Sensory Feedback Induced by Front-Leg Stepping Entrains the Activity of Central Pattern Generators in Caudal Segments of the Stick Insect Walking System

SUMMARYEarlier observations had suggested that cockroaches might show multiple patterns of leg coordination, or gaits, but these were not followed by detailed behavioral or kinematic measurements that would allow a definite conclusion. We measured the walking speeds of cockroaches exploring a large arena and found that the body movements tended to cluster at one of two preferred speeds, either very slow (<10cms ). To highlight the neural control of walking leg movements, we experimentally reduced the mechanical coupling among the various legs by tethering the animals and allowing them to walk in place on a lightly oiled glass plate. Under these conditions, the rate of stepping was bimodal, clustering at fast and slow speeds. We next used high-speed videos to extract three-dimensional limb and joint kinematics for each segment of all six legs. The angular excursions and three-dimensional motions of the leg joints over the course of a stride were variable, but had different distributions in each gait. The change in gait occurs at a Froude number of ~0.4, a speed scale at which a wide variety of animals show a transition between walking and trotting. We conclude that cockroaches do have multiple gaits, with corresponding implications for the collection and interpretation of data on the neural control of locomotion. Supplementary material available online at

Section: Gait Controlmentioning

confidence: 92%

Kinematic and behavioral evidence for a distinction between trotting and ambling gaits in the cockroachBlaberus discoidalis

Bender

Simpson

Tietz

et al. 2011

“…In insects, both temporal and spatial co-ordination among legs is known to depend on sensory feedback (Wendler, 1964;Cruse, 1990;Ritzmann and Büschges, 2007), involving information about limb posture (Wong and Pearson, 1976;Cruse et al, 1984), load (Borgmann et al, 2009;Zill et al, 2009;Zill et al, 2012) and ground contact (Zill et al, 2010;Theunissen and Dürr, 2013). Thus the second objective of this study was to reveal the contribution of a proprioceptive hair field on the accuracy of spatial co-ordination between middle and hindlegs.…”

Section: Introductionmentioning

confidence: 98%

Spatial coordination of foot contacts in unrestrained climbing insects

Theunissen

Vikram

Dürr

2014

Animals that live in a spatially complex environment such as the canopy of a tree, constantly need to find reliable foothold in threedimensional (3D) space. In multi-legged animals, spatial co-ordination among legs is thought to improve efficiency of finding foothold by avoiding searching-movements in trailing legs. In stick insects, a 'targeting mechanism' has been described that guides foot-placement of hind-and middle legs according to the position of their leading ipsilateral leg. So far, this mechanism has been shown for standing and tethered walking animals on horizontal surfaces. Here, we investigate the efficiency of this mechanism in spatial limb coordination of unrestrained climbing animals. For this, we recorded whole-body kinematics of freely climbing stick insects and analysed foot placement in 3D space. We found that touch-down positions of adjacent legs were highly correlated in all three spatial dimensions, revealing 3D co-ordinate transfer among legs. Furthermore, targeting precision depended on the position of the leading leg. A second objective was to test the importance of sensory information transfer between legs. For this, we ablated a proprioceptive hair field signaling the levation of the leg. After ablation, the operated leg swung higher and performed unexpected searching movements. Furthermore, targeting of the ipsilateral trailing leg was less precise in anteroposterior and dorsoventral directions. Our results reveal that the targeting mechanism is used by unrestrained climbing stick insects in 3D space and that information from the trochanteral hair field is used in ipsilateral spatial co-ordination among legs.

“…However, studies have shown the role of local sensory feedback in establishing inter-leg coordination, e.g. in the hawk moth (Johnston and Levine, 1996;Johnston and Levine, 2002) and the stick insect C. morosus (Borgmann et al, 2009;Büschges et al, 1995).…”

Section: Introductionmentioning

confidence: 99%

Inter-leg coordination in the control of walking speed inDrosophila

Wosnitza

Bockemühl

Dübbert

et al. 2012

160

259

SUMMARYLegged locomotion is the most common behavior of terrestrial animals and it is assumed to have become highly optimized during evolution. Quadrupeds, for instance, use distinct gaits that are optimal with regard to metabolic cost and have characteristic kinematic features and patterns of inter-leg coordination. In insects, the situation is not as clear. In general, insects are able to alter inter-leg coordination systematically with locomotion speed, producing a continuum of movement patterns. This notion, however, is based on the study of several insect species, which differ greatly in size and mass. Each of these species tends to walk at a rather narrow range of speeds. We have addressed these issues by examining four strains of Drosophila, which are similar in size and mass, but tend to walk at different speed ranges. Our data suggest that Drosophila controls its walking speed almost exclusively via step frequency. At high walking speeds, we invariably found tripod coordination patterns, the quality of which increased with speed as indicated by a simple measure of tripod coordination strength (TCS). At low speeds, we also observed tetrapod coordination and wave gait-like walking patterns. These findings not only suggest a systematic speed dependence of inter-leg movement patterns but also imply that inter-leg coordination is flexible. This was further supported by amputation experiments in which we examined walking behavior in animals after the removal of a hindleg. These animals show immediate adaptations in body posture, leg kinematics and inter-leg coordination, thereby maintaining their ability to walk.