Locomotion In Conditions Research Articles

Collective movement of schooling fish reduces the costs of locomotion in turbulent conditions

Collective movement of schooling fish reduces the costs of locomotion in turbulent conditions

Enhancing wet surface adhesion in walking robots: finite element-based analysis and morphology-changeable soft pads

In recent studies concerning walking robots, there has been a notable emphasis on investigating tribological phenomena and elucidating the role of capillary forces in tangential resistance. However, majority of these investigations have been restricted to specific geometric shapes, primarily spherical domes. In this research, we propose a novel approach based on the finite element method to address broader challenge of wet adhesion applicable to objects of various shapes. Additionally, we investigate the role of distributed domes on a soft foot in quantifying the tangential capillary force, which plays a crucial role in enhancing the performance of walking robots on wet surfaces. Through the optimization application, we identify that our designed foot (measuring 20 mm × 14 mm, comprising 78 domes with a radius of 0.5 mm and a distance of 1.5 mm between the two nearest domes) maximizes the value of the tangential capillary force. Moreover, we develop a finite element method using the Simulation Open Framework Architecture (SOFA) to model the interaction between wet liquid on a solid object's curved surface, enabling the calculation of wet adhesion force and capillary forces. Finally, to demonstrate the effectiveness of our proposed morphology-changeable soft pads foot, we conduct a presented a demonstration of a hexapod robot walking on different dry/wet condition of the surface. The obtained results are expected to pave a way to morphological design of soft pads for facilitating locomotion in various conditions. Supplementary video URL: https://youtu.be/yVteC95eqbo

Bio-Inspired Untethered Robot-Sensor Platform for Minimally Invasive Biomedical Sensing.

Conventional catheter- or probe-based in vivo biomedical sensing is uncomfortable, inconvenient, and sometimes infeasible for long-term monitoring. Existing implantable sensors often require an invasive procedure for sensor placement. Untethered soft robots with the capability to deliver the sensor to the desired monitoring point hold great promise for minimally invasive biomedical sensing. Inspired by the locomotion modes of snakes, we present here a soft kirigami robot for sensor deployment and real-time wireless sensing. The locomotion mechanism of the soft robot is achieved by kirigami patterns that offer asymmetric tribological properties that mimic the skin of the snake. The robot exhibits good deployability, excellent load capacity (up to 150 times its own weight), high-speed locomotion (0.25 body length per step), and wide environmental adaptability with multimodal movements (obstacle crossing, locomotion in wet and dry conditions, climbing, and inverted crawling). When integrated with passive sensors, the versatile soft robot can locomote inside the human body, deliver the passive sensor to the desired location, and hold the sensor in place for real-time monitoring in a minimally invasive manner. The proof-of-concept prototype demonstrates that the platform can perform real-time impedance monitoring for the diagnosis of gastroesophageal reflux disease.

SPATIO-TEMPORAL PATTERNS OF CORTICAL-MUSCULAR INTERACTION DURING LOCOMOTION

The paper considers the synergetic effects manifested at the cortical and muscular levels during locomotor activity showed in conditions of horizontal hanging of the lower extremities. The analysis of the synergies’ spatio-temporal structure was carried out using the data matrix factorization methods. It was found out the control of the movements’ structure is mainly realized through the three muscle synergies. The activity synchronization of the motor, associative, visual and sensorimotor regions of the cortex bilateral part is due to the specifics of performing locomotion in conditions of gravitational unloading and the associated features of receptor signaling. The identified components indicating synchronization of different areas of the right and left cortex may reflect the control processes associated with the control of alternate activation of the flexor and extensor muscles of the contralateral limb during locomotion. The data on the cortical activity spatial-temporal structuring indicate the separate management of muscle synergies through synchronization of cortical commands and the temporary organization of muscle synergies in the frequency ranges 0.30 to 8.00 Hz. Such patterns may reflect the activity of the rhythm-generating mechanism involved in the management of cyclic locomotor activity.

Morphology-Changeable Soft Pads Facilitate Locomotion in Wet Conditions

Stable robot walking requires effective gait planning and control. The mechanical properties of contact between feet and ground are important factors in this process. In this paper, we propose and test a design for a robot foot that houses soft pads, which adapt to facilitate locomotion on wet and dry floors. The morphology of each soft pad distributed in the sole of the foot is changed from a thin elastic sheet to a spherical dome that protrudes from the sole with the use of compressed air to adapt the foot for walking. We constructed an analytical model to estimate how soft pad dome shape is effected by air pressure and associated properties regarding friction and forces when in contact with a dry or wet floor. The contribution of wet adhesion to enhance shear force among the floor and the soft pads was elaborated theoretically. We report results of practical experiments with a sole (35 mm×15 mm) housing 14 such soft pads (radius 1.5 mm) comparing walking in dry and wet conditions. Finally, we present a setup of a walking robot leg with the proposed foot and soft pad on flat ground. The results demonstrate that soft pad domes improved walking stability under wet conditions on flat ground whereas they made no noticeable difference under dry conditions. Changeable morphology of the soft pads (stiffness, radius of the domes), which is controlled by adjusting air pressure, contributed to adaptive walking. The results obtained here may inform attempts at morphological design of soft pads to facilitate locomotion of legged robots under various terrain conditions.

Panx1b Modulates the Luminance Response and Direction of Locomotion in the Zebrafish.

Pannexin1 (Panx1) can form ATP-permeable channels that play roles in the physiology of the visual system. In the zebrafish two ohnologs of Panx1, Panx1a and Panx1b, have unique and shared channel properties and tissue expression patterns. Panx1a channels are located in horizontal cells of the outer retina and modulate light decrement detection through an ATP/pH-dependent mechanisms and adenosine/dopamine signaling. Here, we decipher how the strategic localization of Panx1b channels in the inner retina and ganglion cell layer modulates visually evoked motor behavior. We describe a panx1b knockout model generated by TALEN technology. The RNA-seq analysis of 6 days post-fertilization larvae is confirmed by real-time PCR and paired with testing of locomotion behaviors by visual motor and optomotor response tests. We show that the loss of Panx1b channels disrupts the retinal response to an abrupt loss of illumination and it decreases the larval ability to follow leftward direction of locomotion in low light conditions. We concluded that the loss of Panx1b channels compromises the final output of luminance as well as motion detection. The Panx1b protein also emerges as a modulator of the circadian clock system. The disruption of the circadian clock system in mutants suggests that Panx1b could participate in non-image forming processes in the inner retina.

Optogenetic stimulation of glutamatergic neurons in the cuneiform nucleus controls locomotion in a mouse model of Parkinson’s disease

In Parkinson's disease (PD), the loss of midbrain dopaminergic cells results in severe locomotor deficits, such as gait freezing and akinesia. Growing evidence indicates that these deficits can be attributed to the decreased activity in the mesencephalic locomotor region (MLR), a brainstem region controlling locomotion. Clinicians are exploring the deep brain stimulation of the MLR as a treatment option to improve locomotor function. The results are variable, from modest to promising. However, within the MLR, clinicians have targeted the pedunculopontine nucleus exclusively, while leaving the cuneiform nucleus unexplored. To our knowledge, the effects of cuneiform nucleus stimulation have never been determined in parkinsonian conditions in any animal model. Here, we addressed this issue in a mouse model of PD, based on the bilateral striatal injection of 6-hydroxydopamine, which damaged the nigrostriatal pathway and decreased locomotor activity. We show that selective optogenetic stimulation of glutamatergic neurons in the cuneiform nucleus in mice expressing channelrhodopsin in a Cre-dependent manner in Vglut2-positive neurons (Vglut2-ChR2-EYFP mice) increased the number of locomotor initiations, increased the time spent in locomotion, and controlled locomotor speed. Using deep learning-based movement analysis, we found that the limb kinematics of optogenetic-evoked locomotion in pathological conditions were largely similar to those recorded in intact animals. Our work identifies the glutamatergic neurons of the cuneiform nucleus as a potentially clinically relevant target to improve locomotor activity in parkinsonian conditions. Our study should open avenues to develop the targeted stimulation of these neurons using deep brain stimulation, pharmacotherapy, or optogenetics.

Mechanical work as a (key) determinant of energy cost in human locomotion: recent findings and future directions.

What is the topic of this review? This narrative review explores past and recent findings on the mechanical determinants of energy cost during human locomotion, obtained by using a mechanical approach based on König's theorem (Fenn's approach). What advances does it highlight? Developments in analytical methods and their applications allow a better understanding of the mechanical-bioenergetic interaction. Recent advances include the determination of 'frictional' internal work; the association between tendon work and apparent efficiency; a better understanding of the role of energy recovery and internal work in pathological gait (amputees, stroke and obesity); and a comprehensive analysis of human locomotion in (simulated) low gravity conditions. During locomotion, muscles use metabolic energy to produce mechanical work (in a more or less efficient way), and energetics and mechanics can be considered as two sides of the same coin, the latter being investigated to understand the former. A mechanical approach based on König's theorem (Fenn's approach) has proved to be a useful tool to elucidate the determinants of the energy cost of locomotion (e.g., the pendulum-like model of walking and the bouncing model of running) and has resulted in many advances in this field. During the past 60 years, this approach has been refined and applied to explore the determinants of energy cost and efficiency in a variety of conditions (e.g., low gravity, unsteady speed). This narrative review aims to summarize current knowledge of the role that mechanical work has played in our understanding of energy cost to date, and to underline how recent developments in analytical methods and their applications in specific locomotion modalities (on a gradient, at low gravity and in unsteady conditions) and in pathological gaits (asymmetric gait pathologies, obese subjects and in the elderly) could continue to push this understanding further. The recent in vivo quantification of new aspects that should be included in the assessment of mechanical work (e.g., frictional internal work and elastic contribution) deserves future research that would improve our knowledge of the mechanical-bioenergetic interaction during human locomotion, as well as in sport science and space exploration.

Dehydration and persistence hunting in Homo erectus

Persistence hunting has been suggested to be a key strategy for meat acquisition in Homo erectus. However, prolonged locomotion in hot conditions is associated with considerable water losses due to sweating. Consequently, dehydration has been proposed to be a critical limiting factor, effectively curtailing the usefulness of persistence hunting prior to the invention of water containers. In this study, we aimed to determine the extent to which dehydration limited persistence hunting in H. erectus.We simulated ambient conditions and spatiotemporal characteristics of nine previously reported persistence hunts in the Kalahari. We used a newly developed and validated heat exchange model to estimate the water loss in H. erectus and a recent Kalahari hunter. Water loss equivalent to 10% of the hunter's body mass was considered the physiological limit of a hunt with no drinking. Our criterion for ruling dehydration out of being a limit for persistence hunting was the ability to hunt without drinking for at least 5 h, as this was the longest duration reported for a successful persistence hunt of large prey.Our results showed that H. erectus would reach the dehydration limit in 5.5–5.7 h of persistence hunting at the reported Kalahari conditions, which we argue represent a conservative model also for Early Pleistocene East Africa. Maximum hunt duration without drinking was negatively related to the relative body surface area of the hunter. Moreover, H. erectus would be able to persistence hunt over 5 h without drinking despite possible deviations from modern-like heat dissipation capacity, aerobic capacity, and locomotor economy. We conclude that H. erectus could persistence hunt large prey without the need to carry water.

Post-stroke visual neglect affects goal-directed locomotion in different perceptuo-cognitive conditions and on a wide visual spectrum.

Unilateral spatial neglect (USN), a highly prevalent and disabling post-stroke deficit, has been shown to affect the recovery of locomotion. However, our current understanding of USN role in goal-directed locomotion control, and this, in different cognitive/perceptual conditions tapping into daily life demands, is limited. To examine goal-directed locomotion abilities in individuals with and without post-stroke USN vs. healthy controls. Participants (n = 45, n = 15 per group) performed goal-directed locomotion trials to actual, remembered and shifting targets located 7 m away at 0° and 15° right/left while immersed in a 3-D virtual environment. Greater end-point mediolateral displacement and heading errors (end-point accuracy measures) were found for the actual and the remembered left and right targets among those with post-stroke USN compared to the two other groups (p < 0.05). A delayed onset of reorientation to the left and right shifting targets was also observed in USN+ participants vs. the other two groups (p < 0.05). Results on clinical near space USN assessment and walking speed explained only a third of the variance in goal-directed walking performance. Post-stroke USN was found to affect goal-directed locomotion in different perceptuo-cognitive conditions, both to contralesional and ipsilesional targets, demonstrating the presence of lateralized and non-lateralized deficits. Beyond neglect severity and walking capacity, other factors related to attention, executive functioning and higher-order visual perceptual abilities (e.g. optic flow perception) may account for the goal-directed walking deficits observed in post-stroke USN+. Goal-directed locomotion can be explored in the design of future VR-based evaluation and training tools for USN to improve the currently used conventional methods.

Post-stroke unilateral spatial neglect: virtual reality-based navigation and detection tasks reveal lateralized and non-lateralized deficits in tasks of varying perceptual and cognitive demands

BackgroundUnilateral spatial neglect (USN), a highly prevalent and disabling post-stroke impairment, has been shown to affect the recovery of locomotor and navigation skills needed for community mobility. We recently found that USN alters goal-directed locomotion in conditions of different cognitive/perceptual demands. However, sensorimotor post-stroke dysfunction (e.g. decreased walking speed) could have influenced the results.Analogous to a previously used goal-directed locomotor paradigm, a seated, joystick-driven navigation experiment, minimizing locomotor demands, was employed in individuals with and without post-stroke USN (USN+ and USN-, respectively) and healthy controls (HC).MethodsParticipants (n = 15 per group) performed a seated, joystick-driven navigation and detection time task to targets 7 m away at 0°, ±15°/30° in actual (visually-guided), remembered (memory-guided) and shifting (visually-guided with representational updating component) conditions while immersed in a 3D virtual reality environment.ResultsGreater end-point mediolateral errors to left-sided targets (remembered and shifting conditions) and overall lengthier onsets in reorientation strategy (shifting condition) were found for USN+ vs. USN- and vs. HC (p < 0.05). USN+ individuals mostly overshot left targets (− 15°/− 30°). Greater delays in detection time for target locations across the visual spectrum (left, middle and right) were found in USN+ vs. USN- and HC groups (p < 0.05).ConclusionUSN-related attentional-perceptual deficits alter navigation abilities in memory-guided and shifting conditions, independently of post-stroke locomotor deficits. Lateralized and non-lateralized deficits in object detection are found. The employed paradigm could be considered in the design and development of sensitive and functional assessment methods for neglect; thereby addressing the drawbacks of currently used traditional paper-and-pencil tools.

A Novel Approach to Study Locomotion in Under-g Load Bearing Conditions

The purpose of this study was to develop a methodology for systematically unloading in locomotion, which allows for a simple and comfortable weight reduction to study individual movement patterns and adaptations to under-g conditions. For this purpose an unloading harness was constructed. Further vertical ground reaction forces (vertical GRF) were used to develop a formula to calculate the individual unloading situation with respect to the body weight. The constructed unloading harness system allows for a systematical reduction of body weight. Using vertical GRF data, the developed methods enable to calculate the required system settings to obtain the desired individual unloading situation in static as well as in dynamic situations.

Microelectrode arrays in combination with in vitro models of spinal cord injury as tools to investigate pathological changes in network activity: facts and promises

Microelectrode arrays (MEAs) represent an important tool to study the basic characteristics of spinal networks that control locomotion in physiological conditions. Fundamental properties of this neuronal rhythmicity like burst origin, propagation, coordination, and resilience can, thus, be investigated at multiple sites within a certain spinal topography and neighboring circuits. A novel challenge will be to apply this technology to unveil the mechanisms underlying pathological processes evoked by spinal cord injury (SCI). To achieve this goal, it is necessary to fully identify spinal networks that make up the locomotor central pattern generator (CPG) and to understand their operational rules. In this review, the use of isolated spinal cord preparations from rodents, or organotypic spinal slice cultures is discussed to study rhythmic activity. In particular, this review surveys our recently developed in vitro models of SCI by evoking excitotoxic (or even hypoxic/dysmetabolic) damage to spinal networks and assessing the impact on rhythmic activity and cell survival. These pathological processes which evolve via different cell death mechanisms are discussed as a paradigm to apply MEA recording for detailed mapping of the functional damage and its time-dependent evolution.

Short-term individual housing induced social deficits in female Mongolian gerbils: Attenuation by chronic but not acute imipramine

Mongolian gerbils are highly sensitive to manipulations of their social environments. Housing females individually for short periods (in the order of 7–21 days) has been shown to produce robust and reliable impairments of their subsequent social behaviour. These effects are typified by a marked reduction in the social investigation of an unfamiliar male in a neutral arena and/or a marked increases in levels of freezing whilst and only whilst they are being socially investigated (Immobile in contact). These responses demonstrate housing induced impaired motivation to socially interact. These effects have also been shown to be sensitive to treatment with chronic (but not acute) administration of the selective serotonin reuptake inhibitor (SSRI) fluoxetine. It was therefore of interest to know if similar effects would be produced by treatment with the tricyclic antidepressant Imipramine. This mixed NA/5-HT reuptake inhibitor first developed in the 1950's is a commonly used standard in animal models of depression and remains in clinical use today.Female gerbils were individually housed for 7 days or maintained in single-sex groups of 4 for the same period. All animals were then randomly allocated to be administered with either 0, 10 or 20 mg/kg imipramine. Acute administration did not reverse the social impairments produced by the individual housing but did produce non-specific stimulant effects on locomotion in both housing conditions. These social impairments were however reduced after a further 14 days chronic treatment with 10 or 20 mg/kg imipramine and stimulant effects were no longer seen. Following chronic administration in group-housed animals locomotor stimulation was replaced with sedation, which resulted in a reduction in social behaviour. That is, opposite to the effect seen in Individual housed animals. It is therefore concluded that chronic treatment with imipramine serves to increase social behaviour but only in those animals with a pre-existing social deficit.

A comparison of epigean and subterranean locomotion in the domestic ferret ( Mustela putorius furo: Mustelidae: Carnivora)

Burrows are used by many mammals to escape predation, cache food and for parturition. Although the construction of burrows has been studied in some taxa, the locomotion while inside of them has received scant attention. In this study we collected simultaneous video and force data to characterize gaits, kinematics, peak ground reaction forces (GRFs) and external mechanical energy profiles in the domestic ferret, an animal that displays the typical morphology and behaviors associated with subterranean adaptations in mustelines. We compared kinematics and kinetics between locomotion in two experimental conditions: subterranean, simulated by a Plexiglass tunnel designed such that the ferrets’ peak back height was reduced by 40% and hip height by 25%, and epigean, or unconstrained overground. Despite the large change in posture, a striking number of gait and force variables were not statistically different between experimental conditions. In both subterranean and epigean conditions, the ferrets in our study traveled at similar average velocities (∼0.8 m s −1), preferred to use a lateral-sequence diagonal-couplet gait, and were more likely to demonstrate the in-phase fluctuations of external mechanical energy indicative of running mechanics (68% of all trials). The ferrets conformed to gait and mechanical patterns seen in a variety of other small (<1 kg) mammals rather than being unique, despite the divergent morphology of mustelines. Our results demonstrated biodynamically similar locomotion in both epigean and subterranean conditions and support the hypothesis that ferrets possess adaptations for tunnel locomotion.

A biomimetic approach to robot locomotion in unstructured and slippery environments

While much attention has been given to bio-robotics in recent years, not much of this has been given to the challenging subject of locomotion in slippery conditions. This study begins to rectify this by proposing a biomimetic approach to generating the friction required to give sufficient propulsive force on a slippery substrate. We took inspiration from a successful biological solution — that of applying hair-like structures to the propulsive appendages, similar to the setae found in nereid polychaetes living in muddy habitats. We began by examining the morphology and the mean locomotion parameters of one of the most common nereids: Nereis diversicolor. Following this study, we designed and fabricated a robotic system with appendages imitating the biological shape found in the worm. A flexible control system was developed to allow most of the locomotion parameters observed in the real worm to be applied to the robot. Experiments on three different natural substrates ranging from fine sand to gravel showed that, whereas a plate attached to the appendage generated most thrust on a small particle substrate, a bundle of artificial setae attached to the appendage generated most thrust on a large particle substrate. On all types of substrate tested, an appendage without any attachment did significantly worse than one with. This suggests that hair-like structures can be advantageous.

Improving fluorescence-based assays for the in vitro analysis of cell adhesion and migration.

Cell adhesion and cell migration are two primary cellular phenomena to be approached in vitro in order to allow for the effective dissection of the individual events and the unravelling of their underlying molecular mechanisms. The use of assays dedicated to the analysis of cell adhesion and migration in vitro also affords an efficient way of conducting larger basic and applied research screenings of the conditions affecting these processes and are potentially exploitable in the context of routine tests in the biological and medical fields. Therefore, there is a substantial interest in devicing more rationale such assays and major contributions in this direction have been provided by the advent of procedures based on fluorescent cell tagging. In this article we describe three fluorescence-based model assays for the qualitative and quantitative assessment of cell adhesion and cell locomotion in static and dynamic conditions. The assays are easily performed, accurate and reproducible, and can be automatized for high-throughput screenings of cell behavior in vitro. Performance of the assays involves the use of certain dedicated disposable accessories, which are commercially available, and a few instruments that, due to their versatility, can be regarded as constituents of a more generic laboratory setup.

Three-dimensional kinematic technique for evaluation of horse locomotion in outdoor conditions.

Three-dimensional kinematic technique for evaluation of horse locomotion in outdoor conditions.

Differential behavioral effects following microinjection of an NMDA antagonist into nucleus accumbens subregions.

Recent studies have demonstrated the existence of two distinct regions within the nucleus accumbens (N.Acc) known as "core" and "shell". In order to investigate whether the behavioral functions of excitatory amino acid receptors differed between these two subregions, rats were administered microinjections of 2-amino-5-phosphonovaleric acid (AP-5), a competitive NMDA antagonist (0, 0.05, 0.2, 0.5, 1.0 microgram/0.5 microliter) into selected central and medial regions of the accumbens. The central and medial sites were assumed to correspond approximately to core and shell subregions, respectively. The animals were tested in two exploratory tasks: the open field and a novel object test. In the open field test, AP-5 significantly decreased peripheral locomotion and center rearing frequency in the central but not the medial group. Locomotion and rearing were not affected by AP5 infusion into a control site, the anterior dorsal striatum (ADS). In the novel object test, animals were tested in the same open field, with prior habituation, and with several novel objects placed within it. In this test, infusions of AP-5 (0, 1.0 microgram/0.5 microliter) decreased the number and duration of contacts with the novel objects in the central but not the medial group. In addition, peripheral and center locomotion were decreased by AP-5 infusions into the central site, whether objects were present or not. In contrast, AP-5 infusions into the medial site elicited an increase in peripheral locomotion in both stimulus conditions. These findings provide behavioral-pharmacological evidence that the central and medial subregions of the nucleus accumbens can be differentiated.(ABSTRACT TRUNCATED AT 250 WORDS)

Computer simulation of human locomotion in extreme conditions

Computer simulation of human locomotion in extreme conditions