一般口演（若手道場）
若手道場 行動の基盤
Wakate Dojo: Behavior Foundations
座長：尾藤 晴彦（東京大学 大学院医学系研究科脳神経医学専攻神経生化学分野）・臼井 紀好（大阪大学医学系研究科神経細胞生物学講座） |
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| 2022年7月1日 15:00～15:15 沖縄コンベンションセンター 会議場B5～7 第4会場
2WD04a2-01
Genetic mechanisms of Caenorhabditis elegans isothermal tracking behavior
*Tzu-Ting Huang(1,2), Shunji Nakano(1,2), Ikue Mori(1,2)
1. Graduate School of Science, Nagoya University, Nagoya, Japan, 2. Neuroscience Institute, Nagoya University, Nagoya, Japan
Keyword: GPCR kinase, Learning and memory, Sensorimotor control, Neural circuits
Maintaining goal-oriented behaviors in a dynamic environment could be a demanding task, which requires perpetual transformation between multisensory signals and motor commands to actuate actions in a coherent sequence. Nervous systems can precisely process such dynamical signals beyond perception levels to execute complex behaviors in a changing environment. How do the nervous systems achieve this efficient computation in animals performing complex tasks? To address neural mechanisms of precise sensory-motor computation required for complex behaviors, we focused on the C. elegans isothermal tracking behavior, a plastic behavior subject to their cultivation experiences. On a thermal gradient under their physiological temperature range, C. elegans can migrate toward their previous cultivation temperature (thermotaxis) and track isothermally along it at the precision of less than 0.1°C differences for up to several minutes (isothermal tracking). Previous works from our lab and others have revealed principal circuit components required for isothermal tracking behaviors, but detailed genetic mechanisms underlying its precise sensorimotor computation remain unexplored. From a candidate screen for mutants defective in isothermal tracking behaviors but not thermotaxis, we found that mutants carrying null mutations in the G-protein coupled receptor kinase gene grk-1 displayed fragmented isothermal tracks instead of long isothermal tracks at the cultivation temperature observed in the wild type. Pan-neuronal grk-1 expression is required and sufficient to restore the grk-1 null isothermal tracking phenotype. However, expressing grk-1 in key sensory neurons and interneurons shared in the thermotaxis and isothermal tracking circuits, including AFD, AWC, AIY, and RIA, failed to restore the isothermal tracking defect of the grk-1 null mutant. Only simultaneous grk-1 expression, but not either of the combination, in the glutamatergic interneuron RIM with the two cholinergic interneurons AVA and AVE fully rescued isothermal tracking defects of the grk-1 null mutant. While animals with genetic ablation in either AVA, AVE or RIM performed mostly intact isothermal tracking as shown previously, our genetic analysis on grk-1 identifies regulatory roles of the AVA/AVE/RIM circuit exclusively for maintaining isothermal tracking behaviors that are distinguishable from those for the thermotaxis. Our study provides genetic insights into the precise sensorimotor computation of goal-driven behaviors in a dynamic environment. | | 2022年7月1日 15:15～15:30 沖縄コンベンションセンター 会議場B5～7 第4会場
2WD04a2-02
Applying and testing the integrated information theory of consciousness in flies
*Angus Leung(1), Naotsugu Tsuchiya(1,2,3)
1. School of Psychological Sciences, Monash University, Melbourne, Australia, 2. Center for Information and Neural Networks, National Institute of Information and Communications Technology, Osaka, Japan, 3. Advanced Telecommunications Research Computational Neuroscience Laboratories, Kyoto, Japan
Keyword: Consciousness, Integrated information, Anaesthesia, Drosophila melanogaster
How conscious experience arises from physical interactions is a key question in neuroscience. One approach towards addressing this question, as taken by the integrated information theory of consciousness (IIT), is to introspect our own conscious experiences to identify its core aspects. Then, to be considered as a physical substrate of consciousness, physical interactions must implement these core aspects. IIT identifies 5 core aspects of conscious experience, and from these, postulates the necessary physical interactions to support them. The theory then derives measures which characterise the degree to which physical interactions in a system align with its postulates: integrated information (Φ), which characterises the extent to which a system can be considered as greater than the sum of its parts, and a corresponding cause-effect structure, which characterises the information intrinsically available to the system. These measures are posited to correspond respectively to the level and contents of conscious experience, with Φ emerging at some temporal scale corresponding to the timescale of conscious experience. We apply these measures to local field potentials from simple fly brains (N = 13) obtained during wakefulness and anaesthesia, and test two predictions of IIT: that 1) these measures should be high during consciousness and low during loss of consciousness, and 2) Φ should emerge to be maximal at some macro timescale, rather than at a micro timescale as would be expected from reductionism. Consistent with IIT’s expectations, we find Φ and its associated cause-effect structure to be reduced during anaesthesia (Leung et al. 2021 PLOS Computational Biology). Further, we find that the ratio of Φ during wakefulness to Φ during anaesthesia is maximal at a timescale of roughly 10 ms, which corresponds roughly to the timescale of neuronal interactions. These results demonstrate the utility of testing the computationally expensive measures of IIT in relatively simple biological systems. | | 2022年7月1日 15:30～15:45 沖縄コンベンションセンター 会議場B5～7 第4会場
2WD04a2-03
海馬台における空間情報を表現する神経多様体
Neural manifold representing spatial information in subiculum
*中井 槙也(1,2)、北西 卓磨(1,3)、水関 健司(1)
1. 大阪市立大学大学院医学研究科、2. 名古屋市立大学大学院薬学研究科、3. 科学技術振興機構さきがけ
*Shinya Nakai(1,2), Takuma Kitanishi(1,3), Kenji Mizuseki(1)
1. Grad Sch Med, Osaka City Univ, Osaka, Japan, 2. Grad Sch Phar, Nagoya City Univ, Aichi, Japan, 3. PRESTO, JST, Saitama, Japan
Keyword: Subiculum, Hippocampus, Neural manifold, Spatial information
海馬台は、場所・移動スピード・道順などの空間情報を表現する神経細胞を多く含み、空間探索などに重要な脳領域である。しかし、単一神経細胞レベルでの情報表現に対し、神経細胞集団レベルでの情報表現はよく分かっていない。神経細胞集団の活動は、個々の神経細胞の発火頻度を各座標軸とする高次元空間として捉えられる。このような高次元空間における集団活動は、最大で神経細胞の数だけ自由度を持ちうる。ところが実際には、海馬CA1野や視床の集団活動は、低次元空間内の限られた領域である低次元神経多様体で表現されることが示されている。しかし、海馬台の集団活動が低次元神経多様体を形成するかは不明である。そこで本研究は、海馬台において低次元神経多様体が存在するかどうか、また、存在するのであれば、神経多様体上で多様な空間情報がどのように表現されるかについて調べた。
T字路迷路課題を遂行するラット海馬台から、256点のシリコンプローブを用いて発火活動を計測したデータを解析に用いた。神経細胞集団の活動の次元数をGrassberger-Procaccia法によって推定したところ、数十個の神経細胞集団の活動は4次元程度で表現されることが分かった。また、この神経多様体を可視化するために、非線形次元削減法であるIsomap法を用いた。すると、3次元空間で表された神経多様体は、T字路迷路に類似した幾何学的構造を有することが分かった。これらの結果から、海馬台の神経細胞集団の活動は低次元神経多様体として表現されることが示唆された。
次に、次元削減によって得られた神経多様体がどのような空間情報を保持するかを検討するため、神経多様体上の座標から空間情報を予測するガウス過程回帰分析を行った。その結果、神経多様体は場所・移動スピード・T字路における道順選択という空間情報を符号化することが分かった。また、これらの空間情報の予測精度は海馬CA1野と比較して海馬台の方が高いことも明らかとなった。
最後に、神経多様体は個体間・遂行課題間において共通した構造を持つかについて検討した。まず、あるラットの神経多様体と場所情報の関係を回帰モデルとして学習させ、異なるラットの神経多様体を用いて場所情報を推定した。この結果から、神経多様体は個体をまたいで部分的に共通した構造を持つことが分かった。さらに、T字路迷路課題における神経多様体とオープンフィールド課題における神経多様体との構造の共通性を調べたところ、海馬CA1野よりも海馬台の方が高い課題間の共通性を示すことが明らかとなった。
以上の結果から、海馬台の集団活動は低次元神経多様体を形成することが分かった。この神経多様体は多様な空間情報を符号化しており、その構造には個体間や課題間において共通性が見られることが明らかとなった。これらのことから、海馬台における神経細胞集団は神経多様体を形成し、空間情報表現の基礎となすと考えられる。 | | 2022年7月1日 15:45～16:00 沖縄コンベンションセンター 会議場B5～7 第4会場
2WD04a2-04
Effects of Left Inferior Prefrontal Cortex Anodal Stimulation on Second Language Acquisition
*Daniel Cory Gallagher(1), Kyosuke Matsumoto(2), Shinri Ohta(3)
1. Dept Ling, Grad Sch Hum, Kyushu Univ, Fukuoka, Japan, 2. Dept Ling, Sch Letters, Kyushu Univ, Fukuoka, Japan, 3. Dept Ling, Fac Hum, Kyushu Univ, Fukuoka, Japan
Keyword: HD-tDCS, BROCA'S AREA, LEFT INFERIOR FRONTAL GYRUS (IFG), SECOND LANGUAGE ACQUISITION (SLA)
Research on the effects of anodal transcranial direct current stimulation (tDCS) over the left inferior frontal gyrus (IFG) or Broca’s area (Brodmann areas 44 and 45) in healthy individuals has been largely dedicated to observing its effects on language processing, novel word acquisition, and artificial grammar acquisition. By contrast, we examine the effects of left IFG anodal tDCS on natural language acquisition, i.e., second language acquisition. Twenty-eight native Japanese speakers (14 male), all of whom were naïve to Spanish before the experiment, were subjected to 20 minutes of either online anodal HD-tDCS or sham stimulation over the left IFG during a training phase. During the training phase, participants were taught and practiced subject pronouns and their corresponding regular present tense verb conjugation rules in Spanish. After the training phase, participants completed a grammaticality judgment reception task, a verb conjugation production task, and a rapid serial visual presentation working memory task, completed within 30 minutes post-stimulation. This procedure was repeated in three separate sessions at one-week intervals. Stimulation, task, and session made up the factors in a three-way repeated measures ANOVA, which was carried out for both accuracy and reaction time (RT). Stimulation (F(1,23) = 8.1, p < 0.01), task (F(2,46) = 104, p < 0.001), and session (F(2,46) = 170, p < 0.001) were each found to have a significant main effect on accuracy. Importantly, post-hoc analysis revealed a significant facilitatory effect of stimulation on the reception task in the first and third sessions (p < 0.05) and on the production task in the first session (p < 0.001), but no such effect on the working memory task. Similarly, stimulation (F(1,23) = 8.1, p < 0.01), task (F(2,46) = 2114, p < 0.001), and session (F(2,46) = 120, p < 0.01) all had a significant main effects on RT. Post-hoc analysis revealed that stimulation had a significant facilitatory effect on RT in the reception task in each session (p < 0.05), and in the production task in the second and third sessions (p < 0.05), but no such effect on the working memory task. In sum, tDCS over left IFG differentially improved performance on language acquisition tasks compared to a working memory task, demonstrating a language-selective causal relationship between Broca’s area and second language acquisition. | |
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