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PLoS Biology Apr 2020Interhemispheric connections enable interaction and integration of sensory information in bilaterian nervous systems and are thought to optimize sensory computations....
Interhemispheric connections enable interaction and integration of sensory information in bilaterian nervous systems and are thought to optimize sensory computations. However, the cellular and spatial organization of interhemispheric networks and the computational properties they mediate in vertebrates are still poorly understood. Thus, it remains unclear to what extent the connectivity between left and right brain hemispheres participates in sensory processing. Here, we show that the zebrafish olfactory bulbs (OBs) receive direct interhemispheric projections from their contralateral counterparts in addition to top-down inputs from the contralateral zebrafish homolog of olfactory cortex. The direct interhemispheric projections between the OBs reach peripheral layers of the contralateral OB and retain a precise topographic organization, which directly connects similarly tuned olfactory glomeruli across hemispheres. In contrast, interhemispheric top-down inputs consist of diffuse projections that broadly innervate the inhibitory granule cell layer. Jointly, these interhemispheric connections elicit a balance of topographically organized excitation and nontopographic inhibition on the contralateral OB and modulate odor responses. We show that the interhemispheric connections in the olfactory system enable the modulation of odor response and contribute to a small but significant improvement in the detection of a reproductive pheromone when presented together with complex olfactory cues by potentiating the response of the pheromone selective neurons. Taken together, our data show a previously unknown function for an interhemispheric connection between chemosensory maps of the olfactory system.
Topics: Animals; Animals, Genetically Modified; Calcium; Interneurons; Odorants; Olfactory Bulb; Olfactory Cortex; Olfactory Pathways; Smell; Zebrafish
PubMed: 32310946
DOI: 10.1371/journal.pbio.3000701 -
The Journal of Comparative Neurology Feb 2023Circuit operations of the olfactory bulb are modulated by higher order projections from multiple regions, many of which are themselves targets of bulbar output. Multiple...
Circuit operations of the olfactory bulb are modulated by higher order projections from multiple regions, many of which are themselves targets of bulbar output. Multiple glutamatergic regions project to the olfactory bulb, including the anterior olfactory nucleus (AON), prefrontal cortex (PFC), piriform cortex (PC), entorhinal cortex (EC), and tenia tecta (TT). In contrast, only one region provides GABAergic projections to the bulb. These GABA neurons are located in the horizontal limb of the diagonal band of Broca extending posteriorly through the magnocellular preoptic nucleus to the nucleus of the lateral olfactory bulb. However, it was unclear whether bulbar projecting GABAergic neurons collaterallize projecting to other brain regions. To address this, we mapped collateral projections from bulbar projecting GABAergic neurons using intersectional strategies of viral and traditional tract tracers. This approach revealed bulbar projecting GABAergic neurons show remarkable specificity targeting other primary olfactory cortical regions exhibiting abundant collateral projections into the accessory olfactory bulb, AON, PFC, PC, and TT. The only "nonolfactory" region receiving collateral projections was sparse connectivity to the medial prefrontal orbital cortex. This suggests that basal forebrain inhibitory feedback also modulates glutamatergic feedback areas that are themselves prominent bulbar projection regions. Thus, inhibitory feedback may be simultaneously modulating both synaptic processing of olfactory information in the bulb and associational processing of olfactory information from primary olfactory cortex. We hypothesize that these olfactory GABAergic feedback neurons are a regulator of the entire olfactory system.
Topics: Olfactory Bulb; Brain; Prefrontal Cortex; Preoptic Area; GABAergic Neurons; Olfactory Pathways
PubMed: 36463397
DOI: 10.1002/cne.25434 -
Journal of Chemical Neuroanatomy Dec 2011Adult neurogenesis is due to the persistence of pools of constitutive stem cells able to give rise to a progeny of proliferating progenitors. In rodents, adult... (Review)
Review
Adult neurogenesis is due to the persistence of pools of constitutive stem cells able to give rise to a progeny of proliferating progenitors. In rodents, adult neurogenic niches have been found in the subventricular zone (SVZ) along the lateral ventricles and in the subgranular zone of the dentate gyrus in the hippocampus. SVZ progenitors undergo a unique process of tangential migration from the lateral ventricle to the olfactory bulb (OB) where they differentiate mainly into GABAergic interneurons in the granule and glomerular layers. SVZ progenitor proliferation, migration and differentiation into fully integrated neurons, are strictly related processes regulated by complex interactions between cell intrinsic and extrinsic influences. Numerous observations demonstrate that neurotrasmitters are involved in all steps of the adult neurogenic process, but the understanding of their role is hampered by their intricate mechanism of action and by the highly complex network in which neurotransmitters work. By considering the three main steps of olfactory adult neurogenesis (proliferation, migration and integration), this review will discuss recent advances in the study of neurotransmitters, highlighting the regulatory mechanisms upstream and downstream their action.
Topics: Adult; Animals; Cell Differentiation; Cellular Senescence; Humans; Neurogenesis; Neurons; Neurotransmitter Agents; Olfactory Bulb; Stem Cells
PubMed: 21641990
DOI: 10.1016/j.jchemneu.2011.05.006 -
Frontiers in Neural Circuits 2018The mammalian basal forebrain (BF), a heterogenous structure providing the primary cholinergic inputs to cortical and limbic structures, plays a crucial role in various...
Different Subgroups of Cholinergic Neurons in the Basal Forebrain Are Distinctly Innervated by the Olfactory Regions and Activated Differentially in Olfactory Memory Retrieval.
The mammalian basal forebrain (BF), a heterogenous structure providing the primary cholinergic inputs to cortical and limbic structures, plays a crucial role in various physiological processes such as learning/memory and attention. Despite the involvement of the BF cholinergic neurons (BFCNs) in olfaction related memory has been reported, the underlying neural circuits remain poorly understood. Here, we combined viral trans-synaptic tracing systems and ChAT-cre transgenic mice to systematically reveal the relationship between the olfactory system and the different subsets of BFCNs. The retrograde adeno-associated virus and rabies virus (AAV-RV) tracing showed that different subregional BFCNs received diverse inputs from multiple olfactory cortices. The cholinergic neurons in medial and caudal horizontal diagonal band Broca (HDB), magnocellular preoptic area (MCPO) and ventral substantia innominate (SI; hereafter HMS complex, HMSc) received the inputs from the entire olfactory system such as the olfactory bulb (OB), anterior olfactory nucleus (AON), entorhinal cortex (ENT), basolateral amygdala and especially the piriform cortex (PC) and hippocampus (HIP); while medial septum (MS/DB) and a part of rostral HDB (hereafter MS/DB complex, MS/DBc), predominantly from HIP; and nucleus basalis Meynert (NBM) and dorsal SI (hereafter NBM complex, NBMc), mainly from the central amygdala. The anterograde vesicular stomatitis virus (VSV) tracing further validated that the major target of the OB to the BF is HMSc. To correlate these structural relations between the BFCNs and olfactory functions, the neurons activated in the BF during olfaction related task were mapped with c-fos immunostaining. It was found that some of the BFCNs were activated in go/no-go olfactory discrimination task, but with different activated patterns. Interestingly, the BFCNs in HMSc were more significantly activated than the other subregions. Therefore, our data have demonstrated that among the different subgroups of BFCNs, HMSc is more closely related to the olfactory system, both structurally and functionally. This work provides the evidence for distinct roles of different subsets of BFNCs in olfaction associated memory.
Topics: Animals; Basal Forebrain; Cholinergic Neurons; Female; Male; Memory; Mice; Mice, Inbred C57BL; Mice, Transgenic; Olfactory Bulb; Smell
PubMed: 30483067
DOI: 10.3389/fncir.2018.00099 -
Cellular and Molecular Life Sciences :... Oct 2011Axons of primary olfactory neurons are intimately associated with olfactory ensheathing cells (OECs) from the olfactory epithelium until the final targeting of axons...
Axons of primary olfactory neurons are intimately associated with olfactory ensheathing cells (OECs) from the olfactory epithelium until the final targeting of axons within the olfactory bulb. However, little is understood about the nature and role of interactions between OECs and axons during development of the olfactory nerve pathway. We have used high resolution time-lapse microscopy to examine the growth and interactions of olfactory axons and OECs in vitro. Transgenic mice expressing fluorescent reporters in primary olfactory axons (OMP-ZsGreen) and ensheathing cells (S100ß-DsRed) enabled us to selectively analyse these cell types in explants of olfactory epithelium. We reveal here that rather than providing only a permissive substrate for axon growth, OECs play an active role in modulating the growth of pioneer olfactory axons. We show that the interactions between OECs and axons were dependent on lamellipodial waves on the shaft of OEC processes. The motility of OECs was mediated by GDNF, which stimulated cell migration and increased the apparent motility of the axons, whereas loss of OECs via laser ablation of the cells inhibited olfactory axon outgrowth. These results demonstrate that the migration of OECs strongly regulates the motility of axons and that stimulation of OEC motility enhances axon extension and growth cone activity.
Topics: Animals; Axons; Cell Culture Techniques; Cell Movement; Luminescent Proteins; Mice; Mice, Transgenic; Olfactory Bulb; Olfactory Mucosa; Pseudopodia
PubMed: 21318262
DOI: 10.1007/s00018-011-0630-9 -
Scientific Reports Mar 2021A respiration-locked activity in the olfactory brain, mainly originating in the mechano-sensitivity of olfactory sensory neurons to air pressure, propagates from the...
A respiration-locked activity in the olfactory brain, mainly originating in the mechano-sensitivity of olfactory sensory neurons to air pressure, propagates from the olfactory bulb to the rest of the brain. Interestingly, changes in nasal airflow rate result in reorganization of olfactory bulb response. By leveraging spontaneous variations of respiratory dynamics during natural conditions, we investigated whether respiratory drive also varies with nasal airflow movements. We analyzed local field potential activity relative to respiratory signal in various brain regions during waking and sleep states. We found that respiration regime was state-specific, and that quiet waking was the only vigilance state during which all the recorded structures can be respiration-driven whatever the respiratory frequency. Using CO-enriched air to alter respiratory regime associated to each state and a respiratory cycle based analysis, we evidenced that the large and strong brain drive observed during quiet waking was related to an optimal trade-off between depth and duration of inspiration in the respiratory pattern, characterizing this specific state. These results show for the first time that changes in respiration regime affect cortical dynamics and that the respiratory regime associated with rest is optimal for respiration to drive the brain.
Topics: Action Potentials; Animals; Olfactory Bulb; Olfactory Cortex; Olfactory Receptor Neurons; Plethysmography; Rats; Respiratory Rate
PubMed: 33782487
DOI: 10.1038/s41598-021-86525-3 -
Behavioural Brain Research Dec 2012The olfactory system is a useful model for studying central nervous system recovery from damage due to its neuroplasticity. We recently developed a novel method of...
The olfactory system is a useful model for studying central nervous system recovery from damage due to its neuroplasticity. We recently developed a novel method of deafferentation by repeated exposure of Triton X-100 to the olfactory organ of adult zebrafish. This long-term, reversible method of deafferentation allows both degeneration and regeneration to be observed in the olfactory bulb. The aim of the present study is to examine olfactory bulb innervation, glomerular patterns, and olfactory-mediated behavior with repeated Triton X-100 treatment and the potential for recovery following cessation of treatment. Olfactory bulbs of control, chronic-treated, and recovery animals were examined for the presence or absence of glomeruli that have been identified in the zebrafish glomerular map. Following chronic treatment, the number of glomeruli was dramatically reduced; however, partial innervation remained in the lateral region of the bulb. When animals were given time to recover, complete glomerular distribution returned. A behavioral assay was developed to determine if innervation remaining correlated with behavior of the fish. Chronic-treated fish did not respond to odorants involved with social behavior but continued to react to odorants that mediate feeding behavior. Following recovery, responses to odorants involved with social behavior returned. The morphological and behavioral effects of chronic Triton X-100 treatment in the olfactory system suggest there may be differential susceptibility or resistance to external damage in a subset of sensory neurons. The results of this study demonstrate the remarkable regenerative ability of the olfactory system following extensive and long-term injury.
Topics: Amino Acids; Analysis of Variance; Animals; Behavior, Animal; Female; Functional Laterality; Hemocyanins; Male; Nerve Net; Octoxynol; Odorants; Olfactory Bulb; Olfactory Receptor Neurons; Smell; Taurocholic Acid; Zebrafish
PubMed: 22963994
DOI: 10.1016/j.bbr.2012.08.018 -
Journal of Neurochemistry Nov 2020Damaged axons in the adult mammalian central nervous system have a restricted regenerative capacity mainly because of Nogo protein, which is a major myelin-associated...
Damaged axons in the adult mammalian central nervous system have a restricted regenerative capacity mainly because of Nogo protein, which is a major myelin-associated axonal growth inhibitor with binding to both receptors of Nogo receptor-1 (NgR1) and paired immunoglobulin-like receptor (PIR)-B. Lateral olfactory tract usher substance (LOTUS) exerts complete suppression of NgR1-mediated axonal growth inhibition by antagonizing NgR1. However, the regulation of PIR-B functions in neurons remains unknown. In this study, protein-protein interactions analyses found that LOTUS binds to PIR-B and abolishes Nogo-binding to PIR-B completely. Reverse transcription-polymerase chain reaction and immunocytochemistry revealed that PIR-B is expressed in dorsal root ganglions (DRGs) from wild-type and Ngr1-deficient mice (male and female). In these DRG neurons, Nogo induced growth cone collapse and neurite outgrowth inhibition, but treatment with the soluble form of LOTUS completely suppressed them. Moreover, Nogo-induced growth cone collapse and neurite outgrowth inhibition in Ngr1-deficient DRG neurons were neutralized by PIR-B function-blocking antibodies, indicating that these Nogo-induced phenomena were mediated by PIR-B. Our data show that LOTUS negatively regulates a PIR-B function. LOTUS thus exerts an antagonistic action on both receptors of NgR1 and PIR-B. This may lead to an improvement in the defective regeneration of axons following injury.
Topics: Animals; Animals, Newborn; Axons; COS Cells; Cells, Cultured; Chlorocebus aethiops; Female; HEK293 Cells; Humans; Male; Mice; Mice, Inbred C57BL; Mice, Transgenic; Nerve Tissue Proteins; Nogo Receptor 1; Olfactory Bulb; Receptors, Immunologic
PubMed: 32201946
DOI: 10.1111/jnc.15013 -
The Journal of Neuroscience : the... Oct 2004Experimental rats had their right olfactory bulb removed on postnatal day 2 (P2) and their left olfactory bulb removed on P90. Control rats had one or both olfactory...
Experimental rats had their right olfactory bulb removed on postnatal day 2 (P2) and their left olfactory bulb removed on P90. Control rats had one or both olfactory bulbs removed on P90. Before and after their adult-stage surgery, rats were trained using olfactometry and operant conditioning to detect and discriminate odors. Anterograde transport of horseradish peroxidase applied to the olfactory epithelium revealed numerous axons of olfactory sensory neurons in the right hemisphere of 27 experimental rats. These axons terminated in glomerular-like clusters within the frontal neocortex (n = 5) or anterior olfactory nucleus with some axons extending into the subventricular epithelium (n = 22). Seventeen of the experimental rats were able to detect a variety of odors and to discriminate between odors. Performance accuracy was related to the location and density of these anomalous inputs; experimental rats with inputs confined to frontal neocortex and those lacking any inputs to the forebrain were anosmic, as were adult-operated bilaterally bulbectomized rats. Our results provide strong support for the contention that, in the absence of the olfactory bulbs, olfactory connections to novel forebrain sites can support both odor detection and odor discrimination.
Topics: Animals; Behavior, Animal; Discrimination Learning; Esters; Female; Male; Neurosurgical Procedures; Odorants; Olfactory Bulb; Rats; Rats, Sprague-Dawley; Sensory Thresholds; Smell; Stimulation, Chemical
PubMed: 15483138
DOI: 10.1523/JNEUROSCI.1936-04.2004 -
The Journal of Neuroscience : the... May 2008
Review
Topics: Animals; Brain-Derived Neurotrophic Factor; Cell Differentiation; Cell Movement; Cell Proliferation; Neuronal Plasticity; Neurons; Olfactory Bulb; Signal Transduction; Stem Cells
PubMed: 18480269
DOI: 10.1523/JNEUROSCI.1327-08.2008