supports motor planning, as indexed by the motor-related mu-rhythm.

1 November 2006
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HSHiroaki Shigemasu
Hiroaki Shigemasu
TMToshiya Morita
Toshiya Morita
NMNaoyuki Matsuzaki
Naoyuki Matsuzaki
TSTakao Sato
Takao Sato
MHMasamitsu Harasawa
Masamitsu Harasawa
KAKiyoharu Aizawa
Kiyoharu Aizawa

15 May 2014 in Journal of Neurophysiology
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YYYoshiko Yabe
Yoshiko Yabe
Melvyn A. GoodaleMelvyn A. Goodale
Melvyn A. Goodale
HSHiroaki Shigemasu
Hiroaki Shigemasu
We do not always perceive the sequence of events as they actually unfold. For example, when two events occur before a rapid eye movement (saccade), the interval between them is often perceived as shorter than it really is and the order of those events can be sometimes reversed (Morrone MC, Ross J, Burr DC. Nat Neurosci 8: 950–954, 2005). In the present article we show that these misperceptions of the temporal order of events critically depend on whether the saccade is reflexive or voluntary. In the first experiment, participants judged the temporal order of two visual stimuli that were presented one after the other just before a reflexive or voluntary saccadic eye movement. In the reflexive saccade condition, participants moved their eyes to a target that suddenly appeared. In the voluntary saccade condition, participants moved their eyes to a target that was present already. Similarly to the above-cited study, we found that the temporal order of events was often misjudged just before a reflexive saccade to a suddenly appearing target. However, when people made a voluntary saccade to a target that was already present, there was a significant reduction in the probability of misjudging the temporal order of the same events. In the second experiment, the reduction was seen in a memory-delay task. It is likely that the nature of the motor command and its origin determine how time is perceived during the moments preceding the motor act.

19 January 2021 in Brain and Behavior
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JYJiajia Yang
Jiajia Yang
YYYinghua Yu
Yinghua Yu
HSHiroaki Shigemasu
Hiroaki Shigemasu
HKHiroshi Kadota
Hiroshi Kadota
KNKiyoshi Nakahara
Kiyoshi Nakahara
JWJinglong Wu
Jinglong Wu
Background: Vision and touch are thought to contribute information to object perception in an independent but complementary manner. The left lateral posterior parietal cortex (LPPC) has long been associated with multisensory information processing, and it plays an important role in visual and haptic crossmodal information retrieval. However, it remains unclear how LPPC subregions are involved in visuo‐haptic crossmodal retrieval processing.Methods: In the present study, we used an fMRI experiment with a crossmodal delayed match‐to‐sample paradigm to reveal the functional role of LPPC subregions related to unimodal and crossmodal dot‐surface retrieval.Results: The visual‐to‐haptic condition enhanced the activity of the left inferior parietal lobule relative to the haptic unimodal condition, whereas the inverse condition enhanced the activity of the left superior parietal lobule. By contrast, activation of the left intraparietal sulcus did not differ significantly between the crossmodal and unimodal conditions. Seed‐based resting connectivity analysis revealed that these three left LPPC subregions engaged distinct networks, confirming their different functions in crossmodal retrieval processing.Conclusion: Taken together, the findings suggest that functional heterogeneity of the left LPPC during visuo‐haptic crossmodal dot‐surface retrieval processing reflects that the left LPPC does not simply contribute to retrieval of past information; rather, each subregion has a specific functional role in resolving different task requirements.