1,508 research outputs found
Increased Entorhinal–Prefrontal Theta Synchronization Parallels Decreased Entorhinal–Hippocampal Theta Synchronization during Learning and Consolidation of Associative Memory
Memories are thought to be encoded as a distributed representation in the neocortex. The medial prefrontal cortex (mPFC) has been shown to support the expression of memories that initially depend on the hippocampus (HPC), yet the mechanisms by which the HPC and mPFC access the distributed representations in the neocortex are unknown. By measuring phase synchronization of local field potential (LFP) oscillations, we found that learning initiated changes in neuronal communication of the HPC and mPFC with the lateral entorhinal cortex (LEC), an area that is connected with many other neocortical regions. LFPs were recorded simultaneously from the three brain regions while rats formed an association between an auditory stimulus (CS) and eyelid stimulation (US) in a trace eyeblink conditioning paradigm, as well as during retention 1 month following learning. Over the course of learning, theta oscillations in the LEC and mPFC became strongly synchronized following presentation of the CS on trials in which rats exhibited a conditioned response (CR), and this strengthened synchronization was also observed during remote retention. In contrast, CS-evoked theta synchronization between the LEC and HPC decreased with learning. Our results suggest that communication between the LEC and mPFC are strengthened with learning whereas the communication between the LEC and HPC are concomitantly weakened, suggesting that enhanced LEC–mPFC communication may be a neuronal correlate for theoretically proposed neocortical reorganization accompanying encoding and consolidation of a memory
ラミン遺伝子変異キャリアにおける遺伝子型を用いた心疾患リスクの層別化
京都大学新制・論文博士博士(医学)乙第13568号論医博第2294号京都大学大学院医学研究科医学専攻(主査)教授 森田 智視, 教授 石見 拓, 教授 佐藤 俊哉学位規則第4条第2項該当Doctor of Medical ScienceKyoto UniversityDFA
ASCA Observations of the Twin Supernova Remnants in the Large Magellanic Cloud, DEM L316
We report results from an ASCA X-ray study of DEM L316, an emission nebula in
the Large Magellanic Cloud (LMC) consisting of two closely-spaced supernova
remnants (SNRs). The SIS image shows separate X-ray sources located at the
positions of the two radio- and optically-emitting SNR shells, 054769.7A and
054769.7B (hereafter, shell A and B). The individual X-ray spectrum of each
shell is well described by optically-thin thermal emission, although the
characteristics of the emission differ in important details between them. Shell
A exhibits strong iron L emission, which we attribute to the presence of
iron-rich ejecta leading to the suggestion that this SNR originates from a Type
Ia SN, an explosion of a moderate mass progenitor. Shell B, on the other hand,
has a chemical composition similar to that of the interstellar medium of the
LMC and so its X-ray emission is dominated by swept-up matter. The different
spectral features strongly disfavor the hypothesis that the two shells are due
to one supernova explosion into an interconnected bubble. We could not obtain
the evidence which positively supports the collision between two SNRs.Comment: 5 pages, 1 table, 7 figures Also available at
http://www-cr.scphys.kyoto-u.ac.jp/MC
Review of Discrete X-Ray Sources in the Small Magellanic Cloud: Summary of the ASCA Results and Implication on the Recent Star Forming Activity
We made 22 observations on the Small Magellanic Cloud (SMC) and covered full
regions by the end of the ASCA mission. We detected 106 discrete sources with a
criterion of S/N > 5 and performed systematic analyses on all of the sources.
We determined the source positions with an ~40'' error radius (90% confidence)
for sources detected in the central 20' radius of the GIS. We detected coherent
pulsations from 17 sources. Among them, eight were newly discovered during this
study. We classified most of these pulsars as X-ray binary pulsars (XBPs) based
on their properties, such as the flux variability and the existence of an
optical counterpart. We detected X-ray emission from eight supernova remnants
(SNRs). Among them, five SNRs showed emission lines in their spectra, hence we
regarded the five as thermal SNRs. We found that XBPs and thermal SNRs in the
SMC can be clearly separated by their spectral hardness ratio. Applying this
empirical law to faint (thus unclassified) sources, we found 19 XBP candidates
and four thermal SNR candidates. We also found several tens of candidates for
active galactic nuclei, both from the hardness ratio and the logN--logS
relation of extragalactic sources. Based on these ASCA results and further
information from other sattelites, we compiled comprehensive catalogues of
discrete X-ray sources in the Small Magellanic Cloud. Using the catalogues, we
derived the spatial distributions of XBPs and SNRs. XBPs and SNRs were found to
be concentrated in the main body and eastern wing, which resembles the
distribution of young stars with ages of ~2e7yr. By comparing the source
populations in the SMC and our Galaxy, we suggest that the star-forming rate
(per unit mass) in the SMC was much higher than the Galaxy 1e7yr ago. We also
discuss the recent change of the star-forming rate in the SMC.Comment: 61 pages, 19 figures, to be published in PASJ. Also available at
http://www-cr.scphys.kyoto-u.ac.jp/member/jun/job/ (with high-resolution
images
A Fundamental Study on Evaluation of Public Transport Transfer Nodes by Data Envelop Analysis Approach Using Smart Card Data
AbstractThis research proposes a method of evaluating transfer nodes based on smart card data with the objective of making a contribution to public transportation restructuring in regional cities. The study seeks to better comprehend the use of public transportation systems (trams and buses) in central Kochi City in Japan based on the transportation mode transfers recorded on user Smart Cards. Specifically, this study seeks to use the Data Envelop Analysis (DEA) model, which allows us to reference multiple indices, in order to evaluate the efficiency of user transfers between transportation systems while also considering transfer times and user age groups. The study results show that efficiency varied according to the time of day and user age groups, even at the same transfer nodes, and identified the need for more thorough understanding of the properties of each transfer point based on the efficiency values of multiple indices
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