@article{RoesslerGrobFleischmann2023, author = {R{\"o}ssler, Wolfgang and Grob, Robin and Fleischmann, Pauline N.}, title = {The role of learning-walk related multisensory experience in rewiring visual circuits in the desert ant brain}, series = {Journal of Comparative Physiology A}, volume = {209}, journal = {Journal of Comparative Physiology A}, number = {4}, doi = {10.1007/s00359-022-01600-y}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-325096}, pages = {605-623}, year = {2023}, abstract = {Efficient spatial orientation in the natural environment is crucial for the survival of most animal species. Cataglyphis desert ants possess excellent navigational skills. After far-ranging foraging excursions, the ants return to their inconspicuous nest entrance using celestial and panoramic cues. This review focuses on the question about how na{\"i}ve ants acquire the necessary spatial information and adjust their visual compass systems. Na{\"i}ve ants perform structured learning walks during their transition from the dark nest interior to foraging under bright sunlight. During initial learning walks, the ants perform rotational movements with nest-directed views using the earth's magnetic field as an earthbound compass reference. Experimental manipulations demonstrate that specific sky compass cues trigger structural neuronal plasticity in visual circuits to integration centers in the central complex and mushroom bodies. During learning walks, rotation of the sky-polarization pattern is required for an increase in volume and synaptic complexes in both integration centers. In contrast, passive light exposure triggers light-spectrum (especially UV light) dependent changes in synaptic complexes upstream of the central complex. We discuss a multisensory circuit model in the ant brain for pathways mediating structural neuroplasticity at different levels following passive light exposure and multisensory experience during the performance of learning walks.}, language = {en} } @article{NguyenBeetzMerlinetal.2022, author = {Nguyen, Tu Anh Thi and Beetz, M. Jerome and Merlin, Christine and Pfeiffer, Keram and el Jundi, Basil}, title = {Weighting of celestial and terrestrial cues in the monarch butterfly central complex}, series = {Frontiers in Neural Circuits}, volume = {16}, journal = {Frontiers in Neural Circuits}, issn = {1662-5110}, doi = {10.3389/fncir.2022.862279}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-279445}, year = {2022}, abstract = {Monarch butterflies rely on external cues for orientation during their annual long-distance migration from Northern US and Canada to Central Mexico. These external cues can be celestial cues, such as the sun or polarized light, which are processed in a brain region termed the central complex (CX). Previous research typically focused on how individual simulated celestial cues are encoded in the butterfly's CX. However, in nature, the butterflies perceive several celestial cues at the same time and need to integrate them to effectively use the compound of all cues for orientation. In addition, a recent behavioral study revealed that monarch butterflies can rely on terrestrial cues, such as the panoramic skyline, for orientation and use them in combination with the sun to maintain a directed flight course. How the CX encodes a combination of celestial and terrestrial cues and how they are weighted in the butterfly's CX is still unknown. Here, we examined how input neurons of the CX, termed TL neurons, combine celestial and terrestrial information. While recording intracellularly from the neurons, we presented a sun stimulus and polarized light to the butterflies as well as a simulated sun and a panoramic scene simultaneously. Our results show that celestial cues are integrated linearly in these cells, while the combination of the sun and a panoramic skyline did not always follow a linear integration of action potential rates. Interestingly, while the sun and polarized light were invariantly weighted between individual neurons, the sun stimulus and panoramic skyline were dynamically weighted when both stimuli were simultaneously presented. Taken together, this dynamic weighting between celestial and terrestrial cues may allow the butterflies to flexibly set their cue preference during navigation.}, language = {en} } @article{GrobHeinigGruebeletal.2021, author = {Grob, Robin and Heinig, Niklas and Gr{\"u}bel, Kornelia and R{\"o}ssler, Wolfgang and Fleischmann, Pauline N.}, title = {Sex-specific and caste-specific brain adaptations related to spatial orientation in Cataglyphis ants}, series = {Journal of Comparative Neurology}, volume = {529}, journal = {Journal of Comparative Neurology}, number = {18}, doi = {10.1002/cne.25221}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-257299}, pages = {3882-3892}, year = {2021}, abstract = {Cataglyphis desert ants are charismatic central place foragers. After long-ranging foraging trips, individual workers navigate back to their nest relying mostly on visual cues. The reproductive caste faces other orientation challenges, i.e. mate finding and colony foundation. Here we compare brain structures involved in spatial orientation of Cataglyphis nodus males, gynes, and foragers by quantifying relative neuropil volumes associated with two visual pathways, and numbers and volumes of antennal lobe (AL) olfactory glomeruli. Furthermore, we determined absolute numbers of synaptic complexes in visual and olfactory regions of the mushroom bodies (MB) and a major relay station of the sky-compass pathway to the central complex (CX). Both female castes possess enlarged brain centers for sensory integration, learning, and memory, reflected in voluminous MBs containing about twice the numbers of synaptic complexes compared with males. Overall, male brains are smaller compared with both female castes, but the relative volumes of the optic lobes and CX are enlarged indicating the importance of visual guidance during innate behaviors. Male ALs contain greatly enlarged glomeruli, presumably involved in sex-pheromone detection. Adaptations at both the neuropil and synaptic levels clearly reflect differences in sex-specific and caste-specific demands for sensory processing and behavioral plasticity underlying spatial orientation.}, language = {en} } @article{HabensteinAminiGruebeletal.2020, author = {Habenstein, Jens and Amini, Emad and Gr{\"u}bel, Kornelia and el Jundi, Basil and R{\"o}ssler, Wolfgang}, title = {The brain of Cataglyphis ants: Neuronal organization and visual projections}, series = {Journal of Comparative Neurology}, volume = {528}, journal = {Journal of Comparative Neurology}, number = {18}, doi = {10.1002/cne.24934}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-218212}, pages = {3479 -- 3506}, year = {2020}, abstract = {Cataglyphis ants are known for their outstanding navigational abilities. They return to their inconspicuous nest after far-reaching foraging trips using path integration, and whenever available, learn and memorize visual features of panoramic sceneries. To achieve this, the ants combine directional visual information from celestial cues and panoramic scenes with distance information from an intrinsic odometer. The largely vision-based navigation in Cataglyphis requires sophisticated neuronal networks to process the broad repertoire of visual stimuli. Although Cataglyphis ants have been subjected to many neuroethological studies, little is known about the general neuronal organization of their central brain and the visual pathways beyond major circuits. Here, we provide a comprehensive, three-dimensional neuronal map of synapse-rich neuropils in the brain of Cataglyphis nodus including major connecting fiber systems. In addition, we examined neuronal tracts underlying the processing of visual information in more detail. This study revealed a total of 33 brain neuropils and 30 neuronal fiber tracts including six distinct tracts between the optic lobes and the cerebrum. We also discuss the importance of comparative studies on insect brain architecture for a profound understanding of neuronal networks and their function.}, language = {en} } @article{HensgenEnglandHombergetal.2021, author = {Hensgen, Ronja and England, Laura and Homberg, Uwe and Pfeiffer, Keram}, title = {Neuroarchitecture of the central complex in the brain of the honeybee: Neuronal cell types}, series = {Journal of Comparative Neurology}, volume = {529}, journal = {Journal of Comparative Neurology}, doi = {10.1002/cne.24941}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-215566}, pages = {159-186}, year = {2021}, abstract = {The central complex (CX) in the insect brain is a higher order integration center that controls a number of behaviors, most prominently goal directed locomotion. The CX comprises the protocerebral bridge (PB), the upper division of the central body (CBU), the lower division of the central body (CBL), and the paired noduli (NO). Although spatial orientation has been extensively studied in honeybees at the behavioral level, most electrophysiological and anatomical analyses have been carried out in other insect species, leaving the morphology and physiology of neurons that constitute the CX in the honeybee mostly enigmatic. The goal of this study was to morphologically identify neuronal cell types of the CX in the honeybee Apis mellifera. By performing iontophoretic dye injections into the CX, we traced 16 subtypes of neuron that connect a subdivision of the CX with other regions in the bee's central brain, and eight subtypes that mainly interconnect different subdivisions of the CX. They establish extensive connections between the CX and the lateral complex, the superior protocerebrum and the posterior protocerebrum. Characterized neuron classes and subtypes are morphologically similar to those described in other insects, suggesting considerable conservation in the neural network relevant for orientation.}, language = {en} } @article{HeldBerzHensgenetal.2016, author = {Held, Martina and Berz, Annuska and Hensgen, Ronja and Muenz, Thomas S. and Scholl, Christina and R{\"o}ssler, Wolfgang and Homberg, Uwe and Pfeiffer, Keram}, title = {Microglomerular Synaptic Complexes in the Sky-Compass Network of the Honeybee Connect Parallel Pathways from the Anterior Optic Tubercle to the Central Complex}, series = {Frontiers in Behavioral Neuroscience}, volume = {10}, journal = {Frontiers in Behavioral Neuroscience}, number = {186}, doi = {10.3389/fnbeh.2016.00186}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-165080}, year = {2016}, abstract = {While the ability of honeybees to navigate relying on sky-compass information has been investigated in a large number of behavioral studies, the underlying neuronal system has so far received less attention. The sky-compass pathway has recently been described from its input region, the dorsal rim area (DRA) of the compound eye, to the anterior optic tubercle (AOTU). The aim of this study is to reveal the connection from the AOTU to the central complex (CX). For this purpose, we investigated the anatomy of large microglomerular synaptic complexes in the medial and lateral bulbs (MBUs/LBUs) of the lateral complex (LX). The synaptic complexes are formed by tubercle-lateral accessory lobe neuron 1 (TuLAL1) neurons of the AOTU and GABAergic tangential neurons of the central body's (CB) lower division (TL neurons). Both TuLAL1 and TL neurons strongly resemble neurons forming these complexes in other insect species. We further investigated the ultrastructure of these synaptic complexes using transmission electron microscopy. We found that single large presynaptic terminals of TuLAL1 neurons enclose many small profiles (SPs) of TL neurons. The synaptic connections between these neurons are established by two types of synapses: divergent dyads and divergent tetrads. Our data support the assumption that these complexes are a highly conserved feature in the insect brain and play an important role in reliable signal transmission within the sky-compass pathway.}, language = {en} } @article{GrobFleischmannGruebeletal.2017, author = {Grob, Robin and Fleischmann, Pauline N. and Gr{\"u}bel, Kornelia and Wehner, R{\"u}diger and R{\"o}ssler, Wolfgang}, title = {The role of celestial compass information in Cataglyphis ants during learning walks and for neuroplasticity in the central complex and mushroom bodies}, series = {Frontiers in Behavioral Neuroscience}, volume = {11}, journal = {Frontiers in Behavioral Neuroscience}, number = {226}, doi = {10.3389/fnbeh.2017.00226}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-159235}, year = {2017}, abstract = {Central place foragers are faced with the challenge to learn the position of their nest entrance in its surroundings, in order to find their way back home every time they go out to search for food. To acquire navigational information at the beginning of their foraging career, Cataglyphis noda performs learning walks during the transition from interior worker to forager. These small loops around the nest entrance are repeatedly interrupted by strikingly accurate back turns during which the ants stop and precisely gaze back to the nest entrance—presumably to learn the landmark panorama of the nest surroundings. However, as at this point the complete navigational toolkit is not yet available, the ants are in need of a reference system for the compass component of the path integrator to align their nest entrance-directed gazes. In order to find this directional reference system, we systematically manipulated the skylight information received by ants during learning walks in their natural habitat, as it has been previously suggested that the celestial compass, as part of the path integrator, might provide such a reference system. High-speed video analyses of distinct learning walk elements revealed that even exclusion from the skylight polarization pattern, UV-light spectrum and the position of the sun did not alter the accuracy of the look back to the nest behavior. We therefore conclude that C. noda uses a different reference system to initially align their gaze directions. However, a comparison of neuroanatomical changes in the central complex and the mushroom bodies before and after learning walks revealed that exposure to UV light together with a naturally changing polarization pattern was essential to induce neuroplasticity in these high-order sensory integration centers of the ant brain. This suggests a crucial role of celestial information, in particular a changing polarization pattern, in initially calibrating the celestial compass system.}, language = {en} }