scholarly journals The transfer of signals from photoreceptor cells to large second-order neurones in the ocellar visual system of the locust Locusta migratoria

1995 ◽  
Vol 198 (2) ◽  
pp. 537-549 ◽  
Author(s):  
P Simmons
Keyword(s):  
Light Intensity ◽  
Signal To Noise Ratio ◽  
Locusta Migratoria ◽  
Photoreceptor Cells ◽  
Initial Response ◽  
Second Order ◽  
Constant Current ◽  
Background Illumination ◽  
Maximum Slope ◽  
Intensity Axis

The operation of the first synapse in the ocellar pathway of the locust Locusta migratoria has been studied by making simultaneous intracellular recordings from photoreceptors and large, second-order L-neurones. 1. The transfer curve for the synapse, obtained by plotting the amplitudes of the initial peak responses by the two cells to pulses of light against each other, shows that L-neurones are extremely sensitive to changes in photoreceptor potential and that the connection is tonically active in darkness. 2. Postsynaptic current in an L-neurone, produced when pulses of light are delivered from a dark background, saturates at a slightly brighter light intensity than does the postsynaptic potential. 3. The signal-to-noise ratio improves with increases in light intensity in both cells, but the reduction in noise as signals are transmitted from photoreceptors to L-neurones is less than would be expected from the number of photoreceptors that probably converge on each L-neurone. 4. In both cells, in the presence of different intensities of background illumination, the slope of the intensity­response curve is maintained as the curve moves along the light intensity axis. Adaptation is relatively slow so that, at least for several minutes after an increase in background illumination, both cells maintain a sustained response and the responses to stimuli of increased illumination are reduced in amplitude. During sustained background illumination, the transfer curve for the synapse between a photoreceptor and an L-neurone shifts along both axes without a change in its maximum slope. 5. The slope of the synaptic transfer curve depends on the speed as well as the amplitude of changes in light. 6. In response to injection of depolarising pulses of current into a photoreceptor, an L-neurone generates brief, hyperpolarising responses. The amplitude of the responses depends on the strength and speed of the depolarising stimuli. After an initial response by an L-neurone, subsequent responses are reduced in amplitude for 200 ms. 7. The amplitude of L-neurone responses to electrical stimulation of a photoreceptor increases when the hyperpolarising constant current is injected into the photoreceptor.

COMPLEX DYNAMICS AND FAST-SLOW SCALE INSTABILITY IN CURRENT-MODE CONTROLLED BUCK CONVERTER WITH CONSTANT CURRENT LOAD

2013 ◽  
Vol 23 (04) ◽  
pp. 1350062 ◽  
Author(s):  
GUOHUA ZHOU ◽  
BOCHENG BAO ◽  
JIANPING XU
Keyword(s):  
Complex Dynamics ◽  
Period Doubling ◽  
Current Mode ◽  
Input Voltage ◽  
Second Order ◽  
Buck Converter ◽  
Constant Current ◽  
Current Load ◽  
Time Model ◽  
Conduction Mode

The complex dynamics and coexisting fast-slow scale instability in current-mode controlled buck converter with constant current load (CCL), operating in both continuous conduction mode (CCM) and discontinuous conduction mode (DCM), are investigated in this paper. Via cycle-by-cycle computer simulation and experimental measurement of current-mode controlled buck converter with CCL, it is found that a unique fast-slow scale instability exists in the second-order switching converter. It is also found that a unique period-doubling accompanied by Neimark–Sacker bifurcation exists in this simple second-order converter, which is different from period-doubling or Neimark–Sacker bifurcations reported previously. Based on a nonlinear discrete-time model and the corresponding Jacobian, the effects of CCL and input voltage on the dynamics of current-mode controlled buck converter are investigated and verified theoretically. Fixed point analysis for slow-scale low-frequency oscillation is also given to verify the dynamics and the coexisting fast-slow scale instability.

BIFURCATIONS OF PERIODIC ORBITS IN A JOSEPHSON EQUATION WITH A PHASE SHIFT

2002 ◽  
Vol 12 (07) ◽  
pp. 1515-1530 ◽  
Author(s):  
ZHUJUN JING ◽  
HONGJUN CAO
Keyword(s):  
Numerical Simulation ◽  
Phase Shift ◽  
Periodic Orbits ◽  
Averaging Method ◽  
Melnikov Function ◽  
Second Order ◽  
Constant Current ◽  
Small Perturbations ◽  
Theoretical Predictions ◽  
Simulation Results

The Josephson equation with constant current and sinusoidal forcings and a phase shift is investigated in detail: the existence and the bifurcations of harmonics and subharmonics under small perturbations are given, by using the second-order averaging method and Melnikov function; the influence on bifurcations of periodic or subharmonics as the phase shift varies is considered; some numerical simulation results are reported in order to prove our theoretical predictions.

The accuracy of the patterns of connexions of the first- and second-order neurons of the visual system of Calliphora

1970 ◽  
Vol 175 (1038) ◽  
pp. 69-82 ◽  
Keyword(s):  
Single Neuron ◽  
Compound Eye ◽  
Photoreceptor Cells ◽  
Mirror Image ◽  
Second Order ◽  
Visual Axis ◽  
First Order ◽  
Definite Pattern ◽  
Small Bundle ◽  
Do So

The axons of the primary photoreceptor cells of the compound eye of the fly interweave in a complex but definite pattern before they terminate upon the second-order neurons. Of approximately 650 short retinula axons from behind 120 facets of the eye none terminated at an incorrect lamina cartridge. Six, seven, or eight first-order terminals upon one pair of second-order cells are arranged in a rotational sequence that is related to the positions of the retinula cells within the ommatidia. Errors in location of the terminal among its neighbours occurred only ten times. The asymmetry of the receptor pattern in the dorsal half of the eye has a mirror image in the ventral half. Along the equator of the eye is a plane of symmetry which many axons necessarily cross in maintaining the appropriate connexions of their receptors. Axons which cross this plane of symmetry have somehow found their appropriate second-order cells, although to do so they must have grown through a milieu which is the mirror image of that in their own half of the eye. Each pair of second-order axons proceeding from the lamina forms a small bundle with the axons of the two long retinula cells that have the same visual axis. Between the lamina and the medulla is a chiasma (with the crossing in the horizontal plane) through which bundles from the lamina pass to project in exactly reverse order upon the medulla. No errors of projection have been found at the single neuron level in this chiasma.

scholarly journals Self-Adaptive Image Reconstruction Inspired by Insect Compound Eye Mechanism

2012 ◽  
Vol 2012 ◽  
pp. 1-7 ◽  
Author(s):  
Jiahua Zhang ◽  
Aiye Shi ◽  
Xin Wang ◽  
Linjie Bian ◽  
Fengchen Huang ◽  
...  
Keyword(s):  
Light Intensity ◽  
Compound Eye ◽  
Signal To Noise Ratio ◽  
Processing System ◽  
Reconstruction Method ◽  
Sparse Model ◽  
Reconstruction Methods ◽  
Adaptive Reconstruction ◽  
Distinct Block ◽  
Block Effect

Inspired by the mechanism of imaging and adaptation to luminosity in insect compound eyes (ICE), we propose an ICE-based adaptive reconstruction method (ARM-ICE), which can adjust the sampling vision field of image according to the environment light intensity. The target scene can be compressive, sampled independently with multichannel through ARM-ICE. Meanwhile, ARM-ICE can regulate the visual field of sampling to control imaging according to the environment light intensity. Based on the compressed sensing joint sparse model (JSM-1), we establish an information processing system of ARM-ICE. The simulation of a four-channel ARM-ICE system shows that the new method improves the peak signal-to-noise ratio (PSNR) and resolution of the reconstructed target scene under two different cases of light intensity. Furthermore, there is no distinct block effect in the result, and the edge of the reconstructed image is smoother than that obtained by the other two reconstruction methods in this work.

Observations on Rate of Growth, Coloration, and the abnormal Six-instar Life-cycle in Locusta migratoria migratorioides, R. &. F.

1936 ◽  
Vol 27 (1) ◽  
pp. 77-85 ◽  
Author(s):  
K. H. L. Key
Keyword(s):  
Life Cycle ◽  
Relative Humidity ◽  
Light Intensity ◽  
Locusta Migratoria ◽  
Fourth Instar ◽  
The Other ◽  
Locusta Migratoria Migratorioides ◽  
The Third ◽  
Rate Of Growth ◽  
Progression Factor

1. All material was reared under constant conditions of temperature, light intensity and relative humidity. Two relative humidities were used—very wet and very dry. In some cases various coloured backgrounds were used. All material was solitaria, and was kept isolated.2. Average weights were calculated from weighings made at all periods within the stadia, and thus represent the weights at the mid-points of the stadia.3. The figures could not be fitted to the theory of a progression factor of 2.4. Females are on the average 50 per cent, heavier than males even in the third instar; the sexes can probably be distinguished in this way much earlier.5. The first three stadia are of about the same length; the fourth is longer, the fifth much longer.6. The percentage rate of growth between the mid-points of successive stadia is of the same order for all pairs, though somewhat lower for the first and last pairs.7. Hoppers kept in a very dry atmosphere are much lighter than those kept wet —proportionally more so in the later than in the earlier instars; on the other hand each stadium is lengthened—proportionally more so in the earlier than in the later stadia; the percentage rate of growth is just half that of hoppers kept wet.8. The findings of Faure in regard to the causes of differences in coloration were fully confirmed.9. The occurrence of a sixth instar in the females is due to an inherited factor.10. This “ extra ” instar may represent an extra morphological third instar or an extra morphological fourth instar.

scholarly journals The visual system of the genetically tractable crustacean Parhyale hawaiensis: diversification of eyes and visual circuits associated with low-resolution vision

2019 ◽  
Author(s):  
Ana Patricia Ramos ◽  
Ola Gustafsson ◽  
Nicolas Labert ◽  
Iris Salecker ◽  
Dan-Eric Nilsson ◽  
...  
Keyword(s):  
Light Intensity ◽  
Visual System ◽  
Photoreceptor Cell ◽  
Optic Lobe ◽  
Photoreceptor Cells ◽  
Single Species ◽  
Low Resolution ◽  
Parhyale Hawaiensis ◽  
Visual Tasks ◽  
Significant Divergence

AbstractBackgroundArthropod eyes have diversified during evolution to serve multiple needs, such as finding mates, hunting prey, and navigating in complex surroundings under varying light conditions. This diversity is reflected in the optical apparatus, photoreceptors and neural circuits that underpin vision. While this diversity has been extensively documented, our ability to genetically manipulate the visual system to investigate its function is largely limited to a single species, the fruitfly Drosophila melanogaster. Here, we describe the visual system of Parhyale hawaiensis, an amphipod crustacean for which we have established tailored genetic tools.ResultsAdult Parhyale have apposition-type compound eyes made up of ∼50 ommatidia. Each ommatidium contains four photoreceptor cells with large rhabdomeres (R1-4), expected to be sensitive to the polarisation of light, and one photoreceptor cell with a smaller rhabdomere (R5). The two types of photoreceptors express different opsins, belonging to families with distinct wavelength sensitivities. Using the cis.-regulatory regions of opsin genes, we established transgenic reporters expressed in each photoreceptor cell type. Based on these reporters, we show that R1-4 and R5 photoreceptors extend axons to the first optic lobe neuropil, revealing striking differences compared with the photoreceptor projections found in related crustaceans and insects. Investigating visual function, we show that Parhyale has a positive phototactic response and is capable of adapting its eyes to different levels of light intensity.ConclusionsWe propose that the visual system of Parhyale serves low-resolution visual tasks, such as orientation and navigation, based on broad gradients of light intensity and polarisation. Optic lobe structure and photoreceptor projections point to significant divergence from the conserved visual circuits found in other malacostracan crustaceans and insects, which could be associated with a shift to low-resolution vision. Our study provides the foundation for research in the visual system of this genetically tractable species.

Amplified thermal state: Properties and decoherence

2021 ◽  
pp. 2150448
Author(s):  
Zheng-Yin Zhao ◽  
Xue-Xiang Xu
Keyword(s):  
Light Intensity ◽  
Amplification Factor ◽  
Thermal State ◽  
Signal To Noise Ratio ◽  
Photon Number ◽  
Gaussian State ◽  
Matrix Elements ◽  
Number Operator ◽  
Signal To Noise ◽  
Photon Loss

In this paper, we introduce the amplified thermal state (ATS) by operating [Formula: see text] on the thermal state (TS). Here, [Formula: see text] is the amplification factor and [Formula: see text] is the photon number operator. We study its properties, such as light intensity, signal-to-noise ratio (SNR), Fock matrix elements and Wigner function. In addition, we study its decoherence in photon-loss channel by analyzing evolution of all above properties. All considered properties are derived analytically and simulated numerically. Compared with the original TS, the amplification can enhance light intensity and SNR, remain the mixed character, and exhibit non-Gaussianity. While the decoherence will weaken light intensity and SNR, remain the mixed character, and return to Gaussian state.

Compensatory synaptic growth in the rod terminals as a sequel to partial photoreceptor cell loss in the retina of chimaeric mice

Development ◽  
1992 ◽  
Vol 114 (3) ◽  
pp. 797-803
Author(s):  
S. Sanyal ◽  
R.K. Hawkins ◽  
H.G. Jansen ◽  
G.H. Zeilmaker
Keyword(s):  
Photoreceptor Cell ◽  
Three Dimensional ◽  
Photoreceptor Cells ◽  
Cell Loss ◽  
Afferent Input ◽  
Second Order ◽  
Visual Sensitivity ◽  
Synaptic Ribbons ◽  
Synaptic Growth ◽  
Initial Development

In the retina of chimaeric mice of rd and wild-type genotypic combination, selective loss of rd/rd photoreceptor cells, after initial development, leads to a mosaic retina with variable amounts of normal photoreceptor cells present over the retinal surface. In some of the rod terminals of these retinas the synaptic complexes with the second order retinal neurons are seen to contain multiple synaptic ribbons and an increased number of profiles of the postsynaptic elements. These changes are observed only in the rod terminals and not in the cone pedicles. Computer aided three-dimensional reconstruction of the altered synapses shows that these changes result from an increase in the number of synaptic sites, characterized by multiplication of the synaptic ribbons and enlargement of the second order neuronal processes. A quantitative analysis of such synapses, based on serial electron micrographs, shows that these are most frequently located in the retinal regions of the chimaeric individuals that have suffered maximum photoreceptor cell loss. Thus synaptic growth appears to take place as a reaction to the reduction of afferent input to the postsynaptic components. These findings demonstrate persistent synaptic plasticity in the rod terminals of mammalian retina during the maturational phase of late postnatal development. Compensatory synaptic growth in the rod terminals, as recorded here, can have important implications for the maintenance of visual sensitivity in the diseased or ageing retina.

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