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Biomedical subjects

C W Oyster

Publications and source records attributed to C W Oyster.

17 recordsLinked to original sources
PubMed1989

Morphologies of rabbit retinal ganglion cells with concentric receptive fields.

Rabbit retinal ganglion cells with concentric receptive fields were intracellularly recorded and stained in the isolated superfused eyecup preparation to relate specific physiological response properties to dendritic morphology. Concentric ganglion cells, as traditionally defined, were those that had On or Off centers with antagonistic surrounds but lacked complex response properties such as direction or orientation selectivity. Concentric cells were classified into different groups by extracellular recordings of their On- or Off-center response sign, excitatory receptive field center size, linearity of spatial summation, and brisk vs. sluggish and transient vs. sustained responses to step changes in light intensity. The cells were then impaled, confirmed in identity during intracellular recording, and iontophoretically injected with horseradish peroxidase for histological analysis. Twenty-three concentric ganglion cells were recovered and morphometrically analyzed. Their physiological response properties were found to be related to a number of underlying two- and three-dimensional attributes of the cell's dendritic branching patterns. The dendrites of all 20 brisk concentric cells and two of the three sluggish cells were found to ramify narrowly in either the proximal or distal half of the inner plexiform layer, corresponding to whether they are On center or Off center, respectively. One of the sluggish concentric cells was found to have a more complex, partially bistratified ramification. Physiologically identified brisk-sustained-linear, brisk-transient-nonlinear, brisk-transient-linear, and at least two classes of sluggish concentric ganglion cells were stained. Each of these physiological classes appears to exhibit a distinct and identifiable dendritic branching pattern.

Action Potentials↗
PubMed1989

Morphologies of rabbit retinal ganglion cells with complex receptive fields.

Ganglion cells that had complex receptive field properties, namely, On-Off and On direction-selective cells, orientation-selective cells, local edge detectors, and uniformity detectors (suppressed by contrast cells) were recorded in an isolated superfused rabbit eyecup preparation. Cells were first classified by their characteristic extracellular responses to manually controlled stimuli similar to those which have been used in previous in vivo studies. Ganglion cells were then impaled, confirmed in identity by intracellular recording, and iontophoretically injected with horseradish peroxidase for staining. Twenty-two ganglion cells, which included members of all the major classes mentioned above, were recovered from the visual streak or near periphery. All recovered cells were drawn in camera lucida from flat-mounted retinas and entered into a computer as two-dimensional stick figures; nearly all were three-dimensionally reconstructed to determine the level and manner of dendritic ramification in the inner plexiform layer (IPL). The location of ganglion cell dendrites in sublaminar regions of the IPL was found to be consistent with the hypothesis of a division of the IPL into excitatory On (proximal) and Off (distal) sublaminae, with some qualifications for particular classes. Each of the complex receptive field ganglion cell classes exhibited a distinctive three-dimensional dendritic arborization pattern uniquely associated with that physiological class.

Action Potentials↗
PubMed1987

Ganglion cell density in albino and pigmented rabbit retinas labeled with a ganglion cell-specific monoclonal antibody.

Retinas from two rabbits, one normally pigmented and one albino, were labeled with monoclonal antibody AB5, which has been shown to be a specific marker for ganglion cells. This method obviates criteria for distinguishing among ganglion cells, displaced amacrine cells, and glia. Labeled cells were counted within small fields at some 2000 regularly spaced points on each retina. These counts were transformed to maps of ganglion cell density. In general, the density map for the pigmented retina was similar to those obtained by earlier studies with non-specific stains, thereby confirming the basic validity of most previous studies and demonstrating the applicability of AB5 labeling to work of this type. The ganglion cell density map of the albino retina was abnormal, showing a clear deficit of ganglion cells in the nasal portion of the visual streak. This result not only indicates that the albino anomaly has retinal effects, but also suggests a major impact on ganglion cells whose projections (in normal animals) are contralateral.

Albinism↗
PubMed1985

Morphology and distribution of tyrosine hydroxylase-like immunoreactive neurons in the cat retina.

In cat retina, antisera directed against tyrosine hydroxylase (tyrosine 3-monooxygenase; EC 1.14.16.2) labeled three morphologically distinct classes of neurons; amacrine cells, displaced amacrine cells, and interplexiform cells. These three cell populations differed not only in their morphologies but also in their numbers, densities, and retinal distributions. Insofar as tyrosine hydroxylase-like immunoreactivity is associated with dopaminergic neurons, these observations suggest that the dopamine system in cat retina is morphologically heterogeneous and that the cat retina contains functional subdivisions based on the different distributions of specific cell populations.

Animals↗
PubMed1984

Morphology of on-off direction-selective ganglion cells in the rabbit retina.

On-off direction-selective ganglion cells in rabbit retina have been stained by intracellular injection of horseradish peroxidase (HRP). The dendritic ramification is basically bistratified . Global asymmetries related to the preferred direction are not apparent, but the small diameter dendrites, spines, and complex branching pattern are consistent with models based on local, non-linear mechanisms for direction-selectivity.

Animals↗
PubMed1984

Identification and characterization of tyrosine hydroxylase immunoreactive amacrine cells.

Using immunohistochemical techniques and antiserum directed to the enzyme tyrosine hydroxylase, dopaminergic amacrine cells have been directly visualized in the rabbit retina. Tyrosine hydroxylase-like (TH) immunoreactive somata are observed only within the proximal inner nuclear layer (INL). These cells give rise to varicose processes, which are distributed to laminae 1, 3, and 5 of the inner plexiform layer. TH immunoreactive amacrine cells as observed from flat mounted, whole retina preparations have a medium- to large-sized somata. Their processes have extensive fields that provide at least a threefold coverage of any retinal region. As a population, these cells are located in all areas of the retina and are distributed in a sparse, nonrandom manner. These general features of the rabbit dopaminergic cell population appear to be representative of dopaminergic cell systems in other vertebrate retinas.

Animals↗
PubMed1982

Analysis of neuronal soma size distributions.

Neuronal soma size distributions are often very skewed, leading to difficulty in their characterization and in the application of statistics commonly used to describe normally distributed variables. A particular family of curves, called Weibull functions, can be shown to fit cell size data extremely well. These functions not only characterize these skewed distributions, but do so in a way which permits powerful, sensitive comparisons of differences between distributions. Because of the flexibility of the Weibull functions, they may be used to describe a variety of morphological attributes. Several applications of these functions to neuroanatomical data are described using methods which require only graph paper and hand calculator for curve fitting. An extension of the basic curve fitting method permits mixtures of Weibull functions to be used in describing multimodal size histograms.

Animals↗
PubMed1977

Retinogeniculate projections in the rabbit: an autoradiographic study.

As shown by autoradiographic techniques, the pattern of retinogeniculate projections in the pigmented rabbit is generally similar to that described in previous studies. Each retina projects bilaterally to the alpha segment of the dorsal lateral geniculate nucleus (LGd) and to the external segment of the ventral lateral geniculate nucleus (LGv). The beta segment of the LGd and internal layer of the LGv receive contralateral inputs only. The alpha segment of the LGd contains an irregularly shaped region which receives overlapping bilateral projections. Within this region the ipsilateral input is continuous and predominant. This pattern of ipsilateral projection can account for both the laminar arrangement perpendicular to the lines of projection and the "hidden lamination" which have been described previously for the rabbit LGd. A separate bilateral projection is identified for a group of cells lying between the LGd and LGv rostrally. Caudally this intergeniculate leaflet extends medial and ventral to the LGv and appears to merge with the zona incerta.

Animals↗
PubMed1975

Responses of rabbit superior colliculus neurons to repeated visual stimuli.

It has been shown that cells in the superficial layers of the superior colliculus exhibit response decrements when a visual stimulus is repeated. These response decrements have some of the properties associated with habituation, in particular, 1) spontaneous recovery and 2) habituation rate dependent on stimulus frequency. These observations have been made in two classes of neurons; direction-selective cells and so-called modified concentric cells. All of these neurons had small receptive fields and well-defined response properties. Some neurons in both the direction-selective and modified concentric groups do not show habituation. On the basis of area-threshold curves and other observations, it is suggested that those neurons which habituate possess strong inhibitory inputs which are weak or lacking in thenonhabituating neurons. This generalization leads to a hypothesis that inhibition in the superior colliculus has a long decay time and that a response to a given stimulus is affected by inhibition activated by preceding stimuli.

Animals↗
PubMed1969

Rabbit lateral geniculate nucleus: sharpener of directional information.

Direction-selective neurons in the rabbit lateral geniculate nucleus signal movement-direction more precisely than their retinal counterparts. This increased selectivity arises from the interaction of retinal inputs to the geniculate cell. A direction-selective geniculate neuron is fed by at least two retinal direction-selective cells, whose preferred directions are 180 degrees apart. One retinal input is excitatory to the geniculate cell and the other is inhibitory.

Animals↗
PubMed1968

The analysis of image motion by the rabbit retina.

1. Micro-electrode recordings were made from rabbit retinal ganglion cells or their axons. Of particular interest were direction-selective units; the common on-off type represented 20.6% of the total sample (762 units), and the on-type comprised 5% of the total.2. From the large sample of direction-selective units, it was found that on-off units were maximally sensitive to only four directions of movement; these directions, in the visual field, were, roughly, anterior, superior, posterior and inferior. The on-type units were maximally sensitive to only three directions: anterior, superior and inferior.3. The direction-selective unit's responses vary with stimulus velocity; both unit types are more sensitive to velocity change than to absolute speed. On-off units respond to movement at speeds from 6'/sec to 10 degrees /sec; the on-type units responded as slowly as 30''/sec up to about 2 degrees /sec. On-type units are clearly slow-movement detectors.4. The distribution of direction-selective units depends on the retinal locality. On-off units are more common outside the ;visual streak' (area centralis) than within it, while the reverse is true for the on-type units.5. A stimulus configuration was found which would elicit responses from on-type units when the stimulus was moved in the null direction. This ;paradoxical response' was shown to be associated with the silent receptive field surround.6. The four preferred directions of the on-off units were shown to correspond to the directions of retinal image motion produced by contractions of the four rectus eye muscles. This fact, combined with data on velocity sensitivity and retinal distribution of on-off units, suggests that the on-off units are involved in control of reflex eye movements.7. The on-off direction-selective units may provide error signals to a visual servo system which minimizes retinal image motion. This hypothesis agrees with the known characteristics of the rabbit's visual following reflexes, specifically, the slow phase of optokinetic nystagmus.

Animals↗
PubMed1967

Direction-selective units in rabbit retina: distribution of preferred directions.

The preferred directions of 102 direction-selective ganglion cells in the rabbit retina have been determined. Cells of the "on-off" type form four nonoverlapping groups; cells of the "on" type fall into three groups. The on-off groups appear to correspond to the directions of apparent object displacement produced by contractions of the four rectus muscles. Each group of cells could, without further processing, provide the error signal for a visual servo-systerm minimizing retinal image motion.

Animals↗