Optic flow representation in the optic lobes of Diptera: modeling innervation matrices onto collators and their evolutionary implications

A network model of optic flow processing, based on physiological and anatomical features of motion-processing neurons, is used to investigate the role of small-field motion detectors emulating T5 cells in producing optic flow selective properties in wide-field collator neurons. The imposition of different connectivities can mimic variations observed in comparative studies of lobula plate architecture across the Diptera. The results identify two features that are crucial for optic flow selectivity: the broadness of the spatial patterns of synaptic connections from motion detectors to collators, and the relative contributions of excitatory and inhibitory synaptic outputs. If these two aspects of the innervation matrix are balanced appropriately, the network's sensitivity to perturbations in physiological properties of the small-field motion detectors is dramatically reduced, suggesting that sensory systems can evolve robust mechanisms that do not rely upon precise control of network parameters. These results also suggest that alternative lobula plate architectures observed in insects are consistent in allowing optic flow selective properties in wide-field neurons. The implications for the evolution of optic flow selective neurons are discussed.     

Control theoretic interpretation of directional motion preferences in optic flow processing interneurons

In this article, we formalize the processing of optic flow in identified fly lobula plate tangential cells and develop a control theoretic framework that suggests how the signals of these cells may be combined and used to achieve reflex-like navigation behavior. We show that this feedback gain synthesis task can be cast as a combined static state estimation and linear feedback control problem. Our framework allows us to analyze and determine the relationship between optic flow measurements and actuator commands, which greatly simplifies the implementation of biologically inspired control architectures on terrestrial and aerial robotic platforms.     

Cortical dynamic tuning: the role of intrinsic connections, as revealed by modeling

A current challenge in computational neuroscience is to elucidate the role of cortical circuitry in information processing and in generating motor output. Our understanding of the functional significance of specifically organized feedback connections is progressing rapidly as researchers establish the equivalence of theoretical models to biological neural circuits. Modeling studies of different neural structures, along with quantitative comparisons of model performance to biological data, have recently helped to identify the basic features of synaptic connectivity that may play important roles in cortical operations.     

日本弓背蚁视叶中5-羟色胺阳性神经元的分布

采用树脂石腊(Colophony-paraffin,CP)组织包埋切片技术和链霉菌抗生物素蛋白—过氧化酶(Streptavidin-peroxidase,SP)免疫组织化学方法,研究了5—HT能神经元在日本弓背蚁(Componotus japonicus)视叶中的分布。5—HT阳性纤维起源于少量的细胞体,但在其视叶不同纤维网中有广泛的分布,呈现明显的静脉曲张状。染色强度在3个视觉纤维网各不相同,并出现分层现象。结果表明5—HT是在大面积神经丛区域,而不是在局部神经丛区域起作用[动物学报49(2)：224—229,2003]。     

Serotonin-like immunoreactivity in the optic lobes of three insect species

The cellular localization of 5-HT in the optic lobes of three insect species was assayed with the use of antibodies raised against 5-HT. In Schistocerca, Periplaneta, and Calliphora all neuropil regions of the optic lobe, the lamina, medulla and lobula, contain 5-HT-immunoreactive varicose fibres in different patterns, like columns and layers. Such fibres also connect the lobula to neuropil in the lateral protocerebrum. In Calliphora also 5-HT-positive fibres of the medulla and lobula plate have projections to the lateral protocerebrum, whereas the origin of the lamina fibres is not certain. In all species the processes displaying 5-HT-like immunoreactivity appear to be derived from a relatively small number of cell bodies, each neuron thus having processes over a large volume of the neuropil of the optic lobe in different layers.     

Pre-existing neuronal pathways in the developing optic lobes of Drosophila

We have identified a set of larval neurones in the developing adult optic lobes of Drosophila by selectively labelling cells that have undergone only a few mitoses. A cluster of three cells is located in each of the optic lobes near the insertion site of the optic stalk. Their axons fasciculate with fibres of the larval optic nerve, the Bolwig's nerve, and then form part of the posterior optic tract. These cells are likely to be first order interneurones of the larval visual system. Unlike the Bolwig's nerve, they persist into the adult stage. The possibility of a pioneering function of the larval visual system during formation of the adult optic lobe neuropil is discussed.     

Fine tuning T lymphocytes: A role for the lipid phosphatase SHIP-1

The phosphoinositide 3-kinase signaling pathway regulates a range of T lymphocyte cellular functions including growth, proliferation, cytokine secretion and survival. Aberrant regulation of phosphoinositide 3-kinase-dependent signaling in T lymphocytes has been implicated in inflammatory and autoimmune diseases. In common with much of the immune system, several mechanisms exist to ensure the pathway is tightly regulated to elicit appropriate responses. One level of control involves the Src homology 2 domain-containing inositol-5-phosphatase-1 (SHIP-1) that modulates phosphoinositide 3-kinase signaling by degrading the key signaling lipid PI(3,4,5)P₃ to PI(3,4)P₂, but also serves as a key scaffolding molecule in the formation of multi-protein complexes. Here we discuss the role of SHIP-1 in regulating T lymphocyte and immune function, as well as its potential as a therapeutic target.     

Binocular interactions of motion detection fibers in the optic lobes of flies

Zusammenfassung Nervenfasern, die die optischen Ganglien beider Kopfseiten von Musca und Phaenicia verbinden und die selektiv auf Musterbewegungen antworten, zeigen binoculare Wechselwirkungen. Details dieser Wechselwirkungen und der Ort an dem sie in den optischen Ganglien stattfinden wurden ermittelt. Die Bedeutung dieser Einheiten für die direkte Steuerung von Wendereaktionen beim Flug wurde ebenfalls untersucht.

---

---

This research was supported by the National Institutes Health, United States Public Health Service Grant NB 03627.     

Distribution of GABA-like immunoreactive neurons in the optic lobes of Periplaneta americana

Summary Specific antisera against protein-conjugated -aminobutyric acid (GABA) were used in immunocytochemical staining procedures to study the distribution of the putative GABA-like immunoreactive neurons in the optic lobes of Periplaneta. GABA-like immunoreactive structures are evident in all three optic neuropil regions. Six different populations of GABAergic neurons, whose perikarya are grouped around the medulla, are found within the optic lobe. The number of these immunoreactive cells varies greatly and corresponds to the number of ommatidia of the eye. In the proximal part of the lamina, a coarse network of GABA-positive fibres is recognizable. These are the processes of large field tangential cells whose fibres pass through the distal surface of the medulla. A second fibre population of the lamina is made up of the processes of the centrifugal columnar neurons whose perikarya lie proximally to the medulla. The medulla contains 9 layers with GABAergic elements of variable immunoreactivity. Layers 1, 3, 5, 7 and 9 exhibit strong labelling, as a result of partial overlapping of the processes of centrifugal and centripetal columnar neurons, tangential fibres and/or lateral processes of perpendicular fibres and (possibly) processes of amacrines. A strong immunoreactivity is found in the proximal and distal layers of the lobula.     

Proliferation pattern and early differentiation of the optic lobes in Drosophila melanogaster

Summary The larval and early pupal development of the optic lobes in Drosophila is described qualitatively and quantitatively using [³H]thymidine autoradiography on 2-m plastic sections. The optic lobes develop from 30–40 precursor cells present in each hemisphere of the freshly hatched larva. During the first and second larval instars, these cells develop to neuroblasts arranged in two epithelial optic anlagen. In the third larval instar and in the early pupa these neuroblasts generate the cells of the imaginal optic lobes at discrete proliferation zones, which can be correlated with individual visual neuropils.The different neuropils as well as the repetitive elements of each neuropil are generated in a defined temporal sequence. Cells of the medulla are the first to become postmitotic with the onset of the third larval instar, followed by cells of the lobula complex and finally of the lamina at about the middle of the third instar. The elements of each neuropil connected to the most posterior part of the retina are generated first, elements corresponding to the most anterior retina are generated last.The proliferation pattern of neuroblasts into ganglion mother cells and ganglion cells is likely to include equal as well as unequal divisions of neuroblasts, followed by one or two generations of ganglion mother cells. For the lamina the proliferation pattern and its temporal coordination with the differentiation of the retina are shown.     

Deltamethrin-induced changes in synaptosomal transport of 3H-epinephrine in the squid optic lobes

In fresh synaptosomal preparation from the squid optic lobe 3H-epinephrine transport was significantly affected by deltamethrin at greater than 10(-9) M. Under the experimental conditions such an effect of deltamethrin manifested as either a reduction (at nondepolarized state) or an increase (at depolarized state) in the final level of 3H-epinephrine accumulated in the synaptosomes. Only a part of such a deltamethrin effect was due to its effect on the sodium channel. The remainder of the deltamethrin effect was strongly influenced by agents or treatments which are known to influence internal Ca2+ concentration, suggesting a possible involvement of Ca2+ regulatory mechanisms in the process of stimulation of transmitter release by deltamethrin.     

Daily variation of melatonin content in the optic lobes of the crab Neohelice granulata.

Melatonin is a biogenic amine, known from almost all phyla of living organisms. In vertebrates melatonin is produced rhythmically in the pinealocytes of the pineal gland, relaying information of the environmental light/dark cycle to the organism. With regard to crustaceans only a handful of studies exist that has attempted to identify the presence and possible daily variation of this substance. We set out to investigate whether in the crab Neohelice granulata melatonin was produced in the optic lobes of these animals and underwent rhythmic fluctuations related to the daily light/dark cycle. Our experimental animals were divided into three groups exposed to different photoperiods: normal photoperiod (12L:12D), constant dark (DD), and constant light (LL). The optic lobes were collected every 4 hours over a 24-h period for melatonin quantification by radioimmunoassay (RIA). N. granulata kept under 12 L:12D and DD conditions, showed daily melatonin variations with two peaks of abundance (p<0.05), one during the day and another, more extensive one, at night. Under LL-conditions no significant daily variations were noticeable (p>0.05). These results demonstrate the presence of a daily biphasic fall and rise of melatonin in the eyestalk of N. granulata and suggest that continuous exposure to light inhibits the production of melatonin synthesis.     

Neural cell types surviving congenital sensory deprivation in the optic lobes of Drosophila melanogaster

Golgi staining of neuronal cell types in the optic lobe rudiments of adult eyeless flies of the sine oculis (so) mutant of Drosophila melanogaster reveals partial independence of optic lobe's development from compound eye formation. (1) Differentiation and maintenance of many neuronal cell types of medulla and lobular complex do not require innervation of the medulla from the retina and the lamina. Neurons derived from the outer and inner optic anlage have been found in adult eyeless flies. (2) The rudiments of ipsilateral medulla, lobula, and lobular plate are isotopically connected with each other. (3) Stratification of the lobular complex is retained. (4) Equivalent parts of the dorsal lobulae are connected by heterolateral small field neurons. (5) The shapes of many tangential neurons of the medulla show sprouting and compensatory innervation of the lobular complex. The basic results reported here for eyeless flies have many parallels in what is known about anophthalmic mice.     

Analysis of neural elements in head-mutant Drosophila embryos suggests segmental origin of the optic lobes

We describe the development of 20 sensory organs in the embryonic Drosophila head, which give rise to 7 sensory nerves of the peripheral nervous system (PNS), and 4 ganglia of the stomatogastric nervous system (SNS). Using these neural elements and the optic lobes as well as expression domains of the segment polarity gene engrailed in the wild-type head of Drosophila embryos as markers we examined the phenotype of different mutants which lack various and distinct portions of the embryonic head. In the mutants, distinct neural elements and engrailed expression domains, serving as segmental markers, are deleted. These mutants also affect the optic lobes to various degrees. Our results suggest that the optic lobes are of segmental origin and that they derive from the ocular segment anteriorly adjacent to the antennal segment of the developing head.     

Neurosecretory cells in the optic lobes of the brain and activity rhythms in Lycosa tarentula (Araneae: Lycosidae)

Several paired groups of neurosecretory cells (NS) were identified in the dorsal cortical neurons of the optic lobes of the brain of Lycosa tarentula (Araneae). Two large bottle-shaped cells (NS A1, A2) and a cluster of ca. 20 smaller cells (NS B) were found between the lamina and medulla of the anterior median eyes (AM). The forward oriented bundles of NS B axons run alongside large fibres linked to the synaptic zones of the indirect eyes. In front of the arcuate body, an islet of about 10 fusiform cells (NS C1) sends short axons close to the internal cortical border. Other large cells (NS C2, C3) are found from the medulla of the AM to the anterior border of the central body. Their long axons end deeply in the brain neuropil. NS B and C1 function synchronously. The secretory cycles of NS A1 and A2 seem to be in opposition. The activity of these three types of NS depends on the phase of the day. Anatomical relationships of NS A, B and C1 with visual afferent/efferent fibres via synaptic buttons indicate a role of these cells in the modulation of circadian rhythms of visual and locomotor activity. On the other hand, NS C2 and C3, the functioning of which is not synchronous, might be involved in the modulation or control of the elementary movements of L. tarentula when active or at rest.     

Optic nerve regeneration after intravitreal peripheral nerve implants: trajectories of axons regrowing through the optic chiasm into the optic tracts

We have studied axon regeneration through the optic chiasm of adult rats 30 days after prechiasmatic intracranial optic nerve crush and serial intravitreal sciatic nerve grafting on day 0 and 14 post-lesion. The experiments comprised three groups of treated rats and three groups of controls. All treated animals received intravitreal grafts either into the left eye after both left sided (unilateral) and bilateral optic nerve transection, or into both eyes after bilateral optic nerve transection. Control eyes were all sham grafted on day 0 and 14 post-lesion, and the optic nerves either unlesioned, or crushed unilaterally or bilaterally. No regeneration through the chiasm was seen in any of the lesioned control optic nerves. In all experimental groups, large numbers of axons regenerated across the optic nerve lesions ipsilateral to the grafted eyes, traversed the short distal segment of the optic nerve and invaded the chiasm without deflection. Regeneration was correlated with the absence of the mesodermal components in the scar. In all cases, axon regrowth through the chiasm appeared to establish a major crossed and a minor uncrossed projection into both optic tracts, with some aberrant growth into the contralateral optic nerve. Axons preferentially regenerated within the degenerating trajectories from their own eye, through fragmented myelin and axonal debris, and reactive astrocytes, oligodendrocytes, microglia and macrophages. In bilaterally lesioned animals, no regeneration was detected in the optic nerve of the unimplanted eye. Although astrocytes became reactive and their processes proliferated, the architecture of their intrafascicular processes was little perturbed after optic nerve transection within either the distal optic nerve segment or the chiasm. The re-establishment of a comparatively normal pattern of passage through the chiasm by regenerating axons in the adult might therefore be organised by this relatively immutable scaffold of astrocyte processes. Binocular interactions between regenerating axons from both nerves (after bilateral optic nerve transection and intravitreal grafting), and between regenerating axons and the intact transchiasmatic projections from the unlesioned eye (after unilateral optic nerve lesions and after ipsilateral grafting) may not be important in establishing the divergent trajectories, since regenerating axons behave similarly in the presence and absence of an intact projection from the other eye.     

The role of chromophore coupling in tuning the spectral properties of peripheral light-harvesting protein of purple bacteria

The publication of a structure for the peripheral light-harvesting complex of a purple photosynthetic bacterium (McDermott et al. (1995), Nature 374: 517–521) provides a framework within which we can begin to understand various functional aspects of these complexes, in particular the relationship between the structure and the red-shift of the bacteriochlorophyll Q_y transition. In this article we describe calculations of some of the spectral properties expected for an array of chromophores with the observed geometry. We report the stability of the calculated absorption spectrum to minor structural alterations, and deduce that the observed red shift of the 850 nm Q_y transition in the B800–850 antenna complexes is about equally attributable to chromophore-chromophore and chromophore-protein interactions, while chromophore-chromophore interactions predominate in generating the red-shift of the 820 nm Q_y transition in B800–820 type peripheral liggt-harvesting complexes. Finally we suggest that the red shift in the absorbance of the monomeric Bchl a found in antenna complexes to 800 nm, from 770 nm as observed in most solvents, is largely attributable to a hydrogen bond with the 2-acetyl group of this chromophore.