SEARCH · PubMed Health

Results for “Retinal Horizontal Cells”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 451 records · Page 25Linked to original sources

PubMed1984

The intermediate filament complement of the retina: a comparison between different mammalian species.

We compared the intermediate filament expression of the various cell types in the fully differentiated neural retina from rat, mouse, rabbit, guinea pig, cow, pig, and cat. Many cell types had an intermediate filament complement conserved across species boundaries, such as Müller cells and retinal ganglion cells. In some species (rabbit, guinea pig, and cow), however, we were unable to visualize GFA (glial fibrillary acidic)-positive retinal astrocytes, although such profiles were clearly visible in the remainder. Horizontal cell staining proved to be extremely species-variable. In rat and mouse the processes of these cells were identically displayed with antibodies to vimentin and all three neurofilament triplet proteins. In cow they decorated with antibodies to vimentin and antibodies to the two lower molecular weight neurofilament proteins alone, whereas in pig, rabbit and guinea pig all three neurofilament proteins but not vimentin were present. Finally cat horizontal cells stained for all three neurofilament proteins, some finer processes being additionally stainable with vimentin. A further surprise was the visualization of profiles positive only for the two lower molecular weight neurofilament proteins in the inner nuclear layer of both rabbit and guinea pig retina but not the other species. The implications of these results will be discussed.

Animals↗

PubMed1972

Spatial distribution of potential in a flat cell. Application to the catfish horizontal cell layers.

An analytical solution is obtained for the three-dimensional spatial distribution of potential inside a flat cell, such as the layer of horizontal cells, as a function of its geometry and resistivity characteristics. It was found that, within a very large range of parameter values, the potential is given by [Formula: see text] where r = rho/rho(0), z = z/rho(0), rho = (R(i)/R(m)).rho(0), delta = h/rho(0); K is a constant; J is the assumed synaptic current; rho, z are cylindrical coordinates; rho(0) is the radius of the synaptic area of excitation; h is the cell thickness; and R(i), R(m) are the intracellular and membrane resistivities, respectively. Formula A closely fits data for the spatial decay of potential which were obtained from the catfish internal and external horizontal cells. It predicts a decay which is exponential down to about 40% of the maximum potential but is much slower than exponential below that level, a characteristic also exhibited by the data. Such a feature in the decay mode allows signal integration over the large retinal areas which have been observed experimentally both at the horizontal and ganglion cell stages. The behavior of the potential distribution as a function of the flat cell parameters is investigated, and it is found that for the range of the horizontal cell thicknesses (10-50 mu) the decay rate depends solely on the ratio R(m)/R(i). Data obtained from both types of horizontal cells by varying the diameter of the stimulating spot and for three widely different intensity levels were closely fitted by equation A. In the case of the external horizontal cell, the fit for different intensities was obtained by varying the ratio R(m)/R(i); in the case of the internal horizontal cell it was found necessary, in order to fit the data for different intensities, to vary the assumed synaptic current J.

Animals↗

PubMed1998

Clonal boundary analysis in the developing retina using X-inactivation transgenic mosaic mice.

Transgenic mice harboring the lacZ reporter gene on one X chromosome have been used to mark 50% of all retinal progenitors. The distribution of clones arising from this population of marked progenitors reveals a conspicuous columnar segregation of clonally related cells, indicating that most retinal neuroblasts migrate exclusively radially. Against this columnar background of the transgenic retina, single cone, horizontal, amacrine and ganglion cells are observed to transgress clonal borders, mixing freely with cells derived from different precursors. This tangential dispersion is due to the lateral movement of postmitotic neuroblasts around the time of their differentiation, rather than to the dispersion of a proliferative sibling at the time of cell birth. Tangential dispersion is suggested to play a significant role in creating the functional architecture of the mature retina, being the means by which the orderly spacing, or regularity, of retinal mosaics is established during development.

Animals↗

PubMed1975

The effects of laser photocoagulation in the retinal capillaries.

Using ruby and argon lasers, we produced multiple lesions on normal rhesus monkey retinas. The clinically used energy levels of both lasers produced identical cellular changes in the retina. Neither laser directly produced obliteration of capillaries. However, after the cellular damage in each burn lesion was repaired, we observed delayed degeneration of capillaries in a small segment at the burned areas. The marked reduction of active retinal cells that reduce vascular activity may beneficially affect laser treatment of diabetic retinopathy. The retinal tissue appears to have excessive photoreceptor cells and the horizontal connection of other cells seems to compensate for visual function after loss of many photoreceptor cells. We demonstrated severe damage in the ganglion cells by argon laser when it was aimed at the thick blood films in the vitreous cavity. Certain precautions must be taken when peripapillary neovascularization is treated by laser beam.

Animals↗

PubMed1982

A physiological and morphological study of the horizontal cell types of the rabbit retina.

A perfused, isolated retina-eyecup preparation of the rabbit was utilized to correlate the physiology and morphology of horizontal cells. Neurons were physiologically characterized by intracellular recording techniques and subsequently stained with intracellular iontophoretically injected horseradish peroxidase for morphological identification. Three types of rabbit horizontal cell recordings have been differentiated, based on variations in response waveform, amplitude-intensity properties, and area summation characteristics. These three types have been unequivocally associated with the axonless A-type horizontal cells and the somatic and axon terminal endings (each displaying its own distinct physiology) of B-type horizontal cells first described in studies using Golgi-impregnation techniques (Fisher and Boycott, '74). In addition, the sizes of A-type horizontal cells were found to be directly related to their retinal eccentricities from the optic desk. However a unique subclass of A-type cells has been discovered (elongated or Ae type) which displayed the largest dendritic field of any cells studied here, yet had the smallest eccentricities--within 1.4 mm of the optic disk. Moreover, elongated A-type cells exhibited long asymmetrical dendritic fields which were oriented parallel with the visual streak. The unique asymmetry and orientation of these cells suggests that they may have orientation-biased receptive field properties. Physiological evidence for an orientation-biased horizontal cell is presented in support of this notion.

Animals↗

PubMed1995

Ethambutol alters spinule-type synaptic connections and induces morphologic alterations in the cone pedicles of the fish retina.

PURPOSE: Ethambutol can cause optic neuropathy and deficiencies in color-opponent visual processing in patients treated for tuberculosis. In fish, Ethambutol induces color vision deficiencies similar to those observed in humans and affects color coding in retinal ganglion cells. Color opponency in fish is mainly mediated by a horizontal cell feedback onto cones thought to be provided by spinules. The authors examined whether Ethambutol affects spinules and is, therefore, able to alter color processing at a distal stage, that is, at the first synaptic connection within the retina. METHODS: Ethambutol was injected into the vitreous of either dark- or light-adapted fish. After drug application, fish were held under different illumination conditions. Thereafter, the retinas were dissected and prepared for electron microscopy. Ultrathin tangential sections of retinas were examined at the level of the outer plexiform layer. RESULTS: In already light-adapted retinas, a high dose of Ethambutol (10 mM) reduced the number of spinules by 30%. Ethambutol application in the dark with subsequent light adaptation resulted in severe dose-related inhibition of light-induced spinule formation. In these experiments, low doses (0.1 mM) of Ethambutol caused 40% inhibition, and high doses (10 mM) caused 70% inhibition. Besides affecting spinules, Ethambutol occasionally induced a degeneration of cone pedicles. This neurotoxicity only occurred in cones exposed to light. CONCLUSIONS: Results show that Ethambutol alters synaptic connections between horizontal cells and cones in a dose-related fashion; Ethambutol treatment can be toxic for cone pedicles and can cause their degeneration; and the rod pathway is not affected by the drug. This indicates that Ethambutol influences the color-coding process already at the level of the cone-horizontal cell synapse.

Animals↗

PubMed1991

Contralateral visual field representation in area 17 of the cerebral cortex of the agouti: a comparison between the cortical magnification factor and retinal ganglion cell distribution.

The cortical representation of the contralateral visual field in area 17 of the agouti's brain was studied by multiunit recording. The borders of area 17 were determined by electrophysiological, cytoarchitectonic and myeloarchitectonic criteria. The results were plotted in flat, bidimensional representations of the cerebral cortex to minimize perspective distortions. The V1 map, a first order topological transformation of the visual field, shows a magnified representation of the horizontal meridian that corresponds to a retinal specialization, the visual streak. The visual field representation has asymmetries that are not directly related to the topography of the retinal ganglion cell density. Whereas the ganglion cell density shows a plateau along the visual streak, the areal cortical magnification factor is higher in the region that corresponds to the intersection of the horizontal and vertical meridians. This suggests functional specializations that are not obvious when one considers the distribution of the whole ganglion cell population but which might be related to the distribution of specific ganglion cell classes.

Animals↗

PubMed1990

Retinal dopamine D1 and D2 receptors: characterization by binding or pharmacological studies and physiological functions.

1. In the retinal inner nuclear layer of the majority of species, a dopaminergic neuronal network has been visualized in either amacrine cells or the so-called interplexiform cells. 2. Binding studies of retinal dopamine receptors have revealed the existence of both D1- as well D2-subtypes. The D1-subtype was characterized by labeled SCH 23390 (Kd ranging from 0.175 to 1.6 nM and Bmax from 16 to 482 fmol/mg protein) and the D2-subtype by labelled spiroperidol (Kd ranging from 0.087 to 1.35 nM and Bmax from 12 to 1500 fmol/mg protein) and more selectively by iodosulpiride (Kd 0.6 nM and Bmax 82 fmol/mg protein) or methylspiperone (Kd 0.14 nM and Bmax 223 fmol/mg protein). 3. Retinal dopamine receptors have been also shown to be positively coupled with adenylate cyclase activity in most species, arguing for the existence of D1-subtype, whereas in some others (lower vertebrates and rats), a negative coupling (D2-subtype) has been also detected in peculiar pharmacological conditions implying various combinations of dopamine or a D2-agonist with a D1-antagonist or a D2-antagonist in the absence or presence of forskolin. 4. A subpopulation of autoreceptors of D2-subtype (probably not coupled to adenylate cyclase) also seems to be involved in the modulation of retinal dopamine synthesis and/or release. 5. Light/darkness conditions can affect the sensitivity of retinal dopamine D1 and/or D2-receptors, as studied in binding or pharmacological experiments (cAMP levels, dopamine synthesis, metabolism and release). 6. Visual function(s) of retinal dopamine receptors were connected with the regulation of electrical activity and communication (through gap junctions) between horizontal cells mediated by D1 and D2 receptor stimulation. Movements of photoreceptor cells and migration of melanin granules in retinal pigment epithelial cells as well as synthesis of melatonin in photoreceptors were on the other hand mediated by the stimulation of D2-receptors. 7. Other physiological functions of dopamine D1-receptors respectively in rabbit and in embryonic avian retina would imply the modulation of acetylcholine release and the inhibition of neuronal growth cones.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗

PubMed2004

Developmental defects in Rb-deficient retinae.

We recently found that the Rb protein is important for the regulation of retinal progenitor cell proliferation and rod photoreceptor development in the mouse retina. These two functions are separate for Rb and in this study we further characterize the role of Rb in retinal development. At postnatal day 12 in the retinae of Chx10-Cre;RbLox/- mice, immature cells are found in the outer nuclear layer where rods normally are differentiating. This results in alternating patches of the outer nuclear layer (ONL) that are lacking rod inputs. At this stage of development, horizontal cell processes at the outer plexiform layer do not mature appropriately and they extend into the outer nuclear layer. These disruptions in horizontal cell differentiation can persist for several weeks into the adult stage. While there are several secondary effects of the loss of Rb on retinal development including, limited cell death in the ONL, Müller glial cell activation, persistence of immature cells in the ONL, and altered nuclear morphology of cells in the ONL, we suggest that the defect in horizontal cell synapse formation at the OPL results from fewer rod inputs. Mice with other developmental defects in photoreceptor cell fate specification or glial cell activation do not exhibit a similar alteration in horizontal cell differentiation. Therefore, the retinae from Chx10-Cre;RbLox/- mice represent a unique model to study the role of rod photoreceptor inputs in horizontal cell differentiation and synapse formation.

Animals↗

PubMed1976

Influence of ouabain on the fine structure of teleost retina.

In this study the effect of intraocular injection of 10 mul 10(-5) M ouabain on the retinal fine structure of the cyprinide teleost Carassius carassius is described. The final concentration of the drug in the eye-bulb was approximately 3-10(-6)M. After 8--24 h the ouabain application produces alterations in the retinal ganglion cells, that progress subsequently to necrobiosis. The outer horizontal cells of the inner nuclear layer show a severe cytoplasmic swelling that is reversible and disappears 8 days after ouabain injection. Amacrines, bipolars and receptor cells are relatively insensitive to the ouabain-induced Na+-K+-ATPase-inhibition. The differential susceptibility to ouabain in the retina possibly reflects a cell-specific pattern of Na+-K+-ATPase-activity or -concentration, whose physiological significance is discussed.

Adenosine Triphosphate↗

PubMed1996

Spatiotemporal gradients of cell genesis in the primate retina.

A cardinal event in the development of all brain structures is the time at which progenitor cells leave the cell cycle and begin to differentiate. We examined cell genesis in the retina of the macaque monkey (Macaca mulatta) by labeling dividing cells with radioactive thymidine ([3H]TdR) and following their fate at terminal division by virtue of their remaining radiolabeled after a long survival period. A number of distinct patterns of cell genesis were observed. The two tissues generated by the optic vesicle, the retinal pigment epithelium and neuroretina, share closely coincident temporal and spatial patterns of cell genesis, indicating that this process may be controlled by a common mechanism. Although overlapping to varying degrees, a clear sequence of genesis was revealed between specific cell types within the neuroretina: ganglion cells are generated first, followed by horizontal cells, cone photoreceptors, amacrine cells, Müller cells, bipolar cells, and, finally, rod photoreceptors. Retinal ganglion cells of differing soma diameter are born at different times-the smallest cells are generated early, the largest late, suggesting a further refined sequence of the functional classes of monkey retinal ganglion cells (first P gamma, then P beta, last P alpha). In addition, at sites where a homogeneous population of cells are crowded and stacked on top of each other (the foveola and perifovea for cones and ganglion cells, respectively) there is a vitreal-to-scleral intralaminar pattern of [3H]TdR labeled cell placement, which reflects both time of genesis and pattern of movement during foveation. These gradients suggest several scenarios for cell fate specification in the retina, many of which might not be obvious in mammals that develop more quickly and have less specialized retinal structure. Thus, data from the highly specialized and slowly developing macaque retina can help to understand visual development in humans and indicate useful avenues for future experimental studies in other species.

Animals↗

PubMed1985

Retinofugal and retinopetal projections in the cichlid fish Astronotus ocellatus.

The retinofugal and retinopetal projections of the cichlid fish Astronotus ocellatus were studied by applying cobaltous-lysine to the optic nerve. Retinal axons terminate bilaterally in a preoptic-suprachiasmatic region between the base of the third ventricle and the anterior genu of the horizontal commissure and among periventricular cells along the sides of the ventricle. Other retinal axons innervate the tuberal region of the hypothalamus anterior to the infundibulum. Targets innervated in the pretectum include nucleus lateralis geniculatus and dorsal, medial, and ventral pretectal nuclei. Three other targets (nucleus opticus dorsolateralis, nucleus opticus commissurae posterior, nucleus opticus ventrolateralis) are innervated by fibers that leave the medial edge of the dorsal optic tract. Two other targets (basal optic nucleus and accessory optic nucleus) are innervated by fibers from the ventral optic tract. These retinal projections are similar to those previously reported for goldfish in an experiment that used the cobaltous-lysine method (Springer and Gaffney, J. Comp. Neurol. 203:401-424, '81). Retinotectal optic axons were found in a superficial lamina just above the stratum opticum, in the stratum opticum, in three layers of the stratum fibrosum et griseum superficiale, in a lamina just beneath the stratum fibrosum et griseum superficiale, and in the stratum album centrale just above the stratum periventriculare. This result is similar to that previously reported for goldfish; however, the spatial relationships between the various retinorecipient laminae differ for goldfish and Astronotus ocellatus. Efferents to the retina originate in two nuclei and both project contralaterally. The first is the nucleus olfactoretinalis, which is located ventrally between the olfactory lobe and telencephalon. It consists of about 400 cells, of which, approximately 200 cells project to the retina. The second retinopetal nucleus, nucleus thalamoretinalis, is a diffuse group of about 200 cells that project to the retina.

Animals↗

PubMed2002

A metabotropic glutamate receptor regulates transmitter release from cone presynaptic terminals in carp retinal slices.

The role of group III metabotropic glutamate receptors (mGluRs) in photoreceptor-H1 horizontal cell (HC) synaptic transmission was investigated by analyzing the rate of occurrence and amplitude of spontaneous excitatory postsynaptic currents (sEPSCs) in H1 HCs uncoupled by dopamine in carp retinal slices. Red light steps or the application of 100 microM cobalt reduced the sEPSC rate without affecting their peak amplitude, which is consistent with hyperpolarization or the suppression of Ca(2+) entry into cone synaptic terminals reducing vesicular transmitter release. Conversely, postsynaptic blockade of H1 HC AMPA receptors by 500 nM CNQX reduced the amplitude of sEPSCs without affecting their rate. This analysis of sEPSCs represents a novel methodology for distinguishing between presynaptic and postsynaptic sites of action. The selective agonist for group III mGluRs, l-2-amino-4-phosphonobutyrate (L-APB or L-AP4; 20 microM), reduced the sEPSC rate with a slight reduction in amplitude, which is consistent with a presynaptic action on cone synaptic terminals to reduce transmitter release. During L-APB application, recovery of sEPSC rate occurred with 500 microM (s)-2-methyl-2-amino-4-phosphonobutyrate (MAP4), a selective antagonist of group III mGluR, and with 200 microM 4-aminopyridine (4-AP), a blocker of voltage-dependent potassium channels. Whole-cell recordings from cones in the retinal slice showed no effect of L-APB on voltage-activated Ca(2+) conductance. These results suggest that the activation of group III mGluRs suppresses transmitter release from cone presynaptic terminals via a 4-AP-sensitive pathway. Negative feedback, operating via mGluR autoreceptors, may limit excessive glutamate release from cone synaptic terminals.

Animals↗

PubMed1996

Mammalian hairy and Enhancer of split homolog 1 regulates differentiation of retinal neurons and is essential for eye morphogenesis.

Mammalian hairy and Enhancer of split homolog 1 (HES1), a basic helix-loop-helix factor gene, is expressed in retinal progenitor cells, and its expression decreases as differentiation proceeds. Retinal progenitor cells infected with HES1-transducing retrovirus did not differentiate into mature retinal cells, suggesting that persistent expression of HES1 blocks retinal development. In contrast, in the retina of HES1-null mutant mice, differentiation was accelerated, and rod and horizontal cells appeared prematurely and formed abnormal rosette-like structures. Lens and cornea development was also severely disturbed. Furthermore, in the mutant retina, bipolar cells extensively died, and finally disappeared. These studies provide evidence that HES1 regulates differentiation of retinal neurons and is essential for eye morphogenesis.

Animals↗

PubMed1986

Effects of gamma-aminobutyric acid on isolated cone photoreceptors of the turtle retina.

Isolated cones dissociated from the retina of the freshwater turtle were voltage clamped using a single 'patch' pipette electrode. gamma-Aminobutyric acid (GABA) applied ionophoretically to the axon terminal evoked an inward current in cells held at -66 mV when they were recorded with patch pipettes filled with the 'control' pipette solution containing 120 mM-Cl-. Polarity of the GABA-induced current reversed near 0 mV when examined with the pipette filled with the control pipette solution. The reversal potential depended strongly on both external and intrapipette Cl- concentrations ([Cl-]o, and [Cl-]p). The reversal potential agreed with the equilibrium potential for Cl- calculated by the Nernst equation with given [Cl-]o and [Cl-]p. The reversal potential was not affected by concentrations of either external Na or K ions. Voltage responses evoked by GABA were hyperpolarizing from its resting level of about -50 mV immediately after the rupture of the patch membrane. The response polarity reversed into depolarization in a few seconds when [Cl-]p was greater than 24 mM, while hyperpolarizing responses persisted when [Cl-]p was less than 12 mM. Thus, the intracellular Cl- concentration of undisturbed isolated cones was estimated to be between 12 and 24 mM. Cones were desensitized to GABA in the presence of GABA (greater than 100 nM) in the medium, or by a prolonged ionophoretic application. The maximum reduction in response amplitude was about 70% in both experiments. Muscimol was as potent as GABA, while beta-p-chlorophenyl-GABA (baclofen) was ineffective even at 100 microM. GABA was antagonized by bicuculline competitively, and by picrotoxin non-competitively. These observations suggest that turtle cones have GABAA receptors which associate with chloride channels. The present results suggest that GABA, presumably released continuously from monophasic horizontal cells in the dark, would exert a tonic hyperpolarization in red-sensitive and green-sensitive cones. Suppression by light of tonic GABA release would depolarize these types of cones by disinhibition. Disinhibitory depolarization in cones may contribute to the centre surround antagonism in retinal neurones, and to the biphasic colour responses recorded in a subtype of horizontal cells.

Action Potentials↗

PubMed1999

Horizontal cells of the rat retina are resistant to degenerative processes induced by ischemia-reperfusion.

The fate of calbindin D28k (calbindin)-labeled horizontal cells in the ischemic rat retina induced by increasing intraocular pressure was investigated by immunocytochemistry using an antiserum against calbindin. In the normal retina, strong calbindin-like immunoreactivity was seen in the horizontal cells, and the density of the labelled horizontal cells was 815.3+/-15.2 per mm2. The thickness of the treated retina became progressively thinner with increasing reperfusion time after the ischemic insult due to a loss of retinal cells in the inner and outer nuclear layers. However, the densities of the horizontal cells per mm2 were 814.0+/-26.4 at 1 week, 813.3+/-20.8 at 2 weeks, and 812.6+/-11.5 at 4 weeks, indicating that horizontal cells did not degenerate during experimental periods. Thus, calbindin may have a protective role for horizontal cells to ischemic insult by its ability to buffer calcium influx in the rat retina.

Albinism↗

PubMed1993

A quantitative study of the lateral spread of Müller cell responses to retinal lesions in the rabbit.

A wide variety of retinal pathology is associated with an increase in Müller glial cell expression of glial fibrillary acidic protein (GFAP). In this study the time course and spatial spread of the Müller cell GFAP response following argon laser photocoagulation lesions was examined in wholemounted rabbit retina. At 24 hours single focal lesions were surrounded by GFAP positive Müller cell end feet which declined in density with distance but extended as far as 2-3 mm from the lesion. The Müller cell reaction reached a maximal spread of 4-5 mm at 14 to 21 days and had started to contract by 30 days, leaving a core of GFAP positive processes immediately around the lesion site at 60 days. This zone of spread was much larger than the area of disrupted pigment epithelium. Isodensity plots did not reveal any correlation with the trajectory of retinal ganglion cell axons. The spread of reaction was more confined for lesions within the visual streak than in the dorsal or ventral retinal periphery. Multiple lesions within a focal region of retina resulted in a greater density of GFAP reactive end feet with a corresponding greater spread. However, when five to ten lesions were made in a horizontal row, the Müller cells over the entire retina became GFAP immunoreactive. This pan-retinal reaction took several days to spread, peaked at 7-14 days, and contracted back to the primary lesion sites by 2 months. This spread of Müller cell reactivity may be triggered by the diffusion of substances released by injury or it may be due to direct cellular communication. The extensive indirect effect on Müller cells of laser irradiation might be an important component of the clinical effect of laser photocoagulation and indicates a long distance communication mechanism between retinal glia which is poorly understood. This study also shows the importance of the time at which the Müller cell response is assessed.

Animals↗

PubMed1981

A quantitative analysis of the direction-specific response of Neurons in the cat's nucleus of the optic tract.

All cells in the nucleus of the optic tract (NOT) of the cat, that could be activated antidromically from the inferior olive, were shown to be direction-specific, as influenced by horizontal movements of an extensive visual stimulus. Cells in the left NOT were activated by leftward and inhibited by rightward movement, while those in the right NOT were activated by rightward and inhibited by leftward movement. Vertical movements did not modulate the spontaneous activity of the cells. The mean spontaneous discharge rate in 50 NOT cells was 30 spikes/s. This direction-specific response was maintained over a broad velocity range (Less Than 0.1 degrees - Greater Than 100 degrees/s). Velocities over 200 degrees/s could inhibit NOT cells regardless of stimulus direction. All cells in the NOT were driven by the contralateral eye, about half of them by the ipsilateral eye also. In addition, activation through the contralateral eye was stronger in most binocular units. Binocular cells preferred the same direction in the visual space through both eyes. An area approximately corresponding to the visual streak in the cat's retina projected most densely onto NOT cells. This included an extensive ipsilateral projection. No clear retinotopic order was seen. The most sensitive zone in the very large receptive fields (most diameters being Greater Than 20 degrees) was along the horizontal zero meridian of the visual field. The retinal input to NOT cells was mediated by W-fibers. The striking similarities between the input characteristics of NOT-cells and optokinetic nystagmus are discussed. The direction selectivity and ocular dominance of the NOT system as a whole can provide a possible explanation for the directional asymmetry in the cat's optokinetic nystagmus when only one eye is stimulated.

Animals↗