Yoshiro Fukada

Receptive field organization of cat optic nerve fibers with special reference to conduction velocity

Abstract Receptive fields of single optic nerve fibers in the cat have been subdivided into two types. Type I responds briskly to the abrupt change in the luminance of both a spot and diffuse light, but does not continue to respond to a stationary light stimulus, Type II responds very weakly to diffuse light, but continues to respond to stationary spot stimulus. The conduction velocity of Type I-fibers is faster, on the average, than that of Type II-fibers. The size of the receptive field center of Type II is smaller than Type I, and Type II-field has a stronger tendency to be located centrally in the visual field.

The relationship between response characteristics to flicker stimulation and receptive field organization in the cat's optic nerve fibers

Abstract The response characteristics of cats optic nerve fibers to flicker stimulation were investigated. As the flicker frequency increases, the average impulse frequency in Type I-fibers (phasic type) increases, passes through a maximum, and finally falls off. When the flicker frequency is adjusted properly, Type I-fiber which has a distinct surround in its receptive field shows a repetitive firing at high frequency (about 200 Hz). The average impulse frequency in Type II-fibers (tonic type) remains almost unchanged over a wide range of flicker frequencies.

Gain control mechanisms in X- and Y-type retinal ganglion cells of the cat

A change in responsiveness caused by a spot of light (conditioning spot, CS; 3 sec in duration) presented within a central region of the receptive field of X- and Y-type retinal ganglion cells of the cat was investigated by measuring the magnitude of responses to another spot of light (test spot, TS; 50 msec in duration) which was juxtaposed with the CS within the same receptive fields central region. Responses to the TS were suppressed steadily during the on-phase of the CS as if it were divided by a certain value. This fact indicates that the gain of the center mechanism was changed by the CS presentation. The setting of the gain to a new level was rapid (within 100 msec after the onset or the cessation of the CS), and the magnitude of a gain change was not affected by the surround antagonism. These characteristics of the gain control were common to X- and Y-cells under both mesopic and scotopic levels of light adaptation.

Gain control mechanisms within the receptive field center of cats retinal ganglion cells

In the previous studies (Fukada, 1971; Fukada and light (5’ dia) were presented on a tangent screen which Saito, 1971X the cat’s retinal ganglion cells have been was placed 1.37m in front of the cat’s eyes and illuclassified into Type-I and Type-II, independently of minated at 59 cd/m2 by distant fluorescent tubes. The onor off-center subdivision, on the basis of the TS was presented at the center of the RF (the most receptive field proper&s and the axonal conduction sensitive part of the center region) and CS was located velocities. Since then, accumulated data by us (&to, 15’ eccentric to TS. The CS was still well within the Shimahara and F&da, 1970, 1971) and others (Clecenter region of the RF. In some experiments, the land, Dubin and Levi& 1971; Hoflinann, Stone and positions of TS and CS were interchanged with essenSherman, 1972; Ikeda and Wright, 1972; Cleland, tially the same results. The CS was presented once Levick and San&son, 1973) suggest that our Type-I every 12 set and lasted for 3 sec. The TS was flashed cells correspond to Y-cells of Enroth-Cugell and Robfor 100 or 200 msec with a variable delay relative son (1966) and Type-II to X-&Is. In this paper, X/Y to the onset or the cessation of CS. The luminance terminology will be used because of its familiarity. of the spots of light, which were maximally available It was observed that the response of on-center Xat 3.9 x ld and 6.8 x 103 cd/m2 for TS and CS cell to a flashing spot of light presented at the center respectively, were adjusted with neutral density filters of the receptive field (RF) was gradually suppressed so that an algebraic sum of the responses to TS and with successive stimulation. The suppression of the CS was well within the dynamic range of the cell’s response was aIso observed even when the preceding response. To focus the spot stimuli on the retina and spots had been presented at a little diierent position to keep high image quality, a contact lens (usually, of the center region. By contrast, the response of Y+ 10 D) with 4mm aperture was used. cell remained constant for the repetitive stimulation The magnitude of the test response (TR) was meas(Fukada, 1971). From these observations, some kind ured as follows. First, the averaged PST-histograms of inhibition is suggested to develop in the neuronal were obtained from 20 consecutive responses to TS network which organizes the RF of Xcell with sucalone, CS alone and to combined stimuli of TS and cessive stimulation, and to spread over the RF center CS, respectively. They were expressed as the number region. An inhibitory mechanism in Y-cell, if any, may of impulses for each bin (bin width was usually 20 be different. msec). The maintained discharge rate averaged for 1 In the present study, the inhibitory processes ’ set prior to the presentation of TS alone was caused by a flashing spot itself in the on-center fields expressed also in impulses/bin. The unconditioned TR of Xand Y-cells were investigated by two-spot experwas defined by a total number of impulses which were iment: Response to the RF-centered spot (test spot, elicited by TS alone and exceeded the maintained TS) was measured when an additional spot (condidischarge rate. When TS was combined with CS. the tioning spot, CS) was presented in the same RF center conditioned TR was obtained in the same way except region. that the maintained discharge rate was substituted by Experiments were conducted on 13 adult cats PST-histograms to CS alone. anaesthetized with nitrous oxide and immobilized Forty on-center cells were classitied as either X (20) with gallamine triethiodide. Extracellular spikes were or Y (20) depending on the two criteria. One criterion recorded from the optic tract with tungsten microelecis the difference in the tonic (X) or phasic (Y) response trodes. Spikes were fed to a Schmitt trigger circuit profile of the cell to a long-lasting spot stimulus. The to produce pulses of standard width and amplitude. other is the difference in the fine structure of the imand those pulses were fed to a mini-computer (TOSpulse train of the initial transient response to the BAC-3CHM, Toshiba) to compile the post-stimulus stimulus onset; Y-cells have a clear discontinuity in time histograms (PST-histograms). their discharge rate between the initial burst and SUCThe TS and CS were produced from glow moduceeding discharges whereas Xcells do not show such lator tubes (Sylvania, R1131Q and those spots of discontinuity (Saito et al.. 1970, 1971). It is worth noting that this difference in the initial transient part of response was so marked that it proved to be a 1 A preliminary report of this work was presented at good criterion for X/Y-classiication. XXVI ICPS Satellite Symposium on Vision held in Sydney. For both types of cells, TR was suppressed by CS October 1974. presentation, but the time course of the suppression

An investigation of the lateral spread of potentials in the octopus retina

Abstract A radial organization was found in the spread of the normally positive responses recorded from deep (near the sclera) portions of the octopus retina. Around a locally illuminated region, positive responses are recorded toward the center of the retina and negative responses toward the near periphery. A unique central area of the retina was also found.

Repetitive firing of the cat's retinal ganglion cell

Abstract The induced activity which was previously found to be elicited by flickering lightspots in Type-I cells (phasic cells) of the cats retina could also be elicited by diffuse flicker and by repetitive antidromic stimulation of the ganglion cell. This activity was elicited when the ganglion cell was activated at high frequency for long period (at 120–250 impulses/sec for about 1 min), and lasted for about 1 min with regularly-spaced high frequency discharges (initial frequency, 100–200 impulses/sec) and suddenly ceased when the discharge rate reduced monotonically to about a half. For Type-II cells (tonic cells), either the flickering light stimulation or the repetitive antidromic stimulation of the cells failed to elicit induced activity . The above differences could reflect the differences in the receptive field organization between Type-I and Type-II cells.