Antennal Lobe Processing Increases Separability of Odor Mixture Representations in the Honeybee

2010 ◽  
Vol 103 (4) ◽  
pp. 2185-2194 ◽  
Author(s):  
Nina Deisig ◽  
Martin Giurfa ◽  
Jean Christophe Sandoz
Keyword(s):  
Antennal Lobe ◽  
Second Order ◽  
Insect Brain ◽  
Output Level ◽  
Local Networks ◽  
Odor Mixture ◽  
Receptor Neurons ◽  
Evoked Activity ◽  
Input Level ◽  
Olfactory Space

Local networks within the primary olfactory centers reformat odor representations from olfactory receptor neurons to second-order neurons. By studying the rules underlying mixture representation at the input to the antennal lobe (AL), the primary olfactory center of the insect brain, we recently found that mixture representation follows a strict elemental rule in honeybees: the more a component activates the AL when presented alone, the more it is represented in a mixture. We now studied mixture representation at the output of the AL by imaging a population of second-order neurons, which convey AL processed odor information to higher brain centers. We systematically measured odor-evoked activity in 22 identified glomeruli in response to four single odorants and all their possible binary, ternary and quaternary mixtures. By comparing input and output responses, we determined how the AL network reformats mixture representation and what advantage this confers for odor discrimination. We show that increased inhibition within the AL leads to more synthetic, less elemental, mixture representation at the output level than that at the input level. As a result, mixture representations become more separable in the olfactory space, thus allowing better differentiation among floral blends in nature.

scholarly journals Distinct patterns of activity in individual cortical neurons and local networks in primary somatosensory cortex of mice evoked by mechanical limb stimulation

2020 ◽  
Author(s):  
Mischa V. Bandet ◽  
Bin Dong ◽  
Ian R. Winship
Keyword(s):  
Somatosensory Cortex ◽  
Cortical Neurons ◽  
Optical Recording ◽  
Primary Somatosensory Cortex ◽  
Autofluorescence Imaging ◽  
Neuronal Activation ◽  
Local Networks ◽  
Two Photon ◽  
Evoked Activity ◽  
Sensory Evoked

AbstractTo distinguish between somatic stimuli, the primary somatosensory cortex should process dissimilar stimuli with distinct patterns of neuronal activation. Two-photon calcium imaging permits simultaneous optical recording of sensory evoked activity in hundreds of cortical neurons during varied sensory stimulation. Hence, it allows a visualization of patterns of activity in individual neurons and local cortical networks in response to distinct stimulation. Here, flavoprotein autofluorescence imaging was used to map the somatosensory cortex of anaesthetized C57BL/6 mice, and in vivo two-photon Ca2+ imaging was used to define patterns of neuronal activation during mechanical stimulation of the contralateral forelimb or hindlimb at various frequencies (3, 10, 100, 200, and 300 Hz). The data revealed that neurons within the limb associated somatosensory cortex exhibit stimulus-specific patterns of activity. Subsets of neurons were found to have sensory-evoked activity that is either primarily responsive to single stimulus frequencies or broadly responsive to multiple frequencies of limb movement. High frequency stimuli were shown to elicit more activation across the population, with a greater percentage of the population responding and greater percentage of cells with high amplitude responses. Stimulus-evoked cell-cell correlations within these neuronal networks varied as a function of frequency of stimulation, such that each stimulus elicited a distinct pattern that was more consistent across multiple trials of the same stimulus compared to trials at different frequencies of stimulation. The variation in cortical response to these artificial stimuli can thus be represented by the population pattern of supra-threshold Ca2+ transients, the magnitude and temporal properties of the evoked activity, and the structure of the stimulus-evoked correlation between responsive neurons.

scholarly journals Interplay between axonal Wnt5-Vang and dendritic Wnt5-Drl/Ryk signaling controls glomerular patterning in the Drosophila antennal lobe

2019 ◽  
Author(s):  
Huey Hing ◽  
Jennifer Snyder ◽  
Noah Reger ◽  
Lee G. Fradkin
Keyword(s):  
Antennal Lobe ◽  
Planar Cell Polarity ◽  
Neural Circuit ◽  
Projection Neuron ◽  
Olfactory Receptor Neurons ◽  
Antibody Staining ◽  
Cell Type Specific ◽  
Receptor Neurons ◽  
Signaling Components ◽  
Biphasic Responses

Despite the importance of dendritic targeting in neural circuit assembly, the mechanisms by which it is controlled still remain incompletely understood. We previously showed that in the developing Drosophila antennal lobe, the Wnt5 protein forms a gradient that directs the ~45° rotation of a cluster of projection neuron (PN) dendrites, including the adjacent DA1 and VA1d dendrites. We report here that the Van Gogh (Vang) transmembrane planar cell polarity (PCP) protein is required for the rotation of the DA1/VA1d dendritic pair. Cell type-specific rescue and mosaic analyses showed that Vang functions in the olfactory receptor neurons (ORNs), suggesting a codependence of ORN axonal and PN dendritic targeting. Loss of Vang suppressed the repulsion of the VA1d dendrites by Wnt5, indicating that Wnt5 signals through Vang to direct the rotation of the DA1 and VA1d glomeruli. We observed that the Derailed (Drl)/Ryk atypical receptor tyrosine kinase is also required for the rotation of the DA1/VA1d dendritic pair. Antibody staining showed that Drl/Ryk is much more highly expressed by the DA1 dendrites than the adjacent VA1d dendrites. Mosaic and epistatic analyses showed that Drl/Ryk specifically functions in the DA1 dendrites in which it antagonizes the Wnt5-Vang repulsion and mediates the migration of the DA1 glomerulus towards Wnt5. Thus, the nascent DA1 and VA1d glomeruli appear to exhibit Drl/Ryk-dependent biphasic responses to Wnt5. Our work shows that the final patterning of the fly olfactory map is the result of an interplay between ORN axons and PN dendrites, wherein converging pre- and postsynaptic processes contribute key Wnt5 signaling components, allowing Wnt5 to orient the rotation of nascent synapses through a PCP mechanism.

scholarly journals Structural and Functional Plasticity in the Regenerating Olfactory System of the Migratory Locust

2020 ◽  
Vol 11 ◽  
Author(s):  
Gerd Bicker ◽  
Michael Stern
Keyword(s):  
Olfactory Receptor ◽  
Olfactory System ◽  
Mushroom Body ◽  
Antennal Lobe ◽  
Second Order ◽  
Neural Regeneration ◽  
Current Evidence ◽  
Olfactory Pathway ◽  
Nerve Crush ◽  
Migratory Locust

Regeneration after injury is accompanied by transient and lasting changes in the neuroarchitecture of the nervous system and, thus, a form of structural plasticity. In this review, we introduce the olfactory pathway of a particular insect as a convenient model to visualize neural regeneration at an anatomical level and study functional recovery at an electrophysiological level. The olfactory pathway of the locust (Locusta migratoria) is characterized by a multiglomerular innervation of the antennal lobe by olfactory receptor neurons. These olfactory afferents were axotomized by crushing the base of the antenna. The resulting degeneration and regeneration in the antennal lobe could be quantified by size measurements, dye labeling, and immunofluorescence staining of cell surface proteins implicated in axonal guidance during development. Within 3 days post lesion, the antennal lobe volume was reduced by 30% and from then onward regained size back to normal by 2 weeks post injury. The majority of regenerating olfactory receptor axons reinnervated the glomeruli of the antennal lobe. A few regenerating axons project erroneously into the mushroom body on a pathway that is normally chosen by second-order projection neurons. Based on intracellular responses of antennal lobe output neurons to odor stimulation, regenerated fibers establish functional synapses again. Following complete absence after nerve crush, responses to odor stimuli return to control level within 10–14 days. On average, regeneration of afferents, and re-established synaptic connections appear faster in younger fifth instar nymphs than in adults. The initial degeneration of olfactory receptor axons has a trans-synaptic effect on a second order brain center, leading to a transient size reduction of the mushroom body calyx. Odor-evoked oscillating field potentials, absent after nerve crush, were restored in the calyx, indicative of regenerative processes in the network architecture. We conclude that axonal regeneration in the locust olfactory system appears to be possible, precise, and fast, opening an avenue for future mechanistic studies. As a perspective of biomedical importance, the current evidence for nitric oxide/cGMP signaling as positive regulator of axon regeneration in connectives of the ventral nerve cord is considered in light of particular regeneration studies in vertebrate central nervous systems.

Olfactory Microcircuits in Drosophila Melanogaster

2017 ◽  
pp. 361-368
Author(s):  
Jürgen Rybak ◽  
Bill S. Hansson
Keyword(s):  
Drosophila Melanogaster ◽  
Sensory Neurons ◽  
Mushroom Body ◽  
Antennal Lobe ◽  
Odorant Receptor ◽  
Second Order ◽  
Projection Neurons ◽  
Order Processing ◽  
Vinegar Fly ◽  
Maxillary Palps

In the vinegar fly (Drosophila melanogaster), the neuronal pathway that processes olfactory information is organized into multiple layers: a peripheral set of olfactory sensory neurons (OSNs); the primary olfactory center, or antennal lobe (AL); and two second-order neuropils, the mushroom body (MB) and lateral horn (LH). Odorants are detected by the dendrites of OSNs housed in sensilla on the maxillary palps and antennae. The OSN axons converge onto spherical synaptic neuropil within the AL termed glomeruli. OSNs that express the same odorant receptor project to the same glomerulus in a one-to-one fashion, forming discrete olfactory pathways. In the AL, a network of local interneurons (LNs) and projection neurons (PNs) contribute to the first-order processing within the glomeruli. Two types of PNs constitute the principal, parallel output pathways made by PN axons that end in the second-order neuropils of the MB and LH: uniglomerular PNs (uPNs) and multiglomerular PNs (mPNs).

scholarly journals Cholinergic calcium responses in cultured antennal lobe neurons of the migratory locust

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Gregor A. Bergmann ◽  
Gerd Bicker
Keyword(s):  
Olfactory Receptor ◽  
Intracellular Signaling ◽  
Antennal Lobe ◽  
Locusta Migratoria ◽  
Cytosolic Calcium ◽  
Olfactory Receptor Neurons ◽  
Future Research ◽  
Migratory Locust ◽  
Local Interneurons ◽  
Receptor Neurons

AbstractLocusts are advantageous organisms to elucidate mechanisms of olfactory coding at the systems level. Sensory input is provided by the olfactory receptor neurons of the antenna, which send their axons into the antennal lobe. So far, cellular properties of neurons isolated from the circuitry of the olfactory system, such as transmitter-induced calcium responses, have not been studied. Biochemical and immunocytochemical investigations have provided evidence for acetylcholine as classical transmitter of olfactory receptor neurons. Here, we characterize cell cultured projection and local interneurons of the antennal lobe by cytosolic calcium imaging to cholinergic stimulation. We bulk loaded the indicator dye Cal-520 AM in dissociated culture and recorded calcium transients after applying cholinergic agonists and antagonists. The majority of projection and local neurons respond with increases in calcium levels to activation of both nicotinic and muscarinic receptors. In local interneurons, we reveal interactions lasting over minutes between intracellular signaling pathways, mediated by muscarinic and nicotinic receptor stimulation. The present investigation is pioneer in showing that Cal-520 AM readily loads Locusta migratoria neurons, making it a valuable tool for future research in locust neurophysiology, neuropharmacology, and neurodevelopment.

scholarly journals The wiring logic of an identified serotonergic neuron that spans sensory networks

2020 ◽  
Author(s):  
Kaylynn E. Coates ◽  
Steven A. Calle-Schuler ◽  
Levi M. Helmick ◽  
Victoria L. Knotts ◽  
Brennah N. Martik ◽  
...  
Keyword(s):  
Single Cell ◽  
Synaptic Input ◽  
Antennal Lobe ◽  
Projection Neurons ◽  
Dependent Manner ◽  
Serotonergic Neuron ◽  
Local Interneuron ◽  
Local Networks ◽  
First Order ◽  
Specific Input

AbstractSerotonergic neurons modulate diverse physiological and behavioral processes in a context-dependent manner, based on their complex connectivity. However, their connectivity has not been comprehensively explored at a single-cell resolution. Using a whole-brain EM dataset we determined the wiring logic of a broadly projecting serotonergic neuron (the “CSDn”) in Drosophila. Within the antennal lobe (AL; first-order olfactory region), the CSDn receives glomerulus-specific input and preferentially targets distinct local interneuron subtypes. Furthermore, the wiring logic of the CSDn differs between olfactory regions. The CSDn innervates the AL and lateral horn (LH), yet does not maintain the same synaptic relationship with individual projection neurons that also span both regions. Consistent with this, the CSDn has more distributed connectivity in the LH relative to the AL, preferentially synapsing with principal neuron types based on presumptive transmitter content. Lastly, we identify protocerebral neurons that provide abundant synaptic input to the CSDn. Our study demonstrates how an individual modulatory neuron can interact with local networks and integrate input from non-olfactory sources.

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