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Front Neurorobot
2019 Aug 23;13:66. doi: 10.3389/fnbot.2019.00066.
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Decentralized Control Mechanism for Determination of Moving Direction in Brittle Stars With Penta-Radially Symmetric Body.
Kano T
,
Kanauchi D
,
Aonuma H
,
Clark EG
,
Ishiguro A
.
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A brittle star, an echinoderm with penta-radially symmetric body, can make decisions about its moving direction and move adapting to various circumstances despite lacking a central nervous system and instead possessing a rather simple distributed nervous system. In this study, we aimed to elucidate the essential control mechanism underlying the determination of moving direction in brittle stars. Based on behavioral findings on brittle stars whose nervous systems were lesioned in various ways, we propose a phenomenological mathematical model. We demonstrate via simulations that the proposed model can well reproduce the behavioral findings. Our findings not only provide insights into the mechanism for the determination of moving direction in brittle stars, but also help understand the essential mechanism underlying autonomous behaviors of animals. Moreover, they will pave the way for developing fully autonomous robots that can make decisions by themselves and move adaptively under various circumstances.
Figure 1. Body and nerve structure of a brittle star (Ophiarachna incrassata).
Figure 2. Results of the behavioral experiments: (A) Experiment 1, (B) Experiment 2, (C) Experiment 3, and (D) Experiment 4. Points where the nerve ring is cut and points where an aversive stimulus is added are indicated by scissors and blue circles, respectively. In the snapshots, the moving direction, points where the nerve ring is cut, and points where an aversive stimulus is added are indicated by black, orange, and blue arrows, respectively. Except for (B), data was taken from the work by Clark et al. (2019).
Figure 3. Schematics of the previous model (Kano et al., 2017b) and the proposed model. (A) Body system. (B) Definitions of d and ri. The ai values are also shown schematically. (C) Evaluation of reaction force from the environment when aiâ1 > ai > ai+1. (D) Outline of the decentralized control mechanism. Detailed explanations are provided in the main text. (E) Schematic of the proposed model. Five water tanks are connected by tubes. Water level denotes ai. Dashed lines denote Äi. Black arrows indicate water flow. Schematics in (A,C,D) were reproduced from Kano et al. (2017b).
Figure 4. Simulation results: (A) Experiment 1, (B) Experiment 2, (C) Experiment 3, and (D) Experiment 4. Points where the nerve ring is cut and points where an aversive stimulus is added are indicated by scissors and blue circles, respectively. In the snapshots, points where the nerve ring is cut are indicated by pink lines. Points where aversive stimuli are added are indicated by pink circles. Mass points are colored orange and blue when they contact with and lift off the ground, respectively.
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