scholarly journals Vigabatrin-Induced Retinal Functional Alterations and Second-Order Neuron Plasticity in C57BL/6J Mice

2020 ◽  
Vol 61 (2) ◽  
pp. 17 ◽  
Author(s):  
Kore Chan ◽  
Mrinalini Hoon ◽  
Bikash R. Pattnaik ◽  
James N. Ver Hoeve ◽  
Brad Wahlgren ◽  
...  
Keyword(s):  
Second Order ◽  
Order Neuron

Synaptic limitations to contrast coding in the retina of the blowfly Calliphora

1987 ◽  
Vol 231 (1265) ◽  
pp. 437-467 ◽  
Keyword(s):  
Synaptic Transmission ◽  
Visual Processing ◽  
Light Adaptation ◽  
Characteristic Curve ◽  
Second Order ◽  
Noise Power ◽  
Early Visual Processing ◽  
Synaptic Noise ◽  
Order Neuron ◽  
Synaptic Gain

We investigate the effects of synaptic transmission on early visual processing by examining the passage of signals from photoreceptors to second order neurons (LMCS). We concentrate on the roles played by three properties of synaptic transmission: (1) the shape of the characteristic curve, relating pre- and postsynaptic signal amplitudes, (2) the dynamics of synaptic transmission and (3) the noise introduced during transmission. The characteristic curve is sigmoidal and follows a simple model of synaptic transmission (Appendix) in which transmitter release rises exponentially with presynaptic potential. According to this model a presynaptic depolarization of 1.50–1.86 mV produces an e-fold increase in postsynaptic conductance. The characteristic curve generates a sigmoidal relation between postsynaptic (LMC) response amplitude and stimulus contrast. The shape and slope of the characteristic curve is unaffected by the state of light adaptation. Retinal antagonism adjusts the characteristic curve to keep it centred on the mean level of receptor response generated by the background. Thus the photoreceptor synapses operate in the mid-region of the curve, where the slope or gain is highest and equals approximately 6. The dynamics of transmission of a signal from photoreceptor to second-order neuron approximates to the sum of two processes with exponential time courses. A momentary receptor depolarization generates a postsynaptic hyperpolarization of time constant 0.5–1.0 ms, followed by a slower and weaker depolarization. Light adaptation increases the relative amplitude of the depolarizing process and reduces its time constant from 80 ms to 1.5 ms. The hyperpolarizing process is too rapid to bandlimit receptor signals. The noise introduced during the passage of the signal from receptor to second-order neuron is measured by comparing signal: noise ratios and noise power spectra in the two cell types. Under daylight conditions from 50 to 70% of the total noise power is generated by events associated with the transmission of photoreceptor signals and the generation of LMC responses. According to the exponential model of transmitter release, the effects of synaptic noise are minimized when synaptic gain is maximized. Moreover, both retinal antagonism and the sigmoidal shape of the characteristic curve promote synaptic gain. We conclude that retinal antagonism and nonlinear synaptic amplification act in concert to protect receptor signals from contamination by synaptic noise. This action may explain the widespread occurrence of these processes in early visual processing.

scholarly journals A gustatory second-order neuron that connects sucrose-sensitive primary neurons and a distinct region of the gnathal ganglion in theDrosophilabrain

2015 ◽  
Vol 29 (2-3) ◽  
pp. 144-155 ◽  
Author(s):  
Takaaki Miyazaki ◽  
Tzu-Yang Lin ◽  
Kei Ito ◽  
Chi-Hon Lee ◽  
Mark Stopfer
Keyword(s):  
Second Order ◽  
Distinct Region ◽  
Primary Neurons ◽  
Order Neuron

Amplifying role of convergence in olfactory system a comparative study of receptor cell and second-order neuron sensitivities

1989 ◽  
Vol 61 (5) ◽  
pp. 1085-1094 ◽  
Author(s):  
P. Duchamp-Viret ◽  
A. Duchamp ◽  
M. Vigouroux
Keyword(s):  
Second Order ◽  
Response Ratio ◽  
Recruitment Process ◽  
Entire Concentration Range ◽  
Receptor Cells ◽  
System A ◽  
Wide Range ◽  
Order Neuron ◽  
Amplification Process ◽  
Response Thresholds

1. Extracellular unitary responses of receptor cells of second-order neurons identified as output cells were recorded in the frog. Four odorants of defined concentrations distributed over a wide range were delivered in the form of 2-s square pulses to the olfactory mucosa with a multistage dynamic flow dilution olfactometer. Bulbar responses were studied under two conditions, the stimuli being delivered either to the ventral or to the entire mucosa. 2. Overall responsiveness of the cells was compared. For the second-order neurons, the response ratio (excitation or inhibition) clearly depended on the condition of stimulation when the entire mucosa was stimulated, the bulbar response ratio was increased, as compared with that obtained when only the ventral mucosa received stimuli. Furthermore, when the stimuli were delivered to the whole mucosa, the bulbar excitation ratio was found to be similar to those of receptor cells and second-order neurons. 3. Response thresholds were determined from a comparison of the interspike interval values in the 30-s pre- and in the 12-s poststimulus time periods, using the Mann-Whitney U test (Table 2). The distribution of response thresholds of receptor cells as a function of stimulus concentration did not significantly differ from that of second-order neurons as excited by stimulating the ventral mucosa. These two distributions differed significantly from the distribution of second-order neurons as stimulated through the entire mucosa. In this last experimental condition, the bulbar neurons displayed an improved sensitivity. 4. The overall recruitment process, represented by the cumulative percentage of cells responding with excitation as a function of concentration, was found to be continuous over the entire concentration range. At the bulbar level, when the entire mucosa was stimulated, the recruitment occurred at lower concentrations than when only the ventral mucosa was stimulated. In this last case, the dynamics of the bulbar recruitment did not differ from that of receptor cells. 5. The recruitment process was further studied for each stimulus, for receptor cells as well as for second-order neurons. Differences in recruitment were found between stimuli and, as for the bulbar neurons, they depended on the condition of stimulation. 6. The main outcome of these results is the demonstration that the convergence of receptor cells onto second-order neurons is functionally implicated in an amplification process of the primary signal in olfaction.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals Dynamics of cockroach ocellar neurons.

1986 ◽  
Vol 88 (2) ◽  
pp. 275-292 ◽  
Author(s):  
M Mizunami ◽  
H Tateda ◽  
K Naka
Keyword(s):  
White Noise ◽  
Periplaneta Americana ◽  
Second Order ◽  
Response Dynamics ◽  
Slow Potential ◽  
Order Neuron ◽  
Amplitude Compression ◽  
Noise Input ◽  
Modulated Light ◽  
Order Kernel

The incremental responses from the second-order neurons of the ocellus of the cockroach, Periplaneta americana, have been measured. The stimulus was a white-noise-modulated light with various mean illuminances. The kernels, obtained by cross-correlating the white-noise input against the resulting response, provided a measure of incremental sensitivity as well as of response dynamics. We found that the incremental sensitivity of the second-order neurons was an exact Weber-Fechner function; white-noise-evoked responses from second-order neurons were linear; the dynamics of second-order neurons remain unchanged over a mean illuminance range of 4 log units; the small nonlinearity in the response of the second-order neuron was a simple amplitude compression; and the correlation between the white-noise input and spike discharges of the second-order neurons produced a first-order kernel similar to that of the cell's slow potential. We conclude that signal processing in the cockroach ocellus is simple but different from that in other visual systems, including vertebrate retinas and insect compound eyes, in which the system's dynamics depend on the mean illuminance.

Analysis of vestibulocollic reflexes by sinusoidal polarization of vestibular afferent fibers

1979 ◽  
Vol 42 (2) ◽  
pp. 331-346 ◽  
Author(s):  
V. J. Wilson ◽  
B. W. Peterson ◽  
K. Fukushima ◽  
N. Hirai ◽  
Y. Uchino
Keyword(s):  
Second Order ◽  
Wave Form ◽  
Phase Lag ◽  
Frequency Range ◽  
Low Frequencies ◽  
New Information ◽  
Afferent Fibers ◽  
Order Neuron ◽  
The Mean ◽  
Decerebrate Cats

1. Canal vestibular-neck (vestibulocollic) reflexes have been studied in decerebrate cats by applying modulated polarizing current to individual ampullary nerves, usually the horizontal nerve. 2. Computer-generated stimuli sometimes consisted of sine or square waves at frequencies of 0.01--5 Hz. More often we used a compound wave form of nine superimposed sinusoids within an available frequency range of 0.009--6.11 Hz. The frequencies used were odd, relatively prime multiples of a base frequency selected to minimize distortion or interaction of responses. The response to each of the nine stimulating frequencies could be obtained in subsequent data analysis. 3. Responses to these stimuli were studied by recording the EMG of contralateral neck muscles and extracellular activity of second-order neurons. These neurons were identified by their monosynaptic responses to single-shock stimulation of ampullary nerves. 4. EMG was modulated sinusoidally. Below 0.1 Hz the response was variable, most likely due to differences in the preparations. In the frequency range of 0.1--0.4 Hz there was usually a phase lag, which decreased with incresing frequency and often reversed to a lead at 3 and 6 Hz. Gain decreased from the lowest frequencies, occasionally with an upturn at 3 or 6 Hz. 5. Second-order neuron firing was approximately in phase with the stimulus at the lowest frequencies. Phase advanced with increasing frequency to a lead of 30--50 degrees at 6 Hz. Gain generally increased with frequency. 6. By recording simultaneously from muscle and from second-order neurons, or by comparing the mean behavior of the two, it was possible to determine the central phase lag and gain of the vestibulocollic reflex. The lag was variable at low frequencies, had an average of 50 degrees at 0.18 Hz, and decreased to 20 degrees at 6 Hz. These results are comparable to those obtained by others using natural stimulation at frequencies of 1.0 Hz and below, and provide new information about the behavior of the central processer at higher frequencies. 7. The medial vestibulospinal tract (MVST), which contains the axons of crossed second-order vestibular neurons, was transected in six experiments. In agreement with previous workers there was no effect on phase at frequencies up to 0.4 Hz. There was also no selective effect of phase or gain at the higher frequencies. This shows that the disynaptic pathways in the MVST do not play any role that cannot be taken over by parallel pathways.

scholarly journals Fast electrical potentials arising from activation of metarhodopsin in the fly.

1980 ◽  
Vol 75 (4) ◽  
pp. 381-402 ◽  
Author(s):  
B Minke ◽  
K Kirschfeld
Keyword(s):  
Light Intensity ◽  
Receptor Potential ◽  
Second Order ◽  
Intracellular Recordings ◽  
M1 Phase ◽  
Cellular Origin ◽  
Electrical Potentials ◽  
Early Receptor Potential ◽  
Order Neuron

The cellular origin and properties of fast electrical potentials arising from activation of Calliphora photopigment were investigated. It was found by intracellular recordings that only the corneal-negative M1 phase of fly M potential arises in the photoreceptors' membrane. This M1 phase has all the accepted characteristics of an early receptor potential (ERP). It has no detectable latency, it survives fixation with glutaraldehyde, it is linear with light intensity below pigment saturation, and it is linear with the amount of metarhodopsin activated by light. The Calliphora ERP was found, however, to be exceptional because activation of rhodopsin, which causes the formation of metarhodopsin in 125 microsecond (25 degrees C), was not manifested in the ERP. Also, the extracellularly recorded ERP was not proportional to the rate of photopigment conversion. The corneal-positive M2 phase of the M potential was found to arise from second-order lamina neurons (L neurons). Intracellular recordings from these cells showed a fast hyperpolarizing potential, which preceded the normal hyperpolarizing transient of these cells. This fast potential appeared only when metarhodopsin was activated by a strong flash. The data indicate that the intracellularly recorded positive ERP, which arises from activation of metarhodoposin, elicits a hyperpolarizing fast potential in the second-order neuron. This potential is most likely the source of the corneal-positive M potential.

scholarly journals Nonlinear signal transmission between second- and third-order neurons of cockroach ocelli.

1990 ◽  
Vol 95 (2) ◽  
pp. 297-317 ◽  
Author(s):  
M Mizunami
Keyword(s):  
Synaptic Transmission ◽  
Signal Transmission ◽  
Cutoff Frequency ◽  
Second Order ◽  
Output Curve ◽  
Third Order ◽  
Pass Filter ◽  
Low Pass Filter ◽  
The Third ◽  
Order Neuron

Transfer characteristics of the synapse made from second- to third-order neurons of cockroach ocelli were studied using simultaneous microelectrode penetrations and the application of tetrodotoxin. Potential changes were evoked in second-order neurons by either an extrinsic current or a sinusoidally modulated light. The synapse had a low-pass filter characteristic with a cutoff frequency of 25-30 Hz, which passed most presynaptic signals. The synapse operated at an exponentially rising part of the overall sigmoidal input/output curve relating pre- and postsynaptic voltages. Although the response of the second-order neuron to sinusoidal light was essentially linear, the response of the third-order neuron contained an accelerating nonlinearity: the response amplitude was a positively accelerated function of the stimulus contrast, reflecting nonlinear synaptic transmission. The response of the third-order neuron exhibited a half-wave rectification: the depolarizing response to light decrement was much larger than the hyperpolarizing response to light increment. Nonlinear synaptic transmission also enhanced the transient response to step-like intensity changes. I conclude that (a) the major function of synaptic transmission between second- and third-order neurons of cockroach ocelli is to convert linear presynaptic signals into nonlinear ones and that (b) signal transmission at the synapse between second- and third-order neurons of cockroach ocelli fundamentally differs from that at the synapse between photoreceptors and second-order neurons of visual systems so far studied, where the synapse operates in the midregion of the characteristic curve and the transmission is essentially linear.

Disappearance Voltage Determinations Using a Convergent Beam

1971 ◽  
Vol 29 ◽  
pp. 184-185
Author(s):  
W. L. Bell
Keyword(s):  
Second Order ◽  
Objective Method ◽  
Uniform Thickness ◽  
Rocking Curve ◽  
Crystal Perfection ◽  
Kikuchi Line ◽  
Central Maximum ◽  
Diffraction Patterns ◽  
Convergent Beam ◽  
Beam Technique

Disappearance voltages for second order reflections can be determined experimentally in a variety of ways. The more subjective methods, such as Kikuchi line disappearance and bend contour imaging, involve comparing a series of diffraction patterns or micrographs taken at intervals throughout the disappearance range and selecting that voltage which gives the strongest disappearance effect. The estimated accuracies of these methods are both to within 10 kV, or about 2-4%, of the true disappearance voltage, which is quite sufficient for using these voltages in further calculations. However, it is the necessity of determining this information by comparisons of exposed plates rather than while operating the microscope that detracts from the immediate usefulness of these methods if there is reason to perform experiments at an unknown disappearance voltage.The convergent beam technique for determining the disappearance voltage has been found to be a highly objective method when it is applicable, i.e. when reasonable crystal perfection exists and an area of uniform thickness can be found. The criterion for determining this voltage is that the central maximum disappear from the rocking curve for the second order spot.

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