@article{StiebKelberWehneretal.2011,
  author    = {Stieb, Sara Mae and Kelber, Christina and Wehner, R{\"u}diger and R{\"o}ssler, Wolfgang},
  title     = {Antennal-Lobe Organization in Desert Ants of the Genus Cataglyphis},
  series = {Brain, Behavior and Evolution},
  volume    = {77},
  journal   = {Brain, Behavior and Evolution},
  number    = {3},
  issn      = {0006-8977},
  doi       = {10.1159/000326211},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-196815},
  pages     = {136-146},
  year      = {2011},
  abstract  = {Desert ants of the genus Cataglyphis possess remarkable visual navigation capabilities. Although Cataglyphis species lack a trail pheromone system, Cataglyphis fortis employs olfactory cues for detecting nest and food sites. To investigate potential adaptations in primary olfactory centers of the brain of C. fortis, we analyzed olfactory glomeruli (odor processing units) in their antennal lobes and compared them to glomeruli in different Cataglyphis species. Using confocal imaging and 3D reconstruction, we analyzed the number, size and spatial arrangement of olfactory glomeruli in C. fortis, C.albicans, C.bicolor, C.rubra, and C.noda. Workers of all Cataglyphis species have smaller numbers of glomeruli (198-249) compared to those previously found in olfactory-guided ants. Analyses in 2 species of Formica - a genus closely related to Cataglyphis - revealed substantially higher numbers of olfactory glomeruli (c. 370), which is likely to reflect the importance of olfaction in these wood ant species. Comparisons between Cataglyphis species revealed 2 special features in C. fortis. First, with c. 198 C. fortis has the lowest number of glomeruli compared to all other species. Second, a conspicuously enlarged glomerulus is located close to the antennal nerve entrance. Males of C. fortis possess a significantly smaller number of glomeruli (c. 150) compared to female workers and queens. A prominent male-specific macroglomerulus likely to be involved in sex pheromone communication occupies a position different from that of the enlarged glomerulus in females. The behavioral significance of the enlarged glomerulus in female workers remains elusive. The fact that C. fortis inhabits microhabitats (salt pans) that are avoided by all other Cataglyphis species suggests that extreme ecological conditions may not only have resulted in adaptations of visual capabilities, but also in specializations of the olfactory system.},
  language  = {en}
}
@article{GrohRoessler2020,
  author    = {Groh, Claudia and R{\"o}ssler, Wolfgang},
  title     = {Analysis of Synaptic Microcircuits in the Mushroom Bodies of the Honeybee},
  series = {Insects},
  volume    = {11},
  journal   = {Insects},
  number    = {1},
  issn      = {2075-4450},
  doi       = {10.3390/insects11010043},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-200774},
  year      = {2020},
  abstract  = {Mushroom bodies (MBs) are multisensory integration centers in the insect brain involved in learning and memory formation. In the honeybee, the main sensory input region (calyx) of MBs is comparatively large and receives input from mainly olfactory and visual senses, but also from gustatory/tactile modalities. Behavioral plasticity following differential brood care, changes in sensory exposure or the formation of associative long-term memory (LTM) was shown to be associated with structural plasticity in synaptic microcircuits (microglomeruli) within olfactory and visual compartments of the MB calyx. In the same line, physiological studies have demonstrated that MB-calyx microcircuits change response properties after associative learning. The aim of this review is to provide an update and synthesis of recent research on the plasticity of microcircuits in the MB calyx of the honeybee, specifically looking at the synaptic connectivity between sensory projection neurons (PNs) and MB intrinsic neurons (Kenyon cells). We focus on the honeybee as a favorable experimental insect for studying neuronal mechanisms underlying complex social behavior, but also compare it with other insect species for certain aspects. This review concludes by highlighting open questions and promising routes for future research aimed at understanding the causal relationships between neuronal and behavioral plasticity in this charismatic social insect.},
  language  = {en}
}
@article{KropfRoessler2018,
  author    = {Kropf, Jan and R{\"o}ssler, Wolfgang},
  title     = {In-situ recording of ionic currents in projection neurons and Kenyon cells in the olfactory pathway of the honeybee},
  series = {PLoS ONE},
  volume    = {13},
  journal   = {PLoS ONE},
  number    = {1},
  doi       = {10.1371/journal.pone.0191425},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-175869},
  pages     = {e0191425},
  year      = {2018},
  abstract  = {The honeybee olfactory pathway comprises an intriguing pattern of convergence and divergence: ~60.000 olfactory sensory neurons (OSN) convey olfactory information on ~900 projection neurons (PN) in the antennal lobe (AL). To transmit this information reliably, PNs employ relatively high spiking frequencies with complex patterns. PNs project via a dual olfactory pathway to the mushroom bodies (MB). This pathway comprises the medial (m-ALT) and the lateral antennal lobe tract (l-ALT). PNs from both tracts transmit information from a wide range of similar odors, but with distinct differences in coding properties. In the MBs, PNs form synapses with many Kenyon cells (KC) that encode odors in a spatially and temporally sparse way. The transformation from complex information coding to sparse coding is a well-known phenomenon in insect olfactory coding. Intrinsic neuronal properties as well as GABAergic inhibition are thought to contribute to this change in odor representation. In the present study, we identified intrinsic neuronal properties promoting coding differences between PNs and KCs using in-situ patch-clamp recordings in the intact brain. We found very prominent K+ currents in KCs clearly differing from the PN currents. This suggests that odor coding differences between PNs and KCs may be caused by differences in their specific ion channel properties. Comparison of ionic currents of m- and l-ALT PNs did not reveal any differences at a qualitative level.},
  language  = {en}
}
@article{FalibeneRocesRoessler2015,
  author    = {Falibene, Augustina and Roces, Flavio and R{\"o}ssler, Wolfgang},
  title     = {Long-term avoidance memory formation is associated with a transient increase in mushroom body synaptic complexes in leaf-cutting ants},
  series = {Frontiers in Behavioural Neuroscience},
  volume    = {9},
  journal   = {Frontiers in Behavioural Neuroscience},
  number    = {84},
  doi       = {10.3389/fnbeh.2015.00084},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-148763},
  year      = {2015},
  abstract  = {Long-term behavioral changes related to learning and experience have been shown to be associated with structural remodeling in the brain. Leaf-cutting ants learn to avoid previously preferred plants after they have proved harmful for their symbiotic fungus, a process that involves long-term olfactory memory. We studied the dynamics of brain microarchitectural changes after long-term olfactory memory formation following avoidance learning in Acromyrmex ambiguus. After performing experiments to control for possible neuronal changes related to age and body size, we quantified synaptic complexes (microglomeruli, MG) in olfactory regions of the mushroom bodies (MB) at different times after learning. Long-term avoidance memory formation was associated with a transient change in MG densities. Two days after learning, MG density was higher than before learning. At days 4 and 15 after learning when ants still showed plant avoidance MG densities had decreased to the initial state. The structural reorganization of MG triggered by long-term avoidance memory formation clearly differed from changes promoted by pure exposure to and collection of novel plants with distinct odors. Sensory exposure by the simultaneous collection of several, instead of one, non-harmful plant species resulted in a decrease in MG densities in the olfactory lip. We hypothesize that while sensory exposure leads to MG pruning in the MB olfactory lip, the formation of long-term avoidance memory involves an initial growth of new MG followed by subsequent pruning.},
  language  = {en}
}
@article{FalibeneRocesRoessleretal.2016,
  author    = {Falibene, Augustine and Roces, Flavio and R{\"o}ssler, Wolfgang and Groh, Claudia},
  title     = {Daily Thermal Fluctuations Experienced by Pupae via Rhythmic Nursing Behavior Increase Numbers of Mushroom Body Microglomeruli in the Adult Ant Brain},
  series = {Frontiers in Behavioral Neuroscience},
  volume    = {10},
  journal   = {Frontiers in Behavioral Neuroscience},
  number    = {73},
  doi       = {10.3389/fnbeh.2016.00073},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-146711},
  year      = {2016},
  abstract  = {Social insects control brood development by using different thermoregulatory strategies. Camponotus mus ants expose their brood to daily temperature fluctuations by translocating them inside the nest following a circadian rhythm of thermal preferences. At the middle of the photophase brood is moved to locations at 30.8°C; 8 h later, during the night, the brood is transferred back to locations at 27.5°C. We investigated whether daily thermal fluctuations experienced by developing pupae affect the neuroarchitecture in the adult brain, in particular in sensory input regions of the mushroom bodies (MB calyces). The complexity of synaptic microcircuits was estimated by quantifying MB-calyx volumes together with densities of presynaptic boutons of microglomeruli (MG) in the olfactory lip and visual collar regions. We compared young adult workers that were reared either under controlled daily thermal fluctuations of different amplitudes, or at different constant temperatures. Thermal regimes significantly affected the large (non-dense) olfactory lip region of the adult MB calyx, while changes in the dense lip and the visual collar were less evident. Thermal fluctuations mimicking the amplitudes of natural temperature fluctuations via circadian rhythmic translocation of pupae by nurses (amplitude 3.3°C) lead to higher numbers of MG in the MB calyces compared to those in pupae reared at smaller or larger thermal amplitudes (0.0, 1.5, 9.6°C), or at constant temperatures (25.4, 35.0°C). We conclude that rhythmic control of brood temperature by nursing ants optimizes brain development by increasing MG densities and numbers in specific brain areas. Resulting differences in synaptic microcircuits are expected to affect sensory processing and learning abilities in adult ants, and may also promote interindividual behavioral variability within colonies.},
  language  = {en}
}
@article{FalibeneRocesRoessler2015,
  author    = {Falibene, Agustina and Roces, Flavio and R{\"o}ssler, Wolfgang},
  title     = {Long-term avoidance memory formation is associated with a transient increase in mushroom body synaptic complexes in leaf-cutting ants},
  series = {Frontiers in Behavioral Neuroscience},
  volume    = {9},
  journal   = {Frontiers in Behavioral Neuroscience},
  number    = {84},
  doi       = {10.3389/fnbeh.2015.00084},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-125522},
  year      = {2015},
  abstract  = {Long-term behavioral changes related to learning and experience have been shown to be associated with structural remodeling in the brain. Leaf-cutting ants learn to avoid previously preferred plants after they have proved harmful for their symbiotic fungus, a process that involves long-term olfactory memory. We studied the dynamics of brain microarchitectural changes after long-term olfactory memory formation following avoidance learning in Acromyrmex ambiguus. After performing experiments to control for possible neuronal changes related to age and body size, we quantified synaptic complexes (microglomeruli, MG) in olfactory regions of the mushroom bodies (MBs) at different times after learning. Long-term avoidance memory formation was associated with a transient change in MG densities. Two days after learning, MG density was higher than before learning. At days 4 and 15 after learning—when ants still showed plant avoidance—MG densities had decreased to the initial state. The structural reorganization of MG triggered by long-term avoidance memory formation clearly differed from changes promoted by pure exposure to and collection of novel plants with distinct odors. Sensory exposure by the simultaneous collection of several, instead of one, non-harmful plant species resulted in a decrease in MG densities in the olfactory lip. We hypothesize that while sensory exposure leads to MG pruning in the MB olfactory lip, the formation of long-term avoidance memory involves an initial growth of new MG followed by subsequent pruning.},
  language  = {en}
}