Campaniform sensilla

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Sasha N Zill - One of the best experts on this subject based on the ideXlab platform.

  • Force dynamics and synergist muscle activation in stick insects: the effects of using joint torques as mechanical stimuli
    Journal of Neurophysiology, 2018
    Co-Authors: Sasha N Zill, Ansgar Büschges, Sumaiya Chaudhry, Chris J. Dallmann, Josef Schmitz
    Abstract:

    The effects of force receptors (Campaniform sensilla) on leg muscles and synergies were characterized in stick insects using both ramp and hold functions and waveforms of joint torques calculated b...

  • Effects of force detecting sense organs on muscle synergies are correlated with their response properties.
    Arthropod Structure & Development, 2017
    Co-Authors: Sasha N Zill, Josef Schmitz, Sumaiya Chaudhry, David Neff, Annelie Exter, Ansgar Büschges
    Abstract:

    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). The factors underlying the differential effects are unclear as the responses of femoral Campaniform sensilla have not previously been characterized. The present study characterized the structure and response properties (via extracellular recording) of the femoral sensilla in both insects. The cockroach trochantero-femoral (TrF) joint is mobile and the joint membrane acts as an elastic antagonist to the reductor muscle. Cockroach femoral Campaniform sensilla show weak discharges to forces in the coxo-trochanteral (CTr) joint plane (in which forces are generated by coxal muscles) but instead encode forces directed posteriorly (TrF joint plane). In stick insects, the TrF joint is fused and femoral Campaniform sensilla discharge both to forces directed posteriorly and forces in the CTr joint plane. These findings support the idea that receptors that enhance synergies encode forces in the plane of action of leg muscles used in support and propulsion.

  • Force feedback reinforces muscle synergies in insect legs.
    Arthropod Structure & Development, 2015
    Co-Authors: Sasha N Zill, Ansgar Büschges, Sumaiya Chaudhry, Josef Schmitz
    Abstract:

    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. We tested the hypothesis that integration of force feedback from receptors of different leg segments during grip occurs through activation of specific muscle synergies. We characterized the effects of Campaniform sensilla of the feet (tarsi) and proximal segments (trochanter and femur) on activities of leg muscles in stick insects and cockroaches. In both species, mechanical stimulation of tarsal sensilla activated the leg muscle that generates substrate grip (retractor unguis), as well as proximal leg muscles that produce inward pull (tibial flexor) and support/propulsion (trochanteral depressor). Stimulation of Campaniform sensilla on proximal leg segments activated the same synergistic group of muscles. In stick insects, the effects of proximal receptors on distal leg muscles changed and were greatly enhanced when animals made active searching movements. In insects, the task-specific reinforcement of muscle synergies can ensure that substrate adhesion is rapidly established after substrate contact to provide a stable point for force generation.

  • Positive force feedback in development of substrate grip in the stick insect tarsus
    Arthropod Structure & Development, 2014
    Co-Authors: Sasha N Zill, Ansgar Büschges, Sumaiya Chaudhry, Annelie Exter, Josef Schmitz
    Abstract:

    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. Morphological studies showed that one to four Campaniform sensilla are located on the distal end of each segment. Activities of the receptors were recorded neurographically and sensilla were identified by stimulation and ablation of their cuticular caps. Responses were characterized to bending forces and axial loads, muscle contractions and to forces applied to the retractor apodeme (tendon). The tarsal sensilla effectively encoded both the rate and amplitude of loads and muscle forces, but only when movement was resisted. Mechanical stimulation of the receptors produced activation of motor neurons in the retractor unguis and tibial flexor muscles. These findings indicate that Campaniform sensilla can provide information about the effectiveness of the leg muscles in generating substrate adherence. They can also produce positive force feedback that could contribute to the development of substrate grip and stabilization of the tarsal chain.

  • directional specificity and encoding of muscle forces and loads by stick insect tibial Campaniform sensilla including receptors with round cuticular caps
    Arthropod Structure & Development, 2013
    Co-Authors: Sasha N Zill, Ansgar Büschges, Sumaiya Chaudhry, Josef Schmitz
    Abstract:

    Abstract 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). All sensilla 1) were maximally sensitive to loads applied in the plane of joint movement and 2) encoded muscle forces but did not discharge to unresisted movements. Identification of 6B sensilla by stimulation of cuticular caps demonstrated that receptor responses were correlated with their morphology. sensilla with small cuticular collars produced small extracellular potentials, had low thresholds and strong tonic sensitivities that saturated at moderate levels. These receptors could effectively signal sustained loads. The largest spikes, derived from sensilla with large cuticular collars, had strong dynamic sensitivities and signaled a wide range of muscle forces and loads. Tibial sensilla are apparently tuned to produce no responses to inertial forces, as occur in the swing phase of walking. This conclusion is supported by tests in which animals 'stepped' on a compliant surface and sensory discharges only occurred in stance.

Josef Schmitz - One of the best experts on this subject based on the ideXlab platform.

  • Force dynamics and synergist muscle activation in stick insects: the effects of using joint torques as mechanical stimuli
    Journal of Neurophysiology, 2018
    Co-Authors: Sasha N Zill, Ansgar Büschges, Sumaiya Chaudhry, Chris J. Dallmann, Josef Schmitz
    Abstract:

    The effects of force receptors (Campaniform sensilla) on leg muscles and synergies were characterized in stick insects using both ramp and hold functions and waveforms of joint torques calculated b...

  • Effects of force detecting sense organs on muscle synergies are correlated with their response properties.
    Arthropod Structure & Development, 2017
    Co-Authors: Sasha N Zill, Josef Schmitz, Sumaiya Chaudhry, David Neff, Annelie Exter, Ansgar Büschges
    Abstract:

    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). The factors underlying the differential effects are unclear as the responses of femoral Campaniform sensilla have not previously been characterized. The present study characterized the structure and response properties (via extracellular recording) of the femoral sensilla in both insects. The cockroach trochantero-femoral (TrF) joint is mobile and the joint membrane acts as an elastic antagonist to the reductor muscle. Cockroach femoral Campaniform sensilla show weak discharges to forces in the coxo-trochanteral (CTr) joint plane (in which forces are generated by coxal muscles) but instead encode forces directed posteriorly (TrF joint plane). In stick insects, the TrF joint is fused and femoral Campaniform sensilla discharge both to forces directed posteriorly and forces in the CTr joint plane. These findings support the idea that receptors that enhance synergies encode forces in the plane of action of leg muscles used in support and propulsion.

  • Force feedback reinforces muscle synergies in insect legs.
    Arthropod Structure & Development, 2015
    Co-Authors: Sasha N Zill, Ansgar Büschges, Sumaiya Chaudhry, Josef Schmitz
    Abstract:

    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. We tested the hypothesis that integration of force feedback from receptors of different leg segments during grip occurs through activation of specific muscle synergies. We characterized the effects of Campaniform sensilla of the feet (tarsi) and proximal segments (trochanter and femur) on activities of leg muscles in stick insects and cockroaches. In both species, mechanical stimulation of tarsal sensilla activated the leg muscle that generates substrate grip (retractor unguis), as well as proximal leg muscles that produce inward pull (tibial flexor) and support/propulsion (trochanteral depressor). Stimulation of Campaniform sensilla on proximal leg segments activated the same synergistic group of muscles. In stick insects, the effects of proximal receptors on distal leg muscles changed and were greatly enhanced when animals made active searching movements. In insects, the task-specific reinforcement of muscle synergies can ensure that substrate adhesion is rapidly established after substrate contact to provide a stable point for force generation.

  • Positive force feedback in development of substrate grip in the stick insect tarsus
    Arthropod Structure & Development, 2014
    Co-Authors: Sasha N Zill, Ansgar Büschges, Sumaiya Chaudhry, Annelie Exter, Josef Schmitz
    Abstract:

    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. Morphological studies showed that one to four Campaniform sensilla are located on the distal end of each segment. Activities of the receptors were recorded neurographically and sensilla were identified by stimulation and ablation of their cuticular caps. Responses were characterized to bending forces and axial loads, muscle contractions and to forces applied to the retractor apodeme (tendon). The tarsal sensilla effectively encoded both the rate and amplitude of loads and muscle forces, but only when movement was resisted. Mechanical stimulation of the receptors produced activation of motor neurons in the retractor unguis and tibial flexor muscles. These findings indicate that Campaniform sensilla can provide information about the effectiveness of the leg muscles in generating substrate adherence. They can also produce positive force feedback that could contribute to the development of substrate grip and stabilization of the tarsal chain.

  • directional specificity and encoding of muscle forces and loads by stick insect tibial Campaniform sensilla including receptors with round cuticular caps
    Arthropod Structure & Development, 2013
    Co-Authors: Sasha N Zill, Ansgar Büschges, Sumaiya Chaudhry, Josef Schmitz
    Abstract:

    Abstract 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). All sensilla 1) were maximally sensitive to loads applied in the plane of joint movement and 2) encoded muscle forces but did not discharge to unresisted movements. Identification of 6B sensilla by stimulation of cuticular caps demonstrated that receptor responses were correlated with their morphology. sensilla with small cuticular collars produced small extracellular potentials, had low thresholds and strong tonic sensitivities that saturated at moderate levels. These receptors could effectively signal sustained loads. The largest spikes, derived from sensilla with large cuticular collars, had strong dynamic sensitivities and signaled a wide range of muscle forces and loads. Tibial sensilla are apparently tuned to produce no responses to inertial forces, as occur in the swing phase of walking. This conclusion is supported by tests in which animals 'stepped' on a compliant surface and sensory discharges only occurred in stance.

Faith S Frazier - One of the best experts on this subject based on the ideXlab platform.

  • post embryonic development of cuticular caps of Campaniform sensilla of the cockroach leg potential implications in scaling force detection
    Arthropod Structure & Development, 2003
    Co-Authors: Angela L Ridgel, Faith S Frazier, Sasha N Zill
    Abstract:

    Abstract 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. Each sensory neuron possesses a dendrite that inserts into a cuticular cap in the exoskeleton. The cap is the site of mechanotransduction. We measured the sizes and numbers of receptor caps on the cockroach hindleg at different developmental stages. Our goal was to identify morphological features that could be correlated with the range of forces that must be detected. As cockroaches increase in size through successive molts, the number of cuticular caps in each group increases. The tibial group, for example, has two sensilla in first instar animals and 10–12 in the adult. There is also an increase in the range of cap sizes within each group. Observations of animals and their molted exoskeletons suggest that this increase occurs as the caps of existing receptors increase in size and smaller ones are added with each molt. These changes may be important in increasing the range of forces the receptors can signal while retaining sensitivity to low levels of force.

  • force detection in cockroach walking reconsidered discharges of proximal tibial Campaniform sensilla when body load is altered
    Journal of Comparative Physiology A-neuroethology Sensory Neural and Behavioral Physiology, 2001
    Co-Authors: Adam J Noah, L. Quimby, Faith S Frazier, Sasha N Zill
    Abstract:

    We examined the mechanisms underlying force feedback in cockroach walking by recording sensory and motor activities in freely moving animals under varied load conditions. Tibial Campaniform sensilla monitor forces in the leg via strains in the exoskeleton. A subgroup (proximal receptors) discharge in the stance phase of walking. This activity has been thought to result from leg loading derived from body mass. We compared sensory activities when animals walked freely in an arena or on an oiled glass plate with their body weight supported. The plate was oriented either horizontally (70–75% of body weight supported) or vertically (with the gravitational vector parallel to the substrate). Proximal sensilla discharged following the onset of stance in all load conditions. In addition, activity was decreased in the middle third of the stance phase when the effect of body weight was reduced. Our results suggest that sensory discharges early in stance result from forces generated by contractions of muscles that press the leg as a lever against the substrate. These forces can unload legs already in stance and assure the smooth transition of support among the limbs. Force feedback later in stance may adjust motor output to changes in leg loading.

  • dynamic responses of tibial Campaniform sensilla studied by substrate displacement in freely moving cockroaches
    Journal of Comparative Physiology A-neuroethology Sensory Neural and Behavioral Physiology, 2001
    Co-Authors: Angela L Ridgel, Faith S Frazier, Sasha N Zill
    Abstract:

    Responses of the tibial Campaniform sensilla, receptors that encode strains in the exoskeleton, were characterized by recording sensory activities during perturbations in freely standing cockroaches. The substrate upon which the animal stood was displaced horizontally using ramp and hold stimuli at varied rates. The sensilla showed short latency responses that were initiated in the first 30 ms of platform movement. Responses of individual receptors depended upon the direction of displacement and the orientation of their cuticular cap. Proximal receptors, whose caps are perpendicular to the long axis of the tibia, responded to displacements directed from the contralateral side of the body and from the head toward the abdomen. The distal sensilla, oriented parallel to the tibia, discharged at longer latency to displacements in opposite directions. Plots of receptor activity versus displacement direction showed that proximal and distal sensilla are activated in non-overlapping ranges of movement direction. Afferent responses also increased as the platform was displaced more rapidly. These results are consistent with a model in which displacements produce forces that result in bending of the tibia. This information could be utilized to detect the direction and rate of forces that occur during leg slipping or in walking on unstable terrains.

  • load signalling by cockroach trochanteral Campaniform sensilla
    Brain Research, 1999
    Co-Authors: Sasha N Zill, Angela L Ridgel, Ralph A Dicaprio, Faith S Frazier
    Abstract:

    A major problem in sensory motor integration is to delineate how forces acting upon a leg are encoded and regulated in the control of posture and locomotion. We have studied responses of the trochanteral Campaniform sensilla, the largest array of force detecting mechanoreceptors in the cockroach leg. Afferents from two groups of sensilla (Groups 3 and 4) encode forces applied to the leg in the plane of joint movement of the coxo-trochanteral joint. The receptors within Group 3 exhibit fixed patterns of recruitment that could differentially indicate when force levels are adequate to provide support and propulsion during walking.

Ansgar Büschges - One of the best experts on this subject based on the ideXlab platform.

  • location and arrangement of Campaniform sensilla in drosophila melanogaster
    The Journal of Comparative Neurology, 2020
    Co-Authors: Gesa F Dinges, Alexander S Chockley, Till Bockemuhl, Alexander Blanke, Ansgar Büschges
    Abstract:

    Sensory systems provide input to motor networks on the state of the body and environment. One such sensory system in insects is the Campaniform sensilla (CS), which detect deformations of the exoskeleton arising from resisted movements or external perturbations. When physical strain is applied to the cuticle, CS external structures are compressed, leading to transduction in an internal sensory neuron. In Drosophila melanogaster, the distribution of CS on the exoskeleton has not been comprehensively described. To investigate CS number, location, spatial arrangement and potential differences between individuals, we compared the front, middle, and hind legs of multiple flies using scanning electron microscopy. Additionally, we imaged the entire body surface to confirm known CS locations. On the legs, the number and relative arrangement of CS varied between individuals, and single CS of corresponding segments showed characteristic differences between legs. This knowledge is fundamental for studying the relevance of cuticular strain information within the complex neuromuscular networks controlling posture and movement. This comprehensive account of all D. melanogaster CS helps set the stage for experimental investigations into their responsivity, sensitivity, and roles in sensory acquisition and motor control in a light-weight model organism. This article is protected by copyright. All rights reserved.

  • Force dynamics and synergist muscle activation in stick insects: the effects of using joint torques as mechanical stimuli
    Journal of Neurophysiology, 2018
    Co-Authors: Sasha N Zill, Ansgar Büschges, Sumaiya Chaudhry, Chris J. Dallmann, Josef Schmitz
    Abstract:

    The effects of force receptors (Campaniform sensilla) on leg muscles and synergies were characterized in stick insects using both ramp and hold functions and waveforms of joint torques calculated b...

  • Effects of force detecting sense organs on muscle synergies are correlated with their response properties.
    Arthropod Structure & Development, 2017
    Co-Authors: Sasha N Zill, Josef Schmitz, Sumaiya Chaudhry, David Neff, Annelie Exter, Ansgar Büschges
    Abstract:

    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). The factors underlying the differential effects are unclear as the responses of femoral Campaniform sensilla have not previously been characterized. The present study characterized the structure and response properties (via extracellular recording) of the femoral sensilla in both insects. The cockroach trochantero-femoral (TrF) joint is mobile and the joint membrane acts as an elastic antagonist to the reductor muscle. Cockroach femoral Campaniform sensilla show weak discharges to forces in the coxo-trochanteral (CTr) joint plane (in which forces are generated by coxal muscles) but instead encode forces directed posteriorly (TrF joint plane). In stick insects, the TrF joint is fused and femoral Campaniform sensilla discharge both to forces directed posteriorly and forces in the CTr joint plane. These findings support the idea that receptors that enhance synergies encode forces in the plane of action of leg muscles used in support and propulsion.

  • Force feedback reinforces muscle synergies in insect legs.
    Arthropod Structure & Development, 2015
    Co-Authors: Sasha N Zill, Ansgar Büschges, Sumaiya Chaudhry, Josef Schmitz
    Abstract:

    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. We tested the hypothesis that integration of force feedback from receptors of different leg segments during grip occurs through activation of specific muscle synergies. We characterized the effects of Campaniform sensilla of the feet (tarsi) and proximal segments (trochanter and femur) on activities of leg muscles in stick insects and cockroaches. In both species, mechanical stimulation of tarsal sensilla activated the leg muscle that generates substrate grip (retractor unguis), as well as proximal leg muscles that produce inward pull (tibial flexor) and support/propulsion (trochanteral depressor). Stimulation of Campaniform sensilla on proximal leg segments activated the same synergistic group of muscles. In stick insects, the effects of proximal receptors on distal leg muscles changed and were greatly enhanced when animals made active searching movements. In insects, the task-specific reinforcement of muscle synergies can ensure that substrate adhesion is rapidly established after substrate contact to provide a stable point for force generation.

  • Positive force feedback in development of substrate grip in the stick insect tarsus
    Arthropod Structure & Development, 2014
    Co-Authors: Sasha N Zill, Ansgar Büschges, Sumaiya Chaudhry, Annelie Exter, Josef Schmitz
    Abstract:

    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. Morphological studies showed that one to four Campaniform sensilla are located on the distal end of each segment. Activities of the receptors were recorded neurographically and sensilla were identified by stimulation and ablation of their cuticular caps. Responses were characterized to bending forces and axial loads, muscle contractions and to forces applied to the retractor apodeme (tendon). The tarsal sensilla effectively encoded both the rate and amplitude of loads and muscle forces, but only when movement was resisted. Mechanical stimulation of the receptors produced activation of motor neurons in the retractor unguis and tibial flexor muscles. These findings indicate that Campaniform sensilla can provide information about the effectiveness of the leg muscles in generating substrate adherence. They can also produce positive force feedback that could contribute to the development of substrate grip and stabilization of the tarsal chain.

Angela L Ridgel - One of the best experts on this subject based on the ideXlab platform.

  • post embryonic development of cuticular caps of Campaniform sensilla of the cockroach leg potential implications in scaling force detection
    Arthropod Structure & Development, 2003
    Co-Authors: Angela L Ridgel, Faith S Frazier, Sasha N Zill
    Abstract:

    Abstract 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. Each sensory neuron possesses a dendrite that inserts into a cuticular cap in the exoskeleton. The cap is the site of mechanotransduction. We measured the sizes and numbers of receptor caps on the cockroach hindleg at different developmental stages. Our goal was to identify morphological features that could be correlated with the range of forces that must be detected. As cockroaches increase in size through successive molts, the number of cuticular caps in each group increases. The tibial group, for example, has two sensilla in first instar animals and 10–12 in the adult. There is also an increase in the range of cap sizes within each group. Observations of animals and their molted exoskeletons suggest that this increase occurs as the caps of existing receptors increase in size and smaller ones are added with each molt. These changes may be important in increasing the range of forces the receptors can signal while retaining sensitivity to low levels of force.

  • dynamic responses of tibial Campaniform sensilla studied by substrate displacement in freely moving cockroaches
    Journal of Comparative Physiology A-neuroethology Sensory Neural and Behavioral Physiology, 2001
    Co-Authors: Angela L Ridgel, Faith S Frazier, Sasha N Zill
    Abstract:

    Responses of the tibial Campaniform sensilla, receptors that encode strains in the exoskeleton, were characterized by recording sensory activities during perturbations in freely standing cockroaches. The substrate upon which the animal stood was displaced horizontally using ramp and hold stimuli at varied rates. The sensilla showed short latency responses that were initiated in the first 30 ms of platform movement. Responses of individual receptors depended upon the direction of displacement and the orientation of their cuticular cap. Proximal receptors, whose caps are perpendicular to the long axis of the tibia, responded to displacements directed from the contralateral side of the body and from the head toward the abdomen. The distal sensilla, oriented parallel to the tibia, discharged at longer latency to displacements in opposite directions. Plots of receptor activity versus displacement direction showed that proximal and distal sensilla are activated in non-overlapping ranges of movement direction. Afferent responses also increased as the platform was displaced more rapidly. These results are consistent with a model in which displacements produce forces that result in bending of the tibia. This information could be utilized to detect the direction and rate of forces that occur during leg slipping or in walking on unstable terrains.

  • encoding of forces by cockroach tibial Campaniform sensilla implications in dynamic control of posture and locomotion
    Journal of Comparative Physiology A-neuroethology Sensory Neural and Behavioral Physiology, 2000
    Co-Authors: Angela L Ridgel, Ralph A Dicaprio, S. F. Frazier, Sasha N Zill
    Abstract:

    Forces exerted by a leg in support and propulsion can vary considerably when animals stand upon or traverse irregular terrains. We characterized the responses of the cockroach tibial Campaniform sensilla, mechanoreceptors which encode force via strains produced in the exoskeleton, by applying forces to the leg at controlled magnitudes and rates. We also examined how sensory responses are altered in the presence of different levels of static load. All receptors exhibit phasico-tonic discharges that reflect the level and rate of force application. Our studies show that: (1) tonic discharges of sensilla can signal the level of force, but accurate encoding of static loads may be affected by substantial receptor adaptation and hysteresis; (2) the absolute tonic sensitivities of receptors decrease when incremental forces are applied at different initial load levels; (3) phasic discharges of sensilla accurately encode the rate of force application; and (4) sensitivities to changing rates of force are strictly preserved in the presence of static loads. These findings imply that discharges of the sensilla are particularly tuned to the rate of change of force at all levels of leg loading. This information could be utilized to adapt posture and walking to varying terrains and unexpected perturbations.

  • load signalling by cockroach trochanteral Campaniform sensilla
    Brain Research, 1999
    Co-Authors: Sasha N Zill, Angela L Ridgel, Ralph A Dicaprio, Faith S Frazier
    Abstract:

    A major problem in sensory motor integration is to delineate how forces acting upon a leg are encoded and regulated in the control of posture and locomotion. We have studied responses of the trochanteral Campaniform sensilla, the largest array of force detecting mechanoreceptors in the cockroach leg. Afferents from two groups of sensilla (Groups 3 and 4) encode forces applied to the leg in the plane of joint movement of the coxo-trochanteral joint. The receptors within Group 3 exhibit fixed patterns of recruitment that could differentially indicate when force levels are adequate to provide support and propulsion during walking.