scholarly journals Dynamics of turtle horizontal cell response.

1985 ◽  
Vol 86 (3) ◽  
pp. 423-453 ◽  
Author(s):  
R L Chappell ◽  
K Naka ◽  
M Sakuranaga
Keyword(s):  
Response Time ◽  
Cell Response ◽  
Horizontal Cell ◽  
Horizontal Cells ◽  
Dynamic Responses ◽  
Large Field ◽  
Lower Vertebrate ◽  
Peak Response ◽  
The Mean ◽  
Mean Luminance

The small- and large-field (cone) horizontal cells produce similar dynamic responses to a stimulus whose mean luminance is modulated by a white-noise signal. Nonlinear components increase with an increase in the mean luminance and may produce a mean square error (MSE) of up to 15%. Increases in the mean luminance of the field stimulus bring about three major changes: the incremental sensitivity defined by the amplitude of the kernels decreases in a Weber-Fechner fashion; the waveforms of the kernels are transformed from monophasic (integrating) to biphasic (differentiating); the peak response time of the kernels becomes shorter and the cells respond to much higher-frequency inputs. The dynamics of the horizontal cell response also depend on the area of the retina stimulated. Smaller spots of light produce monophasic kernels of a longer peak response time. The presence of a steady background produces three major changes in the spot kernels: the kernel's amplitude becomes larger (incremental sensitivity increases); the peak response times become shorter; the waveform of the kernels changes in a fashion similar to that observed with an increase in the mean luminance of the field stimulus. A similar enhancement in the incremental sensitivity by a steady background has also been observed in catfish, which shows that this phenomenon is a common feature of the horizontal cells in the lower vertebrate retina.

Dark-suppression and light-sensitization of horizontal cell responses in the hybrid bass retina

1995 ◽  
Vol 12 (4) ◽  
pp. 611-620 ◽  
Author(s):  
William H. Baldridge ◽  
Reto Weiler ◽  
John E. Dowling
Keyword(s):  
Response Time ◽  
Horizontal Cell ◽  
Time Of Day ◽  
Horizontal Cells ◽  
Continuous Illumination ◽  
Constant Darkness ◽  
Peak Response ◽  
Cell Responses ◽  
Significant Difference ◽  
Short Time

AbstractThe responsiveness of luminosity-type horizontal cells, recorded intracellularly from isolated hybrid bass retinas, decreased after superfusion for 2 h in constant darkness. Responsiveness was subsequently increased (light-sensitized) up to 10-fold after exposure to several short (~0.5 min) periods of continuous illumination. The increase in horizontal cell responsiveness following light-sensitization was due to an increase of peak response amplitude rather than a reduction of peak response time. The increased responsiveness after light-sensitization was intensity-dependent with brighter sensitizing stimuli causing a greater increase than dimmer stimuli. The extent of LHC dark-suppression was affected by the time of day, being greater when induced during the night than during the day. However, there was no significant difference in horizontal cell responsiveness after light-sensitization in retinas studied during the night compared to those studied during the day The responsiveness of light-sensitized horizontal cells from isolated hybrid bass retinas was found to be suppressed by relatively brief periods of darkness. The responsiveness of horizontal cells, that were first light-sensitized, decreased by more than 50% following only 5 min of darkness. Suppression of light-sensitized horizontal cell responsiveness after such a short time in the dark has not been described in other teleost retinas. The suppression of light-sensitized horizontal cell responsiveness in hybrid bass retinas may be rapid in comparison to other teleosts.

Background-induced flicker enhancement in cat retinal horizontal cells. II. Spatial properties

1990 ◽  
Vol 64 (2) ◽  
pp. 326-340 ◽  
Author(s):  
R. Nelson ◽  
R. Pflug ◽  
S. M. Baer
Keyword(s):  
Test Stimulus ◽  
Exponential Decay ◽  
Horizontal Cell ◽  
Stimulus Size ◽  
Slit Width ◽  
Horizontal Cells ◽  
Test Region ◽  
Length Constant ◽  
Region Model ◽  
The Mean

1. Intracellular recordings have been made from cat retinal horizontal cells stimulated with flickering test spots. Dim backgrounds increase flicker amplitudes in response to small but not large test stimuli. 2. This background-induced flicker enhancement has been measured for different slit- and square-test stimulus widths and the results compared with two spatial models for the enhancement effect. 3. In the "dark test-region" model it is argued that rods within the test region are unresponsive to background stimuli because of prior saturation by the test stimulus. Background-evoked rod signals decay passively from regions outside the test stimulus through a syncytial network into the recording site, where they act on the cone-to-horizontal-cell synapse, increasing its gain. 4. In the "changing length-constant" model rod signals reduce the length constant of a syncytial network by uncoupling the cells within it. This causes an increased response to small but not large test stimuli. 5. Both models are analytically evaluated with the use of a conductive-sheet approximation to the syncytial network. Expressions are derived for network polarization [(V(0, 0)] as a function of stimulus size. The specific stimulus shapes considered are disks, rectangles, slits, and squares in both bright and dark varieties. From these expressions predictions of response enhancement as a function of stimulus size are made for both models. 6. The dark test-region model provides for an exponential decay of flicker enhancement as a function of slit width but a steeper-than-exponential decay with the width of squares, in close agreement with experimental data. 7. The changing length-constant model makes qualitatively similar predictions. Flicker enhancement declines nearly exponentially with slit width. For square-shaped test stimuli the predicted decline of flicker enhancement with size is somewhat shallower than either the dark test-region-model curve or the experimentally determined curve. 8. As recorded in the same set of cells and under the same set of stimulus conditions (with the use of both slit- and square-test stimuli), the mean length constant of the peak-to-peak flicker component in the horizontal-cell response is 168 +/- 18 (SE) microns with the background and 232 +/- 45 microns in the dark. The mean length constant for the background-induced flicker enhancement, as fit by dark test-region-model curves, is 186 +/- 22 microns (n = 9).(ABSTRACT TRUNCATED AT 250 WORDS)

Sensitivity transformation for vertebrate vision

1991 ◽  
Vol 6 (4) ◽  
pp. 371-374 ◽  
Author(s):  
Richard L. Chappell ◽  
Ken-Ichi Naka
Keyword(s):  
Light Adaptation ◽  
Light Response ◽  
Horizontal Cells ◽  
Visual Response ◽  
Maximum Point ◽  
Half Maximum ◽  
Peak Response ◽  
Vertebrate Retina ◽  
Mean Luminance

AbstractThe visual response to a flash given in the dark is known to saturate according to the Michaelis-Menten relationship. Nevertheless, the incremental response from increasing levels of mean luminance tends to follow a Weber-Fechner relationship well into the saturation range determined from the Michaelis-Menten results. This sensitivity transformation from Michaelis-Menten to Weber-Fechner is an important characteristic of light adaptation in the vertebrate retina. Recent studies concerning the role of calcium in photoreceptor adaptation have shown that the relaxation from peak to plateau in the response of isolated photoreceptors was absent under conditions in which adaptation was blocked. Comparing the pronounced relaxation from peak to plateau in turtle horizontal cells with the absence of such relaxation in the catfish response, we noted also that turtle incremental sensitivity shows a Weber-Fechner relationship while catfish incremental sensitivity more closely follows the local slope of the Michaelis-Menten relation. Based on these observations, we have obtained an expression to relate the relaxation from peak to plateau with the sensitivity transformation. We assume that adaptation shifts the half-maximum point of the Michaelis-Menten curve so that the light response relaxes to a plateau value equal to a specified fraction φ of the peak response. We show that this manipulation alone results in a transformation from Michaelis-Menten kinetics to Weber-Fechner sensitivity.

Modulation of A-type potassium currents in retinal horizontal cells by extracellular calcium and zinc

2006 ◽  
Vol 23 (5) ◽  
pp. 825-832 ◽  
Author(s):  
DAO-QI ZHANG ◽  
ZIYI SUN ◽  
DOUGLAS G. MCMAHON
Keyword(s):  
Steady State ◽  
Potassium Channels ◽  
Horizontal Cell ◽  
Horizontal Cells ◽  
Resting Membrane Potential ◽  
Inactivation Curve ◽  
Outward Currents ◽  
Steady State Inactivation ◽  
The Mean ◽  
Kinetics Of

Extracellular Ca2+ and Zn2+ influence many aspects of retinal function. Here, we examined the effect of external Ca2+ and Zn2+ on potassium channels of retinal horizontal cells. When extracellular Ca2+ was lowered from 3 mM to 0.3 mM, horizontal cell transient outward currents elicited by voltage steps from resting membrane potential (−70 mV) were decreased by approximately 50%, whereas the sustained currents remained unchanged. This effect was due to a hyperpolarizing shift in the steady-state inactivation curve of A-type K+ currents when extracellular Ca2+ concentration was lowered. The mean half inactivation potential of the steady-state inactivation curves was hyperpolarized from −56.3 ± 4.7 mV in 3 mM Ca2+ to −76.4 ± 3.9 mV in 0.3 mM Ca2+. Neither the state-steady activation curve nor the kinetics of inactivation was significantly changed in low extracellular Ca2+. The addition of 30 μM Zn2+ restored peak outward currents in 0.3 mM Ca2+. The half inactivation voltages were depolarized from −70 ± 2.8 mV in 0.3 mM Ca2+ to −56 ± 2.6 mV in 0.3 mM Ca2+ plus 30 μM Zn2+. Taken together, the results indicate that external Ca2+ and Zn2+ maintain the activity of A-type potassium channels in retinal horizontal cells by influencing the voltage dependence of steady-state inactivation.

scholarly journals Development of Perceptual Inhibition in Adolescents—a Critical Period?

Symmetry ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 457
Author(s):  
Isabel María Introzzi ◽  
María Marta Richard’s ◽  
Yesica Aydmune ◽  
Eliana Vanesa Zamora ◽  
Florencia Stelzer ◽  
...  
Keyword(s):  
Response Time ◽  
Executive Functions ◽  
Critical Period ◽  
Search Task ◽  
Probability Distributions ◽  
Linear Trajectory ◽  
Gaussian Functions ◽  
Mean Response Time ◽  
The Mean ◽  
One Year

Recent studies suggest that the developmental curves in adolescence, related to the development of executive functions, could be fitted to a non-linear trajectory of development with progressions and retrogressions. Therefore, the present study proposes to analyze the pattern of development in Perceptual Inhibition (PI), considering all stages of adolescence (early, middle, and late) in intervals of one year. To this aim, we worked with a sample of 275 participants between 10 and 25 years, who performed a joint visual and search task (to measure PI). We have fitted ex-Gaussian functions to the probability distributions of the mean response time across the sample and performed a covariance analysis (ANCOVA). The results showed that the 10- to 13-year-old groups performed similarly in the task and differ from the 14- to 19-year-old participants. We found significant differences between the older group and all the rest of the groups. We discuss the important changes that can be observed in relation to the nonlinear trajectory of development that would show the PI during adolescence.

scholarly journals Lateral feedback from monophasic horizontal cells to cones in carp retina. I. Experiments.

1989 ◽  
Vol 93 (4) ◽  
pp. 681-694 ◽  
Author(s):  
M Kamermans ◽  
B W van Dijk ◽  
H Spekreijse ◽  
R C Zweypfenning
Keyword(s):  
Horizontal Cell ◽  
Horizontal Cells ◽  
Color Coding ◽  
Cell Adaptation ◽  
Test Spot ◽  
Displacement Experiments ◽  
High Stimulus ◽  
Integration Area

The spatial and color coding of the monophasic horizontal cells were studied in light- and dark-adapted retinae. Slit displacement experiments revealed differences in integration area for the different cone inputs of the monophasic horizontal cells. The integration area measured with a 670-nm stimulus was larger than that measured with a 570-nm stimulus. Experiments in which the diameter of the test spot was varied, however, revealed at high stimulus intensities a larger summation area for 520-nm stimuli than for 670-nm stimuli. The reverse was found for low stimulus intensities. To investigate whether these differences were due to interaction between the various cone inputs to the monophasic horizontal cell, adaptation experiments were performed. It was found that the various cone inputs were not independent. Finally, some mechanisms for the spatial and color coding will be discussed.

Influences of Wind Barriers on the Train Running Safety on a Highway-Railway One-Story Bridge

2021 ◽  
pp. 2140009
Author(s):  
Ye Liu ◽  
Yan Han ◽  
Peng Hu ◽  
C. S. Cai ◽  
Xuhui He
Keyword(s):  
Dynamic Responses ◽  
Response Analysis ◽  
Train Track ◽  
Wheel Load ◽  
Wind Barrier ◽  
The Mean ◽  
Wind Pressures ◽  
Track Bridge ◽  
Fluctuating Wind ◽  
Bridge System

In this study, the influences of wind barriers on the aerodynamic characteristics of trains (e.g. a CRH2 train) on a highway-railway one-story bridge were investigated by using wind pressure measurement tests, and a reduction factor of overturning moment coefficients was analyzed for trains under wind barriers. Subsequently, based on a joint simulation employing SIMPACK and ANSYS, a wind–train–track–bridge system coupled vibration model was established, and the safety and comfort indexes of trains on the bridge were studied under different wind barrier parameters. The results show that the mean wind pressures and fluctuating wind pressures on the trains’ surface decrease generally if wind barriers are used. As a result, the dynamic responses of the trains also decrease in the whole process of crossing the bridge. Of particular note, the rate of the wheel load reductions and lateral wheel-axle forces can change from unsafe states to relative safe states due to the wind barriers. The influence of the porosity of the wind barriers on the mean wind pressures and fluctuating wind pressures on the windward sides and near the top corner surfaces of the trains are significantly greater than the influence from the height of the wind barriers. Within a certain range, decreasing the wind barrier porosities and increasing the wind barrier heights will significantly reduce the safety and comfort index values of trains on the bridge. It is found that when the porosity of the wind barrier is 40%, the optimal height of the wind barrier is determined as approximately 3.5[Formula: see text]m. At this height, the trains on the bridges are safer and run more smoothly and comfortably. Besides, through the dynamic response analysis of the wind–train–track–bridge system, it is found that the installation of wind barriers in cases with high wind speeds (30[Formula: see text]m/s) may have an adverse effect on the vertical vibration of the train–track–bridge system.

Receptive field of the retinal bipolar cell: a pharmacological study in the tiger salamander

1996 ◽  
Vol 76 (3) ◽  
pp. 2005-2019 ◽  
Author(s):  
W. A. Hare ◽  
W. G. Owen
Keyword(s):  
Receptive Field ◽  
Gaba Receptors ◽  
Bipolar Cell ◽  
Horizontal Cell ◽  
Pharmacological Study ◽  
Bipolar Cells ◽  
Horizontal Cells ◽  
Gaba Uptake ◽  
Gamma Aminobutyric Acid ◽  
Gabaergic Synapse

1. It is widely believed that signals contributing to the receptive field surrounds of retinal bipolar cells pass from horizontal cells to bipolar cells via GABAergic synapses. To test this notion, we applied gamma-aminobutyric acid (GABA) agonists and antagonists to isolated, perfused retinas of the salamander Ambystoma tigrinum while recording intracellularly from bipolar cells, horizontal cells, and photoreceptors. 2. As we previously reported, administration of the GABA analogue D-aminovaleric acid in concert with picrotoxin did not block horizontal cell responses or the center responses of bipolar cells but blocked the surround responses of both on-center and off-center bipolar cells. 3. Surround responses were not blocked by the GABA, antagonists picrotoxin or bicuculline, the GABAB agonist baclofen or the GABAB antagonist phaclofen, and the GABAC antagonists picrotoxin or cis-4-aminocrotonic acid. Combinations of these drugs were similarly ineffective. 4. GABA itself activated a powerful GABA uptake mechanism in horizontal cells for which nipecotic acid is a competitive agonist. It also activated, both in horizontal cells and bipolar cells, large GABAA conductances that shunted light responses but that could be blocked by picrotoxin or bicuculline. 5. GABA, administered together with picrotoxin to block the shunting effect of GABAA activation, did not eliminate bipolar cell surround responses at concentrations sufficient to saturate the known types of GABA receptors. 6. Surround responses were not blocked by glycine or its antagonist strychnine, or by combinations of drugs designed to eliminate GABAergic and glycinergic pathways simultaneously. 7. Although we cannot fully discount the involvement of a novel GABAergic synapse, the simplest explanation of our findings is that the primary pathway mediating the bipolar cell's surround is neither GABAergic nor glycinergic.

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