Dynamics of skate horizontal cells.

The all-rod retina of the skate (Raja erinacea or R. oscellata) is known to have the remarkable capability of responding to incremental flashes superimposed on background intensities that initially block all light-evoked responses and are well above the level at which rods saturate in mixed rod/cone retinas. To examine further the unusual properties of the skate visual system, we have analyzed responses of their horizontal cells to intensity-modulated step, sinusoidal, and white-noise stimuli.

Dynamics of the ganglion cell response in the catfish and frog retinas.

Responses were evoked from ganglion cells in catfish and frog retinas by a Gaussian modulation of the mean luminance. An algorithm was devised to decompose intracellularly recorded responses into the slow and spike components and to extract the time of occurrence of a spike discharge. The dynamics of both signals were analyzed in terms of a series of first-through third-order kernels obtained by cross-correlating the slow (analog) or spike (discrete or point process) signals against the white-noise input.

Nonlinear analysis: mathematical theory and biological applications.

Wiener's method of a nonlinear system analysis and its application to neurophysiology are surveyed. His theory is explained on the orthogonal functional series expansion of a nonlinear noise with respect to the Brownian motion whose formal derivative is understood as the white Gaussian noise. Then, efforts made for applying the method to practice are discussed.

Dynamics of turtle horizontal cell response.

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.

Signal transmission in the catfish retina. III. Transmission to type-C cell.

Current injected into horizontal-cell somas and axons produced transient (on-off) depolarizations from type-C cells (commonly known as transient amacrine cells) similar to those produced by light. Both the light- and current-induced responses had very small linear components and nonlinear components as represented by the second-order kernels, which reproduced the cell's response with a reasonable degree of accuracy. The second-order kernels were well defined and stereotyped.

Signal transmission in the catfish retina. II. Transmission to type-N cell.

Responses from channel catfish type-N (sustained amacrine) cells were evoked either by step changes in illuminance, i.e. brightening or dimming from a mean illuminance, or by a white-noise modulated light stimulus.

Signal transmission in the catfish retina. I. Transmission in the outer retina.

Extrinsic current, either pulsatile or white-noise modulated, was injected into the (cone) horizontal-cell soma and axon, and resulting responses were recorded from nearby points. In the case of white-noise inputs, signal transmission between the two points was characterized by Wiener kernels. The signal transmission within the lamina, the S-space, formed by the (cone) horizontal-cell somas and axons is quasi-linear and very fast, indicating that the laminae are purely resistive networks within the frequency range of the light-evoked response.

Visual sensitivity and Wiener kernels.

Visual sensitivity is defined in terms of the static and dynamic parts of a photo-evoked response. The first-order kernel induced by a white-noise modulated light is associated directly with both the incremental and contrast sensitivities classically defined, making a comprehensive measure of neuron sensitivity in the visual system.

Turtle and catfish horizontal cells show different dynamic response.

Horizontal cell responses of catfish and turtle have been found to differ in a characteristic way. These characteristics established by white-noise analysis show that the impulse response (first order Wiener kernel) of the catfish horizontal cell has a substantially shorter latency as well as peak response time than that of the turtle. The turtle horizontal cell, on the other hand, has a dynamic gain which is twice that of the catfish.

Spontaneous hyperpolarizations in pyramidal cells of chronically stimulated rabbit hippocampus.

Through daily electrical stimulation of one of the hippocampi in the rabbit, EEG spikes were "kindled" in both hippocampi. Such hippocampi (termed kindled hippocampi) were then studied with the microelectrode in acute experiments. The electrical activities of the kindled hippocampus were characterized by spontaneous occurrence of hyperpolarizing potentials of various magnitudes (3-27 mV) and various durations (50-600 msec) in the pyramidal cell.