Kagoshima University · Graduate School of Science and Engineering · 准教授

Research keywordsauditory cortex・spectrotemporal integration・guinea pig neurophysiology・auditory thalamocortical pathways・cortical subfield organization・timed action precision・multisensory cortical overlap・postnatal cortical development

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• Nishimura M., Song W.J. . Region-dependent Millisecond Time-scale Sensitivity in Spectrotemporal Integrations in Guinea Pig Primary Auditory Cortex . Neuroscience4802021 · 担当区分： 筆頭著者, 責任著者 記述言語： 日本語 掲載種別： 研究論文（学術雑誌） 出版者・発行元： Neuroscience Spectrotemporal integration is a key function of our auditory system for discriminating spectrotemporally complex sounds, such as words. Response latency in the auditory cortex is known to change with the millisecond time-scale depending on acoustic parameters, such as sound frequency and intensity. The functional significance of the millisecond-range latency difference in the integration remains unclear. Actually, whether the auditory cortex has a sensitivity to the millisecond-range difference has not been systematically examined. Herein, we examined the sensitivity in the primary auditory cortex (A1) using voltage-sensitive dye imaging techniques in guinea pigs. Bandpass noise bursts in two different bands (band-noises), centered at 1 and 16 kHz, respectively, were used for the examination. Onset times of individual band-noises (spectral onset-times) were varied to virtually cancel or magnify the latency difference observed with the band-noises. Conventionally defined nonlinear effects in integration were analyzed at A1 with varying sound intensities (or response latencies) and/or spectral onset-times of the two band-noises. The nonlinear effect measured in the high-frequency region of the A1 linearly changed depending on the millisecond difference of the response onset-times, which were estimated from the spatially-local response latencies and spectral onset-times. In contrast, the low-frequency region of the A1 had no significant sensitivity to the millisecond difference. The millisecond-range latency difference may have functional significance in the spectrotemporal integration with the millisecond time-scale sensitivity at the high-frequency region of A1 but not at the low-frequency region. DOI： 10.1016/j.neuroscience.2021.10.030 Scopus PubMed
• Chen F., Takemoto M., Nishimura M., Tomioka R., Song W.J. . Postnatal development of subfields in the core region of the mouse auditory cortex . Hearing Research4002020 · 記述言語： 英語 掲載種別： 研究論文（学術雑誌） 出版者・発行元： Hearing Research The core region of the rodent auditory cortex has two subfields: the primary auditory area (A1) and the anterior auditory field (AAF). Although the postnatal development of A1 has been studied in several mammalian species, few studies have been conducted on the postnatal development of AAF. Using a voltage-sensitive-dye-based imaging method, we examined and compared the postnatal development of AAF and A1 in mice from postnatal day 11 (P11) to P40. We focused on the postnatal development of tonotopy, the relative position between A1 and AAF, and the properties of tone-evoked responses in the subfields. Tone-evoked responses in the mouse auditory cortex were first observed at P12, and tonotopy was found in both A1 and AAF at this age. Quantification of tonotopy using the cortical magnification factor (CMF; octave difference per unit cortical distance) revealed a rapid change from P12 to P14 in both A1 and AAF, and a stable level from P14. A similar time course of postnatal development was found for the distance between the 4 kHz site in A1 and AAF, the distance between the 16 kHz site in A1 and AAF, and the angle between the frequency axis of A1 and AAF. The maximum amplitude and rise time of tone-evoked signals in both A1 and AAF showed no significant change from P12 to P40, but the latency of the responses to both the 4 kHz and 16 kHz tones decreased during this period, with a more rapid decrease in the latency to 16 kHz tones in both subfields. The duration of responses evoked by 4 kHz tones in both A1 and AAF showed no significant postnatal change, but the duration of responses to 16 kHz tones decreased exponentially in both subfields. The cortical area activated by 4 kHz tones in AAF was always larger than that in A1 at all ages (P12-P40). Our results demonstrated that A1 and AAF developed in parallel postnatally, showing a rapid maturation of tonotopy, slow maturation of response latency and response duration, and a dorsal-to-ventral order (high-frequency site to low-frequency site) of functional maturation. DOI： 10.1016/j.heares.2020.108138 Scopus PubMed
• 生き物と音の事典2019 · 朝倉書店 2019年10月
• Masataka Nishimura, Hiroyuki Sawatari, Makoto Takemoto, Wen-Jie Song . Identification of the somatosensory parietal ventral area and overlap of the somatosensory and auditory cortices i2015 · 担当区分： 筆頭著者 記述言語： 英語 掲載種別： 研究論文（学術雑誌） 出版者・発行元： ELSEVIER IRELAND LTD This study aimed to identify the parietal ventral (PV) area of the somatosensory cortex in mice and to determine whether auditory cortex and somatosensory cortex overlap. Using high resolution, voltage-sensitive dye-based imaging, we identified the PV area, which exhibited strong responses to stimulation of distal body parts but weak responses to stimulation of proximal and facial body parts. We further demonstrated a substantial overlap between the auditory and non-primary somatosensory areas, including the PV area. We found statistically significant non-additive integration of auditory and somatosensory inputs in the overlapping region, suggesting convergence of the two input streams at the cellular level. We have thus delineated the PV area in mice for the first time, and have shown that it is a likely site for the integration of auditory and somatic inputs. (C) 2015 Elsevier Ireland Ltd and the Japan Neuroscience Society. All rights reserved. DOI： 10.1016/j.neures.2015.06.001 Web of Science PubMed

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