シンポジウム（Symposium）

Symposium From sensory systems to goal-directed social behaviors シンポジウム感覚入力が駆動する他者への社会的行動の神経基盤とその起源

7月25日（木）16:55～17:15　第4会場（朱鷺メッセ　3F　301） 1S04e-1 ショウジョウバエにおける化学コミュニケーションに寄与する神経回路の進化 Yuki Ishikawa（石川由希），Naoki Maeda（前田直希），Azusa Kamikouchi（上川内あづさ）名古屋大院理生命理学 Animals utilize chemicals for communication. Such chemicals often vary among species, which exclude heterospecifics from intraspecific community. Accompanied with the signal divergence, the recognition systems have diverged among species. Especially for mating, animals evolve the neural system to discriminate conspecific- and heterospecific- chemicals, resulting the species-specific mating preference, which contributes to reproductive isolation. However, what changes in the neural circuits achieve evolution of the chemical preference is not well understood. Drosophila melanogaster males utilize 7,11-heptacosadiene (7,11-HD), a female-specific pheromone, to discriminate the mating partners; 7,11-HD on target females increases male courtship. In sister species D. simulans, on the other hand, females lost 7,11-HD expression, and males inhibit courtship by the presence of 7,11-HD. These facts indicate that their 7,11-HD preference has reversed from positive to negative in the evolutionary process. To elucidate what changes in the neural circuits causes the evolutionary change, we utilized F1 hybrids of the two species as a model, because they have negative 7,11-HD preference similar to D. simulans, and are easy to be applied by various genetic tools introduced by interspecific crossing. By using optogenetic tools, we found that artificial activation of a particular neural pathway promoted courtship in D. melanogaster, but inhibited it in hybrids. This indicates that the behavioral function of the pathway is reversed between D. melanogaster and hybrids. Artificial activation of the downstream neurons increased courtships both in D. melanogaster and hybrids, suggesting that the functions of the downstream neurons are conversed between D. melanogaster and hybrids. To elucidate the neural changes related to the functional reverse, GFP reconstitution across synaptic partners (GRASP) analysis on each neural connection in the pathway was performed. We found that GRASP signals on a particular pair of neurons were only observed in D. melanogaster, but not in hybrids. These results suggest that the loss of neural connection in a particular neural circuit causes the evolutionary reverse of a pheromone preference in the closely-related Drosophila species.		7月25日（木）17:15～17:35　第4会場（朱鷺メッセ　3F　301） 1S04e-2 親密度に依存した社会性行動の分子神経基盤解析 Saori Yokoi（横井佐織）北海道大院薬 Some social animals can recognize socially-familiarized conspecific individuals (social recognition) and familiarity affects their behavior, which may be important for social adaptation. Disorders in human brain function for this system are assumed to cause mental illnesses, such as autism, and great attention has recently been paid to the underlying neural/molecular mechanisms of these disorders. Oxytocin (OT) is considered to be involved in social recognition and social behavior in rodents and humans. For example, social familiarization (repeated encounters) decreases approach behaviors of male wild-type mice toward unfamiliar females, but not OT KO males. Thus, the OT KO males are thought to have defects in social recognition (social amnesia). In this study, we investigated social behaviors of individual medaka fish, which is a model organism commonly used for molecular genetics, toward group-reared fish (defined as familiar fish) in the same tank and toward unfamiliar conspecifics reared in a different tank. Wild-type males exhibit mating behaviors, irrespective of social familiarity. In contrast, we found that social familiarity strongly affects male social behaviors (e.g., courtship, aggressive, and mate-guarding behaviors) in isotocin-related gene mutants. Isotocin (IT) is a fish homologue of OT. This result suggested that IT-related gene mutants lost social motivation toward conspecifics. In some fish, imprinting affects the social preferences of the juvenile fish based on the traits of their parents that care for them during the early development period. Next, to examine whether or not imprinting mediates social recognition of mutants for IT mutants, we investigated whether social familiarization (rearing in the same tank only as adults) could recover the lost of social motivation in the mutants toward unfamiliar fish.

7月25日（木）17:35～17:55　第4会場（朱鷺メッセ　3F　301） 1S04e-3 経験依存的な行動変化を司る神経回路 Hiroshi Nomura（野村洋）北海道大院薬薬理 Past experience produces memory traces to lead to adaptive emotional and social behavior. In particular, fear experience produces long-lasting memory traces and affects future behavior for long time periods. Here, we show that late gene expression after fear experience refines neuronal circuits to perpetuate memory traces. Arc/Arg3.1 (Arc) is an immediate early gene that is required for the consolidation of synaptic plasticity and long-term memory. We found that mouse hippocampal CA1 neurons exhibit biphasic Arc elevations after contextual fear conditioning. An early Arc increase returned to the baseline after 6 h, followed by a second Arc increase after 12 h in the same neuronal subpopulation. Early Arc expression depended on neuronal activity whereas late Arc expression depended on BDNF. Antisense-induced blockade of late Arc expression disrupted memory persistence but not formation. Since spine elimination in the late phase after learning has been proposed as a mechanism for memory persistence, we examined whether late Arc expression is involved in spine remodeling associated with memory persistence. The density of mushroom spines on CA1 basal dendrites was reduced 7 days after fear conditioning. This spine reduction depended on the late Arc expression. Selective reactivation of neurons activated during learning is essential for memory recall. Spine elimination potentially enhances signal-to-noise ratios to encode information during learning and then contributes to reactivation of neuronal ensembles that were established during learning. Therefore, we examined that late Arc expression is involved in reactivation of neuronal ensembles, possibly through spine elimination. The CA1 neurons that were activated during fear conditioning were more likely to be activated during test at 7 days after conditioning. However, inhibition of late Arc expression abolished reactivation of the CA1 neurons that were activated during conditioning. Taken together, these findings suggest late Arc expression refines functional circuits in a delayed fashion to prolong fear memory.		7月25日（木）17:55～18:15　第4会場（朱鷺メッセ　3F　301） 1S04e-4 視床下部における性行動の神経表現 Tomomi Karigo（苅郷友美）¹，Bin Yang（Yang Bin）¹，Ann Kennedy（Kennedy Ann）¹，David J Anderson（Anderson David）^1,2 ¹Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, USA ²Howard Hughes Medical Institute, California Institute of Technology, Pasadena, USA Sexual behavior is essential for the survival and prosperity of all animal species. Past studies utilizing loss of function and gain of function experiments have shown that parts of the hypothalamus are necessary and sufficient for sexual behaviors. However, our understanding of how sexual behaviors are coordinated at circuit-level are quite limited. To understand how sexual behaviors are represented across hypothalamic nuclei, we focused on two hypothalamic regions in male mice: medial preoptic area (MPA) and ventrolateral subdivision of the ventromedial hypothalamus (VMHvl). Both two regions have been suggested to be important for sexual behaviors. Optogenetic stimulation and inhibition of subpopulation of MPA and VMHvl neurons showed both MPA and VMHvl are necessary and sufficient for mounting behaviors. However, both nuclei are contributing to mounting behaviors differently. Dual-site fiber photometry revealed bulk activities of MPA neurons are strongly representing interactions with female conspecifics and `reproductive state'. On the other hand, bulk activities of VMHvl neurons are strongly representing interactions with male conspecifics and `aggressive state'. Using in vivo endoscopic microscope imaging, we demonstrate how differently MPA and VMHvl neural populations represent mounting behaviors during interactions with conspecific males and females.

7月25日（木）18:15～18:35　第4会場（朱鷺メッセ　3F　301） 1S04e-5 霊長類養育行動の神経基盤の検討 Kazutaka Shinozuka（篠塚一貴）¹，Saori Nashimoto Yano（矢野梨本沙織）¹，Chihiro Yoshihara（吉原千尋）¹，Anna Truzzi（Truzzi Anna）²，Gianluca Esposito（Esposito Gianluca）²，Kenichi Tokita（時田賢一）³，Sayaka Shindo（進藤さやか）¹，Dai Watanabe（渡邉大）⁴，Ryosuke Matsui（松井亮介）⁴，Atsuko Saito（齋藤慈子）⁵，Kumi Kuroda（黒田公美）¹ ¹理研CBS 親和性社会行動 ²Dept Psychol and Cognitive Sci, Univ of Trento, Trento, Italy ³専修大学法学部 ⁴京都大学大学院医学研究科 ⁵上智大学総合人間科学部心理学科 Our previous studies demonstrate that a central part of the medial preoptic area (cMPOA) has a crucial role on parental behavior in mice. cMPOA lesioned mice show infanticidal behavior instead of parental behavior when pups are presented (Tsuneoka et al., 2013; Tsuneoka & Tokita et al., 2015). There has been, however, no neuroanatomical study identified the brain locus responsible for parental care in primates. Here we report a role of the MPOA on parental behavior in common marmosets, a small New World monkey. Common marmosets form a breeding pair and live as an extended family. Family members also take care of infants by carrying and licking them. Such breeding system is a good nonhuman primate model for human parenting. Daily observations of marmoset families revealed that infants were almost carried by family members until 2 weeks old. Only fathers showed significant drop and recovery of carrying ratio in first three weeks, suggesting trade-off of motivational state between parenting and mating. Then overall carrying ratio rapidly decreased and dropped below 50% around postnatal day 35. Some behaviors such as locomotion and eating are significantly decreased during carrying, indicating biological cost of parenting. An infant retrieval test was conducted to measure parental motivation. Two adjacent home cages were connected through a mesh tunnel. A subject was put in one of two cages (a start cage), and an infant, that was temporally separated from a carrier, was put in a mesh basket and positioned in another cage (a goal cage). A subject could enter the goal cage through the tunnel to retrieve and carry an infant. Latency for retrieval and carrying behavior after retrieval was recorded. These two variables represent parental responsiveness and tolerance to infants, and can be considered to correspond to two axes of human parenting style. Intact subjects generally showed rapid retrieval and continuous carrying in the retrieval test, indicating high responsiveness and tolerance to an infant. MPOA lesioned subjects, however, markedly decreased carrying behavior by rejecting infant, without strong effect on retrieval latency nor other kinds of social interactions within family members. Thus, specific MPOA mechanism is suggested to keep parental motivation to tolerate to carry an infant. This study will unveil common details of marmoset and human parenting styles, and identify the brain area mediating parental tolerance for the first time in primates.