Bats perceive the three-dimensional environment by emitting ultrasound pulses from their nose or mouth and receiving echoes through both ears. To determine the position of a target object, it is necessary to know the distance and direction of the target. Certain bat species that use a combined signal of long constant frequency and short frequency modulated ultrasounds synchronize their pinnae movement with pulse emission, and this behavior has been regarded as helpful for localizing the elevation angle of a reflective sound source. However, the significance of bats' ear motions remains unclear. In this study, we construct a model of an active listening system including the motion of the ears, and conduct mathematical investigations to clarify the importance of ear motion in direction detection of the reflective sound source. In the simulations, direction detection under rigid ear movements with interaural level differences was mathematically investigated by assuming that bats accomplish direction detection using the amplitude modulation in the echoes caused by ear movements. In particular, the ear motion conditions required for direction detection are theoretically investigated through exhaustive simulations of the pseudo-motion of the ears, rather than simulations of the actual ear motions of bats. The theory suggests that only certain ear motions, namely three-axis rotation, allow for accurate and robust direction detection. Our theoretical analysis also strongly supports the behavior whereby bats move their pinnae in the antiphase mode. In addition, we suggest that simple shaped hearing directionality and well-selected uncomplicated ear motions are sufficient to achieve precise and robust direction detection. Our findings and mathematical approach have the potential to be used in the design of active sensing systems in various engineering fields.

Higher-order genomic architecture varies according to cell type and changes dramatically during differentiation. One of the remarkable examples of spatial genomic reorganization is the rod photoreceptor cell differentiation in nocturnal mammals. The inverted nuclear architecture found in adult mouse rod cells is formed through the reorganization of the conventional architecture during terminal differentiation. However, the mechanisms underlying these changes remain largely unknown. Here, we found that the dynamic deformation of nuclei via actomyosin-mediated contractility contributes to chromocenter clustering and promotes genomic architecture reorganization during differentiation by conducting an in cellulo experiment coupled with phase-field modeling. Similar patterns of dynamic deformation of the nucleus and a concomitant migration of the nuclear content were also observed in rod cells derived from the developing mouse retina. These results indicate that the common phenomenon of dynamic nuclear deformation, which accompanies dynamic cell behavior, can be a universal mechanism for spatiotemporal genomic reorganization.

The underwater soft-robot inspired by polyclad flatworms has been developed. The oval, flat, soft body of the flatworm was represented by a rubber sheet. The sheet was controlled by controls with three degrees of freedom to allow flapping of both the lateral sides and the body axis. Swimming patterns, such as swimming forward, hovering, and swimming backwards, were achieved by coordinated movement of the lateral side flaps and the body axis of the soft robot.

Snakes actively utilize terrain irregularities and attain propulsion force by pushing their bodies against scaffolds. The objective of this study is to understand the mechanism underlying this locomotion on the basis of a synthetic approach. Our previous control scheme of a snake-like robot, in which the curvature derivative control method is combined with a reflexive mechanism using local pressures on the body wall, could not fully reproduce innate behavior of real snakes. In this study, we improve our previous control scheme. We show that the locomotion of a simulated robot with the improved control scheme is surprisingly in good agreement with the locomotion of a real snake. We also present a physical robot that we are currently developing.

Snakes actively utilize irregularities in terrains and attain propulsion force by pushing their bodies against scaffolds. The objective of this study is to understand the mechanism underlying such functionalities of snakes on the basis of a synthetic approach. We construct a model of a serpentine robot with viscoelastic properties, and we design an autonomous decentralized control scheme that employs local sensory feedback based on the muscle length and strain of the body, the latter of which is generated by the body softness. Simulation results show that the robot exhibits locomotion effectively by utilizing scaffolds such as high-friction areas and pegs, which is in fairly good agreement with biological findings.

The mechanism of multi-articular muscles that contributes to the emergence of macroscopic behavior of animals has not been clarified thus far. To address this issue, we focus on the slithering motion of snakes, which have numerous antagonistic muscle-tendon chains that span several tens of vertebrae. From theoretical analyses based on the continuum model, the acceleration of the body in the longitudinal direction is found to be proportional to the number of segments spanned by each muscle. On the basis of this theoretical result, we propose a decentralized control scheme for the efficient locomotion of a multi-articular snake-like robot. We conduct simulations using this control scheme, and the results show that the locomotion efficiency increases as the number of segments spanned by each muscle increases.

Animals exhibit astoundingly adaptive and supple locomotion under real world constraints. In order to endow robots with similar capabilities, we must implement large degrees of freedom, equivalent to animals, into the robots' bodies. For taming large degrees of freedom, the concept of autonomous decentralized control plays a pivotal role. However, a systematic way of designing such autonomous decentralized control system is still missing. Aiming at understanding the principles that underlie animals' locomotion, in our early studies, we focused on true slime mold, a primitive living organism, and extracted a decentralized control scheme. In order to validate this control scheme, this paper presents a soft-bodied amoeboid robot inspired by true slime mold. Significant features of this robot are twofold: (1) the robot has truly soft and deformable body stemming from real-time tunable springs and a balloon, the former is used for an outer skin of the body and the latter serves as protoplasm; and (2) a fully decentralized control using coupled oscillators with completely local sensory feedback mechanism is realized by exploiting the long-distance physical interaction between the body parts stemming from both the softness of the body and the law of conservation of protoplasmic mass. Experimental results show that this robot exhibits truly supple locomotion without relying on any hierarchical structure. The results obtained are expected to shed new light on design scheme for autonomous decentralized control system.

Decentralized control is a key concept to understand the mechanism of versatile and adaptive locomotion of animals under various environments. However, a systematic design of an autonomous decentralized control system has not been well established, because previous studies mainly focused on the control of phase relationship among body parts, i.e., phasic control, but not on the control of the spatio-temporal dynamics of muscle tonus, i.e., tonic control. In this paper, we propose a decentralized control scheme that enables to reconcile phasic control and tonic control, by taking serpentine locomotion as a practical example. Through modeling and simulations, we show that well-balanced coupling between the phasic and tonic control is crucial for the generation of adaptive and efficient locomotion.

Animals exhibit astoundingly adaptive and supple locomotion under real world constraints. In order to endow robots with similar capabilities, we must implement many degrees of freedom, equivalent to animals, into the robots' bodies. For taming many degrees of freedom, the concept of autonomous decentralized control plays a pivotal role. However, a systematic way of designing such autonomous decentralized control system is still missing. Aiming at understanding the principles that underlie animals' locomotion, in our early studies, we focused on plasmodium of true slime mold, a primitive living organism, and extracted a design scheme for autonomous decentralized control system. In order to demonstrate the relevance of this design scheme, this paper presents a soft-bodied fluid-driven amoeboid robot inspired by plasmodium of true slime mold. The significant features of this robot are twofold: (1) the robot has fluidic circuit (i.e., cylinders and nylon tubes filled with fluid) and truly soft and deformable body stemming from real-time tunable springs, the former serves as protoplasm and the latter is used for elastic actuators; and (2) a fully decentralized control using coupled oscillators with completely local sensory feedback mechanism is realized by exploiting the long-distance physical interaction between the body parts stemming from the law of conservation of protoplasmic mass. The experimental results show that this robot exhibits truly supple locomotion without relying on any hierarchical structure. The results obtained are expected to shed new light on design scheme for autonomous decentralized control system.