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R W Rodieck

Publications and source records attributed to R W Rodieck.

9 recordsLinked to original sources
PubMed1992

Spatial density and distribution of choline acetyltransferase immunoreactive cells in human, macaque, and baboon retinas.

Whole-mounted human, macaque, and baboon retinas were labelled with an antiserum to human choline acetyltransferase (ChAT), by the immunoperoxidase technique. Previous work in nonprimate species has shown that these cells correspond to the starburst amacrine cells. Labelled somata were disposed on either side of the inner plexiform layer, and their processes formed two narrow zones within it. In human retinas, the ratio of labelled somata in the ganglion cell layer (GCL) to those in the inner nuclear layer (nominal Sb/Sa ratio) was about 60/40 at all locations, similar to that found in nonprimate mammalian species. The density of labelled cells in the human GCL ranged from 1,000 to 1,150 mm-2 near the fovea to 300 to 400 mm-2 in the periphery. Labelling tended to be more erratic in macaque retinas. Nevertheless the Sb/Sa ratio was as high as 70/30 and spatial densities were similar to those of humans. The overlap factor in macaque retinas outside the nasal quadrant was about 10 at all retinal eccentricities, based upon dendritic-field sizes from a Golgi study. About each labelled soma there was a region 20 to 120 microns in diameter in which the probability of the occurrence of other labelled somata was lower than elsewhere. No such nonrandomness was found between labeled cells in the GCL and those in the amacrine cell layer. The packing factor was about 0.3 in well-labelled regions, independent of retinal position or spatial density. Published data on ChAT-labelled cells in rabbit and rat show a similar value. This invariance is consistent with the hypothesis that this nonrandomness is a residual consequence of somal contiguity at an early developmental stage.

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PubMed1991

The density recovery profile: a method for the analysis of points in the plane applicable to retinal studies.

The density recovery profile is a plot of the spatial density of a set of points as a function of the distance of each of those points from all the others. It is based upon a two-dimensional point autocorrelogram. If the points are randomly distributed, then the profile is flat, with a value equal to the mean spatial density. Thus, any deviation from this value indicates that the presence of the object represented by the point alters the probability of encountering nearby objects of the same set. Increased value near an object indicates clustering, decreased value near an object indicates anticlustering. The method appears to be unique in its ability to provide quantitative measures of the anticlustered state. Two examples are presented. The first is based upon a sample of the distribution of the somata of starburst amacrine cells in the macaque retina; the second is based upon the distribution of the terminal enlargements on the dendrites of a single macaque ganglion cell that projects to the superior colliculus. In both cases, the density recovery profile is initially lower than the mean density, and increases up to the plateau at the value of the mean density. Two useful measures can be derived from this profile: an intensive parameter termed the effective radius, which quantifies the extent of the region of decreased probability and is insensitive to random undersampling of the underlying distribution, and an extensive parameter termed the packing factor, which quantifies the degree of packing possible for a given effective radius, and is insensitive to scaling. An extension of this method, applicable to correlations between two superimposed distributions, and based upon a two-dimensional point cross-correlogram, is also described.

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PubMed1979

Visual suppression from nondominant eye in the lateral geniculate nucleus: a comparison of cat and monkey.

We have studied the suppression of firing in single LGN cells of cat and monkey in response to visual stimulation of the nondominant eye. In the cat LGN most of the cells of each of the main laminae show this nondominat suppression. X cells having their dominant input from the ipsilateral eye were suppressed to a significantly greater degree than any other cell type in the cat LGN. In the monkey LGN nondominant suppression was absent in all 19 X-like cells studied, whereas 6 of 21 Y-like cells showed nondominant suppression. Thus nondominant suppression is present in the magnocellular laminae of the monkey LGN, where the Y-like cells are found, but appears to be absent from the parvocellular laminae, where the X-like cells are found.

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PubMed1979

Visual pathways.

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PubMed1976

Isolation of rod and cone contributions to cat ganglion cells by a method of light exchange.

1. The great majority of cat retinal ganglion cells are known to receive signals from rods and from a single (green) cone type. The centre region of the receptive fields of these cells was stimulated by a spot that changed back and forth from orange to white. By adjusting the intensity of the white spot relative to that of the orange a condition could be established at which the photon-catch rate of the rods remained unchanged during the orange-white exchange. At this intensity setting, termed the rod isolept, rods are thus unstimulated by the exchange, however intense, and the ganglion-cell response was found to be due entirely to the green cones. At another intensity setting of the white spot relative to the orange (cone isolept), the photon catch of the green cones remained unchanged during the exchange and ganglion-cell responses were found to arise entirely from the rods. 2. A neutral wedge in the combined exchange beam (but not in the steady background that covered the whole receptive field) regulated the size of the exchange stimulus and thus the magnitude of the ganglion-cell discharge heard from a loud speaker to the exchange. Exchange threshold was the wedge setting at which this change in firing rate could only just be heard. 3. At the cone isolept, cones remain unstimulated however intense the exchange stimulus, and the rod increment threshold curve was determined over its full range from absolute threshold up to saturation. Likewise, at the rod isolept, the cone increment threshold curve was determined over the same intensity range as for the rods. Rod saturation was found to occur at the point where the cone increment threshold curve began to rise from its absolute threshold level toward its Weber region. 4. The exchange approach also enabled both rod and cone dark-adaptation curves following a strong bleaching exposure to be obtained in the same experiment by moving successively between the cone and rod isolepts. At the cone isolept the time course of early rod dark adaptation could thus be determined when the rod threshold to flashing spots lay well above that of the cones.

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PubMed1976

Cancellation of rod signals by cones, and cone signals by rods in the cat retina.

1. The interaction of rod and cone signals at the level of cat retinal ganglion cells was studied by a method of light exchange. Two spectrally distinct lights were exchanged in such a manner that the rate of photon catch by rods increased in a stepwise manner at the same moment that the cone rate decreased in the same manner, and vice versa. 2. Under any conditions of adaptation, where both rods and cones contributed to the ganglion-cell discharge, it was always possible to adjust the ratio of the magnitudes of the rod and cone stimuli so that no change in ganglion-cell discharge could be detected by listening to the recorded activity via a loudspeaker. We term this condition a silent exchange. 3. On the face of it, the condition of silent exchange arises when rod and cone signals are able to cancel one another, when made opposite in phase by the exchange situation. But was this silence due to a true cancellation of the signals from one photoreceptor type by those of the other type, or was it due to our failure to stimulate the photoreceptors adequately? In order to test whether rod signals can cancel those of cones we bleached both visual pigments and set our exchange apparatus to stimulate the two photoreceptors in the antagonistic manner described above. At first no response could be heard on exchange, for the thresholds of both rods and cones lay above that of our apparatus. But the cones soon recovered and a strong response was heard on exchange. With no change in our stimulating situation, this response diminished with time and silence was again restored. This restoration of silence could not be due to the cones alone, for with time their sensitivity could only further increase. It could only be the increasing sensitivity of the rods that quietened the cone signals. In agreement with this conculsion, the dark-adaptation curve of the rods showed that they became sensitive to our stimulus at the time that the cones began to be silenced. 4. By means of coloured backgrounds we have also shown the converse, namely that rods signals can be cancelled by those of cones.

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PubMed1976

Identification, classification and anatomical segregation of cells with X-like and Y-like properties in the lateral geniculate nucleus of old-world primates.

1. All the cells (158) that we studied in the lateral geniculate nuclei of Macaca nemestrina and Macaca irus could be distinguished as either X-like or Y-like on the basis of their responses to tests developed to classify cat retinal and lateral geniculate nucleus cells. These tests include responses to stationary spots, fast moving wands and moving gratings. 2. Response latencies to electrical stimulation of the optic chiasm were determined for 130 cells; no X-like cell showed a latency shorter than 1-7 ms, no Y-like cell showed a latency longer than 1-6 ms. Primate lateral geniculate nucleus cells with X-like properties thus receive their excitatory input from retinal cells with slowly conducting axons and these most probably include the tonic ganglion cells described by Gouras (1968, 1969); Y-like lateral geniculate nucleus cells are driven by retinal cells with faster conducting axons, most probably including the phasic ganglion cells described by Gouras. 3. Wiesel & Hubel (1966) classified monkey lateral geniculate nucleus cells into four main types based on their receptive-field properties, as revealed by spectrally and spatially distinct stimuli. We find that all Type I and Type II cells show X-like properties; all type IV cells show Y-like properties. Type III consists of a subtype that show X-like properties, here termed Type IIIx, and a subtype that show Y-like properties, here termed Type IIIy. 4. The first cells encountered as the micro-electrode reached the lateral geniculate nucleus were always X-like. In some penetrations only X-like cells were encountered as the electrode moved downward through the lateral geniculate nucleus. In the remaining penetrations, after recording X-like cells through most of the lateral geniculate nucleus, Y-like cells were then encountered. No X-like cells were found below Y-like cells. thus these two classes of cells are anatomically segregated within the primate lateral geniculate nucleus. Electrode marking showed the borger between X-like and Y-like cells to correspond to the border between the paro- and magnocellular layers of the lateral geniculate nucleus. Thus X-like cells (i.e. Types I, II and IIIx) occur in the parvocellular layers, Y-like cells (i.e. Types IIIy and IV)in the magnocellular layers.

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