Fast PCA for processing calcium-imaging data from the brain of Drosophila melanogaster

<p>Abstract</p> <p>Background</p> <p>The calcium-imaging technique allows us to record movies of brain activity in the antennal lobe of the fruitfly <it>Drosophila melanogaster</it>, a brain compartment dedicated to information about odors. Signal processing, e.g. with source separation techniques, can be slow on the large movie datasets.</p> <p>Method</p> <p>We have developed an approximate Principal Component Analysis (PCA) for fast dimensionality reduction. The method samples relevant pixels from the movies, such that PCA can be performed on a smaller matrix. Utilising <it>a priori </it>knowledge about the nature of the data, we minimise the risk of missing important pixels.</p> <p>Results</p> <p>Our method allows for fast approximate computation of PCA with adaptive resolution and running time. Utilising <it>a priori </it>knowledge about the data enables us to concentrate more biological signals in a small pixel sample than a general sampling method based on vector norms.</p> <p>Conclusions</p> <p>Fast dimensionality reduction with approximate PCA removes a computational bottleneck and leads to running time improvements for subsequent algorithms. Once in PCA space, we can efficiently perform source separation, e.g to detect biological signals in the movies or to remove artifacts.</p

Odor-driven attractor dynamics in the antennal lobe allow for simple and rapid olfactory pattern classification

The antennal lobe plays a central role for odor processing in insects, as demonstrated by electrophysiological and imaging experiments. Here we analyze the detailed temporal evolution of glomerular activity patterns in the antennal lobe of honeybees. We represent these spatiotemporal patterns as trajectories in a multidimensional space, where each dimension accounts for the activity of one glomerulus. Our data show that the trajectories reach odor-specific steady states (attractors) that correspond to stable activity patterns at about 1 second after stimulus onset. As revealed by a detailed mathematical investigation, the trajectories are characterized by different phases: response onset, steady-state plateau, response offset, and periods of spontaneous activity. An analysis based on support-vector machines quantifies the odor specificity of the attractors and the optimal time needed for odor discrimination. The results support the hypothesis of a spatial olfactory code in the antennal lobe and suggest a perceptron-like readout mechanism that is biologically implemented in a downstream network, such as the mushroom body

Data-driven honeybee antennal lobe model demonstrates how stimulus-onset asynchrony can aid odor segregation

No description supplie

Conditioning your bee - in one, two, three!

Neste estudo argumenta-se que para a análise e a desmontagem dos mecanismos representacionais, é importante considerar não só o contributo carreado pelos estudos mais recentes sobre esterótipos, como também as reflexões sobre a alteridade, a identidade e a complexidade apresentadas por filósofos como E. Levinas, G. Deleuze e Edgar Morin. Tendo como pano de fundo este conjunto de ideias, procede-se à identificação de imagotipos e figurações culturais na ficção de Maria Ondina Braga e de Brigitte Paulino-Neto, com o intuito de surpreender e compreender quer os paralelismos e as diferenças que as suas obras apresentam, quer a forma como a escrita de ambas as autoras espelha as mudanças que o tempo introduz nos intercâmbios culturais. Reflete-se ainda no modo como as experiências diretas e indiretas da diáspora—vivenciadas pelas escritoras—se transpõem literariamente através das narradoras e das personagens, moldando de modo peculiar as suas ficções

Efficacy and use of benralizumab in patients with eosinophilic chronic rhinosinusitis

Abstract Chronic rhinosinusitis has a multifactorial etiology resulting from a dysfunctional interaction between various environmental factors and the host immune system. The patient of case report is affected by chronic rhinosinusitis with nasal polyps and a type 2 molecular pattern, has comorbid asthma and symptoms resistant to adequate medical and surgical therapy. The patient was treated with benralizumab, a mAb that binds IL-5Rα. The therapy resulted in a reduction in blood and tissue eosinophilia, but this was not associated with an improvement in the clinical and objective rhinological picture. Instead, at the lung level, there was a marked improvement in the control of severe asthma. Therefore, the patient was undergoing revision Full FESS in association with biological drug therapy. The patient showed an immediately improvement in the clinical and objective rhinological picture and this association allowed for control of the disease almost one year after surgery

Sensory memory for odors is encoded in spontaneous correlated activity between olfactory glomeruli

Sensory memory is a short-lived persistence of a sensory stimulus in the nervous system, such as iconic memory in the visual system. However, little is known about the mechanisms underlying olfactory sensory memory. We have therefore analyzed the effect of odor stimuli on the first odor-processing network in the honeybee brain, the antennal lobe, which corresponds to the vertebrate olfactory bulb. We stained output neurons with a calcium-sensitive dye and measured across-glomerular patterns of spontaneous activity before and after a stimulus. Such a single-odor presentation changed the relative timing of spontaneous activity across glomeruli in accordance with Hebb's theory of learning. Moreover, during the first few minutes after odor presentation, correlations between the spontaneous activity fluctuations suffice to reconstruct the stimulus. As spontaneous activity is ubiquitous in the brain, modifiable fluctuations could provide an ideal substrate for Hebbian reverberations and sensory memory in other neural systems

Olfactory Sensor Processing in Neural Networks: Lessons from Modeling the Fruit Fly Antennal Lobe

The insect olfactory system can be a model for artificial olfactory devices. In particular, Drosophila melanogaster due to its genetic tractability has yielded much information about the design and function of such systems in biology. In this study we investigate possible network topologies to separate representations of odors in the primary olfactory neuropil, the antennal lobe. In particular we compare networks based on stochastic and homogeneous connection weight distributions to connectivities that are based on the input correlations between the glomeruli in the antennal lobe. We show that moderate homogeneous inhibition implements a soft winner-take-all mechanism when paired with realistic input from a large meta-database of odor responses in receptor cells (DoOR database). The sparseness of representations increases with stronger inhibition. Excitation, on the other hand, pushes the representation of odors closer together thus making them harder to distinguish. We further analyze the relationship between different inhibitory network topologies and the properties of the receptor responses to different odors. We show that realistic input from the DoOR database has a relatively high entropy of activation values over all odors and receptors compared to the theoretical maximum. Furthermore, under conditions in which the information in the input is artificially decreased, networks with heterogeneous topologies based on the similarity of glomerular response profiles perform best. These results indicate that in order to arrive at the most beneficial representation for odor discrimination it is important to finely tune the strength of inhibition in combination with taking into account the properties of the available sensors