scholarly journals Classification of odorants across layers in locust olfactory pathway

2016 ◽  
Vol 115 (5) ◽  
pp. 2303-2316 ◽  
Author(s):  
Pavel Sanda ◽  
Tiffany Kee ◽  
Nitin Gupta ◽  
Mark Stopfer ◽  
Maxim Bazhenov
Keyword(s):  
Antennal Lobe ◽  
Error Rates ◽  
Classification Error ◽  
Mushroom Bodies ◽  
Insect Brain ◽  
Projection Neurons ◽  
Olfactory Pathway ◽  
Lateral Horn ◽  
Odor Classification

Olfactory processing takes place across multiple layers of neurons from the transduction of odorants in the periphery, to odor quality processing, learning, and decision making in higher olfactory structures. In insects, projection neurons (PNs) in the antennal lobe send odor information to the Kenyon cells (KCs) of the mushroom bodies and lateral horn neurons (LHNs). To examine the odor information content in different structures of the insect brain, antennal lobe, mushroom bodies and lateral horn, we designed a model of the olfactory network based on electrophysiological recordings made in vivo in the locust. We found that populations of all types (PNs, LHNs, and KCs) had lower odor classification error rates than individual cells of any given type. This improvement was quantitatively different from that observed using uniform populations of identical neurons compared with spatially structured population of neurons tuned to different odor features. This result, therefore, reflects an emergent network property. Odor classification improved with increasing stimulus duration: for similar odorants, KC and LHN ensembles reached optimal discrimination within the first 300–500 ms of the odor response. Performance improvement with time was much greater for a population of cells than for individual neurons. We conclude that, for PNs, LHNs, and KCs, ensemble responses are always much more informative than single-cell responses, despite the accumulation of noise along with odor information.

Direct and glia-mediated effects of GABA on development of central olfactory neurons

2011 ◽  
Vol 7 (2-4) ◽  
pp. 143-161
Author(s):  
Heather S. Mallory ◽  
Nicholas J. Gibson ◽  
Jon H. Hayashi ◽  
Alan J. Nighorn ◽  
Lynne A. Oland
Keyword(s):  
Glial Cells ◽  
Antennal Lobe ◽  
Neuronal Morphology ◽  
Projection Neurons ◽  
Olfactory Pathway ◽  
Mediated Effects ◽  
Local Interneurons ◽  
Outward Currents ◽  
Olfactory Glomeruli

Previously studied for its role in processing olfactory information in the antennal lobe, GABA also may shape development of the olfactory pathway, acting either through or on glial cells. Early in development, the dendrites of GABAergic neurons extend to the glial border that surrounds the nascent olfactory lobe neuropil. These neuropil glia express both GABAA and GABAB receptors, about half of the glia in acute cultures responded to GABA with small outward currents, and about a third responded with small transient increases in intracellular calcium. The neuronal classes that express GABA in vivo, the local interneurons and a subset of projection neurons, also do so in culture. Exposure to GABA in culture increased the size and complexity of local interneurons, but had no effect on glial morphology. The presence of glia alone did not affect neuronal morphology, but in the presence of both glia and GABA, the growth-enhancing effects of GABA on cultured antennal lobe neurons were eliminated. Contact between the glial cells and the neurons was not necessary. Operating in vivo, these antagonistic effects, one direct and one glia mediated, could help to sculpt the densely branched, tufted arbors that are characteristic of neurons innervating olfactory glomeruli.

scholarly journals Neuronal architecture of the second-order CO2 pathway in the brain of a noctuid moth

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
X. Chu ◽  
P. KC ◽  
E. Ian ◽  
P. Kvello ◽  
Y. Liu ◽  
...  
Keyword(s):  
Antennal Lobe ◽  
The Other ◽  
Projection Neurons ◽  
Target Area ◽  
Learning Mechanisms ◽  
Olfactory Pathway ◽  
Lateral Horn ◽  
Noctuid Moth ◽  
Comprehensive Knowledge ◽  
Plant Odor

AbstractMany insects possess the ability to detect fine fluctuations in the environmental CO2 concentration. In herbivorous species, plant-emitted CO2, in combination with other sensory cues, affect many behaviors including foraging and oviposition. In contrast to the comprehensive knowledge obtained on the insect olfactory pathway in recent years, we still know little about the central CO2 system. By utilizing intracellular labeling and mass staining, we report the neuroanatomy of projection neurons connected with the CO2 sensitive antennal-lobe glomerulus, the labial pit organ glomerulus (LPOG), in the noctuid moth, Helicoverpa armigera. We identified 15 individual LPOG projection neurons passing along different tracts. Most of these uniglomerular neurons terminated in the lateral horn, a previously well-described target area of plant-odor projection neurons originating from the numerous ordinary antennal-lobe glomeruli. The other higher-order processing area for odor information, the calyces, on the other hand, was weakly innervated by the LPOG neurons. The overlapping LPOG terminals in the lateral horn, which is considered important for innate behavior in insects, suggests the biological importance of integrating the CO2 input with plant odor information while the weak innervation of the calyces indicates the insignificance of this ubiquitous cue for learning mechanisms.

scholarly journals Analysis of Synaptic Microcircuits in the Mushroom Bodies of the Honeybee

Insects ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 43 ◽  
Author(s):  
Claudia Groh ◽  
Wolfgang Rössler
Keyword(s):  
Behavioral Plasticity ◽  
Future Research ◽  
Mushroom Bodies ◽  
Insect Brain ◽  
Long Term Memory ◽  
Projection Neurons ◽  
Open Questions ◽  
Neuronal Mechanisms ◽  
Input Region ◽  
Change Response

Mushroom bodies (MBs) are multisensory integration centers in the insect brain involved in learning and memory formation. In the honeybee, the main sensory input region (calyx) of MBs is comparatively large and receives input from mainly olfactory and visual senses, but also from gustatory/tactile modalities. Behavioral plasticity following differential brood care, changes in sensory exposure or the formation of associative long-term memory (LTM) was shown to be associated with structural plasticity in synaptic microcircuits (microglomeruli) within olfactory and visual compartments of the MB calyx. In the same line, physiological studies have demonstrated that MB-calyx microcircuits change response properties after associative learning. The aim of this review is to provide an update and synthesis of recent research on the plasticity of microcircuits in the MB calyx of the honeybee, specifically looking at the synaptic connectivity between sensory projection neurons (PNs) and MB intrinsic neurons (Kenyon cells). We focus on the honeybee as a favorable experimental insect for studying neuronal mechanisms underlying complex social behavior, but also compare it with other insect species for certain aspects. This review concludes by highlighting open questions and promising routes for future research aimed at understanding the causal relationships between neuronal and behavioral plasticity in this charismatic social insect.

scholarly journals Local interneurons and projection neurons in the antennal lobe from a spiking point of view

2013 ◽  
Vol 110 (10) ◽  
pp. 2465-2474 ◽  
Author(s):  
Anneke Meyer ◽  
C. Giovanni Galizia ◽  
Martin Paul Nawrot
Keyword(s):  
Antennal Lobe ◽  
Essential Feature ◽  
Point Of View ◽  
Local Network ◽  
Projection Neurons ◽  
Receptor Repertoire ◽  
Local Interneurons ◽  
Spatio Temporal ◽  
Characteristic Features

Local computation in microcircuits is an essential feature of distributed information processing in vertebrate and invertebrate brains. The insect antennal lobe represents a spatially confined local network that processes high-dimensional and redundant peripheral input to compute an efficient odor code. Social insects can rely on a particularly rich olfactory receptor repertoire, and they exhibit complex odor-guided behaviors. This corresponds with a high anatomical complexity of their antennal lobe network. In the honeybee, a large number of glomeruli that receive sensory input are interconnected by a dense network of local interneurons (LNs). Uniglomerular projection neurons (PNs) integrate sensory and recurrent local network input into an efficient spatio-temporal odor code. To investigate the specific computational roles of LNs and PNs, we measured several features of sub- and suprathreshold single-cell responses to in vivo odor stimulation. Using a semisupervised cluster analysis, we identified a combination of five characteristic features as sufficient to separate LNs and PNs from each other, independent of the applied odor-stimuli. The two clusters differed significantly in all these five features. PNs showed a higher spontaneous subthreshold activation, assumed higher peak response rates and a more regular spiking pattern. LNs reacted considerably faster to the onset of a stimulus, and their responses were more reliable across stimulus repetitions. We discuss possible mechanisms that can explain our results, and we interpret cell-type-specific characteristics with respect to their functional relevance.

scholarly journals Immunocytochemical Mapping of an RDL-Like GABA Receptor Subunit and of GABA in Brain Structures Related to Learning and Memory in the Cricket Acheta domesticus

1998 ◽  
Vol 5 (1) ◽  
pp. 78-89
Author(s):  
Colette Strambi ◽  
Myriam Cayre ◽  
David B. Sattelle ◽  
Roger Augier ◽  
Pierre Charpin ◽  
...  
Keyword(s):  
Learning And Memory ◽  
Gaba Receptors ◽  
Antennal Lobe ◽  
Gaba Receptor ◽  
Brain Structures ◽  
Acheta Domesticus ◽  
Central Complex ◽  
Mushroom Bodies ◽  
Insect Brain ◽  
Ellipsoid Body

The distribution of putative RDL-like GABA receptors and of γ-aminobutyric acid (GABA) in the brain of the adult house cricket Acheta domesticus was studied using specific antisera. Special attention was given to brain structures known to be related to learning and memory. The main immunostaining for the RDL-like GABA receptor was observed in mushroom bodies, in particular the upper part of mushroom body peduncle and the two arms of the posterior calyx. Weaker immunostaining was detected in the distal part of the peduncle and in the α and β lobes. The dorso- and ventrolateral protocerebrum neuropils appeared rich in RDL-like GABA receptors. Staining was also detected in the glomeruli of the antennal lobe, as well as in the ellipsoid body of the central complex. Many neurons clustered in groups exhibit GABA-like immunoreactivity. Tracts that were strongly immunostained innervated both the calyces and the lobes of mushroom bodies. The glomeruli of the antennal lobe, the ellipsoid body, as well as neuropils of the dorso- and ventrolateral protocerebrum were also rich in GABA-like immuno- reactivity. The data demonstrated a good correlation between the distribution of the GABA-like and of the RDL-like GABA receptor immunoreactivity. The prominent distribution of RDL-like GABA receptor subunits, in particular areas of mushroom bodies and antennal lobes, underlines the importance of inhibitory signals in information processing in these major integrative centers of the insect brain.

scholarly journals Evolutionarily conserved anatomical and physiological properties of olfactory pathway till fourth order neurons in a species of grasshopper(Hieroglyphus banian)

2018 ◽  
Author(s):  
Shilpi Singh ◽  
Joby Joseph
Keyword(s):  
Fourth Order ◽  
Antennal Lobe ◽  
Olfactory Pathway ◽  
New Class ◽  
Physiological Properties ◽  
Evolutionarily Conserved ◽  
Olfactory Stimuli ◽  
Olfactory Systems ◽  
First Time

AbstractOlfactory systems of different species show variations in structure and physiology despite some conserved characteristics. We characterized the olfactory circuit of the grasshopperHieroglyphus banianof family Acrididae (subfamily: Hemiacridinae) and compared it to a well-studied species of locust,Schistocerca americana(subfamily: Cyrtacanthacridinae), also belonging to family Acrididae. We used in vivo electrophysiological, immunohistochemical and anatomical (bulk tract tracing) methods to elucidate the olfactory pathway from the second order neurons in antennal lobe to the fourth order neurons in β-lobe ofH. banian.We observe highly conserved anatomical and physiological characteristics till the fourth order neurons in the olfactory circuit ofH. banianandS. americana, though they are evolutionarily divergent (~57 million years ago). However, we found one major difference between the two species-there are four antennal lobe tracts inH. banianwhile only one is reported inS. americana. Besides, we are reporting for the first time, a new class of bilateral neurons which respond weakly to olfactory stimuli even though they innervate densely downstream of Kenyon cells.

scholarly journals Cav3-type α1T calcium channels mediate transient calcium currents that regulate repetitive firing in Drosophila antennal lobe PNs

2013 ◽  
Vol 110 (7) ◽  
pp. 1490-1496 ◽  
Author(s):  
Jorge Iniguez ◽  
Soleil S. Schutte ◽  
Diane K. O'Dowd
Keyword(s):  
Calcium Channels ◽  
Antennal Lobe ◽  
Calcium Currents ◽  
Transient Current ◽  
Repetitive Firing ◽  
Insect Brain ◽  
Projection Neurons ◽  
Gene Encoding ◽  
Voltage Gated ◽  
Type Gene

Projection neurons (PNs), located in the antennal lobe region of the insect brain, play a key role in processing olfactory information. To explore how activity is regulated at the level of single PNs within this central circuit we have recorded from these neurons in adult Drosophila melanogaster brains. Our previous study demonstrated that PNs express voltage-gated calcium currents with a transient and sustained component. We found that the sustained component is mediated by cac gene-encoded Cav2-type channels involved in regulating action potential-independent release of neurotransmitter at excitatory cholinergic synapses. The function of the transient calcium current and the gene encoding the underlying channels, however, were unknown. Here we report that the transient current blocked by prepulse inactivation is sensitive to amiloride, a vertebrate Cav3-type channel blocker. In addition PN-specific RNAi knockdown of α1T, the Drosophila Cav3-type gene, caused a dramatic reduction in the transient current without altering the sustained component. These data demonstrate that the α1T gene encodes voltage-gated calcium channels underlying the amiloride-sensitive transient current. Alterations in evoked firing and spontaneous burst firing in the α1T knockdowns demonstrate that the Cav3-type calcium channels are important in regulating excitability in adult PNs.

scholarly journals Sparsening and Temporal Sharpening of Olfactory Representations in the Honeybee Mushroom Bodies

2005 ◽  
Vol 94 (5) ◽  
pp. 3303-3313 ◽  
Author(s):  
Paul Szyszka ◽  
Mathias Ditzen ◽  
Alexander Galkin ◽  
C. Giovanni Galizia ◽  
Randolf Menzel
Keyword(s):  
Mushroom Body ◽  
Antennal Lobe ◽  
Activity Patterns ◽  
Projection Neuron ◽  
Insect Brain ◽  
Projection Neurons ◽  
Similar Response ◽  
Kenyon Cell ◽  
Cell Responses ◽  
Kenyon Cells

We explored the transformations accompanying the transmission of odor information from the first-order processing area, the antennal lobe, to the mushroom body, a higher-order integration center in the insect brain. Using Ca2+ imaging, we recorded activity in the dendrites of the projection neurons that connect the antennal lobe with the mushroom body. Next, we recorded the presynaptic terminals of these projection neurons. Finally, we characterized their postsynaptic partners, the intrinsic neurons of the mushroom body, the clawed Kenyon cells. We found fundamental differences in odor coding between the antennal lobe and the mushroom body. Odors evoked combinatorial activity patterns at all three processing stages, but the spatial patterns became progressively sparser along this path. Projection neuron dendrites and boutons showed similar response profiles, but the boutons were more narrowly tuned to odors. The transmission from projection neuron boutons to Kenyon cells was accompanied by a further sparsening of the population code. Activated Kenyon cells were highly odor specific. Furthermore, the onset of Kenyon cell responses to projection neurons occurred within the first 200 ms and complex temporal patterns were transformed into brief phasic responses. Thus two types of transformations occurred within the MB: sparsening of a combinatorial code, mediated by pre- and postsynaptic processing within the mushroom body microcircuits, and temporal sharpening of postsynaptic Kenyon cell responses, probably involving a broader loop of inhibitory recurrent neurons.

The Functional Logic of Odor Information Processing in the Drosophila Antennal Lobe

2021 ◽  
Author(s):  
Aurel A Lazar ◽  
Tingkai Liu ◽  
Chung-Heng Yeh
Keyword(s):  
Information Processing ◽  
Steady State ◽  
Antennal Lobe ◽  
Stable Steady State ◽  
Projection Neurons ◽  
Olfactory Pathway ◽  
State Behavior ◽  
Key Characteristics ◽  
Functional Logic ◽  
Event Based

In the early olfactory pathway of Drosophila, Olfactory Sensory Neurons (OSNs) multiplicatively encode the odorant identity and the concentration profile. Projection Neurons (PNs) responses in the Antennal Lobe (AL), in turn, exhibit strong transients at odorant onset/offset and stable steady-state behavior. What is the functional logic the of diverse set of Local Neurons (LNs) in the AL Addressing this question may shed light on the key characteristics of odor information processing in the AL, and odorant recognition and olfactory associative learning in the downstream neuropils of the early olfactory system. To address the computation performed by each LN type, we exhaustively evaluated all circuit configurations of the Antennal Lobe. We found that, across model parameterizations, presynaptic inhibition of the OSN-to-PN synapse is essential for odorant identity recovery in steady-state, while postsynaptic excitation and inhibition facilitate on-/off-set event detection. The onset and offset events indicate changing odorant identities, and together with the identity recovery in steady-state, suggest that the AL is an event-based odorant identity recovery processor.

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