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Kymre JH, Chu X, Ian E, Berg BG. Organization of the parallel antennal-lobe tracts in the moth. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2022; 208:707-721. [PMID: 36112200 PMCID: PMC9734247 DOI: 10.1007/s00359-022-01566-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2022] [Revised: 08/16/2022] [Accepted: 08/25/2022] [Indexed: 12/14/2022]
Abstract
The olfactory pathways of the insect brain have been studied comprehensively for more than 40 years, yet the last decade has included a particularly large accumulation of new information relating to this system's structure. In moths, sharp intracellular recording and staining has been used to elucidate the anatomy and physiology of output neurons from the primary olfactory center, the antennal lobe. This review concentrates on the connection patterns characterizing these projection neurons, which follow six separate antennal-lobe tracts. In addition to highlighting the connections between functionally distinct glomerular clusters and higher-order olfactory neuropils, we discuss how parallel tracts in the male convey distinct features of the social signals released by conspecific and heterospecific females. Finally, we consider the current state of knowledge regarding olfactory processing in the moth's protocerebrum and make suggestions as to how the information concerning antennal-lobe output may be used to design future studies.
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Affiliation(s)
- Jonas Hansen Kymre
- Chemosensory Lab, Department of Psychology, Norwegian University of Science and Technology, Trondheim, Norway
| | - Xi Chu
- Chemosensory Lab, Department of Psychology, Norwegian University of Science and Technology, Trondheim, Norway
| | - Elena Ian
- Chemosensory Lab, Department of Psychology, Norwegian University of Science and Technology, Trondheim, Norway
| | - Bente Gunnveig Berg
- Chemosensory Lab, Department of Psychology, Norwegian University of Science and Technology, Trondheim, Norway
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2
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Kymre JH, Berge CN, Chu X, Ian E, Berg BG. Antennal-lobe neurons in the moth Helicoverpa armigera: Morphological features of projection neurons, local interneurons, and centrifugal neurons. J Comp Neurol 2021; 529:1516-1540. [PMID: 32949023 PMCID: PMC8048870 DOI: 10.1002/cne.25034] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2020] [Revised: 09/02/2020] [Accepted: 09/07/2020] [Indexed: 01/11/2023]
Abstract
The relatively large primary olfactory center of the insect brain, the antennal lobe (AL), contains several heterogeneous neuronal types. These include projection neurons (PNs), providing olfactory information to higher‐order neuropils via parallel pathways, and local interneurons (LNs), which provide lateral processing within the AL. In addition, various types of centrifugal neurons (CNs) offer top‐down modulation onto the other AL neurons. By performing iontophoretic intracellular staining, we collected a large number of AL neurons in the moth, Helicoverpa armigera, to examine the distinct morphological features of PNs, LNs, and CNs. We characterize 190 AL neurons. These were allocated to 25 distinct neuronal types or sub‐types, which were reconstructed and placed into a reference brain. In addition to six PN types comprising 15 sub‐types, three LN and seven CN types were identified. High‐resolution confocal images allowed us to analyze AL innervations of the various reported neurons, which demonstrated that all PNs innervating ventroposterior glomeruli contact a protocerebral neuropil rarely targeted by other PNs, that is the posteriorlateral protocerebrum. We also discuss the functional roles of the distinct CNs, which included several previously uncharacterized types, likely involved in computations spanning from multisensory processing to olfactory feedback signalization into the AL.
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Affiliation(s)
- Jonas Hansen Kymre
- Chemosensory lab, Department of Psychology, Norwegian University of Science and Technology, Trondheim, Norway
| | - Christoffer Nerland Berge
- Chemosensory lab, Department of Psychology, Norwegian University of Science and Technology, Trondheim, Norway.,Laboratory for Neural Computation, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
| | - Xi Chu
- Chemosensory lab, Department of Psychology, Norwegian University of Science and Technology, Trondheim, Norway
| | - Elena Ian
- Chemosensory lab, Department of Psychology, Norwegian University of Science and Technology, Trondheim, Norway
| | - Bente G Berg
- Chemosensory lab, Department of Psychology, Norwegian University of Science and Technology, Trondheim, Norway
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3
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Neuronal architecture of the second-order CO 2 pathway in the brain of a noctuid moth. Sci Rep 2020; 10:19838. [PMID: 33199810 PMCID: PMC7669840 DOI: 10.1038/s41598-020-76918-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2020] [Accepted: 11/04/2020] [Indexed: 12/17/2022] Open
Abstract
Many 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.
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4
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Chu X, Heinze S, Ian E, Berg BG. A Novel Major Output Target for Pheromone-Sensitive Projection Neurons in Male Moths. Front Cell Neurosci 2020; 14:147. [PMID: 32581719 PMCID: PMC7294775 DOI: 10.3389/fncel.2020.00147] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2020] [Accepted: 05/04/2020] [Indexed: 01/13/2023] Open
Abstract
Even though insects have comparably small brains, they achieve astoundingly complex behaviors. One example is flying moths tracking minute amounts of pheromones using olfactory circuits. The tracking distance can be up to 1 km, which makes it essential that male moths respond efficiently and reliably to very few pheromone molecules. The male-specific macroglomerular complex (MGC) in the moth antennal lobe contains circuitry dedicated to pheromone processing. Output neurons from this region project along three parallel pathways, the medial, mediolateral, and lateral tracts. The MGC-neurons of the lateral tract are least described and their functional significance is mainly unknown. We used mass staining, calcium imaging, and intracellular recording/staining to characterize the morphological and physiological properties of these neurons in the noctuid moth, Helicoverpa armigera. All lateral-tract MGC neurons targeted the column, a small region within the superior intermediate neuropil. We identified this region as a unique converging site for MGC lateral-tract neurons responsive to pheromones, as well as a dense congregating site for plant odor information since a substantial number of lateral-tract neurons from ordinary glomeruli (OG) also terminates in this region. The lateral-tract MGC-neurons responded with a shorter peak latency than the well-described neurons in the medial tract. Different from the medial-tract MGC neurons encoding odor quality important for species-specific signal identification, those in the lateral tract convey a more robust and rapid signal-potentially important for fast control of hard-wired behavior.
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Affiliation(s)
- Xi Chu
- Chemosensory Laboratory, Department of Psychology, Norwegian University of Science and Technology, Trondheim, Norway
| | - Stanley Heinze
- Lund Vision Group, Department of Biology, Lund University, Lund, Sweden
| | - Elena Ian
- Chemosensory Laboratory, Department of Psychology, Norwegian University of Science and Technology, Trondheim, Norway
| | - Bente G. Berg
- Chemosensory Laboratory, Department of Psychology, Norwegian University of Science and Technology, Trondheim, Norway
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5
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Evolutionarily conserved anatomical and physiological properties of olfactory pathway through fourth-order neurons in a species of grasshopper (Hieroglyphus banian). J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2019; 205:813-838. [DOI: 10.1007/s00359-019-01369-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2018] [Revised: 08/08/2019] [Accepted: 09/04/2019] [Indexed: 01/18/2023]
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Groothuis J, Pfeiffer K, El Jundi B, Smid HM. The Jewel Wasp Standard Brain: Average shape atlas and morphology of the female Nasonia vitripennis brain. ARTHROPOD STRUCTURE & DEVELOPMENT 2019; 51:41-51. [PMID: 31357033 DOI: 10.1016/j.asd.2019.100878] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2019] [Revised: 07/25/2019] [Accepted: 07/25/2019] [Indexed: 06/10/2023]
Abstract
Nasonia, a genus of parasitoid wasps, is a promising model system in the study of developmental and evolutionary genetics, as well as complex traits such as learning. Of these "jewel wasps", the species Nasonia vitripennis is widely spread and widely studied. To accelerate neuroscientific research in this model species, fundamental knowledge of its nervous system is needed. To this end, we present an average standard brain of recently eclosed naïve female N. vitripennis wasps obtained by the iterative shape averaging method. This "Jewel Wasp Standard Brain" includes the optic lobe (excluding the lamina), the anterior optic tubercle, the antennal lobe, the lateral horn, the mushroom body, the central complex, and the remaining unclassified neuropils in the central brain. Furthermore, we briefly describe these well-defined neuropils and their subregions in the N. vitripennis brain. A volumetric analysis of these neuropils is discussed in the context of brains of other insect species. The Jewel Wasp Standard Brain will provide a framework to integrate and consolidate the results of future neurobiological studies in N. vitripennis. In addition, the volumetric analysis provides a baseline for future work on age- and experience-dependent brain plasticity.
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Affiliation(s)
- Jitte Groothuis
- Laboratory of Entomology, Wageningen University, Droevendaalsesteeg 1, 6708 PB, Wageningen, the Netherlands
| | - Keram Pfeiffer
- Behavioral Physiology and Sociobiology (Zoology II), University of Würzburg, Biocenter, Am Hubland, 97074, Würzburg, Germany
| | - Basil El Jundi
- Behavioral Physiology and Sociobiology (Zoology II), University of Würzburg, Biocenter, Am Hubland, 97074, Würzburg, Germany
| | - Hans M Smid
- Laboratory of Entomology, Wageningen University, Droevendaalsesteeg 1, 6708 PB, Wageningen, the Netherlands.
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Lee SG, Celestino CF, Stagg J, Kleineidam C, Vickers NJ. Moth pheromone-selective projection neurons with cell bodies in the antennal lobe lateral cluster exhibit diverse morphological and neurophysiological characteristics. J Comp Neurol 2019; 527:1443-1460. [PMID: 30723902 DOI: 10.1002/cne.24611] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2018] [Revised: 12/08/2018] [Accepted: 12/10/2018] [Indexed: 11/08/2022]
Abstract
Olfactory projection neurons convey information from the insect antennal lobe (AL) to higher brain centers. Previous reports have demonstrated that pheromone-responsive projection neurons with cell bodies in the moth medial cell cluster (mcPNs) predominantly have dendritic arborizations in the sexually dimorphic macroglomerular complex (MGC) and send an axon from the AL to the calyces of the mushroom body (CA) as well as the lateral horn (LH) of the protocerebrum via the medial AL tract. These neurons typically exhibit a narrow odor tuning range related to the restriction of their dendritic arbors within a single glomerulus (uniglomerular). In this study, we report on the diverse physiological and morphological properties of a group of pheromone-responsive olfactory projection neurons with cell bodies in the AL lateral cell cluster (MGC lcPNs) of two closely related moth species. All pheromone-responsive lcPNs appeared to exhibit "basket-like" dendritic arborizations in two MGC compartments and made connections with various protocerebral targets including ventrolateral and superior neuropils via projections primarily through the lateral AL tract and to a lesser extent the mediolateral antennal lobe tract. Physiological characterization of MGC lcPNs also revealed a diversity of response profiles including those either enhanced by or reliant upon presentation of a pheromone blend. These responses manifested themselves as higher maximum firing rates and/or improved temporal resolution of pulsatile stimuli. MGC lcPNs therefore participate in conveying diverse olfactory information relating to qualitative and temporal facets of the pheromone stimulus to a more expansive number of protocerebral targets than their mcPN counterparts.
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Affiliation(s)
- Seong-Gyu Lee
- School of Biological Sciences, University of Utah, Salt Lake City, Utah
| | - Christine Fogarty Celestino
- School of Biological Sciences, University of Utah, Salt Lake City, Utah.,Program in Neuroscience, University of Utah, Salt Lake City, Utah
| | - Jeffrey Stagg
- School of Biological Sciences, University of Utah, Salt Lake City, Utah
| | | | - Neil J Vickers
- School of Biological Sciences, University of Utah, Salt Lake City, Utah
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8
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Lin T, Li C, Liu J, Smith BH, Lei H, Zeng X. Glomerular Organization in the Antennal Lobe of the Oriental Fruit Fly Bactrocera dorsalis. Front Neuroanat 2018; 12:71. [PMID: 30233333 PMCID: PMC6127620 DOI: 10.3389/fnana.2018.00071] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2018] [Accepted: 08/06/2018] [Indexed: 11/30/2022] Open
Abstract
The oriental fruit fly, Bactrocera dorsalis is one of the most destructive pests of horticultural crops in tropical and subtropical Asia. The insect relies heavily on its olfactory system to select suitable hosts for development and reproduction. To understand the neural basis of its odor-driven behaviors, it is fundamental to characterize the anatomy of its olfactory system. In this study, we investigated the anatomical organization of the antennal lobe (AL), the primary olfactory center, in B. dorsalis, and constructed a 3D glomerular atlas of the AL based on synaptic antibody staining combined with computerized 3D reconstruction. To facilitate identification of individual glomeruli, we also applied mass staining of olfactory sensory neurons (OSNs) and projection neurons (PNs). In total, 64 or 65 glomeruli are identifiable in both sexes based on their shape, size, and relative spatial relationship. The overall glomerular volume of two sexes is not statistically different. However, eight glomeruli are sexually dimorphic: four (named AM2, C1, L2, and L3) are larger in males, and four are larger in females (A3, AD1, DM3, and M1). The results from anterograde staining, obtained by applying dye in the antennal lobe, show that three typical medial, media lateral, and lateral antennal-lobe tracts form parallel connections between the antennal lobe and protocerebrum. In addition to these three tracts, we also found a transverse antennal-lobe tract. Based on the retrograde staining of the calyx in the mushroom body, we also characterize the arrangement of roots and cell body clusters linked to the medial antennal-lobe tracts. These data provide a foundation for future studies on the olfactory processing of host odors in B. dorsalis.
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Affiliation(s)
- Tao Lin
- Guangdong Engineering Research Center for Insect Behavior Regulation, South China Agricultural University, Guangzhou, China
| | - Chaofeng Li
- Guangdong Engineering Research Center for Insect Behavior Regulation, South China Agricultural University, Guangzhou, China
| | - Jiali Liu
- Guangdong Engineering Research Center for Insect Behavior Regulation, South China Agricultural University, Guangzhou, China
| | - Brian H. Smith
- School of Life Sciences, Arizona State University, Tempe, AZ, United States
| | - Hong Lei
- School of Life Sciences, Arizona State University, Tempe, AZ, United States
| | - Xinnian Zeng
- Guangdong Engineering Research Center for Insect Behavior Regulation, South China Agricultural University, Guangzhou, China
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9
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The morphology of antennal lobe projection neurons is controlled by a POU-domain transcription factor Bmacj6 in the silkmoth Bombyx mori. Sci Rep 2017; 7:14050. [PMID: 29070905 PMCID: PMC5656611 DOI: 10.1038/s41598-017-14578-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2017] [Accepted: 10/12/2017] [Indexed: 11/08/2022] Open
Abstract
How to wire a neural circuit is crucial for the functioning of the nervous system. Here, we describe the neuroanatomy of the olfactory neurons in the spli mutant strain of silkmoth (Bombyx mori) to investigate the function of a transcription factor involved in neuronal wiring in the central olfactory circuit. The genomic structure of the gene Bmacj6, which encodes a class IV POU domain transcription factor, is disrupted in the spli mutant. We report the neuroanatomical abnormality in the morphology of the antennal lobe projection neurons (PNs) that process the sex pheromone. In addition to the mis-targeting of dendrites and axons, we found axonal bifurcation within the PNs. These results indicate that the morphology of neurons in the pheromone processing pathway is modified by Bmacj6.
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10
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Ian E, Zhao XC, Lande A, Berg BG. Individual Neurons Confined to Distinct Antennal-Lobe Tracts in the Heliothine Moth: Morphological Characteristics and Global Projection Patterns. Front Neuroanat 2016; 10:101. [PMID: 27822181 PMCID: PMC5075568 DOI: 10.3389/fnana.2016.00101] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2016] [Accepted: 10/05/2016] [Indexed: 11/13/2022] Open
Abstract
To explore fundamental principles characterizing chemosensory information processing, we have identified antennal-lobe projection neurons in the heliothine moth, including several neuron types not previously described. Generally, odor information is conveyed from the primary olfactory center of the moth brain, the antennal lobe, to higher brain centers via projection neuron axons passing along several parallel pathways, of which the medial, mediolateral, and lateral antennal-lobe tract are considered the classical ones. Recent data have revealed the projections of the individual tracts more in detail demonstrating three main target regions in the protocerebrum; the calyces are innervated mainly by the medial tract, the superior intermediate protocerebrum by the lateral tract exclusively, and the lateral horn by all tracts. In the present study, we have identified, via iontophoretic intracellular staining combined with confocal microscopy, individual projection neurons confined to the tracts mentioned above, plus two additional ones. Further, using the visualization software AMIRA, we reconstructed the stained neurons and registered the models into a standard brain atlas, which allowed us to compare the termination areas of individual projection neurons both across and within distinct tracts. The data demonstrate a morphological diversity of the projection neurons within distinct tracts. Comparison of the output areas of the neurons confined to the three main tracts in the lateral horn showed overlapping terminal regions for the medial and mediolateral tracts; the lateral tract neurons, on the contrary, targeted mostly other output areas in the protocerebrum.
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Affiliation(s)
- Elena Ian
- Department of Psychology, Norwegian University of Science and Technology Trondheim, Norway
| | - Xin C Zhao
- Department of Entomology, College of Plant Protection, Henan Agricultural University Zhengzhou, China
| | - Andreas Lande
- Department of Psychology, Norwegian University of Science and Technology Trondheim, Norway
| | - Bente G Berg
- Department of Psychology, Norwegian University of Science and Technology Trondheim, Norway
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11
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Antennal-lobe tracts in the noctuid moth, Heliothis virescens: new anatomical findings. Cell Tissue Res 2016; 366:23-35. [PMID: 27352608 DOI: 10.1007/s00441-016-2448-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2015] [Accepted: 05/17/2016] [Indexed: 10/21/2022]
Abstract
As in other insects, three main tracts in the moth brain form parallel connections between the antennal lobe and the protocerebrum. These tracts, which consist of the antennal-lobe projection-neuron axons, target two main areas in the protocerebrum, the calyces of the mushroom bodies and the lateral horn. In spite of the solid neuroanatomical knowledge already established, there are still unresolved issues regarding the antennal-lobe tracts of the moth. One is the proportion of lateral-tract neurons targeting the calyces. In the study presented here, we have performed both retrograde and anterograde labeling of the antennal-lobe projection neurons in the brain of the moth, Heliothis virescens. The results from the retrograde staining, obtained by applying dye in the calyces, demonstrated that the direct connection between the antennal lobe and this neuropil is maintained primarily by the medial antennal-lobe tract; only a few axons confined to the lateral tract were found to innervate the calyces. In addition, these staining experiments, which allowed us to explore the arborization pattern of labeled neurons within the antennal lobe, resulted in new findings regarding anatomical arrangement of roots and cell body clusters linked to the medial tract. The results from the anterograde staining, obtained by applying dye into the antennal lobe, visualized the total assembly of axons passing along the antennal-lobe tracts. In addition to the three classical tracts, we found a transverse antennal-lobe tract not previously described in the moth. Also, these staining experiments revealed an organized neuropil in the lateral horn formed by terminals of the four antennal-lobe tracts.
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12
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Zhao XC, Chen QY, Guo P, Xie GY, Tang QB, Guo XR, Berg BG. Glomerular identification in the antennal lobe of the male mothHelicoverpa armigera. J Comp Neurol 2016; 524:2993-3013. [DOI: 10.1002/cne.24003] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2016] [Revised: 03/16/2016] [Accepted: 03/24/2016] [Indexed: 01/02/2023]
Affiliation(s)
- Xin-Cheng Zhao
- Department of Entomology, College of Plant Protection; Henan Agricultural University; Zhengzhou 450002 China
| | - Qiu-Yan Chen
- Department of Entomology, College of Plant Protection; Henan Agricultural University; Zhengzhou 450002 China
| | - Pei Guo
- Department of Entomology, College of Plant Protection; Henan Agricultural University; Zhengzhou 450002 China
| | - Gui-Ying Xie
- Department of Entomology, College of Plant Protection; Henan Agricultural University; Zhengzhou 450002 China
| | - Qing-Bo Tang
- Department of Entomology, College of Plant Protection; Henan Agricultural University; Zhengzhou 450002 China
| | - Xian-Ru Guo
- Department of Entomology, College of Plant Protection; Henan Agricultural University; Zhengzhou 450002 China
- Collaborative Innovation Center of Henan Grain Crops; Zhengzhou 450002 China
| | - Bente G. Berg
- Department of Psychology; Norwegian University of Science and Technology; Trondheim 7489 Norway
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13
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Montgomery SH, Merrill RM, Ott SR. Brain composition inHeliconiusbutterflies, posteclosion growth and experience-dependent neuropil plasticity. J Comp Neurol 2016; 524:1747-69. [DOI: 10.1002/cne.23993] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2015] [Revised: 02/12/2016] [Accepted: 02/15/2016] [Indexed: 12/21/2022]
Affiliation(s)
- Stephen H. Montgomery
- Department of Genetics, Evolution & Environment; University College London; London UK
- Smithsonian Tropical Research Institute; Panama
| | - Richard M. Merrill
- Smithsonian Tropical Research Institute; Panama
- Department of Zoology; University of Cambridge; Cambridge UK
| | - Swidbert R. Ott
- Department of Neuroscience, Psychology and Behaviour; University of Leicester; Leicester UK
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14
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Montgomery SH, Ott SR. Brain composition in Godyris zavaleta, a diurnal butterfly, Reflects an increased reliance on olfactory information. J Comp Neurol 2015; 523:869-91. [PMID: 25400217 PMCID: PMC4354442 DOI: 10.1002/cne.23711] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2014] [Revised: 10/17/2014] [Accepted: 11/04/2014] [Indexed: 11/15/2022]
Abstract
Interspecific comparisons of brain structure can inform our functional understanding of brain regions, identify adaptations to species-specific ecologies, and explore what constrains adaptive changes in brain structure, and coevolution between functionally related structures. The value of such comparisons is enhanced when the species considered have known ecological differences. The Lepidoptera have long been a favored model in evolutionary biology, but to date descriptions of brain anatomy have largely focused on a few commonly used neurobiological model species. We describe the brain of Godyris zavaleta (Ithomiinae), a member of a subfamily of Neotropical butterflies with enhanced reliance on olfactory information. We demonstrate for the first time the presence of sexually dimorphic glomeruli within a distinct macroglomerular complex (MGC) in the antennal lobe of a diurnal butterfly. This presents a striking convergence with the well-known moth MGC, prompting a discussion of the potential mechanisms behind the independent evolution of specialized glomeruli. Interspecific analyses across four Lepidoptera further show that the relative size of sensory neuropils closely mirror interspecific variation in sensory ecology, with G. zavaleta displaying levels of sensory investment intermediate between the diurnal monarch butterfly (Danaus plexippus), which invests heavily in visual neuropil, and night-flying moths, which invest more in olfactory neuropil. We identify several traits that distinguish butterflies from moths, and several that distinguish D. plexippus and G. zavaleta. Our results illustrate that ecological selection pressures mold the structure of invertebrate brains, and exemplify how comparative analyses across ecologically divergent species can illuminate the functional significance of variation in brain structure.
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Affiliation(s)
- Stephen H Montgomery
- Department of Genetics, Evolution & Environment, University College LondonLondon, UK, WC1E 6BT
| | - Swidbert R Ott
- Department of Biology, University of LeicesterLeicester, UK, LE1 7RH
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15
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Berg BG, Zhao XC, Wang G. Processing of Pheromone Information in Related Species of Heliothine Moths. INSECTS 2014; 5:742-61. [PMID: 26462937 PMCID: PMC4592608 DOI: 10.3390/insects5040742] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/27/2014] [Revised: 09/22/2014] [Accepted: 09/24/2014] [Indexed: 11/16/2022]
Abstract
In heliothine moths, the male-specific olfactory system is activated by a few odor molecules, each of which is associated with an easily identifiable glomerulus in the primary olfactory center of the brain. This arrangement is linked to two well-defined behavioral responses, one ensuring attraction and mating behavior by carrying information about pheromones released by conspecific females and the other inhibition of attraction via signal information emitted from heterospecifics. The chance of comparing the characteristic properties of pheromone receptor proteins, male-specific sensory neurons and macroglomerular complex (MGC)-units in closely-related species is especially intriguing. Here, we review studies on the male-specific olfactory system of heliothine moths with particular emphasis on five closely related species, i.e., Heliothis virescens, Heliothis subflexa, Helicoverpa zea, Helicoverpa assulta and Helicoverpa armigera.
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Affiliation(s)
- Bente G Berg
- Department of Psychology, Norwegian University of Science and Technology, Trondheim 7489, Norway.
| | - Xin-Cheng Zhao
- Department of Entomology, College of Plant Protection, Henan Agricultural University, Zhengzhou 450002, China.
| | - Guirong Wang
- State Key Laboratory for Biology of Plant Disease and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China.
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Zhao XC, Kvello P, Løfaldli BB, Lillevoll SC, Mustaparta H, Berg BG. Representation of pheromones, interspecific signals, and plant odors in higher olfactory centers; mapping physiologically identified antennal-lobe projection neurons in the male heliothine moth. Front Syst Neurosci 2014; 8:186. [PMID: 25346663 PMCID: PMC4191081 DOI: 10.3389/fnsys.2014.00186] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2014] [Accepted: 09/14/2014] [Indexed: 11/28/2022] Open
Abstract
The arrangement of anatomically separated systems for information about general and pheromone odorants is well documented at the initial levels of the olfactory pathway both in vertebrates and insects. In the primary olfactory center of the moth brain, for example, a few enlarged glomeruli situated dorsally, at the entrance of the antennal nerve, are devoted to information about female-produced substances whereas a set of more numerous ordinary glomeruli (OG) receives input about general odorants. Heliothine moths are particularly suitable for studying central chemosensory mechanisms not only because of their anatomically separated systems for plant odors and pheromones but also due to their use of female-produced substances in communication across the species. Thus, the male-specific system of heliothine moths includes two sub-arrangements, one ensuring attraction and mating behavior by carrying information about pheromones released by conspecifics, and the other inhibition of attraction via signal information emitted from heterospecifics. Based on previous tracing experiments, a general chemotopic organization of the male-specific glomeruli has been demonstrated in a number of heliothine species. As compared to the well explored organization of the moth antennal lobe (AL), demonstrating a non-overlapping representation of the biologically relevant stimuli, less is known about the neural arrangement residing at the following synaptic level, i.e., the mushroom body calyces and the lateral horn. In the study presented here, we have labeled physiologically characterized antennal-lobe projection neurons in males of the two heliothine species, Heliothis virescens and Helicoverpa assulta, for the purpose of mapping their target regions in the protocerebrum. In order to compare the representation of plant odors, pheromones, and interspecific signals in the higher brain regions of each species, we have created standard brain atlases and registered three-dimensional models of distinct uniglomerular projection neuron types into the relevant atlas.
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Affiliation(s)
- Xin-Cheng Zhao
- Department of Psychology, Norwegian University of Science and Technology (NTNU) Trondheim, Norway
| | - Pål Kvello
- Department of Biology/Neuroscience Unit, MTFS, Norwegian University of Science and Technology (NTNU) Trondheim, Norway
| | - Bjarte B Løfaldli
- Department of Biology/Neuroscience Unit, MTFS, Norwegian University of Science and Technology (NTNU) Trondheim, Norway
| | - Siri C Lillevoll
- Department of Psychology, Norwegian University of Science and Technology (NTNU) Trondheim, Norway
| | - Hanna Mustaparta
- Department of Psychology, Norwegian University of Science and Technology (NTNU) Trondheim, Norway
| | - Bente G Berg
- Department of Psychology, Norwegian University of Science and Technology (NTNU) Trondheim, Norway
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17
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Namiki S, Takaguchi M, Seki Y, Kazawa T, Fukushima R, Iwatsuki C, Kanzaki R. Concentric zones for pheromone components in the mushroom body calyx of the moth brain. J Comp Neurol 2013; 521:1073-92. [PMID: 22911613 DOI: 10.1002/cne.23219] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2012] [Revised: 05/26/2012] [Accepted: 08/17/2012] [Indexed: 12/15/2022]
Abstract
The spatial distribution of input and output neurons in the mushroom body (MB) calyx was investigated in the silkmoth Bombyx mori. In Lepidoptera, the brain has a specialized system for processing sex pheromones. How individual pheromone components are represented in the MB has not yet been elucidated. Toward this end, we first compared the distribution of the presynaptic boutons of antennal lobe projection neurons (PNs), which transfer odor information from the antennal lobe to the MB calyx. The axons of PNs that innervate pheromonal glomeruli were confined to a relatively small area within the calyx. In contrast, the axons of PNs that innervate nonpheromonal glomeruli were more widely distributed. PN axons for the minor pheromone component covered a larger area than those for the major pheromone component and partially overlapped with those innervating nonpheromonal glomeruli, suggesting the integration of the minor pheromone component with plant odors. Overall, we found that PN axons innervating pheromonal and nonpheromonal glomeruli were organized into concentric zones. We then analyzed the dendritic fields of Kenyon cells (KCs), which receive inputs from PNs. Despite the strong regional localization of axons of different PN classes, the dendrites of KCs were less well classified. Finally, we estimated the connectivity between PNs and KCs and suggest that the dendritic field may be organized to receive different amounts of pheromonal and nonpheromonal inputs. PNs for multiple pheromone components and plant odors enter the calyx in a concentric fashion, and they are read out by the elaborate dendritic field of KCs.
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Affiliation(s)
- Shigehiro Namiki
- Intelligent Cooperative Systems Laboratory, Research Center for Advanced Science and Technology, University of Tokyo, Tokyo 153-8904, Japan
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18
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Pregitzer P, Schultze A, Raming K, Breer H, Krieger J. Expression of a GABA(B) - receptor in olfactory sensory neurons of sensilla trichodea on the male antenna of the moth Heliothis virescens. Int J Biol Sci 2013; 9:707-15. [PMID: 23904795 PMCID: PMC3729013 DOI: 10.7150/ijbs.6674] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2013] [Accepted: 06/23/2013] [Indexed: 12/03/2022] Open
Abstract
In the olfactory pathway of Drosophila, a GABAB receptor mediated presynaptic gain control mechanism at the first synapse between olfactory sensory neurons (OSNs) and projection neurons has been suggested to play a critical role in setting the sensitivity and detection range of the sensory system. To approach the question if such a mechanism may be realized in the pheromone recognition system of male moths in this study attempts were made to explore if moth's pheromone-responsive cells express a GABAB- receptor. Employing a combination of genome analysis, RT-PCR experiments and screening of an antennal cDNA library we have identified a cDNA which encodes the GABAB-R1 receptor of Heliothis virescens. Moreover, based on the HvirGABAB-R1 sequence we could predict a GABAB-R1 protein from genome sequences of the silkmoth Bombyx mori. To assess whether HvirGABAB-R1 is expressed in OSNs of male antenna we performed whole-mount in situ hybridization (WM-ISH) experiments. Several HvirGABAB-R1 positive cells were visualized under long sensilla trichodea, known to contain pheromone-responsive OSNs. In parallel it was shown that cells under long trichoid hairs were labelled with pheromone receptor specific probes. In addition, the HvirGABAB-R1 specific probe also labelled several cells under shorter olfactory sensilla, but never stained cells under mechanosensory/gustatory sensilla chaetica. Together, the results indicate that a GABAB receptor is expressed in pheromone-responsive OSNs of H. virescens and suggest a presynaptic gain control mechanism in the axon terminals of these cells.
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Affiliation(s)
- Pablo Pregitzer
- University of Hohenheim, Institute of Physiology, Stuttgart, Germany
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19
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Ai H. Sensors and sensory processing for airborne vibrations in silk moths and honeybees. SENSORS (BASEL, SWITZERLAND) 2013; 13:9344-63. [PMID: 23877129 PMCID: PMC3758652 DOI: 10.3390/s130709344] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/09/2013] [Revised: 07/02/2013] [Accepted: 07/13/2013] [Indexed: 11/23/2022]
Abstract
Insects use airborne vibrations caused by their own movements to control their behaviors and produce airborne vibrations to communicate with conspecific mates. In this review, I use two examples to introduce how insects use airborne vibrations to accurately control behavior or for communication. The first example is vibration-sensitive sensilla along the wing margin that stabilize wingbeat frequency. There are two specialized sensors along the wing margin for detecting the airborne vibration caused by wingbeats. The response properties of these sensors suggest that each sensor plays a different role in the control of wingbeats. The second example is Johnston's organ that contributes to regulating flying speed and perceiving vector information about food sources to hive-mates. There are parallel vibration processing pathways in the central nervous system related with these behaviors, flight and communication. Both examples indicate that the frequency of airborne vibration are filtered on the sensory level and that on the central nervous system level, the extracted vibration signals are integrated with other sensory signals for executing quick adaptive motor response.
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Affiliation(s)
- Hiroyuki Ai
- Department of Earth System Science, Faculty of Science, Fukuoka University, Jonan-ku, Fukuoka 814-0180, Japan.
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20
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Tanaka NK, Suzuki E, Dye L, Ejima A, Stopfer M. Dye fills reveal additional olfactory tracts in the protocerebrum of wild-type Drosophila. J Comp Neurol 2013; 520:4131-40. [PMID: 22592823 DOI: 10.1002/cne.23149] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The antennal lobe (AL) is the primary olfactory center in insect brains. It receives sensory input from the olfactory sensory neurons (OSNs) and sends, through its projection neurons (PNs), reformatted output to secondary olfactory centers, including the mushroom body (MB) calyx and the lateral horn (LH) in the protocerebrum. By injecting dye into the AL of wild-type Drosophila, we identified previously unknown direct pathways between the AL and the ventrolateral, superior medial, and posterior lateral protocerebra. We found that most of these areas in the protocerebrum are connected with the AL through multiple tracts, suggesting that these areas are sites of convergence for olfactory information. Furthermore, areas such as the superior medial protocerebrum now appear to receive olfactory output both directly from the AL and indirectly from lobes of the MB and the LH, suggesting a degree of functional interaction among these areas. We also analyzed the length and number of fibers in each tract. We compare our results obtained from wild-type flies with recent results from transgenic strains and discuss how information about odorants is distributed to multiple protocerebral areas.
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Affiliation(s)
- Nobuaki K Tanaka
- National Institute of Child Health and Human Development, Bethesda, Maryland 20892, USA
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21
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Tanaka NK, Endo K, Ito K. Organization of antennal lobe-associated neurons in adult Drosophila melanogaster brain. J Comp Neurol 2013; 520:4067-130. [PMID: 22592945 DOI: 10.1002/cne.23142] [Citation(s) in RCA: 128] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The primary olfactory centers of both vertebrates and insects are characterized by glomerular structure. Each glomerulus receives sensory input from a specific type of olfactory sensory neurons, creating a topographic map of the odor quality. The primary olfactory center is also innervated by various types of neurons such as local neurons, output projection neurons (PNs), and centrifugal neurons from higher brain regions. Although recent studies have revealed how olfactory sensory input is conveyed to each glomerulus, it still remains unclear how the information is integrated and conveyed to other brain areas. By using the GAL4 enhancer-trap system, we conducted a systematic mapping of the neurons associated with the primary olfactory center of Drosophila, the antennal lobe (AL). We identified in total 29 types of neurons, among which 13 are newly identified in the present study. Analyses of arborizations of these neurons in the AL revealed how glomeruli are linked with each other, how different PNs link these glomeruli with multiple secondary sites, and how these secondary sites are organized by the projections of the AL-associated neurons.
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Affiliation(s)
- Nobuaki K Tanaka
- Institute of Molecular and Cellular Biosciences, The University of Tokyo, Yayoi, Bunkyo-ku, Tokyo, Japan
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22
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Zhao XC, Pfuhl G, Surlykke A, Tro J, Berg BG. A multisensory centrifugal neuron in the olfactory pathway of heliothine moths. J Comp Neurol 2013; 521:152-68. [PMID: 22684993 DOI: 10.1002/cne.23166] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2011] [Revised: 12/21/2011] [Accepted: 06/05/2012] [Indexed: 11/07/2022]
Abstract
We have characterized, by intracellular recording and staining, a unique type of centrifugal neuron in the brain olfactory center of two heliothine moth species; one in Heliothis virescens and one in Helicoverpa armigera. This unilateral neuron, which is not previously described in any moth, has fine processes in the dorsomedial region of the protocerebrum and extensive neuronal branches with blebby terminals in all glomeruli of the antennal lobe. Its soma is located dorsally of the central body close to the brain midline. Mass-fills of antennal-lobe connections with protocerebral regions showed that the centrifugal neuron is, in each brain hemisphere, one within a small group of neurons having their somata clustered. In both species the neuron was excited during application of non-odorant airborne signals, including transient sound pulses of broad bandwidth and air velocity changes. Additional responses to odors were recorded from the neuron in Heliothis virescens. The putative biological significance of the centrifugal antennal-lobe neuron is discussed with regard to its morphological and physiological properties. In particular, a possible role in multisensory processes underlying the moth's ability to adapt its odor-guided behaviors according to the sound of an echo-locating bat is considered.
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Affiliation(s)
- Xin-Cheng Zhao
- Department of Psychology, Neuroscience Unit, Norwegian University of Science and Technology, 7491 Trondheim, Norway
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23
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Løfaldli BB, Kvello P, Kirkerud N, Mustaparta H. Activity in Neurons of a Putative Protocerebral Circuit Representing Information about a 10 Component Plant Odor Blend in Heliothis virescens. Front Syst Neurosci 2012; 6:64. [PMID: 23060753 PMCID: PMC3461648 DOI: 10.3389/fnsys.2012.00064] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2012] [Accepted: 08/21/2012] [Indexed: 11/24/2022] Open
Abstract
The olfactory pathway in the insect brain is anatomically well described from the antennal lobe (AL) to the mushroom bodies and the lateral protocerebrum (LP) in several species. Less is known about the further connections of the olfactory network in protocerebrum and how information about relevant plant odorants and mixtures are represented in this network, resulting in output information mediated by descending neurons. In the present study we have recorded intracellularly followed by dye injections from neurons in the LP and superior protocerebrum (SP) of the moth, Heliothis virescens. As relevant stimuli, we have used selected primary plant odorants and mixtures of them. The results provide the morphology and physiological responses of neurons involved in a putative circuit connecting the mushroom body lobes, the SP, and the LP, as well as input to SP and LP by one multiglomerular AL neuron and output from the LP by one descending neuron. All neurons responded to a particular mixture of ten primary plant odorants, some of them also to single odorants of the mixture. Altogether, the physiological data indicate integration in protocerebral neurons of information from several of the receptor neuron types functionally described in this species.
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Affiliation(s)
- Bjarte Bye Løfaldli
- Neuroscience Unit, Department of Biology, Norwegian University of Science and Technology Trondheim, Norway
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24
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Namiki S, Kanzaki R. Heterogeneity in dendritic morphology of moth antennal lobe projection neurons. J Comp Neurol 2012; 519:3367-86. [PMID: 21858820 DOI: 10.1002/cne.22754] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
A population of projection neurons (PNs) in the antennal lobe (AL) integrates sensory information from the antenna and is essential for processing odor information in the insect brain. We examined the anatomy of this neuronal population in the brain of the silkmoth Bombyx mori. Using intracellular dye injection, we labeled a total of 246 PNs and systematically analyzed their morphological features, including the soma position, antennocerebral tract, and number of innervating glomeruli. For example, we analyzed PNs that had somata in the different cell clusters, innervated overlapping but different groups of glomeruli, and ran through different pathways. We also identified glomeruli innervated by PNs using a previously established procedure that first classifies glomeruli into regional groups and then identifies individual glomeruli. We analyzed uniglomerular PNs (75.6% of the total) and found heterogeneity in the dendritic morphology of the PNs that was dependent on the regions and/or the innervating glomeruli. For example, most PNs innervating the macroglomerular complex did not have extraglomerular processes, whereas most PNs innervating ordinary glomeruli did. Moreover, PNs innervating the toroid glomerulus showed heterogeneity in their dendritic morphology. These PNs had dendritic arborization in different areas within the glomerulus. We found that, in some cases, the innervation pattern of the PN dendrite correlated with individual variation in the glomerular organization. These results indicate that PNs are not homogeneous populations, and in some cases morphological heterogeneity in PNs correlated with change in glomerular organization in the silkmoth AL.
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Affiliation(s)
- Shigehiro Namiki
- Intelligent Cooperative Systems Laboratory, Research Center for Advanced Science and Technology, University of Tokyo, Tokyo, Japan
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25
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The anatomical pathways for antennal sensory information in the central nervous system of the cricket, Gryllus bimaculatus. INVERTEBRATE NEUROSCIENCE 2012; 12:103-17. [DOI: 10.1007/s10158-012-0137-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2012] [Accepted: 05/22/2012] [Indexed: 12/19/2022]
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26
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Raffa RB, Raffa KF. Potential insight for drug discovery from high fidelity receptor-mediated transduction mechanisms in insects. Expert Opin Drug Discov 2011; 6:1091-1101. [PMID: 21984882 DOI: 10.1517/17460441.2011.611497] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
INTRODUCTION: There is a pervasive and growing concern about the small number of new pharmaceutical agents. There are many proposed explanations for this trend that do not involve the drug-discovery process per se, but the discovery process itself has also come under scrutiny. If the current paradigms are indeed not working, where are novel ideas to come from? Perhaps it is time to look to novel sources. AREAS COVERED: The receptor-signaling and 2(nd)-messenger transduction processes present in insects are quite similar to those in mammals (involving G proteins, ion channels, etc.). However, a review of these systems reveals an unprecedented degree of high potency and receptor selectivity to an extent greater than that modeled in most current drug-discovery approaches. EXPERT OPINION: A better understanding of insect receptor pharmacology could stimulate novel theoretical and practical ideas in mammalian pharmacology (drug discovery) and, conversely, the application of pharmacology and medicinal chemistry principles could stimulate novel advances in entomology (safer and more targeted control of pest species).
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Affiliation(s)
- Robert B Raffa
- Department of Pharmaceutical Sciences, Temple University School of Pharmacy, Philadelphia, PA 19140, USA
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27
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Martin JP, Beyerlein A, Dacks AM, Reisenman CE, Riffell JA, Lei H, Hildebrand JG. The neurobiology of insect olfaction: sensory processing in a comparative context. Prog Neurobiol 2011; 95:427-47. [PMID: 21963552 DOI: 10.1016/j.pneurobio.2011.09.007] [Citation(s) in RCA: 118] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2011] [Revised: 09/10/2011] [Accepted: 09/19/2011] [Indexed: 10/17/2022]
Abstract
The simplicity and accessibility of the olfactory systems of insects underlie a body of research essential to understanding not only olfactory function but also general principles of sensory processing. As insect olfactory neurobiology takes advantage of a variety of species separated by millions of years of evolution, the field naturally has yielded some conflicting results. Far from impeding progress, the varieties of insect olfactory systems reflect the various natural histories, adaptations to specific environments, and the roles olfaction plays in the life of the species studied. We review current findings in insect olfactory neurobiology, with special attention to differences among species. We begin by describing the olfactory environments and olfactory-based behaviors of insects, as these form the context in which neurobiological findings are interpreted. Next, we review recent work describing changes in olfactory systems as adaptations to new environments or behaviors promoting speciation. We proceed to discuss variations on the basic anatomy of the antennal (olfactory) lobe of the brain and higher-order olfactory centers. Finally, we describe features of olfactory information processing including gain control, transformation between input and output by operations such as broadening and sharpening of tuning curves, the role of spiking synchrony in the antennal lobe, and the encoding of temporal features of encounters with an odor plume. In each section, we draw connections between particular features of the olfactory neurobiology of a species and the animal's life history. We propose that this perspective is beneficial for insect olfactory neurobiology in particular and sensory neurobiology in general.
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Affiliation(s)
- Joshua P Martin
- Department of Neuroscience, College of Science, University of Arizona, 1040 East Fourth Street, Tucson, AZ 85721-0077, USA.
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28
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Lei H, Reisenman CE, Wilson CH, Gabbur P, Hildebrand JG. Spiking patterns and their functional implications in the antennal lobe of the tobacco hornworm Manduca sexta. PLoS One 2011; 6:e23382. [PMID: 21897842 PMCID: PMC3163580 DOI: 10.1371/journal.pone.0023382] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2011] [Accepted: 07/15/2011] [Indexed: 11/18/2022] Open
Abstract
Bursting as well as tonic firing patterns have been described in various sensory systems. In the olfactory system, spontaneous bursts have been observed in neurons distributed across several synaptic levels, from the periphery, to the olfactory bulb (OB) and to the olfactory cortex. Several in vitro studies indicate that spontaneous firing patterns may be viewed as “fingerprints” of different types of neurons that exhibit distinct functions in the OB. It is still not known, however, if and how neuronal burstiness is correlated with the coding of natural olfactory stimuli. We thus conducted an in vivo study to probe this question in the OB equivalent structure of insects, the antennal lobe (AL) of the tobacco hornworm Manduca sexta. We found that in the moth's AL, both projection (output) neurons (PNs) and local interneurons (LNs) are spontaneously active, but PNs tend to produce spike bursts while LNs fire more regularly. In addition, we found that the burstiness of PNs is correlated with the strength of their responses to odor stimulation – the more bursting the stronger their responses to odors. Moreover, the burstiness of PNs was also positively correlated with the spontaneous firing rate of these neurons, and pharmacological reduction of bursting resulted in a decrease of the neurons' responsiveness. These results suggest that neuronal burstiness reflects a physiological state of these neurons that is directly linked to their response characteristics.
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Affiliation(s)
- Hong Lei
- Department of Neuroscience, University of Arizona, Tucson, Arizona, United States of America.
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29
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Dreyer D, Vitt H, Dippel S, Goetz B, El Jundi B, Kollmann M, Huetteroth W, Schachtner J. 3D Standard Brain of the Red Flour Beetle Tribolium Castaneum: A Tool to Study Metamorphic Development and Adult Plasticity. Front Syst Neurosci 2010; 4:3. [PMID: 20339482 PMCID: PMC2845059 DOI: 10.3389/neuro.06.003.2010] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2009] [Accepted: 01/18/2010] [Indexed: 12/21/2022] Open
Abstract
The red flour beetle Tribolium castaneum is emerging as a further standard insect model beside Drosophila. Its genome is fully sequenced and it is susceptible for genetic manipulations including RNA-interference. We use this beetle to study adult brain development and plasticity primarily with respect to the olfactory system. In the current study, we provide 3D standard brain atlases of freshly eclosed adult female and male beetles (A0). The atlases include eight paired and three unpaired neuropils including antennal lobes (ALs), optic lobe neuropils, mushroom body calyces and pedunculi, and central complex. For each of the two standard brains, we averaged brain areas of 20 individual brains. Additionally, we characterized eight selected olfactory glomeruli from 10 A0 female and male beetles respectively, which we could unequivocally recognize from individual to individual owing to their size and typical position in the ALs. In summary, comparison of the averaged neuropil volumes revealed no sexual dimorphism in any of the reconstructed neuropils in A0 Tribolium brains. Both, the female and male 3D standard brain are also used for interspecies comparisons, and, importantly, will serve as future volumetric references after genetical manipulation especially regarding metamorphic development and adult plasticity.
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Affiliation(s)
- David Dreyer
- Department of Biology, Animal Physiology, Philipps-University Marburg Marburg, Germany
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30
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Løfaldli BB, Kvello P, Mustaparta H. Integration of the antennal lobe glomeruli and three projection neurons in the standard brain atlas of the moth heliothis virescens. Front Syst Neurosci 2010; 4:5. [PMID: 20179785 PMCID: PMC2826183 DOI: 10.3389/neuro.06.005.2010] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2009] [Accepted: 01/26/2010] [Indexed: 11/13/2022] Open
Abstract
Digital three dimensional standard brain atlases (SBAs) are valuable tools for integrating neuroimaging data of different preparations. In insects, SBAs of five species are available, including the atlas of the female Heliothis virescens moth brain. Like for the other species, the antennal lobes (ALs) of the moth brain atlas were integrated as one material identity without internal structures. Different from the others, the H. virescens SBA exclusively included the glomerular layer of the AL. This was an advantage in the present study for performing a direct registration of the glomerular layer of individual preparations into the standard brain. We here present the H. virescens female SBA with a new model of the AL glomeruli integrated into the atlas, i.e. with each of the 66 glomeruli identified and labelled with a specific number. The new model differs from the previous H. virescens AL model both in respect to the number of glomeruli and the numbering system; the latter according to the system used for the AL atlases of two other heliothine species. For identifying female specific glomeruli comparison with the male AL was necessary. This required a new male AL atlas, included in this paper. As demonstrated by the integration of three AL projection neurons of different preparations, the new SBA with the integrated glomruli is a helpful tool for determining the glomeruli innervated as well as the relative position of the axonal projections in the protocerebrum.
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Affiliation(s)
- Bjarte Bye Løfaldli
- Neuroscience Unit, Department of Biology, Norwegian University of Science and Technology Trondheim, Norway
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31
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Galizia CG, Rössler W. Parallel olfactory systems in insects: anatomy and function. ANNUAL REVIEW OF ENTOMOLOGY 2010; 55:399-420. [PMID: 19737085 DOI: 10.1146/annurev-ento-112408-085442] [Citation(s) in RCA: 224] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
A striking commonality across insects and vertebrates is the recurring presence of parallel olfactory subsystems, suggesting that such an organization has a highly adaptive value. Conceptually, two different categories of parallel systems must be distinguished. In one, specific sensory organs or processing streams analyze different chemical stimuli (segregate parallel systems). In the other, similar odor stimuli are processed but analyzed with respect to different features (dual parallel systems). Insects offer many examples for both categories. For example, segregate parallel systems for different chemical stimuli are realized in specialized neuronal streams for processing sex pheromones and CO(2). Dual parallel streams related to similar or overlapping odor stimuli are prominent in Hymenoptera. Here, a clear separation of sensory tracts to higher-order brain centers is present despite no apparent differences regarding the classes or categories of olfactory stimuli being processed. In this paper, we review the situation across insect species and offer hypotheses for the function and evolution of parallel olfactory systems.
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Yamagata N, Schmuker M, Szyszka P, Mizunami M, Menzel R. Differential odor processing in two olfactory pathways in the honeybee. Front Syst Neurosci 2009; 3:16. [PMID: 20198105 PMCID: PMC2802323 DOI: 10.3389/neuro.06.016.2009] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2009] [Accepted: 11/17/2009] [Indexed: 11/13/2022] Open
Abstract
An important component in understanding central olfactory processing and coding in the insect brain relates to the characterization of the functional divisions between morphologically distinct types of projection neurons (PN). Using calcium imaging, we investigated how the identity, concentration and mixtures of odors are represented in axon terminals (boutons) of two types of PNs – lPN and mPN. In lPN boutons we found less concentration dependence, narrow tuning profiles at a high concentration, which may be optimized for fine, concentration-invariant odor discrimination. In mPN boutons, however, we found clear rising concentration dependence, broader tuning profiles at a high concentration, which may be optimized for concentration coding. In addition, we found more mixture suppression in lPNs than in mPNs, indicating lPNs better adaptation for synthetic mixture processing. These results suggest a functional division of odor processing in both PN types.
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Affiliation(s)
- Nobuhiro Yamagata
- Institut für Neurobiologie, Freie Universität Berlin Berlin, Germany
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El Jundi B, Huetteroth W, Kurylas AE, Schachtner J. Anisometric brain dimorphism revisited: Implementation of a volumetric 3D standard brain in Manduca sexta. J Comp Neurol 2009; 517:210-25. [PMID: 19731336 DOI: 10.1002/cne.22150] [Citation(s) in RCA: 84] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Lepidopterans like the giant sphinx moth Manduca sexta are known for their conspicuous sexual dimorphism in the olfactory system, which is especially pronounced in the antennae and in the antennal lobe, the primary integration center of odor information. Even minute scents of female pheromone are detected by male moths, facilitated by a huge array of pheromone receptors on their antennae. The associated neuropilar areas in the antennal lobe, the glomeruli, are enlarged in males and organized in the form of the so-called macroglomerular complex (MGC). In this study we searched for anatomical sexual dimorphism more downstream in the olfactory pathway and in other neuropil areas in the central brain. Based on freshly eclosed animals, we created a volumetric female and male standard brain and compared 30 separate neuropilar regions. Additionally, we labeled 10 female glomeruli that were homologous to previously quantitatively described male glomeruli including the MGC. In summary, the neuropil volumes reveal an isometric sexual dimorphism in M. sexta brains. This proportional size difference between male and female brain neuropils masks an anisometric or disproportional dimorphism, which is restricted to the sex-related glomeruli of the antennal lobes and neither mirrored in other normal glomeruli nor in higher brain centers like the calyces of the mushroom bodies. Both the female and male 3D standard brain are also used for interspecies comparisons, and may serve as future volumetric reference in pharmacological and behavioral experiments especially regarding development and adult plasticity. J. Comp. Neurol. 517:210-225, 2009. (c) 2009 Wiley-Liss, Inc.
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Affiliation(s)
- Basil El Jundi
- Department of Biology, Animal Physiology, Philipps-University, Marburg, Germany
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Kvello P, Løfaldli BB, Rybak J, Menzel R, Mustaparta H. Digital, Three-dimensional Average Shaped Atlas of the Heliothis Virescens Brain with Integrated Gustatory and Olfactory Neurons. Front Syst Neurosci 2009; 3:14. [PMID: 19949481 PMCID: PMC2784302 DOI: 10.3389/neuro.06.014.2009] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2009] [Accepted: 10/02/2009] [Indexed: 12/02/2022] Open
Abstract
We use the moth Heliothis virescens as model organism for studying the neural network involved in chemosensory coding and learning. The constituent neurons are characterised by intracellular recordings combined with staining, resulting in a single neuron identified in each brain preparation. In order to spatially relate the neurons of different preparations a common brain framework was required. We here present an average shaped atlas of the moth brain. It is based on 11 female brain preparations, each stained with a fluorescent synaptic marker and scanned in confocal laser-scanning microscope. Brain neuropils of each preparation were manually reconstructed in the computer software Amira, followed by generating the atlas using the Iterative Shape Average Procedure. To demonstrate the application of the atlas we have registered two olfactory and two gustatory interneurons, as well as the axonal projections of gustatory receptor neurons into the atlas, visualising their spatial relationships. The olfactory interneurons, showing the typical morphology of inner-tract antennal lobe projection neurons, projected in the calyces of the mushroom body and laterally in the protocerebral lobe. The two gustatory interneurons, responding to sucrose and quinine respectively, projected in different areas of the brain. The wide projections of the quinine responding neuron included a lateral area adjacent to the projections of the olfactory interneurons. The sucrose responding neuron was confined to the suboesophageal ganglion with dendritic arborisations overlapping the axonal projections of the gustatory receptor neurons on the proboscis. By serving as a tool for the integration of neurons, the atlas offers visual access to the spatial relationship between the neurons in three dimensions, and thus facilitates the study of neuronal networks in the Heliothis virescens brain. The moth standard brain is accessible at http://www.ntnu.no/biolog/english/neuroscience/brain
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Affiliation(s)
- Pål Kvello
- Department of Biology, Norwegian University of Science and Technology Trondheim, Norway
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Fukushima R, Kanzaki R. Modular subdivision of mushroom bodies by Kenyon cells in the silkmoth. J Comp Neurol 2009; 513:315-30. [PMID: 19148932 DOI: 10.1002/cne.21946] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
In insects, olfactory information in the glomeruli of the antennal lobe, the first olfactory center, is transmitted to the lateral protocerebrum and the calyx of the mushroom body via projection neurons. In male silkmoths (Bombyx mori), arborization patterns in the calyx differ markedly between projection neurons that respond to sex pheromones and those that respond to general odors. However, little is known about the organization of the mushroom body's intrinsic neurons, called Kenyon cells (KCs), which receive the inputs from the projection neurons. We investigated the silkmoth mushroom body and identified four parallel subdivisions in the lobes and pedunculus by immunolabeling with antibodies against the catalytic subunit of protein kinase A in Drosophila melanogaster (DC0) and the neuromodulatory peptide FMRFamide. To further understand the detailed organization of the mushroom body, we performed extensive labeling of individual KCs. We identified four morphological types whose axonal projections corresponded to the subdivisions in the lobes, and found that each type of KC had a characteristic dendritic morphology in the calyx. These results show a correlation between the axonal projections of KCs in the lobes and dendritic morphology in the calyx, and indicate different functional roles for the subdivisions.
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Affiliation(s)
- Ryota Fukushima
- Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Ibaraki, Japan
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36
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A 4-dimensional representation of antennal lobe output based on an ensemble of characterized projection neurons. J Neurosci Methods 2009; 180:208-23. [PMID: 19464513 DOI: 10.1016/j.jneumeth.2009.03.019] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2008] [Revised: 03/04/2009] [Accepted: 03/13/2009] [Indexed: 11/20/2022]
Abstract
A central problem facing studies of neural encoding in sensory systems is how to accurately quantify the extent of spatial and temporal responses. In this study, we take advantage of the relatively simple and stereotypic neural architecture found in invertebrates. We combine standard electrophysiological techniques, recently developed population analysis techniques, and novel anatomical methods to form an innovative 4-dimensional view of odor output representations in the antennal lobe of the moth Manduca sexta. This novel approach allows quantification of olfactory responses of characterized neurons with spike time resolution. Additionally, arbitrary integration windows can be used for comparisons with other methods such as imaging. By assigning statistical significance to changes in neuronal firing, this method can visualize activity across the entire antennal lobe. The resulting 4-dimensional representation of antennal lobe output complements imaging and multi-unit experiments yet provides a more comprehensive and accurate view of glomerular activation patterns in spike time resolution.
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Berg BG, Schachtner J, Homberg U. Gamma-aminobutyric acid immunostaining in the antennal lobe of the moth Heliothis virescens and its colocalization with neuropeptides. Cell Tissue Res 2009; 335:593-605. [PMID: 19156440 DOI: 10.1007/s00441-008-0744-z] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2008] [Accepted: 12/12/2008] [Indexed: 11/24/2022]
Abstract
The antennal lobe is the primary processing center for olfactory information in insects. To understand further the neural circuitry of this brain area, we have investigated the distribution of gamma-aminobutyric acid (GABA) and its colocalization with neuropeptides in the antennal lobe of the noctuid moth Heliothis virescens. Immunocytochemical experiments with an antiserum against GABA showed a large number of labeled somata in the antennal lobe; these somata were located exclusively in the lateral cell cluster. Stained neurites innervating all antennal-lobe glomeruli, including the male-specific macroglomerular complex, suggested a prominent role of GABA in processing olfactory information, including signals from pheromones, interspecifically acting odors, and plant odors. Fibers in two antennocerebral tracts (the middle and dorsal antennocerebral tract) exhibited prominent GABA immunoreactivity. Double-labeling experiments revealed that immunostaining for three neuropeptides, viz., A-type allatostatin, Manduca sexta allatotropin, and FMRFamide-related peptides, was largely colocalized with GABA in cell bodies of the lateral cell cluster. The general absence of peptide immunostaining in the antennocerebral tracts strongly indicated that these peptides were colocalized with GABA in local interneurons of the antennal lobe. In contrast, tachykinin-related peptides occurred in a distinct population of local antennal-lobe neurons that did not exhibit GABA immunostaining. Thus, local interneurons that were not GABAergic were present in the moth antennal lobe.
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Affiliation(s)
- Bente G Berg
- Neuroscience Unit/Department of Psychology, Norwegian University of Science and Technology, 7489 Trondheim, Norway.
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Abstract
The mushroom body (MB) of the insect brain has important roles in odor learning and memory and in diverse other brain functions. To elucidate the anatomical basis underlying its function, we studied how the MB of Drosophila is organized by its intrinsic and extrinsic neurons. We screened for the GAL4 enhancer-trap strains that label specific subsets of these neurons and identified seven subtypes of Kenyon cells and three other intrinsic neuron types. Laminar organization of the Kenyon cell axons divides the pedunculus into at least five concentric strata. The alpha', beta', alpha, and beta lobes are each divided into three strata, whereas the gamma lobe appears more homogeneous. The outermost stratum of the alpha/beta lobes is specifically connected with a small, protruded subregion of the calyx, the accessory calyx, which does not receive direct olfactory input. As for the MB extrinsic neurons (MBENs), we found three types of antennal lobe projection neurons, among which two are novel. In addition, we resolved 17 other types of MBENs that arborize in the calyx, lobes, and pedunculus. Lobe-associated MBENs arborize in only specific areas of the lobes, being restricted along their longitudinal axes, forming two to five segmented zones in each lobe. The laminar arrangement of the Kenyon cell axons and segmented organization of the MBENs together divide the lobes into smaller synaptic units, possibly facilitating characteristic interaction between intrinsic and extrinsic neurons in each unit for different functional activities along the longitudinal lobe axes and between lobes. Structural differences between lobes are also discussed.
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Affiliation(s)
- Nobuaki K Tanaka
- Institute of Molecular and Cellular Biosciences, The University of Tokyo, Tokyo 113-0032, Japan
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Lei H, Vickers N. Central processing of natural odor mixtures in insects. J Chem Ecol 2008; 34:915-27. [PMID: 18581181 DOI: 10.1007/s10886-008-9487-2] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2008] [Revised: 04/10/2008] [Accepted: 04/28/2008] [Indexed: 01/24/2023]
Abstract
In nature, virtually all olfactory stimuli are mixtures of many single odorants. Behavioral experiments repeatedly have demonstrated that an animal's olfactory system is capable of discriminating behaviorally relevant from irrelevant odor mixtures. However, the sensory mechanisms that underlie such discriminative capability remain elusive. The limited anatomical and physiological evidence collected from both insect and vertebrate models that pertains to this topic is scattered in the literature dating back to early 1980s. Thus, a synthesis of this information that includes more recent findings is needed in order to provide a basis for probing the fundamental question from a new angle. In this review, we discuss several proposed models for mixture processing, along with experimental data gathered from both the initial stage of olfactory processing (i.e., antennal lobe in insects or olfactory bulb in vertebrates) and higher areas of the brain, with an emphasis on how the lateral circuits in the antennal lobe or olfactory bulb may contribute to mixture processing. Based on empirical data as well as theoretical modeling, we conclude that odor mixtures may be represented both at the single-neuron level and at the population level. The difference between these two types of processing may reside in the degree of plasticity, with the former being hard-wired and the latter being more subjected to network modulation.
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Affiliation(s)
- Hong Lei
- ARL-Neurobiology, University of Arizona, Tucson, AZ 85721, USA.
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Kurylas AE, Rohlfing T, Krofczik S, Jenett A, Homberg U. Standardized atlas of the brain of the desert locust, Schistocerca gregaria. Cell Tissue Res 2008; 333:125-45. [DOI: 10.1007/s00441-008-0620-x] [Citation(s) in RCA: 100] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2008] [Accepted: 03/31/2008] [Indexed: 11/29/2022]
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Jørgensen K, Stranden M, Sandoz JC, Menzel R, Mustaparta H. Effects of two bitter substances on olfactory conditioning in the moth Heliothis virescens. J Exp Biol 2007; 210:2563-73. [PMID: 17601960 DOI: 10.1242/jeb.004283] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
SUMMARY
In nature, moths encounter nutritious and toxic substances in plants, and thus have to discriminate between a diversity of tastants. Whereas olfactory learning allowing memory of nutritious plants is well demonstrated, little is known about learning and memory of toxic items in adult lepidopterans. Moths may use bitter substances to detect and possibly learn to avoid noxious plants. We have studied the physiological and behavioural effects of two bitter substances, quinine and sinigrin, on the moth Heliothis virescens. Electrophysiological recordings showed responses to both compounds in gustatory receptor neurons on the antennae. The response patterns suggested a peripheral discrimination between quinine and sinigrin. We evaluated their putative aversive effect in an appetitive conditioning context where the moths learned to associate an odour with sucrose. We first aimed at enhancing olfactory conditioning of the proboscis extension response by testing the effect of the sucrose concentration on acquisition, retention and extinction. 2 mol l–1 and 3 mol l–1 sucrose concentration gave similar acquisition, retention and extinction performances. Experiments involving pre-exposure or facilitated extinction with an odour paired with quinine, sinigrin or no tastant showed a latent inhibitory effect,as well as an aversive effect of quinine and, to a lesser extent, of sinigrin. The results suggested that the two tastants may act as negative reinforcers in H. virescens.
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Affiliation(s)
- Kari Jørgensen
- Neuroscience Unit, Department of Biology, Norwegian University of Science and Technology, Trondheim, Norway.
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