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Alexander Fleischmann - One of the best experts on this subject based on the ideXlab platform.
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encoding of odor fear memories in the mouse Olfactory Cortex
Current Biology, 2019Co-Authors: Claire Meissnerbernard, Alexander Fleischmann, Yulia Dembitskaya, Laurent VenanceAbstract:Odor memories are exceptionally robust and essential for animal survival. The Olfactory (piriform) Cortex has long been hypothesized to encode odor memories, yet the cellular substrates for Olfactory learning and memory remain unknown. Here, using intersectional, cFos-based genetic manipulations ("Fos tagging"), we show that Olfactory fear conditioning activates sparse and distributed ensembles of neurons in the mouse piriform Cortex. We demonstrate that chemogenetic silencing of these Fos-tagged piriform ensembles selectively interferes with odor fear memory retrieval but does not compromise basic odor detection and discrimination. Furthermore, chemogenetic reactivation of piriform neurons that were Fos tagged during Olfactory fear conditioning causes a decrease in exploratory behavior, mimicking odor-evoked fear memory recall. Together, our experiments identify specific ensembles of piriform neurons as critical components of an Olfactory fear memory trace.
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encoding of odor fear memories in the mouse Olfactory Cortex
Social Science Research Network, 2018Co-Authors: Claire Meissnerbernard, Yulia Dembitskaya, Laurent Venance, Alexander FleischmannAbstract:Odor memories are exceptionally robust and essential for animal survival. The Olfactory (piriform) Cortex has long been hypothesized to encode odor memories, yet the cellular substrates for Olfactory learning and memory remain unknown. Here, using intersectional, cFos-based genetic manipulations (“Fos-tagging”), we show that Olfactory fear conditioning activates sparse and distributed ensembles of neurons in mouse piriform Cortex. We demonstrate that chemogenetic silencing of these Fostagged piriform ensembles selectively interferes with odor fear memory retrieval, but does not compromise basic odor detection and discrimination. Furthermore, chemogenetic reactivation of piriform neurons that were Fos-tagged during Olfactory fear conditioning causes a decrease in exploratory behavior, mimicking odor-evoked fear memory recall. Together, our experiments identify odor-specific ensembles of piriform neurons as necessary and sufficient for odor fear memory recall.
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odor identity coding by distributed ensembles of neurons in the mouse Olfactory Cortex
eLife, 2017Co-Authors: Benjamin Roland, Kevin M Franks, Thomas Deneux, Brice Bathellier, Alexander FleischmannAbstract:Olfactory perception and behaviors critically depend on the ability to identify an odor across a wide range of concentrations. Here, we use calcium imaging to determine how odor identity is encoded in Olfactory Cortex. We find that, despite considerable trial-to-trial variability, odor identity can accurately be decoded from ensembles of co-active neurons that are distributed across piriform Cortex without any apparent spatial organization. However, piriform response patterns change substantially over a 100-fold change in odor concentration, apparently degrading the population representation of odor identity. We show that this problem can be resolved by decoding odor identity from a subpopulation of concentration-invariant piriform neurons. These concentration-invariant neurons are overrepresented in piriform Cortex but not in Olfactory bulb mitral and tufted cells. We therefore propose that distinct perceptual features of odors are encoded in independent subnetworks of neurons in the Olfactory Cortex.
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Molecular signatures of neural connectivity in the Olfactory Cortex
Nature Communications, 2016Co-Authors: Assunta Diodato, Marion Ruinart De Brimont, Yeong Shin Yim, Nicolas Derian, Sandrine Perrin, Juliette Pouch, David Klatzmann, Sonia Garel, Gloria B. Choi, Alexander FleischmannAbstract:The ability to target subclasses of neurons with defined connectivity is crucial for uncovering neural circuit functions. The Olfactory (piriform) Cortex is thought to generate odour percepts and memories, and odour information encoded in piriform is routed to target brain areas involved in multimodal sensory integration, cognition and motor control. However, it remains unknown if piriform outputs are spatially organized, and if distinct output channels are delineated by different gene expression patterns. Here we identify genes selectively expressed in different layers of the piriform Cortex. Neural tracing experiments reveal that these layer-specific piriform genes mark different subclasses of neurons, which project to distinct target areas. Interestingly, these molecular signatures of connectivity are maintained in reeler mutant mice, in which neural positioning is scrambled. These results reveal that a predictive link between a neuron's molecular identity and connectivity in this cortical circuit is determined independent of its spatial position.
Noam Sobel - One of the best experts on this subject based on the ideXlab platform.
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a specialized odor memory buffer in primary Olfactory Cortex
PLOS ONE, 2009Co-Authors: Christina Zelano, Jessica Lena Montag, Rehan M Khan, Noam SobelAbstract:Background The neural substrates of Olfactory working memory are unknown. We addressed the questions of whether Olfactory working memory involves a verbal representation of the odor, or a sensory image of the odor, or both, and the location of the neural substrates of these processes. Methodology/Principal Findings We used functional magnetic resonance imaging to measure activity in the brains of subjects who were remembering either nameable or unnameable odorants. We found a double dissociation whereby remembering nameable odorants was reflected in sustained activity in prefrontal language areas, and remembering unnameable odorants was reflected in sustained activity in primary Olfactory Cortex. Conclusions/Significance These findings suggest a novel dedicated mechanism in primary Olfactory Cortex, where odor information is maintained in temporary storage to subserve ongoing tasks.
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dissociated representations of irritation and valence in human primary Olfactory Cortex
Journal of Neurophysiology, 2007Co-Authors: Christina Zelano, Rehan M Khan, Noam Sobel, Jessica L Montag, B R JohnsonAbstract:Irritation and negative valence are closely associated in perception. However, these perceptual aspects can be dissociated in olfaction where irritation can accompany both pleasant and unpleasant o...
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Attentional modulation in human primary Olfactory Cortex
Nature Neuroscience, 2005Co-Authors: Christina Zelano, Moustafa Bensafi, Jess Porter, Joel Mainland, Brad Johnson, Elizabeth Bremner, Christina Telles, Rehan Khan, Noam SobelAbstract:Central to the concept of attention is the fact that identical stimuli can be processed in different ways. In olfaction, attention may designate the identical flow of air through the nose as either respiration or Olfactory exploration. Here we have used functional magnetic resonance imaging (fMRI) to probe this attentional mechanism in primary Olfactory Cortex (POC). We report a dissociation in POC that revealed attention-dependent and attention-independent subregions. Whereas a temporal subregion comprising temporal piriform Cortex (PirT) responded equally across conditions, a frontal subregion comprising frontal piriform Cortex (PirF) and the Olfactory tubercle responded preferentially to attended sniffs as opposed to unattended sniffs. In addition, a task-specific anticipatory response occurred in the attention-dependent region only. This dissociation was consistent across two experimental designs: one focusing on sniffs of clean air, the other focusing on odor-laden sniffs. Our findings highlight the role of attention at the earliest cortical levels of Olfactory processing.
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sniffing and smelling separate subsystems in the human Olfactory Cortex
Nature, 1998Co-Authors: Noam Sobel, Vivek Prabhakaran, John E Desmond, Gary H Glover, Richard L Goode, Edith V Sullivan, John D E GabrieliAbstract:The sensation and perception of smell (olfaction) are largely dependent on sniffing, which is an active stage of stimulus transport and therefore an integral component of mammalian olfaction1,2. Electrophysiological data obtained from study of the hedgehog, rat, rabbit, dog and monkey indicate that sniffing (whether or not an odorant is present) induces an oscillation of activity in the Olfactory bulb, driving the piriform Cortex in the temporal lobe, in other words, the piriform is driven by the Olfactory bulb at the frequency of sniffing3,4,5,6. Here we use functional magnetic resonance imaging (fMRI) that is dependent on the level of oxygen in the blood to determine whether sniffing can induce activation in the piriform of humans, and whether this activation can be differentiated from activation induced by an odorant. We find that sniffing, whether odorant is present or absent, induces activation primarily in the piriform Cortex of the temporal lobe and in the medial and posterior orbito-frontal gyri of the frontal lobe. The source of the sniff-induced activation is the somatosensory stimulation that is induced by air flow through the nostrils. In contrast, a smell, regardless of sniffing, induces activation mainly in the lateral and anterior orbito-frontal gyri of the frontal lobe. The dissociation between regions activated by Olfactory exploration (sniffing) and regions activated by Olfactory content (smell) shows a distinction in brain organization in terms of human olfaction.
Kensaku Mori - One of the best experts on this subject based on the ideXlab platform.
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respiration phased switching between sensory inputs and top down inputs in the Olfactory Cortex
bioRxiv, 2018Co-Authors: Kimiya Narikiyo, Hiroyuki Manabe, Yoshihiro Yoshihara, Kensaku MoriAbstract:Abstract Olfactory perception depends on respiration phases: Olfactory Cortex processes external odor signals during inhalation whereas it is isolated from the external odor world during exhalation. Olfactory Cortex pyramidal cells receive the sensory signals via bottom-up pathways terminating on superficial layer (SL) dendrites while they receive top-down inputs on deep layer (DL) dendrites. Here we asked whether Olfactory Cortex pyramidal cells spontaneously change the action modes of receiving Olfactory sensory inputs and receiving top-down inputs in relation to respiration phases. Current source density analysis of local field potentials recorded in three different Olfactory Cortex areas of waking immobile rats revealed β- and γ-range fast oscillatory current sinks and a slow current sink in the SL during inhalation, whereas it showed β- and γ-range fast oscillatory current sinks and a slow current sink in the DL during exhalation. Sensory deprivation experiments showed that inhalation-phased Olfactory sensory inputs drove the inhalation-phased fast oscillatory potentials in the SL but they drove neither the inhalation-phased slow current sink in the SL nor the exhalation-phased slow current sink in the DL. The results indicate that independent of inhalation-phased Olfactory sensory inputs, Olfactory Cortex pyramidal cells spontaneously generate a slow depolarization in the SL dendrites during inhalation, which may selectively boost the concomitant Olfactory sensory inputs to elicit spike outputs. In addition, the pyramidal cells spontaneously generate slow depolarization in the DL dendrites during exhalation, which may assist top-down inputs to elicit spike outputs. We thus hypothesize that the Olfactory cortical areas coordinately perform inhalation/exhalation-phased switching of input biasing: inhalation phase is the time window for external odor signals that arrive in the SL dendrites, whereas exhalation phase is assigned to boost top-down signals to the DL dendrites that originate in higher brain centers.
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Tuning of ventral tenia tecta neurons of the Olfactory Cortex to distinct scenes of feeding behavior
2018Co-Authors: Kazuki Shiotani, Yuta Tanisumi, Koshi Murata, Junya Hirokawa, Yoshio Sakurai, Hiroyuki Manabe, Kensaku MoriAbstract:Ventral tenia tecta (vTT) is a part of the Olfactory Cortex that receives both Olfactory sensory signals from the Olfactory bulb and top-down signals from the prefrontal Cortex. To address the question whether and how the neuronal activity of the vTT is modulated by prefrontal cognitive processes such as attention, expectation and working memory that occurs during goal-directed behaviors, we recorded individual neuronal responses in the vTT of freely moving awake mice that performed learned odor-guided feeding and drinking behaviors. We found that the firing pattern of individual vTT cells had repeatable behavioral correlates such that the environmental and behavioral scene the mouse encountered during the learned behavior was the major determinant of when individual vTT neurons fired maximally. Furthermore, spiking activity of these scene cells was modulated not only by the present scene but also by the future scene that the mouse predicted. We show that vTT receives afferent input from the Olfactory bulb and top-down inputs from the medial prefrontal Cortex and piriform Cortex. These results indicate that different groups of vTT cells are activated at different scenes and suggest that processing of Olfactory sensory information is handled by different scene cells during distinct scenes of learned feeding and drinking behaviors. In other words, during the feeding and drinking behavior, vTT changes its working mode moment by moment in accord with the scene change by selectively biasing specific scene cells. The scene effect on Olfactory sensory processing in the vTT has implications for the neuronal circuit mechanisms of top-down attention and scene-dependent encoding and recall of Olfactory memory.
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top down inputs from the Olfactory Cortex in the postprandial period promote elimination of granule cells in the Olfactory bulb
European Journal of Neuroscience, 2014Co-Authors: Sayaka Komanoinoue, Hiroyuki Manabe, Mizuho Ota, Kensaku Mori, Ikue Kusumotoyoshida, Takeshi Yokoyama, Masahiro YamaguchiAbstract:Elimination of granule cells (GCs) in the Olfactory bulb (OB) is not a continual event but is promoted during a short time window in the postprandial period, typically with postprandial sleep. However, the neuronal mechanisms for the enhanced GC elimination during the postprandial period are not understood. Here, we addressed the question of whether top-down inputs of centrifugal axons from the Olfactory Cortex (OC) during the postprandial period are involved in the enhanced GC elimination in the OB. Electrical stimulation of centrifugal axons from the OC of anesthetized mice increased GC apoptosis. Furthermore, pharmacological suppression of top-down inputs from the OC to the OB during the postprandial period of freely behaving mice by γ-aminobutyric acid (GABA)A receptor agonist injection in the OC significantly decreased GC apoptosis. Remarkable apoptotic GC elimination in the sensory-deprived OB was also suppressed by pharmacological blockade of top-down inputs. These results indicate that top-down inputs from the OC to the OB during the postprandial period are the crucial signal promoting GC elimination, and suggest that the life and death decision of GCs in the OB is determined by the interplay between bottom-up sensory inputs from the external world and top-down inputs from the OC.
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parallel tufted cell and mitral cell pathways from the Olfactory bulb to the Olfactory Cortex
2014Co-Authors: Shin Nagayama, Hiroyuki Manabe, Kei M Igarashi, Kensaku MoriAbstract:In the mammalian Olfactory system, sniff-induced odor signals are conveyed from the Olfactory bulb to the Olfactory Cortex by two types of projection neurons, tufted cells and mitral cells. This chapter summarizes recent advances in knowledge of the structural and functional differences between tufted cell and mitral cell circuits. Tufted cells and mitral cells show distinct patterns of lateral dendrite projection and make dendrodendritic reciprocal synaptic connections with different subtypes of granule cell inhibitory interneurons. Tufted cells and mitral cells thus form distinct local circuits within the Olfactory bulb: small-scale tufted cell dendrodendritic circuits and larger-scale mitral cell dendrodendritic circuits. In addition, tufted cells and mitral cells differ dramatically in their axonal projection to the Olfactory Cortex. Individual tufted cells project axons to focal targets in the Olfactory peduncle areas, whereas individual mitral cells send axons in a dispersed way to nearly all areas of the Olfactory Cortex, including nearly all parts of the piriform Cortex. Furthermore, tufted cells and mitral cells differ strikingly in how they respond to odor inhalation. Compared with mitral cells, tufted cells show earlier-onset, higher-frequency spike discharges. Tufted cells are activated at a much lower odor concentration threshold than activating mitral cells. During an inhalation–exhalation sniff cycle, tufted cell circuits generate early-onset fast gamma oscillation while mitral cell circuits give rise to later-onset slow gamma oscillation. From these structural and functional differences, we hypothesize that the two types of projection neurons play distinct roles in sending sniff-induced odor signals to the Olfactory Cortex. Specifically, tufted cells provide specificity-projecting circuits that send specific odor information to focal targets in the Olfactory peduncle areas with early-onset fast gamma synchronization. In contrast, mitral cells give rise to dispersed-projection feed-forward “binding” circuits that transmit the response synchronization timing via their later-onset slow gamma synchronization to pyramidal cells distributed across all parts of the piriform Cortex.
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Olfactory consciousness and gamma oscillation couplings across the Olfactory bulb Olfactory Cortex and orbitofrontal Cortex
Frontiers in Psychology, 2013Co-Authors: Kensaku Mori, Hiroyuki Manabe, Kimiya Narikiyo, Naomi OnisawaAbstract:The orbitofrontal Cortex receives multi-modality sensory inputs, including Olfactory input, and is thought to be involved in conscious perception of the Olfactory image of objects. Generation of Olfactory consciousness requires neuronal circuit mechanisms for the ‘binding’ of distributed neuronal activities, with each constituent neuron representing a specific component of an Olfactory percept. The shortest neuronal pathway for odor signals to reach the orbitofrontal Cortex is Olfactory sensory neuron – Olfactory bulb – Olfactory Cortex – orbitofrontal Cortex, but other pathways exist, including transthalamic pathways. Here, we review studies on the structural organization and functional properties of the shortest pathway, and propose a model of neuronal circuit mechanisms underlying the temporal bindings of distributed neuronal activities in the Olfactory Cortex. We describe a hypothesis that suggests functional roles of gamma oscillations in the bindings. This hypothesis proposes that two types of projection neurons in the Olfactory bulb, tufted cells and mitral cells, play distinct functional roles in bindings at neuronal circuits in the Olfactory Cortex: tufted cells provide specificity-projecting circuits which send odor information with early-onset fast gamma synchronization, while mitral cells give rise to dispersedly-projecting feed-forward binding circuits which transmit the response synchronization timing with later-onset slow gamma synchronization. This hypothesis also suggests a sequence of bindings in the Olfactory Cortex: a small-scale binding by the early-phase fast gamma synchrony of tufted cell inputs followed by a larger-scale binding due to the later-onset slow gamma synchrony of mitral cell inputs. We discuss that behavioral state, including wakefulness and sleep, regulates gamma oscillation couplings across the Olfactory bulb, Olfactory Cortex, and orbitofrontal Cortex.
Robert Pellegrino - One of the best experts on this subject based on the ideXlab platform.
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post traumatic Olfactory loss and brain response beyond Olfactory Cortex
Scientific Reports, 2021Co-Authors: Robert Pellegrino, Dana M. Small, Michael C Farruggia, Maria G VeldhuizenAbstract:Olfactory impairment after a traumatic impact to the head is associated with changes in Olfactory Cortex, including decreased gray matter density and decreased BOLD response to odors. Much less is known about the role of other cortical areas in Olfactory impairment. We used fMRI in a sample of 63 participants, consisting of 25 with post-traumatic functional anosmia, 16 with post-traumatic hyposmia, and 22 healthy controls with normosmia to investigate whole brain response to odors. Similar neural responses were observed across the groups to odor versus odorless stimuli in the primary Olfactory areas in piriform Cortex, whereas response in the frontal operculum and anterior insula (fO/aI) increased with Olfactory function (normosmia > hyposmia > functional anosmia). Unexpectedly, a negative association was observed between response and Olfactory perceptual function in the mediodorsal thalamus (mdT), ventromedial prefrontal Cortex (vmPFC) and posterior cingulate Cortex (pCC). Finally, connectivity within a network consisting of vmPFC, fO, and pCC could be used to successfully classify participants as having functional anosmia or normosmia. We conclude that, at the neural level, Olfactory impairment due to head trauma is best characterized by heightened responses and differential connectivity in higher-order areas beyond Olfactory Cortex.
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beyond Olfactory Cortex severity of post traumatic Olfactory loss is associated with response to odors in frontal parietal insular networks
medRxiv, 2020Co-Authors: Robert Pellegrino, Dana M. Small, Michael C Farruggia, Maria G VeldhuizenAbstract:Olfactory impairment after trauma is associated with changes in Olfactory Cortex, including decreased gray matter density and decreased response to odors. Much less is known about the role of other cortical areas in Olfactory impairment. We used fMRI in a sample of 63 participants, consisting of 25 with post-traumatic functional anosmia, 16 with post-traumatic hyposmia, and 22 healthy controls with normosmia to investigate whole brain response to odors. Similar neural responses were observed across the groups to odor versus odorless stimuli in the primary Olfactory areas in piriform Cortex, whereas response in the frontal operculum and anterior insula (fO/al) increased with Olfactory function (normosmia > hyposmia > functional anosmia). Unexpectedly, a negative association was observed between response and Olfactory function in the mediodorsal thalamus (mdT), ventromedial prefrontal Cortex (vmPFC) and posterior cingulate Cortex (pCC). Finally, connectivity within a network consisting of vmPFC, fO, and pCC could be used to successfully classify participants as having functional anosmia or normosmia. We conclude that, at the neural level, Olfactory impairment due to head trauma is best characterized by heightened responses and differential connectivity in higher-order areas beyond Olfactory Cortex. Significance Statement Olfactory impairment affects a quarter of the population, with subjective complaints usually confirmed with psychophysical measurements. Here, we demonstrate that the degree of Olfactory impairment can also be categorized using neural responses to odors. Remarkably, regions with neural responses that were predictive usually showed an increase in response to odors with degree of impairment, rather than a reduction, as might be expected. Further, predictive cortical regions were not isolated to canonical Olfactory areas.
Hiroyuki Manabe - One of the best experts on this subject based on the ideXlab platform.
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Tuning of Olfactory Cortex ventral tenia tecta neurons to distinct task elements of goal-directed behavior.
eLife, 2020Co-Authors: Kazuki Shiotani, Yuta Tanisumi, Koshi Murata, Junya Hirokawa, Yoshio Sakurai, Hiroyuki ManabeAbstract:The ventral tenia tecta (vTT) is a component of the Olfactory Cortex and receives both bottom-up odor signals and top-down signals. However, the roles of the vTT in odor-coding and integration of inputs are poorly understood. Here, we investigated the involvement of the vTT in these processes by recording the activity from individual vTT neurons during the performance of learned odor-guided reward-directed tasks in mice. We report that individual vTT cells are highly tuned to a specific behavioral epoch of learned tasks, whereby the duration of increased firing correlated with the temporal length of the behavioral epoch. The peak time for increased firing among recorded vTT cells encompassed almost the entire temporal window of the tasks. Collectively, our results indicate that vTT cells are selectively activated during a specific behavioral context and that the function of the vTT changes dynamically in a context-dependent manner during goal-directed behaviors.
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respiration phased switching between sensory inputs and top down inputs in the Olfactory Cortex
bioRxiv, 2018Co-Authors: Kimiya Narikiyo, Hiroyuki Manabe, Yoshihiro Yoshihara, Kensaku MoriAbstract:Abstract Olfactory perception depends on respiration phases: Olfactory Cortex processes external odor signals during inhalation whereas it is isolated from the external odor world during exhalation. Olfactory Cortex pyramidal cells receive the sensory signals via bottom-up pathways terminating on superficial layer (SL) dendrites while they receive top-down inputs on deep layer (DL) dendrites. Here we asked whether Olfactory Cortex pyramidal cells spontaneously change the action modes of receiving Olfactory sensory inputs and receiving top-down inputs in relation to respiration phases. Current source density analysis of local field potentials recorded in three different Olfactory Cortex areas of waking immobile rats revealed β- and γ-range fast oscillatory current sinks and a slow current sink in the SL during inhalation, whereas it showed β- and γ-range fast oscillatory current sinks and a slow current sink in the DL during exhalation. Sensory deprivation experiments showed that inhalation-phased Olfactory sensory inputs drove the inhalation-phased fast oscillatory potentials in the SL but they drove neither the inhalation-phased slow current sink in the SL nor the exhalation-phased slow current sink in the DL. The results indicate that independent of inhalation-phased Olfactory sensory inputs, Olfactory Cortex pyramidal cells spontaneously generate a slow depolarization in the SL dendrites during inhalation, which may selectively boost the concomitant Olfactory sensory inputs to elicit spike outputs. In addition, the pyramidal cells spontaneously generate slow depolarization in the DL dendrites during exhalation, which may assist top-down inputs to elicit spike outputs. We thus hypothesize that the Olfactory cortical areas coordinately perform inhalation/exhalation-phased switching of input biasing: inhalation phase is the time window for external odor signals that arrive in the SL dendrites, whereas exhalation phase is assigned to boost top-down signals to the DL dendrites that originate in higher brain centers.
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Tuning of ventral tenia tecta neurons of the Olfactory Cortex to distinct scenes of feeding behavior
2018Co-Authors: Kazuki Shiotani, Yuta Tanisumi, Koshi Murata, Junya Hirokawa, Yoshio Sakurai, Hiroyuki Manabe, Kensaku MoriAbstract:Ventral tenia tecta (vTT) is a part of the Olfactory Cortex that receives both Olfactory sensory signals from the Olfactory bulb and top-down signals from the prefrontal Cortex. To address the question whether and how the neuronal activity of the vTT is modulated by prefrontal cognitive processes such as attention, expectation and working memory that occurs during goal-directed behaviors, we recorded individual neuronal responses in the vTT of freely moving awake mice that performed learned odor-guided feeding and drinking behaviors. We found that the firing pattern of individual vTT cells had repeatable behavioral correlates such that the environmental and behavioral scene the mouse encountered during the learned behavior was the major determinant of when individual vTT neurons fired maximally. Furthermore, spiking activity of these scene cells was modulated not only by the present scene but also by the future scene that the mouse predicted. We show that vTT receives afferent input from the Olfactory bulb and top-down inputs from the medial prefrontal Cortex and piriform Cortex. These results indicate that different groups of vTT cells are activated at different scenes and suggest that processing of Olfactory sensory information is handled by different scene cells during distinct scenes of learned feeding and drinking behaviors. In other words, during the feeding and drinking behavior, vTT changes its working mode moment by moment in accord with the scene change by selectively biasing specific scene cells. The scene effect on Olfactory sensory processing in the vTT has implications for the neuronal circuit mechanisms of top-down attention and scene-dependent encoding and recall of Olfactory memory.
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top down inputs from the Olfactory Cortex in the postprandial period promote elimination of granule cells in the Olfactory bulb
European Journal of Neuroscience, 2014Co-Authors: Sayaka Komanoinoue, Hiroyuki Manabe, Mizuho Ota, Kensaku Mori, Ikue Kusumotoyoshida, Takeshi Yokoyama, Masahiro YamaguchiAbstract:Elimination of granule cells (GCs) in the Olfactory bulb (OB) is not a continual event but is promoted during a short time window in the postprandial period, typically with postprandial sleep. However, the neuronal mechanisms for the enhanced GC elimination during the postprandial period are not understood. Here, we addressed the question of whether top-down inputs of centrifugal axons from the Olfactory Cortex (OC) during the postprandial period are involved in the enhanced GC elimination in the OB. Electrical stimulation of centrifugal axons from the OC of anesthetized mice increased GC apoptosis. Furthermore, pharmacological suppression of top-down inputs from the OC to the OB during the postprandial period of freely behaving mice by γ-aminobutyric acid (GABA)A receptor agonist injection in the OC significantly decreased GC apoptosis. Remarkable apoptotic GC elimination in the sensory-deprived OB was also suppressed by pharmacological blockade of top-down inputs. These results indicate that top-down inputs from the OC to the OB during the postprandial period are the crucial signal promoting GC elimination, and suggest that the life and death decision of GCs in the OB is determined by the interplay between bottom-up sensory inputs from the external world and top-down inputs from the OC.
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parallel tufted cell and mitral cell pathways from the Olfactory bulb to the Olfactory Cortex
2014Co-Authors: Shin Nagayama, Hiroyuki Manabe, Kei M Igarashi, Kensaku MoriAbstract:In the mammalian Olfactory system, sniff-induced odor signals are conveyed from the Olfactory bulb to the Olfactory Cortex by two types of projection neurons, tufted cells and mitral cells. This chapter summarizes recent advances in knowledge of the structural and functional differences between tufted cell and mitral cell circuits. Tufted cells and mitral cells show distinct patterns of lateral dendrite projection and make dendrodendritic reciprocal synaptic connections with different subtypes of granule cell inhibitory interneurons. Tufted cells and mitral cells thus form distinct local circuits within the Olfactory bulb: small-scale tufted cell dendrodendritic circuits and larger-scale mitral cell dendrodendritic circuits. In addition, tufted cells and mitral cells differ dramatically in their axonal projection to the Olfactory Cortex. Individual tufted cells project axons to focal targets in the Olfactory peduncle areas, whereas individual mitral cells send axons in a dispersed way to nearly all areas of the Olfactory Cortex, including nearly all parts of the piriform Cortex. Furthermore, tufted cells and mitral cells differ strikingly in how they respond to odor inhalation. Compared with mitral cells, tufted cells show earlier-onset, higher-frequency spike discharges. Tufted cells are activated at a much lower odor concentration threshold than activating mitral cells. During an inhalation–exhalation sniff cycle, tufted cell circuits generate early-onset fast gamma oscillation while mitral cell circuits give rise to later-onset slow gamma oscillation. From these structural and functional differences, we hypothesize that the two types of projection neurons play distinct roles in sending sniff-induced odor signals to the Olfactory Cortex. Specifically, tufted cells provide specificity-projecting circuits that send specific odor information to focal targets in the Olfactory peduncle areas with early-onset fast gamma synchronization. In contrast, mitral cells give rise to dispersed-projection feed-forward “binding” circuits that transmit the response synchronization timing via their later-onset slow gamma synchronization to pyramidal cells distributed across all parts of the piriform Cortex.
