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Assistant Professor

Laboratory location

Abeno Campus

Research Areas 【 display / non-display

Neurophysiology / General neuroscience

Association Memberships 【 display / non-display

  • Society for Neurocience


Current Career 【 display / non-display

  • Osaka City University   Graduate School of Medicine   Basic Medicine Course   Assistant Professor  

Career 【 display / non-display

  • 2016.08

    Osaka City University   Graduate School of Medicine   Research Assistant Professor

  • 2011.04

    University of Wisconsin - Milwaukee   Department of Psychology   Postdoctoral Fellow

Graduate School 【 display / non-display

  • 2007.04

    Kyoto University  Graduate school of Science  Department of Biophysics, PhD course 

  • 2005.04

    Kyoto University  Graduate school of Science  Department of Biophysics, MS course 

Graduating School 【 display / non-display

  • 2000.04

    Kyoto University   Faculty of Science  


Published Papers 【 display / non-display

  • 恐怖記憶の基盤となる全脳ダイナミクスの解明

    宮脇 寛行

    (公財)上原記念生命科学財団 上原記念生命科学財団研究報告集  33   1 - 4 2019.12  [Refereed]

  • Hippocampal Reactivation Extends for Several Hours Following Novel Experience

    Giri Bapun, Miyawaki Hiroyuki, Mizuseki Kenji, Cheng Sen, Diba Kamran

    JOURNAL OF NEUROSCIENCE  39 ( 5 ) 866 - 875 2019.01  [Refereed]

     View Summary

    New memories are believed to be consolidated over several hours of post-task sleep. The reactivation or “replay” of hippocampal cell assemblies has been proposed to provide a key mechanism for this process. However, previous studies have indicated that such replay is restricted to the first 10–30 min of post-task sleep, suggesting that it has a limited role in memory consolidation. We performed long-duration recordings in sleeping and behaving male rats and applied methods for evaluating the reactivation of neurons in pairs as well as in larger ensembles while controlling for the continued activation of ensembles already present during pre-task sleep (“preplay”). We found that cell assemblies reactivate for up to 10 h, with a half-maximum timescale of ∼6 h, in sleep following novel experience, even when corrected for preplay. We further confirmed similarly prolonged reactivation in post-task sleep of rats in other datasets that used behavior in novel environments. In contrast, we saw limited reactivation in sleep following behavior in familiar environments. Overall, our findings reconcile the duration of replay with the timescale attributed to cellular memory consolidation and provide strong support for an integral role of replay in memory.

    DOI PubMed

  • Neuronal firing rates diverge during REM and homogenize during non-REM

    Miyawaki Hiroyuki, Watson Brendon O., Diba Kamran

    SCIENTIFIC REPORTS  9 ( 1 ) 689 2019.01  [Refereed]

     View Summary

    Neurons fire at highly variable intrinsic rates and recent evidence suggests that low- and high-firing rate neurons display different plasticity and dynamics. Furthermore, recent publications imply possibly differing rate-dependent effects in hippocampus versus neocortex, but those analyses were carried out separately and with potentially important differences. To more effectively synthesize these questions, we analyzed the firing rate dynamics of populations of neurons in both hippocampal CA1 and frontal cortex under one framework that avoids the pitfalls of previous analyses and accounts for regression to the mean (RTM). We observed several consistent effects across these regions. While rapid eye movement (REM) sleep was marked by decreased hippocampal firing and increased neocortical firing, in both regions firing rate distributions widened during REM due to differential changes in high- versus low-firing rate cells in parallel with increased interneuron activity. In contrast, upon non-REM (NREM) sleep, firing rate distributions narrowed while interneuron firing decreased. Interestingly, hippocampal interneuron activity closely followed the patterns observed in neocortical principal cells rather than the hippocampal principal cells, suggestive of long-range interactions. Following these undulations in variance, the net effect of sleep was a decrease in firing rates. These decreases were greater in lower-firing hippocampal neurons but also higher-firing frontal cortical neurons, suggestive of greater plasticity in these cell groups. Our results across two different regions, and with statistical corrections, indicate that the hippocampus and neocortex show a mixture of differences and similarities as they cycle between sleep states with a unifying characteristic of homogenization of firing during NREM and diversification during REM.

    DOI PubMed

  • Hippocampal Information Processing and Homeostatic Regulation During REM and Non-REM Sleep

    Mizuseki K, Miyawaki H

    Handbook of Behavioral Neuroscience  30   49 - 62 2019  [Refereed]

     View Summary

    The synchronous activity of populations of neurons in patterns known as sharp-wave ripples (SPW-Rs), which contain fragments of time-compressed neuronal sequences that are replayed from those experienced during waking hours, is thought to mediate the transfer of newly acquired hippocampal information to distributed circuits in support of memory consolidation. Consistent with this hypothesis, it has been shown that the perturbation of neuronal activity during SPW-Rs can lead to memory impairment. Waking theta states and rapid eye movement (REM) sleep involve different kinds of temporal coordination in the hippocampal-entorhinal circuit, reflecting the distinct balance of hippocampal and entorhinal input to the CA1 area. The firing rates of individual neurons follow lognormal-like distributions in all brain states. Fast-firing minority and slow-firing majority neurons, which support system stability and mnemonic functions, are under distinct firing-rate regulation that is initiated by spindles and SPW-Rs during non-REM sleep and implemented during REM sleep.

  • Low Activity Microstates During Sleep

    Miyawaki Hiroyuki, Billeh Yazan N., Diba Kamran

    SLEEP  40 ( 6 )  2017.06  [Refereed]

     View Summary

    To better understand the distinct activity patterns of the brain during sleep, we observed and investigated periods of diminished oscillatory and population spiking activity lasting for seconds during non-rapid eye movement (non-REM) sleep, which we call "LOW" activity sleep.

    We analyzed spiking and local field potential (LFP) activity of hippocampal CA1 region alongside neocortical electroencephalogram (EEG) and electromyogram (EMG) in 19 sessions from four male Long-Evans rats (260-360 g) during natural wake/sleep across the 24-hr cycle as well as data from other brain regions obtained from http://crcns.org.1,2.

    LOW states lasted longer than OFF/DOWN states and were distinguished by a subset of "LOW-active" cells. LOW activity sleep was preceded and followed by increased sharp-wave ripple activity. We also observed decreased slow-wave activity and sleep spindles in the hippocampal LFP and neocortical EEG upon LOW onset, with a partial rebound immediately after LOW. LOW states demonstrated activity patterns consistent with sleep but frequently transitioned into microarousals and showed EMG and LFP differences from small-amplitude irregular activity during quiet waking. Their likelihood decreased within individual non-REM epochs yet increased over the course of sleep. By analyzing data from the entorhinal cortex of rats,1 as well as the hippocampus, the medial prefrontal cortex, the postsubiculum, and the anterior thalamus of mice,2 obtained from http://crcns.org, we confirmed that LOW states corresponded to markedly diminished activity simultaneously in all of these regions.

    We propose that LOW states are an important microstate within non-REM sleep that provide respite from high-activity sleep and may serve a restorative function.

    DOI PubMed

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Review Papers (Misc) 【 display / non-display

  • Steered differentiation and prospective selection of cerebellar Purkinje cells in the ES cell culture system

    Keiko Muguruma, Ayaka Nishiyama, Yuichi Ono, Hiroyuki Miyawaki, Eri Mizuhara, Yuchio Yanagawa, Tomoo Hirano, Yoshiki Sasai

    ELSEVIER IRELAND LTD NEUROSCIENCE RESEARCH  68   E243 - E243 2010  [Refereed]  [Invited]


  • Correlations between function and morphology of single synapses on hippocampal pyramidal neurons and cerebellar Purkinje neurons are different

    Hiroyuki Miyawaki, Tomoo Hirano

    ELSEVIER IRELAND LTD NEUROSCIENCE RESEARCH  65   S51 - S52 2009  [Refereed]  [Invited]


  • Characterization of EPSCs at individual synapses on a cerebellar Purkinje cell

    Hiroyuki Miyawaki, Tomoo Hirano

    ELSEVIER IRELAND LTD NEUROSCIENCE RESEARCH  61   S215 - S215 2008  [Refereed]  [Invited]

Conference Activities & Talks 【 display / non-display

  • Homeostatic regulation of hippocampal firing during extended waking and sleep.

    Hiroyuki Miyawaki  [Invited]

    International Workshop on Cutting Edge Tools in Neuroscience  (Ribeirão Preto, Brazil)  2015.07  CETneuro

     View Summary

    Sleep positively impacts various types of memories, including those that are hippocampal dependent. However, it is still not clear how hippocampal activity changes during sleep. To investigate this, we performed in vivo large-scale electrophysiological recordings on hippocampal CA1 region of rats in natural awake/sleep cycles. We recorded neuronal activity continuously up to 72 hours in 12-hour light and 12-hour dark cycles.
    In rodents, sleep consists of two distinct states. One is REM (rapid eye movement) that is characterized by an increase in power in the theta band (5-10 Hz). The other is non-REM that is characterized by transient oscillatory events - sleep spindles and sharp wave ripples (SWRs) and continuous slow (0.5 - 4Hz) oscillation. We found that non-REM firing rates decreased during long-lasting sleep, in contrast to extended wake states where firing rates increased gradually in the hippocampus. In addition, incidences of sleep spindles and SWRs and slow-wave amplitudes decreased across sleep. These changes were not correlated with circadian cycles. These results demonstrate that hippocampal activities depend on sleep/awake history.
    In the triplets of non-REM1/REM/non-REM2, mean firing rates in non-REM2 were significantly lower than in non-REM1. Firing rates in non-REM1 tightly coupled with changes in firing rates between non-REM1 and non-REM2. In addition, incidence of sleep spindles and SWRs were also strongly correlated with firing rates and the firing rates changes. As previously reported by Grosmark et al. (2012), we observed significant correlation between firing rate changes between non-REM epochs and power in theta during interleaved REM. However, this correlation was weaker than incidence of spindles, SWRs, or firing rates in non-REM. In addition, we found firing rates in non-REM were predictive of theta power in the following REM. These results indicate more “excitable” states induce larger decrease of firing in the hippocampus.
    We also investigated correlation between hippocampal firing and slow wave oscillation. In the neocortex, it is argued that slow-wave oscillations have a role to decrease neuronal firing through downscaling synaptic connectivity (Tononi & Cirelli, 2014). However, we did not find significant correlations between slow-wave oscillations in the hippocampus and firing rates or changes in firing rates, which may indicate the hippocampus operate under a different set of rules from the neocortex.
    We found that hippocampal activity gradually decreased across sleep, and enhanced excitability in the hippocampus induced large decrease of hippocampal firing, which may contribute to maintain homeostasis in the hippocampus.

Grant-in-Aid for Scientific Research 【 display / non-display

  • Analyses of off-line learning algorithm during sleep by using super large-scale electrophysiology

    Grant-in-Aid for Scientific Research on Innovative Areas ”AI & Brain” Publicly Offered Research Group Representative

    Project Year :