Antennal motor activity induced by pilocarpine in the American cockroach.

The antennal motor system is activated by the muscarinic agonist pilocarpine in the American cockroach Periplaneta americana, and its output patterns were examined both in restrained intact animals and in isolated CNS preparations. The three-dimensional antennal movements induced by the hemocoelic drug injection were analyzed in in vivo preparations. Pilocarpine effectively induced prolonged rhythmic movements of both antennae. The antennae tended to describe a spatially patterned trajectory, forming loops or the symbol of infinity (infinity). Such spatial regularity is comparable to that during spontaneous tethered-walking. Rhythmic bursting activities of the antennal motor nerves in in vitro preparations were also elicited by bath application of pilocarpine. Cross-correlation analyses of the bursting spike activities revealed significant couplings among certain motor units, implying the spatial regularity of the antennal trajectory. The pilocarpine-induced rhythmic activity of antennal motor nerves was effectively suppressed by the muscarinic antagonist atropine. These results indicate that the activation of the antennal motor system is mediated by muscarinic receptors.The original publication is available at www.springerlink.co

Tactile efficiency of insect antennae with two hinge joints

Krause AF, Dürr V. Tactile efficiency of insect antennae with two hinge joints. Biological Cybernetics. 2004;91(3):168-181.Antennae are the main organs of the arthropod tactile sense. In contrast to other senses that are capable of retrieving spatial information, e.g. vision, spatial sampling of tactile information requires active movement of the sense organ. For a quantitative analysis of basic principles of active tactile sensing, we use a generic model of arbitrary antennae with two hinge joints (revolute joints). This kind of antenna is typical for Orthoptera and Phasmatodea, i.e. insect orders that contain model species for the study of antennal movements, including cricket, locust and stick insect. First, we analyse the significance of morphological properties on workspace and sampling acuity. It is shown how joint axis orientation determines areas out of reach while affecting acuity in the areas within reach. Second, we assume a parametric set of movement strategies, based on empirical data on the stick insect Carausius morosus , and investigate the role of each strategy parameter on tactile sampling performance. A stochastic environment is used to measure sampling density, and a viscous friction model is assumed to introduce energy consumption and, thus, a measure of tactile efficiency. Up to a saturation level, sampling density is proportional to the range or frequency of joint angle modulation. The effect of phase shift is strong if joint angle modulation frequencies are equal, but diminishes for other frequency ratios. Speed of forward progression influences the optimal choice of movement strategy. Finally, for an analysis of environmental effects on tactile performance, we show how efficiency depends on predominant edge direction. For example, with slanted and non-orthogonal joint axis orientations, as present in the stick insect, the optimal sampling strategy is less sensitive to a change from horizontal to vertical edge predominance than with orthogonal and non-slanted joint axes, as present in a cricket. Electronic Supplementary Material Supplementary material is available in the online version of this article at http://dx.doi.org/ 10.1007/s00422-004-0490-

Decomposition of 3D joint kinematics of walking in Drosophila melanogaster

Animals exhibit a rich repertoire of locomotive behaviors. In the context of legged locomotion, i.e. walking, animals can change their heading direction, traverse diverse substrates with different speeds, or can even compensate for the loss of a leg. This versatility emerges from the fact that biological limbs have more joints and/or more degrees of freedom (DOF), i.e. independent directions of motions, than required for any single movement task. However, this further entails that multiple, or even infinitely many, joint configuration can result in the same leg stepping pattern during walking. How the nervous system deals with such kinematic redundancy remains still unknown. One proposed hypothesis is that the nervous system does not control individual DOFs, but uses flexible combinations of groups of anatomical or functional DOFs, referred to as motor synergies. Drosophila melanogaster represents an excellent model organism for studying the motor control of walking, not least because of the extensive genetic toolbox available, which, among others, allows the identification and targeted manipulation of individual neurons or muscles. However, their tiny size and ability for relatively rapid leg movements hampered research on the kinematics at the level of leg joints due to technical limitations until recently. Hence, the main objective of this dissertation was to investigate the three-dimensional (3D) leg joint kinematics of Drosophila during straight walking. For this, I first established a motion capture setup for Drosophila which allowed the accurate reconstruction of the leg joint positions in 3D with high temporal resolution (400 Hz). Afterwards, I created a kinematic leg model based on anatomical landmarks, i.e. joint condyles, extracted from micro computed-tomography scan data. This step was essential insofar that the actual DOFs of the leg joints in Drosophila were currently unknown. By using this kinematic model, I have found that a mobile trochanter-femur joint can best explain the leg movements of the front legs, but is not mandatory in the other leg pairs. Additionally, I demonstrate that rotations of the femur-tibia plane in the middle legs arise from interactions between two joints suggesting that the natural orientation of joint rotational axes can extent the leg movement repertoire without increasing the number of elements to be controlled. Furthermore, each leg pair exhibited distinct joint kinematics in terms of the joint DOFs employed and their angle time courses during swing and stance phases. Since it is proposed that the nervous system could use motor synergies to solve the redundancy problem, I finally aimed to identify kinematic synergies based on the obtained joint angles from the kinematic model. By applying principal component analysis on the mean joint angle sets of leg steps, I found that three kinematic synergies are sufficient to reconstruct the movements of the tarsus tip during stepping for all leg pairs. This suggests that the problem of controlling seven to eight joint DOFs can be in principle reduced to three control parameters. In conclusion, this dissertation provides detailed insights into the leg joint kinematics of Drosophila during forward walking which are relevant for deciphering motor control of walking in insects. When combined with the extensive genetic toolbox offered by Drosophila as model organism, the experimental platform presented here, i.e. the 3D motion capture setup and the kinematic leg model, can facilitate investigations of Drosophila walking behavior in the future

The functional morphology of insect adhesive devices and its implications for ecology

The aim of this thesis is to gain a better understanding of the constraints that affect insect adhesion with an emphasis on biological constraints such as plant defences against insects and the influence of abiotic factors on insect foraging. In chapter one of this theses, a literature review on the mechanisms of insect adhesion, the influence of attachment capabilities on foraging behaviour, plant-insect interactions, and synthetic insect barriers is presented, focusing on hymenoptera and coccinellids as representatives of the two basic insect pad types. In the following chapters we test the four leading hypothesis regarding insect adhesion (Contamination, Fluid absorption, Surface roughness and the effect of Surface Energy), before investigating the role of mechano-sensing via insect antenna on substrate choice and finally probing the link between surface properties and locomotion and adhesion. Throughout this thesis I use species of Hymenoptera and Coccinellids as representative species of the two basic adhesive pad types

Technische Biologie des Tasthaar-Sinnessystems als Gestaltungsgrundlage für taktile stiftführende Mechanosensoren

In der vorliegenden Arbeit wird ein Konzept des Reizleitungsapparates vorgestellt, welches die Aufbereitung und Systematisierung biologischen Wissens ermöglicht und sich für eine Anwendung auf technische Sensoren zur Identifikation des Optimierungspotentials und Entwicklung von Lösungsansätzen eignet. Am Beispiel taktiler stiftführender Sensoren wird dieses Konzept als methodische Leitlinie angewendet. Als Untersuchungsobjekt wird aufgrund seiner technisch relevanten Charakteristika das Tasthaar-Sinnessystem von Säugetieren mit den peripheren Strukturen Haarschaft, Follikel-Sinus-Komplex und Mechanorezeptoren ausgewählt. Ziel der Untersuchungen dieses Sinnesorgans ist nicht die detaillierte Aufklärung aller funktionellen Zusammenhänge von der Peripherie bis zu der neuronalen Verarbeitungskette, sondern eine Abstraktion entscheidender Grundprinzipien, die den Ausgangspunkt für Lösungsansätze sensortechnischer Problemstellungen darstellen.Nature offers an inexhaustible array of phenomena with potential for technical application. A wide range of designs inspired by ideas from biology often fails because no transfer method from research to industrial implementation exists. This work introduces a concept for systematic analysis of function determining principles of biological sensor organs. The concept is based on comparative examination of biological sensor organs and technical sensor systems. Target-oriented evaluation and systematization of biological knowledge in the technological context is accomplished by using the so called stimulus-leading-apparatus concept. Furthermore, this concept can be applied to technical sensor systems to identify design strategies and optimization potential. The concept is tested on tactile sensors. Biological subject of study is the whisker system of mammals because of its technical relevance. Hair shaft, follicle-sinus-complex (FSC) and mechano receptors are the interesting peripheral structures of the whisker system. Aim of the study is not a detailed analysis of all functional correlations from periphery to neural processing but an abstraction of the essential principles which can initiate solutions for technical sensor problems. Therefore, the biological system is analyzed by means of technical methods and models. The whisker system periphery is examined as a beam with a compliant clamping featuring variable stiffness. Structural and mechanical parameters of the hair shaft are determined experimentally. Deductive methods of modeling are used to analyze the follicle-sinus-complex. A mechanical model reduced to basic principles is introduced. The reaction to external forces is studied and compared using static and even dynamic models. Finally, some ideas for optimizing technical tactile sensors are developed. Emphasis is on design concepts for the stimulus receiving structure and the realization of a compliant clamping with variable stiffness.Die Natur bietet ein unerschöpfliches Potential an Phänomenen mit technischer Relevanz. Oft scheitert die breite Anwendung von Ideen aus der Biologie am Fehlen einer effektiven Transfermethode zwischen Forschung und industrieller Anwendung. In der vorliegenden Arbeit wird basierend auf einer vergleichenden Betrachtung biologischer Sinnesorgane und technischer Sensorsysteme ein Konzept zur systematischen Analyse der funktionell entscheidenden Grundprinzipien biologischer Sinnesorgane dargestellt. Dieses Konzept des Reizleitungsapparates ermöglicht die Aufbereitung und Systematisierung biologischen Wissens und eignet sich für eine Anwendung auf technische Sensoren zur Identifikation des Optimierungspotentials und Entwicklung von Lösungsansätzen. Am Beispiel taktiler stiftführender Sensoren wird das Konzept zum Reizleitungsapparat als methodische Leitlinie angewandt. Als Untersuchungsobjekt wird aufgrund seiner technisch relevanten Charakteristika das Tasthaar-Sinnessystem von Säugetieren mit den peripheren Strukturen Haarschaft, Follikel-Sinus-Komplex und Mechanorezeptoren ausgewählt. Ziel der Untersuchungen dieses Sinnesorgans ist nicht die detaillierte Aufklärung aller funktionellen Zusammenhänge von der Peripherie bis zu der neuronalen Verarbeitungskette, sondern eine Abstraktion entscheidender Grundprinzipien, die den Ausgangspunkt für Lösungsansätze sensortechnischer Problemstellungen darstellen. Daher erfolgt die Aufarbeitung der biologischen Kenntnisse unter Zuhilfenahme ingenieur-wissenschaftlicher Methoden und Modelle. Die Peripherie des Tasthaar-Sinnesorgans wird als Biegebalken mit nachgiebiger Lagerung interpretiert, deren Steifigkeit aktiv einstellbar ist. Während der Haarschaft bezüglich seiner Struktur und der mechanischen Eigenschaften mit verschiedenen experimentellen Methoden untersucht werden kann, muss bei der Analyse des Follikel-Sinus-Komplexes auf deduktive Methoden der Modellbildung zurückgegriffen werden. Es wird ein auf Grundprinzipien reduziertes mechanisches Modell vorgestellt und dessen Reaktion einerseits als statisches und andererseits als dynamisches System auf verschiedene Erregerkräfte analysiert. Abschließend werden Ansatzpunkte zur Optimierung taktiler stiftführender Sensoren entwickelt. Schwerpunkte liegen neben Gestaltungsvorschlägen für die reizaufnehmende Struktur auf der Umsetzung einer nachgiebigen und in ihrer Steifigkeit einstellbaren Lagerung

The olfactory pathway of the red flour beetle Tribolium castaneum and its comparison to other Coleoptera

Insects are the most successful animals on earth. They have a great impact on almost all terrestrial ecosystems, affecting mankind by beneficial and harmful ways like facilitating vast amounts of human food production via pollination or by being a devastating pest to agricultural products and food stocks as well as spreading diseases. Among insects, Coleoptera are the most divers and species richest order, containing vast quantities of pest species. The majority of insects depends heavily on their olfactory system to master most tasks they encounter during their lifespan, like finding food sources, hosts, native populations, and mates, or to avoid predators. Despite the diversity and species richness of beetles, as well as their impact as pest, not much is known about the olfactory system of these animals. To investigate the olfactory system of Coleoptera, we analyzed 1) the olfactory pathway of one model organism in highly detail and 2) we examined particular brain regions of the olfactory system of many beetles and insects and compared them with each other. 1: For the highly detailed analysis of the olfactory pathway of one species we worked with the red flour beetle Tribolium castaneum, an already established model organism in some fields of biology like in development and evolution. Experiments requiring genetic methods had been performed in cooperation with the Georg-August-Universität Göttingen. Based on immunohistochemical stainings we created 3D-reconstructions of adult and larval brains, helping us to identifying the most prominent brain structures, as a starting point for following projects. On this basis, we decrypted the olfactory pathway of the adult T. castaneum. This includes A) morphological data of the antenna with its olfactory sensilla and neuroanatomical data of the brain structures involved in olfaction, as well as B) molecular data from antennal structures involved in olfaction (like olfactory respectively gustatory receptors or olfactory binding proteins). Furthermore, we identified neuropeptide families within the primary and one higher integration center for olfaction - namely the antennal lobe (AL) and mushroom body (MB) - of T castaneum. Additionally, we investigated one neuropeptide family and its respective receptor within the brain of T. castaneum in detail. We compared this neuropeptide family and its receptor with two structurally similar and closely related neuropeptide families and their receptors. 2: The second focus of this thesis was the investigation of single features of the olfactory pathway and their comparison between different coleopteran-, respectively insect species. In one project we studied the distribution of eight neuropeptide families within the MB of 24 different insect species and compared them with each other, looking for potential evolutionary correlations. Furthermore, we analyzed the AL of 63 different Coleoptera and found an unusual architecture of the AL in some species. In a related project we investigated such an unusual architectured AL of one species (the small hive beetle Aethina tumida) highly detailed. In this thesis, the brain architecture and especially the olfactory system of Coleoptera had been investigated for the first time in high detail. We revealed new insights regarding the olfactory (respectively chemoreceptive) pathway of these animals. The findings will help to establish T. castaneum as the fist coleopteran model organism for insect neuroscience and in particular for insect olfaction. The single projects of this thesis will be described in-depth in the following eight chapters

Understanding standing

Research objectives. Psychophysical acceleration threshold is a tool for detecting deficits in dynamic postural control. Our lab has shown differences in the acceleration threshold among young adults, elderly adults, and elderly adults with diabetes. Electromyography, Semmes-Weinstein monofilaments, and hearing tests investigate the underlying physiological mechanisms for the detriments in postural control. Due to peri-sway perturbations, the motion of a person\u27s sway affects the signal to noise ratio for perturbed stance. Since increases in sway range accompany postural instabilities, sway entrainment will allow us to investigate changes in acceleration threshold at different points in sway. The center of pressure, observed for entrainment, only changes due to rotations about joints, specifically the ankle. The current method to model rotation about the ankle is a single orthogonal joint, and therefore inaccurate. Methods. The SLIP-FALLS-STEPm Platform has lead to the ability to accurately measure and observe interactions in the range of postural sway. The combination of the platform with other testing modalities such as camera tracking systems, force mats, and accelerometers will allow for a comprehensive testing scheme. The new scheme can be combined with the induced sway produced by a sub-threshold sinusoidal entrainment process. The nonorthogonal modelling is programmed in Matlab®. Results. For constant displacements, anterior accelerations thresholds via two-alternate forced choice (2AFC) showed differences in postural stability in mature, diabetic individuals with peripheral neuropathy (DPN) and those who are neurally intact (DNI) compared to healthy mature adults (HMA), which corresponded with previous results of lateral perturbations. Both DNI and DPN had significantly higher thresholds for acceleration via 2AFC than HMA at 1 and 4 mm displacements (p \u3c 0.01 and p Conclusion. The anterior acceleration thresholds show that peripheral neuropathy is not the sole cause for postural instability with diabetes. The ability to control the motion of sway will allow us to describe acceleration threshold throughout the range of sway. With a realistic ankle model, we will be able to better simulate postural dynamics