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Search Results: 1 - 10 of 145671 matches for " Shannon B Olsson "
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Ostrinia revisited: Evidence for sex linkage in European Corn Borer Ostrinia nubilalis (Hubner) pheromone reception
Shannon B Olsson, Subaharan Kesevan, Astrid T Groot, Teun Dekker, David G Heckel, Bill S Hansson
BMC Evolutionary Biology , 2010, DOI: 10.1186/1471-2148-10-285
Abstract: As part of a larger study to finely map the loci responsible for pheromone communication in this species, we have reanalyzed peripheral physiology among parental, and first and second generation hybrids between the two pheromone strains using tungsten electrode electrophysiology. Our results reveal that differences in spike amplitude ratio between male pheromone-sensitive sensory neurons in O. nubilalis races are controlled, at least partially, by sex-linked genes that exhibit E-strain dominance.We propose that peripheral olfactory response in O. nubilalis may be affected both by autosomal and sex-linked genes exhibiting a cross-locus dominance effect, and suggest that the genetic basis for pheromone reception and response in the species is more closely linked than previously thought.In recent years, sensory systems have received significant attention as catalysts to establish reproductive isolation between populations [1]. Chemical signals are perhaps the most ubiquitous sensory system, mediating behaviors between systems as diverse as gametes [2], and plants [3]. The evolution of pheromone diversity is an excellent resource to evaluate the role of sensory systems in speciation, both for its prevalence among several taxa and its definitive signal [4].In insects, sex pheromones are typically blends of small numbers of volatile organic compounds (e.g. [5]). Minute changes in the ratio or identity of the blend can drastically alter the nature of the response. These characteristics result in both an extraordinary specificity in pheromone communication, as well as the potential for huge diversity in pheromone blends [4]. Sex pheromones thus provide an enticing evolutionary palette for the analysis of reproductive isolation and the development of species diversity.Perhaps the most well studied system for assessing the role of pheromone diversity in reproductive isolation is the European Corn Borer (ECB; Ostrinia nubilalis). This species consists of two sympatric races, e
Insect Odorant Response Sensitivity Is Tuned by Metabotropically Autoregulated Olfactory Receptors
Merid N. Getahun, Shannon B. Olsson, Sofia Lavista-Llanos, Bill S. Hansson, Dieter Wicher
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0058889
Abstract: Insects possess one of the most exquisitely sensitive olfactory systems in the animal kingdom, consisting of three different types of chemosensory receptors: ionotropic glutamate-like receptors (IRs), gustatory receptors (GRs) and odorant receptors (ORs). Both insect ORs and IRs are ligand-gated ion channels, but ORs possess a unique configuration composed of an odorant-specific protein OrX and a ubiquitous coreceptor (Orco). In addition, these two ionotropic receptors confer different tuning properties for the neurons in which they are expressed. Unlike IRs, neurons expressing ORs are more sensitive and can also be sensitized by sub-threshold concentrations of stimuli. What is the mechanistic basis for these differences in tuning? We show that intrinsic regulation of Orco enhances neuronal response to odorants and sensitizes the ORs. We also demonstrate that inhibition of metabotropic regulation prevents receptor sensitization. Our results indicate that Orco-mediated regulation of OR sensitivity provides tunable ionotropic receptors capable of detecting odors over a wider range of concentrations, providing broadened sensitivity over IRs themselves.
Temporal response dynamics of Drosophila olfactory sensory neurons depends on receptor type and response polarity
Merid N. Getahun,Dieter Wicher,Bill S. Hansson,Shannon B. Olsson
Frontiers in Cellular Neuroscience , 2012, DOI: 10.3389/fncel.2012.00054
Abstract: Insect olfactory sensory neurons (OSN) express a diverse array of receptors from different protein families, i.e. ionotropic receptors (IR), gustatory receptors (GR) and odorant receptors (OR). It is well known that insects are exposed to a plethora of odor molecules that vary widely in both space and time under turbulent natural conditions. In addition to divergent ligand specificities, these different receptors might also provide an increased range of temporal dynamics and sensitivities for the olfactory system. To test this, we challenged different Drosophila OSNs with both varying stimulus durations (10–2000 ms), and repeated stimulus pulses of key ligands at various frequencies (1–10 Hz). Our results show that OR-expressing OSNs responded faster and with higher sensitivity to short stimulations as compared to IR- and Gr21a-expressing OSNs. In addition, OR-expressing OSNs could respond to repeated stimulations of excitatory ligands up to 5 Hz, while IR-expressing OSNs required ~5x longer stimulations and/or higher concentrations to respond to similar stimulus durations and frequencies. Nevertheless, IR-expressing OSNs did not exhibit adaptation to longer stimulations, unlike OR- and Gr21a-OSNs. Both OR- and IR-expressing OSNs were also unable to resolve repeated pulses of inhibitory ligands as fast as excitatory ligands. These differences were independent of the peri-receptor environment in which the receptors were expressed and suggest that the receptor expressed by a given OSN affects both its sensitivity and its response to transient, intermittent chemical stimuli. OR-expressing OSNs are better at resolving low dose, intermittent stimuli, while IR-expressing OSNs respond more accurately to long-lasting odor pulses. This diversity increases the capacity of the insect olfactory system to respond to the diverse spatiotemporal signals in the natural environment.
Neuronal Processing of Complex Mixtures Establishes a Unique Odor Representation in the Moth Antennal Lobe
Linda S. Kuebler,Shannon B. Olsson,Richard Weniger,Bill S. Hansson
Frontiers in Neural Circuits , 2011, DOI: 10.3389/fncir.2011.00007
Abstract: Animals typically perceive natural odor cues in their olfactory environment as a complex mixture of chemically diverse components. In insects, the initial representation of an odor mixture occurs in the first olfactory center of the brain, the antennal lobe (AL). The contribution of single neurons to the processing of complex mixtures in insects, and in particular moths, is still largely unknown. Using a novel multicomponent stimulus system to equilibrate component and mixture concentrations according to vapor pressure, we performed intracellular recordings of projection and interneurons in an attempt to quantitatively characterize mixture representation and integration properties of single AL neurons in the moth. We found that the fine spatiotemporal representation of 2–7 component mixtures among single neurons in the AL revealed a highly combinatorial, non-linear process for coding host mixtures presumably shaped by the AL network: 82% of mixture responding projection neurons and local interneurons showed non-linear spike frequencies in response to a defined host odor mixture, exhibiting an array of interactions including suppression, hypoadditivity, and synergism. Our results indicate that odor mixtures are represented by each cell as a unique combinatorial representation, and there is no general rule by which the network computes the mixture in comparison to single components. On the single neuron level, we show that those differences manifest in a variety of parameters, including the spatial location, frequency, latency, and temporal pattern of the response kinetics.
Non-linear blend coding in the moth antennal lobe emerges from random glomerular networks
Alberto Capurro,Shannon B. Olsson,Linda S. Kuebler,Bill S. Hansson,Timothy C. Pearce
Frontiers in Neuroengineering , 2012, DOI: 10.3389/fneng.2012.00006
Abstract: Neural responses to odor blends often exhibit non-linear interactions to blend components. The first olfactory processing center in insects, the antennal lobe (AL), exhibits a complex network connectivity. We attempt to determine if non-linear blend interactions can arise purely as a function of the AL network connectivity itself, without necessitating additional factors such as competitive ligand binding at the periphery or intrinsic cellular properties. To assess this, we compared blend interactions among responses from single neurons recorded intracellularly in the AL of the moth Manduca sexta with those generated using a population-based computational model constructed from the morphologically based connectivity pattern of projection neurons (PNs) and local interneurons (LNs) with randomized connection probabilities from which we excluded detailed intrinsic neuronal properties. The model accurately predicted most of the proportions of blend interaction types observed in the physiological data. Our simulations also indicate that input from LNs is important in establishing both the type of blend interaction and the nature of the neuronal response (excitation or inhibition) exhibited by AL neurons. For LNs, the only input that significantly impacted the blend interaction type was received from other LNs, while for PNs the input from olfactory sensory neurons and other PNs contributed agonistically with the LN input to shape the AL output. Our results demonstrate that non-linear blend interactions can be a natural consequence of AL connectivity, and highlight the importance of lateral inhibition as a key feature of blend coding to be addressed in future experimental and computational studies.
Phosphorylation via PKC Regulates the Function of the Drosophila Odorant Co-Receptor
Vardanush Sargsyan,Merid Negash Getahun,Sofía Lavista Llanos,Shannon B. Olsson,Bill S. Hansson,Dieter Wicher
Frontiers in Cellular Neuroscience , 2011, DOI: 10.3389/fncel.2011.00005
Abstract: Insect odorant receptors (ORs) have a unique design of heterodimers formed by an olfactory receptor protein and the ion channel Orco. Heterologously expressed insect ORs are activated via an ionotropic and a metabotropic pathway that leads to cAMP production and activates the Orco channel. The contribution of metabotropic signaling to the insect odor response remains to be elucidated. Disruption of the Gq protein signaling cascade reduces the odor response (Kain et al., 2008). We investigated this phenomenon in HEK293 cells expressing Drosophila Orco and found that phospholipase C (PLC) inhibition reduced the sensitivity of Orco to cAMP. A similar effect was seen upon inhibition of protein kinase C (PKC), whereas PKC stimulation activated Orco even in the absence of cAMP. Mutation of the five PKC phosphorylation sites in Orco almost completely eliminated sensitivity to cAMP. To test the impact of PKC activity in vivo we combined single sensillum electrophysiological recordings with microinjection of agents affecting PLC and PKC function and observed an altered response of olfactory sensory neurons (OSNs) to odorant stimulation. Injection of the PLC inhibitor U73122 or the PKC inhibitor G?6976 into sensilla reduced the OSN response to odor pulses. Conversely, injection of the PKC activators OAG, a diacylglycerol analog, or phorbol myristate acetate (PMA) enhanced the odor response. We conclude that metabotropic pathways affecting the phosphorylation state of Orco regulate OR function and thereby shape the OSN odor response.
Temporal Features of Spike Trains in the Moth Antennal Lobe Revealed by a Comparative Time-Frequency Analysis
Alberto Capurro, Fabiano Baroni, Linda S. Kuebler, Zsolt Kárpáti, Teun Dekker, Hong Lei, Bill S. Hansson, Timothy C. Pearce, Shannon B. Olsson
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0084037
Abstract: The discrimination of complex sensory stimuli in a noisy environment is an immense computational task. Sensory systems often encode stimulus features in a spatiotemporal fashion through the complex firing patterns of individual neurons. To identify these temporal features, we have developed an analysis that allows the comparison of statistically significant features of spike trains localized over multiple scales of time-frequency resolution. Our approach provides an original way to utilize the discrete wavelet transform to process instantaneous rate functions derived from spike trains, and select relevant wavelet coefficients through statistical analysis. Our method uncovered localized features within olfactory projection neuron (PN) responses in the moth antennal lobe coding for the presence of an odor mixture and the concentration of single component odorants, but not for compound identities. We found that odor mixtures evoked earlier responses in biphasic response type PNs compared to single components, which led to differences in the instantaneous firing rate functions with their signal power spread across multiple frequency bands (ranging from 0 to 45.71 Hz) during a time window immediately preceding behavioral response latencies observed in insects. Odor concentrations were coded in excited response type PNs both in low frequency band differences (2.86 to 5.71 Hz) during the stimulus and in the odor trace after stimulus offset in low (0 to 2.86 Hz) and high (22.86 to 45.71 Hz) frequency bands. These high frequency differences in both types of PNs could have particular relevance for recruiting cellular activity in higher brain centers such as mushroom body Kenyon cells. In contrast, neurons in the specialized pheromone-responsive area of the moth antennal lobe exhibited few stimulus-dependent differences in temporal response features. These results provide interesting insights on early insect olfactory processing and introduce a novel comparative approach for spike train analysis applicable to a variety of neuronal data sets.
A theorem on the cores of partitions
J. B. Olsson
Mathematics , 2008,
Abstract: If s and t are relatively prime positive integers we show that the s-core of a t-core partition is again a t-core partition
Sign conjugacy classes in symmetric groups
Jorn B. Olsson
Mathematics , 2008,
Abstract: A special type of conjugacy classes in symmetric groups is studied and used to answer a question about odd-degree irreducible characters
Truth, Reconcilation, Restorative Justice, and Canadian Discourses of Legitimation in Educational Contexts  [PDF]
Shannon A. Moore, Liana B. Clarysse
Beijing Law Review (BLR) , 2018, DOI: 10.4236/blr.2018.94029
Abstract: Building upon previous research investigating discourses of legitimation informing restorative justice practices in educational contexts in Canada and the United Kingdom, the current study takes forward the same conceptual and analytic framework to engage a preliminary analysis of legitimation in the narrative of documents and testimonies found within the reports of the Truth and Reconciliation Commission of Canada (2015a, 2015b) or TRC. Shared philosophical principles emergent from Indigenous epistemologies are foundational to both restorative justice and truth and reconciliation proceedings and, accordingly, the current study drew upon insights from an original study epistemologically, analytically and methodologically (Clarysse & Moore, 2017). The conceptual framework guiding the analysis is shaped by van Leeuwen’s (2007) framework of four categories for analyzing processes that legitimate social practices in public communication, education, and everyday interaction. Findings indicate unrestricted and extensive use of legitimation within historical discourse related to the residential schooling system disclosed in Canada’s TRC. Subsequent current-day testimonies of the survivors of Canada’s residential schooling system and their ancestors articulate the lived experience and fallout from education related to this historical discourse legitimation. In contrast to text evidence from the Truth and Reconciliation Commission, a comparative analysis of text samples from contemporary restorative justice policy, law and practice documents found less pointed and more holistic application of discourses of legitimation to convey the merit of restorative justice practices in educational contexts. This study reinforces the important role of educational discourses in shaping critical awareness of discursive patterns of legitimation and the impact of these patterns of communication on notions of holism and community in educational contexts.
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