Olfactory perception is initiated by the recognition of odorants by a large repertoire of receptors in the sensory epithelium. A dispersed pattern of neural activity in the nose is converted into a ...segregated map in the olfactory bulb. How is this representation transformed at the next processing center for olfactory information, the piriform cortex? Optical imaging of odorant responses in the cortex reveals that the piriform discards spatial segregation as well as chemotopy and returns to a highly distributed organization in which different odorants activate unique but dispersed ensembles of cortical neurons. Neurons in piriform cortex, responsive to a given odorant, are not only distributed without apparent spatial preference but exhibit discontinuous receptive fields. This representation suggests organizational principles that differ from those in neocortical sensory areas where cells responsive to similar stimulus features are clustered and response properties vary smoothly across the cortex.
A sense of occasion: Around 20 years after the start of their pioneering studies on the function of the nose and brain in odor perception, R. Axel and L. Buck have received the 2004 Nobel Prize for ...Medicine or Physiology. The picture shows schematically the coding of different odors in the olfactory epithelium (OE) and olfactory bulb (OB).
The mushroom body in the fruitfly Drosophila melanogaster is an associative brain centre that translates odour representations into learned behavioural responses. Kenyon cells, the intrinsic neurons ...of the mushroom body, integrate input from olfactory glomeruli to encode odours as sparse distributed patterns of neural activity. We have developed anatomic tracing techniques to identify the glomerular origin of the inputs that converge onto 200 individual Kenyon cells. Here we show that each Kenyon cell integrates input from a different and apparently random combination of glomeruli. The glomerular inputs to individual Kenyon cells show no discernible organization with respect to their odour tuning, anatomic features or developmental origins. Moreover, different classes of Kenyon cells do not seem to preferentially integrate inputs from specific combinations of glomeruli. This organization of glomerular connections to the mushroom body could allow the fly to contextualize novel sensory experiences, a feature consistent with the role of this brain centre in mediating learned olfactory associations and behaviours.
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Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Les romans de Marcel Proust et de Georges Pérec présentent le kitsch sous les états de principes et de modes selon la grille théorique élaborée par Abraham Moles. L’étude a puisé des ressources ...conceptuelles dans la Psychologie du kitsch ou L’art du bonheur pour analyser les œuvres que sont Un amour de Swann et Les choses. Si contester le social, c’est quand même s’inspirer de lui, ces œuvres ne manquent pas de faire plonger dans les réalités du XIXe et du XXe siècles. Cependant, au seuil des intrigues, l’étude s’est appesantie sur l’objet dans son acquisition, son utilisation, son positionnement, sa contemplation, sa manipulation. Ainsi, les mots techniques formulés par Abraham Moles ont offert des énoncés tels que les principes d’inadéquation, de cumulation et les modes hédoniste, surréaliste qui ont révélé leur littérarité. Le kitsch offre un ensemble d’outils linguistiques qui expliquent des phénomènes observables au niveau social et au niveau littéraire. À ce titre, l’objet devient le prisme par lequel les mentalités se définissent. Les romans de Marcel Proust et de Georges Pérec renferment des observations et des informations sociologiques rendues sous formes esthétiques à travers le procès du snobisme.
Marcel Proust’s novels certify kitsch by the presence of architecture, theater and fashion. The writer produced his works using textual accumulation and hybridization. These two processes call for ...other arts in romantic production. From this point of view, the baroque, gothic and modern architectures are represented in the texts through buildings tested by rhetorical descriptions. Images of theater and opera scenes accentuate the flow of kitsch. Ostentatious mode creations are also notified in the intrigues. Marcel Proust is inspired by performing arts to develop an aesthetic of plurality in his novels.
Animals exhibit a behavioral response to novel sensory stimuli about which they have no prior knowledge. We have examined the neural and behavioral correlates of novelty and familiarity in the ...olfactory system of Drosophila. Novel odors elicit strong activity in output neurons (MBONs) of the α′3 compartment of the mushroom body that is rapidly suppressed upon repeated exposure to the same odor. This transition in neural activity upon familiarization requires odor-evoked activity in the dopaminergic neuron innervating this compartment. Moreover, exposure of a fly to novel odors evokes an alerting response that can also be elicited by optogenetic activation of α′3 MBONs. Silencing these MBONs eliminates the alerting behavior. These data suggest that the α′3 compartment plays a causal role in the behavioral response to novel and familiar stimuli as a consequence of dopamine-mediated plasticity at the Kenyon cell-MBONα′3 synapse.
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•α′3 MBONs respond to novel odors but suppress their activity to familiar odors•MBON suppression requires odor-evoked excitation of the α′3 dopaminergic neuron•Flies elicit alerting behavior to novel odors that disappears upon familiarization•The alerting response to novel odors requires the activity of α′3 MBONs
The Drosophila mushroom body, a brain region that functions in classical learning, also helps flies identify novel stimuli and become accustomed to them.
We identified the neurons comprising the Drosophila mushroom body (MB), an associative center in invertebrate brains, and provide a comprehensive map describing their potential connections. Each of ...the 21 MB output neuron (MBON) types elaborates segregated dendritic arbors along the parallel axons of ∼2000 Kenyon cells, forming 15 compartments that collectively tile the MB lobes. MBON axons project to five discrete neuropils outside of the MB and three MBON types form a feedforward network in the lobes. Each of the 20 dopaminergic neuron (DAN) types projects axons to one, or at most two, of the MBON compartments. Convergence of DAN axons on compartmentalized Kenyon cell-MBON synapses creates a highly ordered unit that can support learning to impose valence on sensory representations. The elucidation of the complement of neurons of the MB provides a comprehensive anatomical substrate from which one can infer a functional logic of associative olfactory learning and memory.
Drosophila show innate olfactory-driven behaviours that are observed in naive animals without previous learning or experience, suggesting that the neural circuits that mediate these behaviours are ...genetically programmed. Despite the numerical simplicity of the fly nervous system, features of the anatomical organization of the fly brain often confound the delineation of these circuits. Here we identify a neural circuit responsive to cVA, a pheromone that elicits sexually dimorphic behaviours. We have combined neural tracing using an improved photoactivatable green fluorescent protein (PA-GFP) with electrophysiology, optical imaging and laser-mediated microlesioning to map this circuit from the activation of sensory neurons in the antennae to the excitation of descending neurons in the ventral nerve cord. This circuit is concise and minimally comprises four neurons, connected by three synapses. Three of these neurons are overtly dimorphic and identify a male-specific neuropil that integrates inputs from multiple sensory systems and sends outputs to the ventral nerve cord. This neural pathway suggests a means by which a single pheromone can elicit different behaviours in the two sexes.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
We have developed an experimental strategy to monitor protein interactions in a cell with a high degree of selectivity and sensitivity. A transcription factor is tethered to a membrane-bound receptor ...with a linker that contains a cleavage site for a specific protease. Activation of the receptor recruits a signaling protein fused to the protease that then cleaves and releases the transcription factor to activate reporter genes in the nucleus. This strategy converts a transient interaction into a stable and amplifiable reporter gene signal to record the activation of a receptor without interference from endogenous signaling pathways. We have developed this assay for three classes of receptors: G protein-coupled receptors, receptor tyrosine kinases, and steroid hormone receptors. Finally, we use the assay to identify a ligand for the orphan receptor GPR1, suggesting a role for this receptor in the regulation of inflammation.
The convergence of internal path integration and external sensory landmarks generates a cognitive spatial map in the hippocampus. We studied how localized odor cues are recognized as landmarks by ...recording the activity of neurons in CA1 during a virtual navigation task. We found that odor cues enriched place cell representations, dramatically improving navigation. Presentation of the same odor at different locations generated distinct place cell representations. An odor cue at a proximal location enhanced the local place cell density and also led to the formation of place cells beyond the cue. This resulted in the recognition of a second, more distal odor cue as a distinct landmark, suggesting an iterative mechanism for extending spatial representations into unknown territory. Our results establish that odors can serve as landmarks, motivating a model in which path integration and odor landmarks interact sequentially and iteratively to generate cognitive spatial maps over long distances.
•Localized odor cues can serve as landmarks to guide virtual navigation in the dark•Evolution of the CA1 spatial map reflects iterative recognition of odor landmarks•Path integration imposes spatial meaning on odor cues to establish them as landmarks•A model reveals how odors and path integration interact to extend spatial maps
The recognition of a spatial landmark by its sensory features poses a problem for neural circuits. Fischler-Ruiz, et al. show how this problem is solved when mice use odor cues to navigate in the dark. In the hippocampus, path integration imposes spatial meaning on odor cues, thereby creating new landmarks.
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