Amir Ayali

Research Interests and Current Projects

Insect locomotion: neural generation, coordination and control

    Animal movements result from a dynamic interplay among neural commands, muscle and body mechanics and the environment. It is increasingly evident that a comprehensive understanding of animal locomotion must address the interactions of all these components.

    A collaborative interdisciplinary study (with Dr. Einat Fuchs, a post doc fellow at the laboratory of Prof. Philip Holmes, Princeton University) takes advantage of the cockroach preparation and a combined theoretical and experimental approach to study the functional organization of central pattern generating circuits and inter-limb coordination during locomotion. Einat Fuchs, Tzachy David (PhD student) and Omer Gal (MSc student) monitor the rhythmic motor output of distinct cockroach leg efferents as they control for and manipulate inputs to the rhythm-generating networks. Time series recorded under different experimental conditions are compared and analyzed, utilizing advanced mathematical tools based on coupled oscillator models. The results are used to further improve dynamical models and computer simulations of six-legged locomotion, as well as (potentially) insect-inspired robots.   See image on the right.

     In a related research project, Daniel Knebel (PhD student) is studying descending control over insect locomotion centers, using the locust preparation. This work is in collaboration with Prof. Hans-Joachim Pflüger, Free University of Berlin.

Click the image for a slow-motion clip of cockroach walking

The insect is tethered and walks on a slippery surface, displaying the characteristic double-tripod gate

 

Bioinspiration and biomimetics - linking biology and technical application



In addition to our locomotion-related research described above, in several recent and ongoing collaborative and interdisciplinary projects we further explore various insect systems as a source for applications in engineering and robotics.

A collaborative project with Dr. Gabor Kosa (School of Mechanical Engineering, Tel Aviv University) and Dr. Uri Ben Hanan (Department of Mechanical Engineering, ORT Braude College) focuses on developing a grasshopper-inspired bio-mimetic jumping robot. Omer Gvirtzman (MSc student) studies the biomechanics and kinematics of locust jumps, by way of video  filming, analyzing, and characterizing the parameters of real jumps, and modeling the jumping mechanisms by computer simulation. Click image on the right to see a short clip of locust jumping

 In a  recent study (with Dr. Gal Ribak and Prof. Daniel Weihs, Faculty of Aerospace Engineering, Autonomous Systems Program, Technion, Haifa, Israel), we investigated locust flight kinematics and neural control, aiming at the possible use of insects as controllable miniature Unmanned Aerial Vehicles. The result was shedding light on sensory-motor control during locust flight, specifically on the mechanism generating evasive steering in response to looming visual stimuli. Click image on the right for a short clip: Studying locust looming responses. A computer screen on the right of the tethered insect is showing a looming object. In response the locust is steering to the left.


 Another recent effort  (led by Dr. Offer Shai, Faculty of Engineering, Tel-Aviv) was aimed at presenting a 2-D caterpillar simulation, which mimics caterpillar locomotion using Assur tensegrity structures. The unique engineering properties of the model, together with the suggested control scheme, provide the model with a controllable degree of softness - each segment can be either soft or rigid. The model exhibits several characteristics, which are analogous to those of the biological caterpillar and serves as a first step towards designing a special kind of bio-inspired soft robot. Click image on the left for a short clip.


Some video links:

AFTAU                https://www.youtube.com/watch?v=ZzguqmJuLvk

ILTV ISRAEL DAILY           https://www.youtube.com/watch?v=waf4FQ6Q_To

Haaretz.com        https://www.youtube.com/watch?v=BGqaqimK5JA

Reuters                http://www.reuters.com/video/2016/01/05/researchers-taking-power-of-locust-to-ne?videoId=366921428

New China TV    https://www.youtube.com/watch?v=ImaOx_Wc0ow

Neurophysiological and neuroethological characteristics of locust density dependent phase polymorphism

    Locust phase polymorphism is defined as the ability of some grasshopper species to show within the species, forms or morphs that differ in their morphology as well as their biology, dependent on the population density. Density dependent changes in locusts have been described in many different research areas; from morphology and Anatomy, biochemistry and physiology, to ecology and behavior. The polymorphic characteristics are quantitative, there are innumerable intermediates between the extreme phases and the change is reversible.

    The behavior of individual locusts in the presence of others is a major phase characteristic. The behavior change is the first noticeable change when previously isolated locusts are crowded. This change facilitates the appearance of the various morphological and physiological phase changes that follow it. Yet, the neurophysiological basis of the behavioral phase characteristics has received very little attention.

    We have recently demonstrated, for the first time, neural correlates of locust behavioral density-dependent phase polymorphism. We have studied phase related differences in identified flight related interneurons as well as in DUM neurons (insect octopaminergic neurons) activity. Dr. Moshe Gershon currently further analyzes behavioral phase characteristics and the neurobiological basis of locust phase polymorphism. Guy Amichay (MSc student) is working to reveal the basis of locust coordinated swarming behaviour. This line of research will fill a long lasting gap in the understanding of locust phases and will provide insights into environmental effects on neural plasticity in general. Yiftach Golov (MSc student) is looking into the role of sexual selection in locust phase-related behaviour and phase transformation.

The photograph is of a crowded (left, orange-black) and an isolated reared (right, green) Vth instar locusts. This photo (by Amir Ayali) was used as the cover for Fuchs et al. 2003 (see publication list).

Left: Desert locust (Schistocerca gregaria) in the gregarious phase. The figure shows a swarm of desert locust in Morocco during the 2004 outbreak. Locust density dependent polymorphism is an extreme example of the effects of environmental factors on the animal's behavior. In high population density, locusts actively aggregate, forming large hopper bands or adult swarms. In marked contrast, isolated animals move away from fellow locusts and from crowded groups. Photo is curtsey of Philip Dalton, John Downer Productions.

click the image below to see a 7 min clip summerizing the locust outbreak in Isreal's Negev desert, spring, 2013

Locusts in Israel, Spring 2013


 

Self organization, morphological and functional development of neuronal networks in primary culture of insect neurons

    In the developing nervous system of an animal the growth pattern of single neurons designated to constitute future neural circuits is a dominant factor influencing the nature of the developing networks. The branching pattern of the neurons defines the basic hardware framework of the nervous system. It is thus instrumental in the future output of neural circuits for behavior. In collaboration with Prof. Eshel Ben-Jacob from exact sciences (TAU School of Physics) we have cultured neurons from the locust frontal ganglion and investigated mechanisms of neuronal network self organization. We further investigated correlation and interactions between the neuron's and networks' growth pattern and electrical activity by culturing the neurons on multi electrode arrays (MEA; silicon chips in which an array of electrodes is embedded), and recording the neurons electrical activity as networks evolve. In collaboration with Dr. Yael Hanien of the TAU school of electrical engineering, we have looked at various aspects related to the role of mechanical tension in neuron and network development. As part of this collaboration neurons were cultured on quartz substrates decorated by islands of carbo-nano-tubes.

Based on all the above experience, Ya'ara Saad (PhD. students) has developed a preparation of fly (Drosophila) neurons in culture, and is utilizing it as a novel model in the study of Alzheimer's disease. Neuronal networks developed from neurons of normal and transgenic flies are comparatively investigated.  Various aspects of development are used to characterize the pathological effects of Alzheimer's-related genes and proteins.

The figure shows an example of a locust frontal ganglion neuron in primary culture after 2 days. Click image to open a 90 h timelapse video of network development.

Left: A photograph of a locust and a MEA chip over a tilling map describing the electrical activity of a cultured neuronal network in the time frequency domain. The photo was used as the cover for Ayali et al. 2004 (see publications list).

Right: A processed SEM image of a locust neuron over carbo-nano-tube islands (Hanien, Ayali et al. 2008)

The insect stomatogastric nervous system: circuits underlying feeding and molting-related behavior and their neuromodulation

    A wide variety of behaviors are generated by rhythmic pattern-generating circuits. These include ongoing and stereotyped movements such as breathing, chewing, walking, running, flying, and swimming. Central pattern generators (CPG) are small discrete neural circuits and this together with the repetitive nature of the behavior they produce make them very good candidates for studying behavioral mechanisms at all levels of analysis.

    One of the first and most important tasks when one is about to study rhythmic behavior is the identification of the neurons and synapses that form the neural network that generates the rhythmic output. This has proved to be a very difficult and usually impossible task in vertebrate preparations. Historically it was proven to be more rewarding in invertebrates.

    The locust, and in particular locust flight behavior, were used to show for the first time the ability of the central nervous system to generate a fictive motor output. Using the locust preparation it was possible to show that rhythmic motor patterns can be generated in the absence of patterned sensory inputs. It was again locust flight that was used to demonstrate the importance of sensory control in producing an adaptive motor pattern. Indeed one important characteristic of many rhythmic behaviors is the need of constant modulatory control to produce a virtually endless repertoire of variation on a single motor pattern.

    We are studying the rhythmic output of a central pattern generator networks situated in the stomatogastric nervous system of the locust. The frontal ganglion (~100 cells, see image) constitute the major source of innervation to the locust front gut. We are investigating the characteristic neural patterns that can be recorded from nerves leaving the ganglion and from the network's neurons in two very distinct behavioral contexts; feeding and molting (the periodical shedding of the insect's cuticle during metamorphosis). We are interested in the interactions between this neural circuit and other neural centers as well as endocrine factors specific to the different behavioral states.

The figure shows a section through the locust frontal ganglion. The lower panel shows an example of the rhythmic motor pattern that can be recorded from the indicated nerves in a totally isolated ganglion in-vitro. Ayali and Zilberstein (2002)

Some collaborations on other, vertebrate, systems

Click image below to follow link

Amir Ayali

Last Revised: April 16, 2014

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