Four types of responses to light and dark spot stimuli in the cat optic nerve

Retinal ganglion cell topography in juvenile Pacific bluefin tuna Thunnus orientalis (Temminck and Schlegel)

The retinal ganglion cell distribution, which is known to reflect fish feeding behavior, was investigated in juvenile Pacific bluefin tuna Thunnus orientalis. During the course of examination, regularly arrayed cells with a distinctive larger soma, which may be regarded as motion-sensitive cells, were found. The topographical distribution of ordinary-sized ganglion cells, which is usually utilized to estimate fish visual axis and/or visual field characteristics, showed that the highest-density area, termed the area centralis, was localized in the ventral-temporal retina. The retinal topography of ordinary-sized ganglion cells seems to reflect the bluefin tuna's foraging behavior; while cruising, cells in the area centralis may signal potential prey, such as small schooling pelagic fishes or squids, that are present in the upward-forward direction. Judging from morphological characteristics, the large ganglion cells localized in the small temporal retinal area seem to be equivalent to physiologically categorized off-center Y-cells of cat, which are stimulated by a transient dark spot in a bright visual field. It was inferred that presumed large off-center cells in the temporal retina detect movements of agile prey animals escaping from bluefin tuna as a silhouette against environmental light.

Temporal and mosaic distribution of large ganglion cells in the retina of a daggertooth aulopiform deep-sea fish (Anotopterus pharao)

The daggertooth Anotopterus pharao (Aulopiformes: Anotopteridae) is a large, piscivorous predator that lives within the epipelagic zone at night. In this species, the distribution of retinal ganglion cells has been examined. An isodensity contour map of ganglion cells shows that the cells concentrate in a slightly ventral region of the temporal retina. The region of high ganglion cell density contains 4.07 x 10(3) cells mm(-2), and the resulting visual acuity is 3.5 cycles deg(-1). Outside the area centralis, conspicuously large ganglion cells (LGCs) are observed in the temporal margin of the retina. The LGCs are regularly arrayed, and displaced into the inner plexiform layer. Thick dendrites extend into the outer part (sublamina a) of the inner plexiform layer. In the retinal whole mount, the total number of LGCs is 1590 (90.7 cm specimen), and the mean size of the LGCs is about four times larger than that of the ordinary ganglion cells. The morphological appearance of the LGCs was similar to the off-type alpha cells of the cat retina. The function of these distinctive LGCs is discussed in relation to specific head-up feeding behaviour.

Linear and nonlinear contributions to step responses in cat retinal ganglion cells

We measured excitatory and inhibitory step responses of cat retinal ganglion cells to square wave contrast reversal of stationary sinusoidal gratings. In most Y-cells the initial increase in firing rate (early peak) of the excitatory responses was followed by a distinct second increase in firing rate (late peak). Analysis of the spatial frequency and spatial phase dependence of the two peaks indicated that the early peak appears to be produced by the spatially linear center mechanism, while the late peak appears to be produced by the rectifying subunits described by Hochstein and Shapley (1976) Journal of Physiology, London, 262, 237-264, 265-284. These results indicate that the presence of two peaks in ganglion cell step responses is the result of two excitatory inputs with different time courses, and that inhibitory inputs are not required to explain the appearance of these responses.

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 field's 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.

Morphology of physiologically identified X-, Y-, and W-type retinal ganglion cells of the cat

Retinal ganglion cells of the cat have been classified physiologically into X-, Y-, and W-cells on the basis of the receptive field properties, and morphologically into alpha-, beta-, and gamma-cells. In order to study directly the correspondence between these classifications, intracellular recordings from the ganglion cells in superfused eye-cup preparations were made with the aid of microelectrodes filled with Lucifer yellow CH. The cells were stained after their photic responses were studied under mesopic adaptation. X-cells, showing sustained depolarization (on-center cells) or hyperpolarization (off-center cells) in response to a spot of light had medium-sized round somata and spread bushy dendrites within a narrow retinal area. On the other hand, on-center and off-center Y-cells, showing transient responses to the spot stimulus, had large somata and widely expanded thick dendrites which were sparsely branched. W-cells which showed weak sustained responses had widely extended thin and winding dendrites, despite a small somal size. These morphological features of Y-, X-, and sustained W-cells correspond well to those of alpha-, beta-, and delta-cells (a subtype of gamma-cells), respectively. The hypothesis of "morphology reflecting function" is strongly supported.

The effects of strychnine and bicuculline on the responses of X- and Y-cells of the isolated eye-cut preparation of the cat

The effects of strychnine and bicuculline, the respective antagonists of glycine and GABA, on the inhibitory responses of X- and Y-type retinal ganglion cells of the cat were investigated using an isolated eye-cup preparation. The surround inhibition of the on-center X-cell was blocked by strychnine, whereas that of the on-center Y-cell was blocked by bicuculline. In the case of the off-center cells, bicuculline indifferently blocked the center and the surround responses of either the X-cell or the Y-cell, but strychnine did not.

A late component of flash-evoked potentials in the cat's optic chiasma and superior colliculus: its appearance due to background illumination

Flash-evoked potentials (FEPs) in the cat's optic chiasma and superior colliculus were recorded under the following two conditions: complete darkness and background illumination. Special attention was paid to a specific late component of FEP'S and comparison in the behavior of the late component was made between the two conditions. It was found that a late component of FEPs in the optic chiasma appeared in the presence of background illumination while it was not observed under the condition of complete darkness. A corresponding late component of FEPs was detected in the superior colliculus. The late component might be supposed to be driven from a class of W-cells in the cat's retina.

Physiological identification of a morphological class of cat retinal ganglion cells

1. Small selected patches of retina (approximately 1 mm2) were exhaustively searched electrophysiologically to identify every brisk-transient unit present. The patches were then marked by electrolytic lesions. 2. Whole-mount preparations were made from which the distribution of alpha cells within and around the marked areas could be obtained. 3. A one-to-one correspondence could be demonstrated between brisk-transient units and alpha cells. 4. The correspondence was maintained within a patch of retina including the central area. 5. The correspondences were subject to about 10% of uncertainty attributed to technical limitations of the method.

Brisk and sluggish concentrically organized ganglion cells in the cat's retina

1. Nine hundred and sixty cat retinal ganglion cells were evaluated with respect to receptive-field organization and latency to antidromic activation of their axons from optic-tract and mid-brain positions.2. The vast majority (92%) had the familiar concentric centre/surround organization. As in earlier work these could be classed as sustained or transient, independently of the centre type. About 13% of the concentric cells were characterized by relatively sluggish responses to conventional visual stimuli which yielded brisk responses from the others. The sluggish cells constituted a previously unspecified class of concentric receptive fields.3. The responses of brisk and sluggish cells to a variety of stimuli were described with a view to developing procedures for distinguishing them on functional grounds.4. Measurements of latency to antidromic activation of retinal axons confirmed earlier work in showing that cells classed as brisk-transient had the shortest conduction times from the optic tract. Cells classed as brisk-sustained had intermediate conduction times and from earlier work would constitute an important input to the lateral geniculate nucleus. A proportion of the brisk-sustained axons reached the pretectal region (especially on-centre types) and a small minority reached the superior colliculus (especially off-centre types).5. Sluggish cells had generally slower antidromic conduction times; despite some overlap with the brisk-sustained class, the slower conduction provided independent support for the functional differentiation. Sluggish axons reached the pretectal region and superior colliculus.6. The brisk-sustained cells constituted the majority of the recordings in the area centralis.7. A comparison with the morphological data of Boycott & Wässle is made which suggests that the brisk-transient units corresponded with alpha cells, the brisk-sustained with beta cells, and the sluggish units were included amongst the gamma cells.

Control of retinal sensitivity. 3. Lateral interactions at the inner plexiform layer

Both the "on" and the "on-off" ganglion cells in the mudpuppy retina generate graded responses over a narrow range of log test intensities. Sustained full field or surround backgrounds change the range of center log test intensities that elicits the graded response for both cell types. The on-off, but not the on ganglion cells are further affected by moving or flashing surround backgrounds. These cells are hyperpolarized, threshold is elevated, and the entire graded range of response is elicited by a higher range of log center test intensities. Depolarizing activity is elicited in amacrine cells by moving backgrounds that affect the on-off ganglion cells, but bipolar activity is unaffected. These results suggest that the amacrine cells at the inner plexiform layer mediate a third stage of sensitivity control in the retina, increasing threshold for response to change specifically in the on-off ganglion cells.

Properties of sustained and transient ganglion cells in the cat retina

1. The functional basis for a sustained/transient classification of cat retinal ganglion cells has been strengthened by quantitative measurements of the sizes of the centre and surround components of receptive fields. Transient cells had larger surrounds than sustained; the distributions were non-overlapping. Although the distributions of centre sizes overlapped, the transient cells had very significantly larger centres on average.2. There were characteristic differences in area-threshold and annulus-threshold curves and shapes of responses to brief and long flashes of light, and relative differences in the nature of surround adaptation and maintained discharge rates.3. The distinction of sustained from transient units survived over a wide range of backgrounds including the two principle reorganizations of function: relative weakening of surround components at low background; Purkinje shift at high.4. Sustained and transient units were differentially distributed in the retina: there was an overwhelming preponderance of sustained units in the area centralis.5. It is proposed that the transient units are the so-called multidendritedeep cells and the sustained units are the variously styled small ganglion cells.