Results of studies with this device helped to ascertain what patterns of gait would be most energy efficient and be easiest to control during exploration of the moon's surface.
Ideally, a ground surface interface which might be called a haptic interface for the feet is a device that permits the user to experience active sensations of walking, running, climbing, etc. Such a device must allow the user to move his or her limbs in a natural fashion and provide feedback to the user that is matched to the space-time characteristics of the simulated surface e. Locomotion interfaces can provide the experience of moving about in a large space while actually being confined to a small space.
To the extent that such devices reduce the workspace volume of the synthetic environment SE system, they reduce the requirements on the other system components. For example, both the subsystem for general monitoring of position and the subsystem for grounding of the haptic interface for the hands need not cover large spatial regions.
The term treadmill originated to describe a form of prison punishment: walking on an endless belt driven by rollers has risen socially to a form of voluntary exercise, and the technology has advanced mainly to serve the commercial demands of health clubs.
A typical high-performance treadmill for example, one made by the Quinton Corp. The motor and belt have a combined stiffness that allows the horizontal ground contact forces usually applied in walking to be manipulated.
It is microprocessor-controlled so that users can preprogram their preferred exercise regimens, but real-time control must be achieved by a custom interface. The entire base can be inclined under the control of a motorized drive system, which could also be controlled in real time by an external custom interface. A major limitation of commercial treadmills is their one-dimensional nature.
A first step in expanding their capabilities would be the development of systems with a belt for each foot. A split-belt system would be. The laboratory of Esther Thelen at Indiana University has a custom-built device suitable for such research with infants. A useful addition to treadmill systems is being developed by the Kistler Corporation. This system has a force-plate under the belt that can sense the vertical ground reaction forces produced during locomotion.
This could potentially provide information that could be fed back to the belt through a real-time control algorithm to simulate slippery ground surfaces, for example.
Treadmills will be limited to use in SEs that involve locomotion on uniform but not necessarily horizontal ground surfaces. Stair climbing exercise machines are just vertical treadmills, in this sense. It may be desirable to generate SEs with arbitrary footing conditions, such as sandy, muddy, and icy conditions, discrete obstacles, stairs, wobbly platforms.
A general approach to realizing these conditions would be to develop individual six-degrees-of-freedom platforms or shoes for each foot. Such a system would be analogous to force-feedback haptic devices for the hands. Challenges to development include deciding whether anthropomorphic linkages are necessary, identifying drive systems with sufficient power and bandwidth, and learning more about the role of impedance matching in human locomotion. Programs that have led to the development of improved bicycles and human-powered aircraft have faced some of these problems especially impedance matching and may provide an initial strategy and some data for the present application.
Noninertial displays induce a sense of whole-body movement in stationary individuals although they can also be used in conjunction with moving bases. Many simulators currently work by presenting stationary individuals with stimuli that are normally associated with body motion so as to enhance a sense of self-motion. This section concentrates on new approaches in this area. A variety of devices are being used at present for stimulating individuals with representations of scenes that change in a way that is consistent with body motion through the environment in a vehicle.
The major characteristic of visual displays to be used in SEs involving whole-body motion and locomotion is a large stereoscopic field of view. HMDs require. A high-resolution display is not critical for visual induction of illusory self-motion. However, if a low-resolution display is used, the visual scene must contain low spatial frequencies and strong pictorial depth cues.
Some real visual scenes contain only relatively high spatial frequency textures. If a high-fidelity facsimile of such a scene is moved, an observer experiences self-motion; however, presentation through a low-resolution display unit does not result in perceived self-motion. Obviously, the need for wide and high fields of view, the preference for high resolution, and changes in the visual scene to accommodate head movements will generate a high demand for computational and rendering speeds.
Although there is no clear psychophysical data on required frame rates, occasional skips in a display that is being generated at an average rate of 30 frames per second can reduce the sense of virtual body motion assuming there is no moving base or any other supplementary stimulus.
Research that may help guide the integration of visual displays with other SE subsystems for simulating human locomotion is being carried out in several university laboratories Lackner and DiZio, , ; Warren, One device used for such research includes an independently controllable circular treadmill and visual surround developed by Lackner and DiZio at Graybiel Laboratory, Brandeis University.
The circular treadmill is advantageous because combinations of overground and treadmill walking can be combined in the same apparatus. The subject can move through space without walking away from the treadmill and visual display. In this device it is possible to have a subject walk in place at a set pace on the treadmill while the visual display presents a scene whose movement varies in speed and direction.
In this situation, the subject perceives whole-body movement with a range of speeds and directions and varying patterns of stepping consistent with it Lackner and DiZio, Warren and his colleagues at Brown University have shown that altering the normal ebb and flow of visual feedback expansion-contraction, vertical oscillation associated with the walking cycle can alter the pattern of locomotion and the perception of self-motion.
This points out the need for developing physical models of the visual feedback from voluntary movement and incorporating it into visual simulations of whole-body movement. Two techniques have been used in this area: one involves presenting a binaural auditory stimulus that exhibits the same spatial and temporal pattern as it would during movement through a natural environment; the.
Induction of illusory self-rotation by simulating a sound field rotating around the head of a stationary subject is an example of the former Lackner, , and augmentation of visually induced self-motion by virtual wind or engine noise in an aircraft simulator is an example of the latter Previc et al. Technology for realizing the first approach is discussed in Chapter 3. There are no adequate psychophysical data to specify the exact characteristics of auditory displays that are critical for inducing a sense of self-motion.
However, neither the number of possible sound sources nor the fidelity with which these sources are simulated is critical for inducing a sense of self-motion. Of more importance is creating the impression of a virtual terrain through which self-motion can occur and, toward this end, the ability to simulate a rich set of sound reflecting surfaces. Technology for simulation of echos and reverberation is also discussed in Chapter 3. A sense of body motion in a stationary subject can also be elicited artificially by stimulating the semicircular canals of the vestibular system.
One method consists of directing streams of cool air or water into one auditory canal and warm into the other. A few seconds of such caloric irrigation can lead to several minutes of perceived self-motion and nystagmus.
There are at least two mechanisms governing this response. Altering the temperature of the temporal bone around the external auditory canal 1 locally alters the temperature of the membranous labyrinth of the lateral semicircular canal encased within the bone, and thereby causes a convection current that mechanically stimulates the hair cells of the crista Barany, and 2 alters the temperature of the hair cells and primary afferent fibers by direct conduction, leading to modulation of their activity levels Coats and Smith, The convection component accounts for about 75 percent of the response Minor and Goldberg, This is a standard clinical technique for testing vestibular function that could, in principle, be adapted to SE technology.
Its drawbacks for application to SEs are that the latency to onset is about 15 s, the effect is limited to the yaw plane of the head, and it can be nauseogenic. Galvanic stimulation achieved by applying a current between the mastoid bones can also be used to elicit apparent self-motion by directly exciting the vestibular end organs. Even in darkness, a sense of moving through the environment, as well as compensatory postural and oculomotor reactions, arises when.
These results demonstrate that if individuals produce the locomotory movements that normally propel them through space but without actually displacing , the associated muscular, joint, and tactile feedback, as well as efferent signals, lead to an experience of self-motion.
Even if no locomotor movements are made, patterns of cutaneous or muscular afference that are normally associated with movement through the environment can induce apparent self-motion. One method for achieving this is passing a moving surface against the soles of the feet or the palms of the hands; individuals then report a sense of body motion in the opposite direction.
Presenting differential surface speeds to the hands and feet can lead to the feeling that the torso is twisting Lackner and DiZio, Another method of eliciting whole-body motion utilizes muscle vibration. If a standard physiotherapy vibrator oscillating at Hz is applied to the body surface overlying a muscle tendon, such as the Achilles tendon, the spindle receptors of the associated muscle are stretched relative to the extrafusal force-generating fibers because of differential viscoelastic properties.
This increases the output of muscle spindle Ia and probably Ib fibers relative to the level appropriate for maintenance of the desired posture. The muscle contracts reflexively to relax the spindle and restore its output to the original level, and the limb controlled by the muscle moves—for example, the ankle extends.
This is called a tonic vibration reflex TVR. If a limb is prevented from moving under the influence of a TVR, the spindle activity remains high, and a limb movement will be experienced that is consistent with the muscle's being stretched, for example, flexion of the ankle Goodwin et al. When standing on the ground, ankle flexion would ordinarily mean that either the ground is tilted up or the body is tilted forward. Vibrating the Achilles tendons of a subject who is restrained in a standing posture thus elicits an experience of falling forward Lackner and Levine, Lackner has shown that virtually any apparent movement of the body can be elicited by vibration of the proper postural muscles.
The movements experienced can be supranormal in the sense that anatomically impossible apparent body configurations are generated—for example, hyperextension of limbs.
The research and development efforts on whole-body motion displays that are needed for development of the SE field, beyond those directed. Inertial displays Relatively simple, partial inertial displays need to be developed to replace complex, full-inertial displays because of the cost factor.
Currently, however, there is little technology available for reproducing critical subparts of the accelerations that are present in real situations involving active or passive transport through a large volume.
Development of such systems should take advantage of the intimate relationship that normally exists between whole-body movement in inertial space and the contact forces that must be applied to the body in order to accelerate it.
For example, when a subject is accelerated, the vestibular system senses the inertial motion and cutaneous receptors respond to the contact force propelling the body. Research needs to be focused on this area of haptic-vestibular interactions. An area of technology development that could assist in exploring the roles of these two factors is new padding materials that can allow experimenters to systematically manipulate the distribution of contact forces on the body surface during accelerations in an inertial display.
Electrorheological materials hold some promise for research applications and eventually, perhaps, for SE displays. Another area that could benefit from attention is how active movements affect the perception of whole-body motion induced by noninertial whole-body motion displays. Achieving the same body-referenced limb or head motions requires different muscle forces in stationary and accelerative environments and also leads to different sensory feedback because of noncontact inertial forces on the limb.
The lack of expected feedback for the state of body motion being experienced can inhibit the perception of self-motion and lead to a perceptual mapping that better fits all the current sensors. Making head movements during visually induced illusory self-motion can suppress or enhance the sense of self-motion, depending on whether those movements are in the plane of motion and begin when visual stimulation begins or are out of the motion plane and begin after its onset.
Basic research may help determine methods for preventing the inhibition of perceived whole-body motion when the head or arms move or enhancing a weak sense of self-motion. A crucial issue here concerns the extent to which methods can be found for inducing people to perceive contact cues provided by means of haptic VE displays as noncontact inertial perturbations of their limbs. Locomotion displays Current locomotion displays consist of constant-speed linear treadmills that can provide an individual confined to a small volume with the pattern of visual, auditory, and tactile cues that.
However, the only situation that can physically be mimicked by such a device is constant-velocity, linear locomotion. There are several routes to expanding on these capabilities.
First, visual, auditory, and other displays may be used to enhance simple treadmills. To accomplish this, psychophysical work is needed to determine the degree to which perceived acceleration and deceleration including rotation can be elicited by such displays, even when it is absent in the mechanical stimulus.
Another direction is to improve the treadmills. Linear acceleration can be simulated if hardware and software interfaces are developed that allow control of treadmill acceleration and deceleration when propulsive step forces are generated by the subject.
Another advance would be treadmills with a belt for each foot. This would be the simplest version of individual haptic interfaces for each foot and would better allow simulation of changes in direction, i. Finally, research should be performed with a view toward providing a system that has separate multidegree-of-freedom platforms for each foot with appropriate sensors and feedback subsystems that can mimic the conditions of walking on level or inclined ground, climbing stairs, and navigating around and over obstacles.
The padding materials mentioned above for inertial displays designed for passive whole-body motion might also be useful here for simulating different ground conditions. Visual displays Requirements on visual displays imposed by consideration of passive whole-body motion or active locomotion are similar to those previously mentioned in other chapters: the best displays would be an HMD that is inexpensive, lightweight, and comfortable; has high resolution and a wide field of view both horizontally and vertically ; and includes both full-color images and refined stereopsis.
Of all these characteristics, color is probably the least important. Auditory displays The most important needs in this area concern those features of the synthesized acoustic field relevant to the illusion of moving through the field.
Aside from simulating changes in the direction of sound sources, changes in the apparent distance of the sources and changes in the apparent location of the individual within the reflecting environment are important.
Thus, one of the main special needs associated with passive whole-body motion and active locomotion in this area concerns the inclusion of a rich array of reflecting surfaces in the acoustic simulation.
Motion sickness Over the years, motion sickness has arisen as a significant problem with all new modes of passive transport of the body Guignard and McCauley, Clearly it will be a problem in SEs as well, especially those involving virtual acceleration and motion of the body Biocca, Reports of sickness in SEs are already common.
McCauley, ; McCauley and Sharkey, Research should be directed toward identifying the factors that determine which SEs are especially provocative and how to minimize this while preserving the efficacy of the system. Mechanical factors, such as altered inertial loading of the head by HMDs, as well as sensory factors, need to be considered.
Also, attention must be given to elements of the sopite syndrome that are more subtle then those usually associated with motion sickness. Sensorimotor loops Many SE systems introduce distortions, time delays, gain changes, and statistical variability noise between voluntary movements and associated patterns of sensory feedback. Systematic research is necessary to determine the extent to which these factors degrade performance and the subjective state of the user.
Acceptable tolerances should be determined for these factors, as well as for the extent to which sensory feedback across different modalities must be in temporal synchrony. Multisensory and motor influences on orientation This is a critical research area for designing effective VEs that involve locomotion and haptic exploration. Very little is known at present about these influences, except that they are highly complex and pervasive. They are difficult to identify as such because so much of what we take for granted in our everyday activities, such as the perceptual stability of our environment and our bodies during movement, is due to their action.
Despite widespread interest in virtual reality, research and development efforts in synthetic environments SE —the field encompassing virtual environments, teleoperation, and hybrids—have remained fragmented.
Virtual Reality is the first integrated treatment of the topic, presenting current knowledge along with thought-provoking vignettes about a future where SE is commonplace. This volume discusses all aspects of creating a system that will allow human operators to see, hear, smell, taste, move about, give commands, respond to conditions, and manipulate objects effectively in a real or virtual environment.
The committee of computer scientists, engineers, and psychologists on the leading edge of SE development explores the potential applications of SE in the areas of manufacturing, medicine, education, training, scientific visualization, and teleoperation in hazardous environments.
The committee also offers recommendations for development of improved SE technology, needed studies of human behavior and evaluation of SE systems, and government policy and infrastructure.
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Visit NAP. Looking for other ways to read this? No thanks. Virtual Reality: Scientific and Technological Challenges. Page Share Cite. Sensorimotor Stability During Self-Motion. Head Movements. Arm Movements. Body Orientation. Illusions of Self-Motion. Motion Sickness. Susceptibilities to similar forms of vestibular stimulation also do not correlate that well for different test situations, such as caloric irrigation 1 Velocity storage was hypothesized to account for spatio-temporal differences between signals about rotational velocity of the body in space and responses mediated through the vestibular nuclei.
He explores the roles of mechanical forces in the process of morphogenesis and their impact on the genetic program. Cell division and differentiation depend on massive and rapid organelle remodelling.
The group recently showed that differentiating mouse-brain multiciliated cells could also implement this mitotic clocklike regulatory circuit to orchestrate subcellular reorganisation associated with their differentiation.
The postmitotic progenitors fine-tune mitotic oscillator activity to drive the orderly progression of centriole production, maturation, and motile ciliation while avoiding the mitosis commitment threshold.
Insufficient CDK1 activity hinders differentiation, whereas excessive activity accelerates differentiation yet drive postmitotic progenitors into mitosis. Dr Meunier will further discuss how these postmitotic cells can redeploy and calibrate the mitotic oscillator to uncouple cytoplasmic from nuclear dynamics to drive centriole amplification. Since then, she has been studying how multiciliated cells amplify centrioles, the structures that anchor on the cell membrane to nucleate motile cilia.
She developed cell culture systems and imaging tools to unveil the dynamics and molecular control of centriole amplification in mouse brain multiciliated cells. One of the most fundamental issues in understanding the earliest stage of the evolution of multicellularity is how the simplest such organisms can exhibit coordinated behaviour in the absence of a central nervous system.
Green algae belonging to the lineage that spans from Chlamydomonas to Volvox can serve as model organisms for studying many phenomena in biological fluid dynamics, and are remarkably well-suited to this issue. In this lecture, Professor Goldstein first reviews the group's earlier work on phototaxis in Volvox , which showed by experiment and theory how a rather precise tuning between the timescale of adaptation in the flagellar photoresponse and the organism's rotational period allows for accurate steering.
Professor Goldstein then discusses extensions of this work to Chlamydomonas and the fascinating cell organism Gonium. Taken together, these investigations shed light on the evolutionary steps involved in multicellular phototaxis. Cilia motility in the left-right organiser LRO is a common feature for generating the directional flow necessary for embryonic symmetry breaking. Cilia-mediated flow operates in the LRO to control and maintain the establishment of the internal organ asymmetric polarity.
The group's goal is to understand the dynamics and the roles of biological flow during the process of symmetry breaking. The group uses live imaging techniques, cell biology and genetic analysis to characterise the physical stimuli and the molecular mechanisms that specify cell responses to flow forces.
Here Dr Vermot will discuss how cilia-mediated directional flow is obtained in the KV and its biophysical origin in vivo. Cilias' spatial orientation is a key functional feature for the generation of directional flow and LR determination.
Dr Vermot will also discuss the group's multi-scale live-imaging based methodology to study cilia features in 3D developed to understand the potential mechanism s behind cilia orientation. Overall this work provide key insights into the dynamics of motile cilia orientation during LR determination and potential mechanisms controlling it. In mammalian brains, airways and fallopian tubes, a multitude of motile cilia beat in synchrony enabling efficient fluid transport.
Professor Cicuta will review our understanding of this process based on simple physical models where hydrodynamic interaction leads to large-scale collective dynamics. In the biological systems, the nature of the interaction between cilia is still under debate. Professor Cicuta supports this view with simulations of a minimal model of cilia interacting hydrodynamically, showing the same trends observed experimentally.
Overall the group suggests that hydrodynamic forces between cilia are sufficient as a mechanism behind the synchronisation of motile cilia in the brain of mammals. Developing new experimental techniques to study the mechanics and dynamics of soft and biological systems is the heart of his research. Ciliated mucosal surfaces, including the human airways, regularly harbour microbial symbionts. The biomechanical aspects of this association process are not well understood.
The group proposes that topography and kinematics of ciliated surfaces can generate diverse microhabitats for the recruitment and establishment of the microbiome. In a case study presented here, the group studied the fluid mechanics of cilia-microbiome interactions in an accessible model system, the Hawaiian bobtail squid, which reliably captures and isolates their bacterial symbiont Vibrio fischeri from inhaled seawater.
In joint experimental and computational work the group reveals that two distinct cilia populations act together to produce a complex flow field that facilitates recruitment of symbionts. Specifically, the flow sieves Vibrio-sized particles into a sheltered microniche where local ciliary currents enhance the diffusion of biochemical signals and promote biofilm formation. Dr Nawroth will present these results and introduce the methods, models and metrics the group developed to assess cilia-bacteria interactions.
Finally, Dr Nawroth will discuss how these findings might inform our understanding of cilia-microbiome and cilia-pathogen interactions on mucosal surfaces in other organisms, including humans. Dr Nawroth is conducting cross-disciplinary research in the field of bacteria-host interactions and cilia functions in aquatic organisms as well as human organ tissues to understand basic mechanisms and develop novel research tools.
Based on their Organs-on-Chips technology, Emulate is developing a new living system that places cells within micro-engineered environments, allowing researchers to understand how different diseases, medicines, chemicals and foods affect human health. At Emulate, Dr Nawroth heads the development of the Bronchial Airway-Chip which emulates the biomechanics of ciliary mucus transport.
Nawroth has more than six years' experience in academia and industry in leadership roles in basic research, discovery, and technology development. She has co-authored over 15 peer-reviewed publications and multiple patents. Some animal species such as the planarian flatworm Schmidtea mediterranea use multiciliated cells for locomotion.
Motile cilia beat in a whip-like pattern at the surface of the ventral multiciliated epidermis to allow animal translocation of planarians along the substrate. Directional locomotion requires the proper polarisation of cilia along the polarity axes of the body plan.
Polarity proteins regulate cytoskeleton architecture to coordinate the rotational polarity of centrioles, from which cilia are assembled, with the planar polarity of the epithelium. Cytoskeletal networks are anchored at the centrioles via two types of centriolar appendages, which are essential for the proper polarisation and organization of centrioles.
The group has identified proteins required for the assembly of centriolar appendages in planarians, and found that they allow organising a centriole network with remarkable left-right asymmetric properties. These results provide novel insights into how animals can build mirror symmetric body plans from chiral cellular constituents.
Juliette Azimzadeh studied cytoskeleton organization in plants during her PhD. In she started her own group at the Jacques Monod institute in Paris.
Her current research focuses on understanding how centrioles polarize in response to signalling pathways using planarian flatworms as a model system. She is also interested in the evolution of the molecular architecture and function of centrioles and centrosomes. The ability for self-movement is a primary signature of life: it is the means by which the simplest organisms migrate toward the 'good' and away from the 'bad', moving up gradients of nutrients or light, escaping from harmful chemicals or predators.
Among the most evolutionarily ancient of these strategies is motility through a fluid environment using slender, actively-actuated appendages called cilia and flagella. In different species, these occur in diverse forms and configurations. However wherever multiple cilia arise, there is a clear need to coordinate these appendages effectively for swimming, navigation, or generation of directional flows past surfaces.
Even the simplest unicellular organisms have been found capable of exacting precise and surprising patterns or gaits reminiscent of the breaststroke, trot, pronk, gallop etc, which are normally only associated with vertebrates. Here, the group reveals at the single-cell level the extent to which these gaits of ciliary locomotion are subject to intracellular control, producing motive behaviours that are modulated dynamically depending on perceived changes in environmental circumstances.
Finally, Dr Wan shall demonstrate the functional limits of speed and sensitivity in this unique and ancient sensory-motor apparatus. The inner ear, which mediates the senses of hearing and balance, derives from a simple ectodermal vesicle in the vertebrate embryo. In the zebrafish, every cell of the otic vesicle is ciliated, and at least three different ciliary subtypes can be distinguished on the basis of axoneme length and motility. Long, immotile kinocilia on the sensory hair cells tether the otoliths, biomineralised aggregates of calcium carbonate and protein.
Motile cilia at the poles of the otic vesicle contribute to the accuracy of otolith tethering, but neither the presence of cilia nor ciliary motility are absolutely required for this process. Instead, otolith tethering is dependent on the presence of hair cells and the function of the glycoprotein Otogelin.
Professor Whitfield will present imaging of cilia in the zebrafish ear and discuss the search for the elusive otolith precursor-binding factor, proposed to be located at the kinociliary tip. Her lab in Sheffield studies the developing vertebrate inner ear, using the zebrafish as a model system.
The ear is a fascinating system for study, due to its complex three-dimensional arrangement of interlinked ducts and chambers, and multitude of different cell types, including neurons, sensory hair cells, supporting and secretory cells. The entire organ develops from otic vesicle, an epithelium bearing both motile and immotile cilia. In ciliary swimmers, ciliary beating, arrests, and changes in beat frequency are often coordinated across extended or discontinuous surfaces.
To understand how such coordination is achieved, the group studied the ciliated larvae of Platynereis dumerilii , a marine annelid. Platynereis larvae have segmental multiciliated cells that regularly display spontaneous coordinated ciliary arrests. With whole-body connectomics, activity imaging, transgenesis, and neuron ablation the group characterised the entire ciliomotor circuitry of Platynereis.
The circuit consists of cholinergic, serotonergic, and catecholaminergic ciliomotor neurons. The synchronous rhythmic activation of cholinergic cells drives the coordinated arrests of all cilia. The serotonergic cells are active when cilia are beating.
Serotonin inhibits the cholinergic rhythm, and increases ciliary beat frequency. Based on their connectivity and alternating activity, the catecholaminergic cells may generate the rhythm.
The ciliomotor circuitry thus constitutes a stop-and-go pacemaker system for the whole-body coordination of ciliary locomotion. The cholinergic neurons can also be activated upon hydrodynamic stimulation. This response is part of the startle reaction that contributes to predator avoidance. Coordinated beating of motile cilia leads to a directional fluid flow, which is important for various biological processes from respiration to reproduction.
In the nervous system, motile ciliary beating of ependymal cells allows the cerebrospinal fluid CSF to flow through the ventricular system.
Such flow plays a central role in the nervous system as human patients or animal models with ciliary defects develop neurological features including hydrocephalus and spine curvature. Still, very little is known about how the nervous system generates and regulates specific flow patterns and how flow controls neural activity and animal behaviour. Here, Dr Jurisch-Yaksi will first describe the mechanisms used by motile cilia to generate specific flow pattern in the zebrafish olfactory epithelium and the function of the flow in olfactory processing.
Effectively, our analyses show that for different species of the same size, home range size, daily movement distance, geographic range, group size, terrestriality, diet breadth, trophic level and habitat breadth do not relate to NCOT.
Furthermore, despite the fact that animals which can run faster or more energetically cheaply perhaps have the opportunity to roam more extensively and those with greater energy output might be predicted to carry greater energy stores to buffer against short falls , neither maximum running speed nor percentage body fat levels were related to NCOT. Thus NCOT appears to be disconnected from animal foraging behaviour, broader measures of energetics and varying aspects of ecology.
If either or both possibilities are true, in turn it is important to understand why NCOT has little ecological relevance. Pontzer argues that most extant terrestrial animals may have already evolved to be efficient foragers.
Harris and Steudel report that details of prey pursuit and capture are the factors that describe hind limb length, in contrast finding no predictive power in home range size or daily movement distance. Perhaps other physical factors that influence locomotion energy efficiencies, such as leg muscle mass, for similar reasons are also under minimal selection for enhancement in terms of energy efficiencies, particularly in species for which locomotion costs are a relatively small proportion of their total energy expenditure NCOT, calculated as the slope of the linear fit between rate of energy expenditure and locomotion speed, tends towards the total energy costs of locomotion per unit distance at high running speeds However, the majority of movements by animals are conducted at low speeds relative to their maximum obtainable , , , Furthermore, animals often incur additional energy costs while walking associated with, for example, intermittent locomotion , turning , and negotiating various terrains e.
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