Within group-living animals, individuals appropriately tailor attitudes and responses to other group members according to the social context and external environment. At the simplest level, the behavioral output can be described as approach and affiliation (positive response) versus agonistic behavior and avoidance (negative response). The neural substrate that works between sensory input and behavioral output, or the integrative circuits underlying decision-making processes, however, is vast and mysterious. To address this issue, we have focused on medaka fish, a model animal used mainly in the field of molecular genetics. Previously, we demonstrated that medaka females recognize familiar males following prior visual exposure, and social familiarity influences female mating receptivity. Medaka females exhibit a positive response (high receptivity) to familiar males, and a negative response (low receptivity) to unfamiliar males. Further, we demonstrated the essential role of a subpopulation of gonadotropin-releasing hormone-producing neurons (GnRH3 neurons) in switching from low to high female receptivity (Okuyama et al., 2014).
Next, we found that medaka use faces for individual recognition. Females can discriminate between two male faces and two objects, but upside-down of the faces made it more difficult to discriminate them. When discriminating between two non-face objects, upside-down did not affect it. Thus faces may be special for fish, just as humans (Wang and Takeuchi 2017). This is the first study that shows the face inversion effect in animals other than mammals.
We further established various behavior paradigms to assess social interactions such as schooling behavior (Imada et al., 2010), individual recognition (Okuyama et al., 2014: Isoe et al., 2016, Yokoi et al., 2016), mate-guarding (Yokoi et al., 2015, 2016), and social learning (Ochiai et al., 2013).
We established a new methodology for heat-inducible Cre/LoxP recombination in the medaka brain (Okuyama et al.,2013). Using the IR-LEGO system, heat shock induced in a very small area of the developing brains leads to spatially controlled recombination of progeny cells in adult medaka fish, which allows for genetic modulation and/or visualization of neuronal populations of interest. Now CRISPR/Cas9 system is available in medaka fish, which allows us to generate efficiently knock-out and knock-in medaka. Using the medaka systems we are trying to systematically identify internal factors (genes, neural networks, and brain regions) essential for vertebrate social interactions. On the other hand, to estimate behavior rules underlying social interactions, we developed a hypothesis-independent data mining, which could explain actual fish movement (Ochiai et al., 2013). Our eventual purpose is to how the internal factors (genes, neural networks, and brain regions) influences animal behaviors, which can serve as the basis for the emergence of sociality.
Our laboratory explores the potential and future directions of comparative social neuroscience research using medaka fish. We are establishing a novel research domain that integrates neuroscience and evolutionary ecology to elucidate both proximate (mechanistic) and ultimate (evolutionary) determinants of animal cognition and behavior. Our focus is on investigating the social cognitive capabilities and mate choice behavior in medaka, with particular emphasis on visual-based mate preference mechanisms. We utilize the abundant genetic resources and extensive genomic information available for medaka, taking advantage of their ease of laboratory breeding and genetic manipulation. Our research employs a comparative approach, studying Japanese medaka local populations and closely related Indonesian species to uncover the molecular and cellular mechanisms underlying behavioral diversity. We are applying cutting-edge techniques such as single-cell RNA sequencing technology and developing machine learning-based behavioral analysis methods to gain novel insights into the evolution of social behavior.
Through this comprehensive approach, our research aims to unveil fundamental principles in neuroscience and elucidate general mechanisms responsible for generating behavioral diversity in nature. By conducting comparative social neuroscience research using medaka, we strive to unravel the mysteries of animal behavior evolution and diversity, contributing to a deeper understanding of cognitive and behavioral processes across species.
To our lab: General Information
Life Sciences Project Research Laboratory (4F Room 403), Katahira Campus
2-1-1 Katahira, Aoba-Ku, Sendai 980-8577
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Tohoku University
E-mail Address: hideaki.takeuchi.a8(at)tohoku.ac.jp (at)=@
TEL：+81-(0)22-217-6218