@article{NuernbergerSteffanDewenterHaertel2017,
  author    = {N{\"u}rnberger, Fabian and Steffan-Dewenter, Ingolf and H{\"a}rtel, Stephan},
  title     = {Combined effects of waggle dance communication and landscape heterogeneity on nectar and pollen uptake in honey bee colonies},
  series = {PeerJ},
  volume    = {5},
  journal   = {PeerJ},
  number    = {e3441},
  doi       = {10.7717/peerj.3441},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-170813},
  year      = {2017},
  abstract  = {The instructive component of waggle dance communication has been shown to increase resource uptake of Apis mellifera colonies in highly heterogeneous resource environments, but an assessment of its relevance in temperate landscapes with different levels of resource heterogeneity is currently lacking. We hypothesized that the advertisement of resource locations via dance communication would be most relevant in highly heterogeneous landscapes with large spatial variation of floral resources. To test our hypothesis, we placed 24 Apis mellifera colonies with either disrupted or unimpaired instructive component of dance communication in eight Central European agricultural landscapes that differed in heterogeneity and resource availability. We monitored colony weight change and pollen harvest as measure of foraging success. Dance disruption did not significantly alter colony weight change, but decreased pollen harvest compared to the communicating colonies by 40\%. There was no general effect of resource availability on nectar or pollen foraging success, but the effect of landscape heterogeneity on nectar uptake was stronger when resource availability was high. In contrast to our hypothesis, the effects of disrupted bee communication on nectar and pollen foraging success were not stronger in landscapes with heterogeneous compared to homogenous resource environments. Our results indicate that in temperate regions intra-colonial communication of resource locations benefits pollen foraging more than nectar foraging, irrespective of landscape heterogeneity. We conclude that the so far largely unexplored role of dance communication in pollen foraging requires further consideration as pollen is a crucial resource for colony development and health.},
  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}
}
@phdthesis{Nguyen2023,
  author    = {Nguyen, Tu Anh Thi},
  title     = {Neural coding of different visual cues in the monarch butterfly sun compass},
  doi       = {10.25972/OPUS-30380},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-303807},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2023},
  abstract  = {Monarch butterflies are famous for their annual long-distance migration. Decreasing temperatures and reduced daylight induce the migratory state in the autumn generation of monarch butterflies. Not only are they in a reproductive diapause, they also produce fat deposits to be prepared for the upcoming journey: Driven by their instinct to migrate, they depart from their eclosion grounds in the northern regions of the North American continent and start their southern journey to their hibernation spots in Central Mexico. The butterflies cover a distance of up to 4000 km across the United States. In the next spring, the same butterflies invert their preferred heading direction due to seasonal changes and start their northward spring migration. The spring migration is continued by three consecutive butterfly generations, until the animals repopulate the northern regions in North America as non-migratory monarch butterflies. The monarch butterflies' migratory state is genetically and epigenetically regulated, including the directed flight behavior. Therefore, the insect's internal compass system does not only have to encode the butterflies preferred, but also its current heading direction. However, the butterfly's internal heading representation has to be matched to external cues, to avoid departing from its initial flight path and increasing its risk of missing its desired destination. During the migratory flight, visual cues provide the butterflies with reliable orientation information. The butterflies refer to the sun as their main orientation cue. In addition to the sun, the butterflies likely use the polarization pattern of the sky for orientation. The sky compass signals are processed within a region in the brain, termed the central complex (CX). Previous research on the CX neural circuitry of the monarch butterflies demonstrated that tangential central complex neurons (TL) carry the visual input information into the CX and respond to a simulated sun and polarized light. However, whether these cells process additional visual cues like the panoramic skyline is still unknown. Furthermore, little is known about how the migratory state affects visual cue processing. In addition to this, most experiments studying the monarch butterfly CX focused on how neurons process single visual cues. However, how combined visual stimuli are processed in the CX is still unknown. This thesis is investigating the following questions: 1) How does the migratory state affect visual cue processing in the TL cells within the monarch butterfly brain? 2) How are multiple visual cues integrated in the TL cells? 3) How is compass information modulated in the CX? To study these questions, TL neurons from both animal groups (migratory and non-migratory) were electrophysiologically characterized using intracellular recordings while presenting different simulated celestial cues and visual sceneries. I showed that the TL neurons of migratory butterflies are more narrowly tuned to the sun, possibly helping them in keeping a directed flight course during migration. Furthermore, I found that TL cells encode a panoramic skyline, suggesting that the CX network combines celestial and terrestrial information. Experiments with combined celestial stimuli revealed that the TL cells combine both cue information linearly. However, if exposing the animals to a simulated visual scenery containing a panoramic skyline and a simulated sun, the single visual cues are weighted differently. These results indicate that the CX's input region can flexibly adapt to different visual cue conditions. Furthermore, I characterize a previously unknown neuron in the monarch butterfly CX which responds to celestial stimuli and connects the CX with other brain neuropiles. How this cell type affects heading direction encoding has yet to be determined.},
  subject      = {Monarchfalter},
  language  = {en}
}
@phdthesis{Mronz2004,
  author    = {Mronz, Markus},
  title     = {Die visuell motivierte Objektwahl laufender Taufliegen (Drosophila melanogaster) - Verhaltensphysiologie, Modellbildung und Implementierung in einem Roboter},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-11748},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2004},
  abstract  = {Im Rahmen dieser Arbeit wurden offene Fragen zur Objektwahl, zur Objektbeibehaltung und zur Aufgabe von Zielobjekten bei laufenden Taufliegen (Drosophila melanogaster) untersucht. Die Erkenntnisse zur Objektwahl wurden als kybernetisches Modell formuliert, auf einem eigens daf{\"u}r konstruierten, autonom navigierenden Roboter mit Kameraauge implementiert und dessen Verhalten bei verschiedenen Landmarkenkonstellationen quantitativ mit dem Orientierungsverhalten laufender Fliegen verglichen. Es war bekannt, dass Drosophila in einer Wahlsituation zwischen unterschiedlich weit entfernten Objekten eine ausgepr{\"a}gte Pr{\"a}ferenz f{\"u}r nahe Objekte zeigt, wobei die Entfernung {\"u}ber das Ausmaß der retinalen Bildverschiebung auf dem Auge (Parallaxe) erfasst wird. In der vorliegenden Arbeit wurde analysiert, ob die Parallaxe streng aus der Eigenbewegung der Fliege resultieren muss oder ob Eigenbewegung der Objekte N{\"a}he vort{\"a}uschen und deren Attraktivit{\"a}t erh{\"o}hen kann. Es wurde gezeigt, dass die Pr{\"a}ferenz f{\"u}r ein Objekt bei Drosophila umso gr{\"o}ßer wird, je mehr Bewegung dessen Abbild auf der Retina erzeugt; die relative Verschiebung des Objektabbildes muss dabei nicht mit der Eigenbewegung der Fliege gekoppelt sein. {\"U}berraschenderweise verschwand die Pr{\"a}ferenz f{\"u}r nahe Objekte, wenn eine zusammenstehende Gruppe aus einer nahen und mehreren fernen Objekten pr{\"a}sentiert wurden, solange sie zusammen einen Sehwinkel von weniger als etwa 90° einnahmen. Diese Beobachtung ist konform mit einer Vorstellung, wonach Bewegung {\"u}ber gr{\"o}ßere Augenbereiche integriert und nicht einzelnen Objekten zugeordnet wird. Obwohl Drosophila bei gleichem Pr{\"a}sentationsort auf der Retina die gr{\"o}ßere parallaktische Bewegung bevorzugte, wurden bei gleicher Entfernung dennoch frontalere gegen{\"u}ber lateraleren Objekten bevorzugt. Es wird postuliert, dass der frontale und der caudale Sehbereich eine Verst{\"a}rkung erfahren, die die physikalisch bedingt geringere Parallaxe {\"u}berkompensiert. Laufende Fliegen reagieren verz{\"o}gert auf die Pr{\"a}sentation eines Objekts; dies wird im Sinne einer zeitlichen Bewegungsintegration interpretiert. Die darauf folgende Richtungs{\"a}nderung h{\"a}ngt vom Pr{\"a}sentationswinkel des Objektes ab. Erscheint das Objekt frontolateral, findet eine Hinwendung statt, erscheint es caudolateral, kommt es bevorzugt zur Abwendung. Eine weitere wichtige kognitive Leistung der Fliege ist das Aufgeben eines zuvor ausgew{\"a}hlten Ziels, wenn sich dieses Ziel w{\"a}hrend des Anlaufs als unerreichbar herausstellt. In der vorliegenden Arbeit wurde gezeigt, dass Fliegen mit stark reduzierten Pilzk{\"o}rpern erheblich mehr Zeit ben{\"o}tigen als wildtypische Fliegen, um vom gew{\"a}hlten Zielobjekt abzulassen. Dieser dem Perseveranzverhalten bei Parkinson-kranken Menschen {\"a}hnliche Ph{\"a}notyp wurde unabh{\"a}ngig von der Methode der Ausschaltung der Pilzk{\"o}rper gefunden. Die Dauer der Perseveranz nahm mit zunehmender Attraktivit{\"a}t des Zielobjekts, d. h. mit abnehmender Distanz, zu. Es wird vorgeschlagen, dass die Pilzk{\"o}rper f{\"u}r die Evaluierung von eingehender sensorischer Information oder f{\"u}r Entscheidungsfindungen im Allgemeinen ben{\"o}tig werden. Basierend auf diesen Ergebnissen wurde ein Minimalmodell f{\"u}r die visuelle Orientierung nach Landmarken entwickelt. Das Modell beinhaltet eine zeitliche Integration des optischen Flusses in einem frontolateralen und einem caudolateralen Kompartiment pro Auge. Je nachdem, in welchem Kompartiment eine festgesetzte Schwelle zuerst erreicht wird, kommt es entweder zu einer Hin- (frontolateral) oder zu einer Abwendungsreaktion (caudolateral). Eine Gewichtungsfunktion kompensiert die geringe parallaktische Verschiebung in diesen Sehregionen. Das Modell wurde in einem mobilen Roboter mit Kameraauge implementiert und mit dem visuellen Orientierungsverhalten der Fliege quantitativ verglichen. Der Roboter war in der Lage, viele Aspekte der Landmarkenwahl von laufenden Fliegen erfolgreich zu reproduzieren und fliegen{\"a}hnliches, autonomes Orientierungsverhalten unter verschiedenen Landmarkenkonfigurationen zu zeigen.},
  subject      = {Taufliege},
  language  = {de}
}