Mechanosensory encoding of forces in walking uphill and downhill: force feedback can stabilize leg movements in stick insects.

Force feedback could be valuable in adapting walking to diverse terrains, but the effects of changes in substrate inclination on discharges of sensory receptors that encode forces have rarely been examined. In insects, force feedback is provided by campaniform sensilla, mechanoreceptors that monitor forces as cuticular strains. We neurographically recorded responses of stick insect tibial campaniform sensilla to "naturalistic" forces (joint torques) that occur at the hind leg femur-tibia (FT) joint in uphill, downhill, and level walking.

Adaptive load feedback robustly signals force dynamics in robotic model of stepping.

Animals utilize a number of neuronal systems to produce locomotion. One type of sensory organ that contributes in insects is the campaniform sensillum (CS) that measures the load on their legs. Groups of the receptors are found on high stress regions of the leg exoskeleton and they have significant effects in adapting walking behavior.

Sensory signals of unloading in insects are tuned to distinguish leg slipping from load variations in gait: experimental and modeling studies.

In control of walking, sensory signals of decreasing forces are used to regulate leg lifting in initiation of swing and to detect loss of substrate grip (leg slipping). We used extracellular recordings in two insect species to characterize and model responses to force decrements of tibial campaniform sensilla, receptors that detect forces as cuticular strains. Discharges to decreasing forces did not occur upon direct stimulation of the sites of mechanotransduction (cuticular caps) but were readily elicited by bending forces applied to the leg.

A computational model of insect campaniform sensilla predicts encoding of forces during walking.

Control of forces is essential in both animals and walking machines. Insects measure forces as strains in their exoskeletons via campaniform sensilla (CS). Deformations of cuticular caps embedded in the exoskeleton excite afferents that project to the central nervous system.

Evaluation of force feedback in walking using joint torques as "naturalistic" stimuli.

Control of adaptive walking requires the integration of sensory signals of muscle force and load. We have studied how mechanoreceptors (tibial campaniform sensilla) encode "naturalistic" stimuli derived from joint torques of stick insects walking on a horizontal substrate. Previous studies showed that forces applied to the legs using the mean torque profiles of a proximal joint were highly effective in eliciting motor activities.

Gradients in mechanotransduction of force and body weight in insects.

Posture and walking require support of the body weight, which is thought to be detected by sensory receptors in the legs. Specificity in sensory encoding occurs through the numerical distribution, size and response range of sense organs. We have studied campaniform sensilla, receptors that detect forces as strains in the insect exoskeleton.

Rethinking gross anatomy in a compressed time frame: Clinical symptoms, not case studies, as the basis for introductory instruction.

The goal of this observational study was to develop effective approaches to introduce first year medical students to gross anatomy/embryology in a compressed time frame. Pedagogical reorganization of anatomy instruction in the regions of Lower Extremity and Head and Neck was based upon core clinical conditions taught in second-year and USMLE Step 1 board review courses. These conditions were not presented as clinical problems, as many students had limited prior training in medical terminology, but focused upon clinical symptoms, allowing for direct correlation of structure and function.

Identification of the origin of force-feedback signals influencing motor neurons of the thoraco-coxal joint in an insect.

Force feedback from Campaniform sensilla (CS) on insect limbs helps to adapt motor outputs to environmental conditions, but we are only beginning to reveal the neural control mechanisms that mediate these influences. We studied CS groups that affect control of the thoraco-coxal joint in the stick insect Carausius morosus by applying horizontal and vertical forces to the leg stump. Motor effects of ablation of CS groups were evaluated by recording extracellularly from protractor (ProCx) and retractor (RetCx) nerves.

Force dynamics and synergist muscle activation in stick insects: the effects of using joint torques as mechanical stimuli.

Many sensory systems are tuned to specific parameters of behaviors and have effects that are task-specific. We have studied how force feedback contributes to activation of synergist muscles in serially homologous legs of stick insects. Forces were applied using conventional half-sine or ramp and hold functions.

Effects of force detecting sense organs on muscle synergies are correlated with their response properties.

Sense organs that monitor forces in legs can contribute to activation of muscles as synergist groups. Previous studies in cockroaches and stick insects showed that campaniform sensilla, receptors that encode forces via exoskeletal strains, enhance muscle synergies in substrate grip. However synergist activation was mediated by different groups of receptors in cockroaches (trochanteral sensilla) and stick insects (femoral sensilla).

Speed-dependent interplay between local pattern-generating activity and sensory signals during walking in Drosophila.

In insects, the coordinated motor output required for walking is based on the interaction between local pattern-generating networks providing basic rhythmicity and leg sensory signals, which modulate this output on a cycle-to-cycle basis. How this interplay changes speed-dependently and thereby gives rise to the different coordination patterns observed at different speeds is not sufficiently understood. Here, we used amputation to reduce sensory signals in single legs and decouple them mechanically during walking in Drosophila.

Force feedback reinforces muscle synergies in insect legs.

The nervous system solves complex biomechanical problems by activating muscles in modular, synergist groups. We have studied how force feedback in substrate grip is integrated with effects of sense organs that monitor support and propulsion in insects. Campaniform sensilla are mechanoreceptors that encode forces as cuticular strains.

Positive force feedback in development of substrate grip in the stick insect tarsus.

The mechanics of substrate adhesion has recently been intensively studied in insects but less is known about the sensorimotor control of substrate engagement. We characterized the responses and motor effects of tarsal campaniform sensilla in stick insects to understand how sensory signals of force could contribute to substrate grip. The tarsi consist of a chain of segments linked by highly flexible articulations.

WITHDRAWN: Positive force feedback in development of substrate grip in the stick insect tarsus.

The Publisher regrets that this article is an accidental duplication of an article that has already been published, http://dx.doi.org/10.

Directional specificity and encoding of muscle forces and loads by stick insect tibial campaniform sensilla, including receptors with round cuticular caps.

In many systems, loads are detected as the resistance to muscle contractions. We studied responses to loads and muscle forces in stick insect tibial campaniform sensilla, including a subgroup of receptors (Group 6B) with unusual round cuticular caps in oval-shaped collars. Loads were applied in different directions and muscle contractions were emulated by applying forces to the tibial flexor muscle tendon (apodeme).

Force encoding in stick insect legs delineates a reference frame for motor control.

The regulation of forces is integral to motor control. However, it is unclear how information from sense organs that detect forces at individual muscles or joints is incorporated into a frame of reference for motor control. Campaniform sensilla are receptors that monitor forces by cuticular strains.

Encoding of force increases and decreases by tibial campaniform sensilla in the stick insect, Carausius morosus.

Detection of force increases and decreases is important in motor control. Experiments were performed to characterize the structure and responses of tibial campaniform sensilla, receptors that encode forces through cuticular strains, in the middle leg of the stick insect (Carausius morosus). The sensilla consist of distinct subgroups.

Detecting substrate engagement: responses of tarsal campaniform sensilla in cockroaches.

Sensory signals of contact and engagement with the substrate are important in the control and adaptation of posture and locomotion. We characterized responses of campaniform sensilla, receptors that encode forces as cuticular strains, in the tarsi (feet) of cockroaches using neurophysiological techniques and digital imaging. A campaniform sensillum on the fourth tarsal segment was readily identified by its large action potential in nerve recordings.

Neurobiology: reconstructing the neural control of leg coordination.

Walking is adaptable because the timing of movements of individual legs can be varied while maintaining leg coordination. Recent work in stick insects shows that leg coordination set by interactions of pattern generating circuits can be overridden by sensory feedback.

Sensory signals of unloading in one leg follow stance onset in another leg: transfer of load and emergent coordination in cockroach walking.

The transfer of load from one leg to another is an essential component in walking, but sense organs that signal this process have rarely been identified. We used high-speed digital imaging and neurophysiological recordings to characterize activities of tibial campaniform sensilla, receptors that detect forces via cuticular strains, in the middle legs of cockroaches during walking. Previous studies demonstrated that the distal tibial sensilla discharge when body load is suddenly decreased in freely standing animals.

Neurobiology: venom of wasps and initiation of movements.

The ability to initiate movements can be impaired in some brain injuries even though motor actions proceed normally once they are begun. The effects of venom that wasps use in preying upon cockroaches could provide insights into this problem.

Post-embryonic development of cuticular caps of campaniform sensilla of the cockroach leg: potential implications in scaling force detection.

All animals generate progressively larger forces as they increase in size and mass. Their abilities to detect these forces must be similarly adjusted. In insects, campaniform sensilla monitor strains in the exoskeleton and provide information about forces acting upon the legs.

Invertebrate neurobiology: sensory processing in reverse for backward walking.

Humans and many other animals can readily walk forward or backward. In insects, the nervous system changes the effects of sense organs that signal forces on a leg when the direction of walking is reversed.

Tuning posture to body load: decreases in load produce discrete sensory signals in the legs of freely standing cockroaches.

Decreases in load are important cues in the control of posture and walking. We recorded activities of the tibial campaniform sensilla, receptors that monitor forces as strains in the exoskeleton, in the middle legs of freely moving cockroaches. Small magnets were attached to the thorax and body load was changed by applying currents to a coil below the substrate.

Common motor mechanisms support body load in serially homologous legs of cockroaches in posture and walking.

We studied the mechanisms underlying support of body load in posture and walking in serially homologous legs of cockroaches. Activities of the trochanteral extensor muscle in the front or middle legs were recorded neurographically while animals were videotaped. Body load was increased via magnets attached to the thorax and varied through a coil below the substrate.