81 research outputs found
Ultra high-resolution biomechanics suggest that substructures within insect mechanosensors decisively affect their sensitivity
Insect load sensors, called campaniform sensilla (CS), measure strain changes within the cuticle of appendages. This mechanotransduction provides the neuromuscular system with feedback for posture and locomotion. Owing to their diverse morphology and arrangement, CS can encode different strain directions. We used nano-computed tomography and finite-element analysis to investigate how different CS morphologies within one location-the femoral CS field of the leg in the fruit fly Drosophila-interact under load. By investigating the influence of CS substructures' material properties during simulated limb displacement with naturalistic forces, we could show that CS substructures (i.e. socket and collar) influence strain distribution throughout the whole CS field. Altered socket and collar elastic moduli resulted in 5% relative differences in displacement, and the artificial removal of all sockets caused differences greater than 20% in cap displacement. Apparently, CS sockets support the distribution of distal strain to more proximal CS, while collars alter CS displacement more locally. Harder sockets can increase or decrease CS displacement depending on sensor location. Furthermore, high-resolution imaging revealed that sockets are interconnected in subcuticular rows. In summary, the sensitivity of individual CS is dependent on the configuration of other CS and their substructures
A brainstem neural substrate for stopping locomotion
Locomotion occurs sporadically and needs to be started, maintained, and stopped.
The neural substrate underlying the activation of locomotion is partly known, but
little is known about mechanisms involved in termination of locomotion. Recently,
reticulospinal neurons (stop cells) were found to play a crucial role in stopping
locomotion in the lamprey: their activation halts ongoing locomotion and their
inactivation slows down the termination process. Intracellular recordings of
these cells revealed a distinct activity pattern, with a burst of action
potentials at the beginning of a locomotor bout and one at the end (termination
burst). The termination burst was shown to be time linked to the end of
locomotion, but the mechanisms by which it is triggered have remained unknown. We
studied this in larval sea lampreys (Petromyzon marinus; the sex of the animals
was not taken into account). We found that the mesencephalic locomotor region
(MLR), which is known to initiate and control locomotion, stops ongoing
locomotion by providing synaptic inputs that trigger the termination burst in
stop cells. When locomotion is elicited by MLR stimulation, a second MLR
stimulation stops the locomotor bout if it is of lower intensity than the initial
stimulation. This occurs for MLR-induced, sensory-evoked, and spontaneous
locomotion. Furthermore, we show that glutamatergic and, most likely,
monosynaptic projections from the MLR activate stop cells during locomotion.
Therefore, activation of the MLR not only initiates locomotion, but can also
control the end of a locomotor bout. These results provide new insights onto the
neural mechanisms responsible for stopping locomotion.SIGNIFICANCE STATEMENT The
mesencephalic locomotor region (MLR) is a brainstem region well known to initiate
and control locomotion. Since its discovery in cats in the 1960s, the MLR has
been identified in all vertebrate species tested from lampreys to humans. We now
demonstrate that stimulation of the MLR not only activates locomotion, but can
also stop it. This is achieved through a descending glutamatergic signal, most
likely monosynaptic, from the MLR to the reticular formation that activates
reticulospinal stop cells. Together, our findings have uncovered a neural
mechanism for stopping locomotion and bring new insights into the function of the
MLR
Location and arrangement of campaniform sensilla in Drosophila melanogaster
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
Soma clusters of descending interneurons of the stick insect brain and gnathal ganglion
Goldammer J, Büschges A, Dürr V. Soma clusters of descending interneurons of the stick insect brain and gnathal ganglion. Bielefeld University; 2023.Research data underlying the publication
Goldammer, Büschges and Dürr (in revision): Descending interneurons of the stick insect connecting brain neuropiles with the prothoracic ganglion. PLoS On
Encoding of force increases and decreases by tibial campaniform sensilla in the stick insect, Carausius morosus
Zill SN, Büschges A, Schmitz J. Encoding of force increases and decreases by tibial campaniform sensilla in the stick insect, Carausius morosus. Journal of Comparative Physiology A: Neuroethology, Sensory, Neural, and Behavioral Physiology. 2011;197(8):851-867
Detecting forces in a reference frame: responses of stick insect campaniform sensilla to muscle forces and loads
Zill S, Büschges A, Chaudhry S, Schmitz J. Detecting forces in a reference frame: responses of stick insect campaniform sensilla to muscle forces and loads. In: Proceedings of the 42nd annual meeting of the Society for Neuroscience. Society for Neuroscience; 2012
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