bluuebunny/crossref_metadata_2025_split huggingface dataset:
The effects of lateral geniculate nucleus, area V4, and middle temporal (MT) lesions on visually guided eye movements
Authors: Schiller Peter H. , Lee Kyoungmin 
Published: June 2009

AbstractVisually guided saccadic eye movements to singly presented stationary targets form a bimodal distribution. After superior colliculus lesions, the so called “express saccades” that form the first mode of the distribution are no longer obtained. The aim of this study was to determine what role several other neural systems play in the generation of express and regular saccades, with the latter being those that form the second mode in the bimodal distribution. Lesions were made in the parvocellular and magnocellular portions of the lateral geniculate nucleus to disrupt either the midget system or the parasol system that originates in the retina and areas V4 and MT. The effects of the lesions were examined on the accuracy and latency of saccadic eye movements made to stationary and to moving visual targets. Following magnocellular and MT lesions deficits were observed in smooth pursuit and in the amplitude of saccades made to moving targets. However, none of the lesions produced significant changes in the bimodal distribution of saccadic latencies to stationary targets. The results suggest that express saccades and regular saccades are not selectively mediated by either the midget or the parasol systems or by areas V4 and MT. Neither are the frontal eye fields involved as had previously been shown. We suggest that the superior colliculus plays a central role in producing both express and regular saccades by virtue of highly convergent input from numerous cortical structures.
Organization of simple cell responses in the three-dimensional (3-D) frequency domain
Authors: McLean J. , Palmer L. A. 
Published: June 2009

AbstractThe amplitude spectra of simple cells in areas 17 and 18 were estimated in two and three dimensions (2–D and 3–D) using drifting sinusoidal gratings. In 2–D, responses were sampled with 16 x 16 resolution in spatial and temporal frequency at the optimal orientation. In 3–D, responses were sampled with 12 x 12 x 10 resolution in spatial frequency, orientation, and temporal frequency. For 45/50 cells studied, the spatial attributes of the receptive fields (RFs) were independent of temporal frequency except for a scale factor. The five exceptions to this general finding could be described as follows: For four area 17 cells, responses in the null direction increased with temporal frequency, reducing direction selectivity. For one area 18 cell, the optimal spatial frequency increased with temporal frequency and vice versa. The 2–D discrete Fourier transform was applied to all of the estimated amplitude spectra assuming zero spatial and temporal phase. These transforms were compared with the results of first-order reverse correlations as described in the previous paper (McLean et al., 1994). Direction selective cells exhibited excitatory subregions that were obliquely oriented in space-time in both the raw correlation data and inverse transforms of the spectral data. The slopes of the subregions found in these two measures were highly correlated. Direction indices obtained from space and frequency domain measures were comparable. We demonstrate that the spectral response profiles of most simple cells are aligned with the coordinate axes in frequency domain. That is, they may be considered one-quadrant separable, suggesting that these cells are not velocity tuned per se, but are tuned for spatiotemporal frequency. The spectral bandwidth establishes the range of velocities to which these cells will respond. These findings are consistent with the one-quadrant separability constraint of linear quadrature models. We conclude that most simple cells perform as roughly linear filters in two dimensions of space and time.
Reciprocal connections between the rabbit suprageniculate pretectal nucleus and the superior colliculus: Tracer study with horseradish peroxidase and fluorogold
Authors: Lagares C. , Caballero-Bleda M. , Fernández B. , Puelles L. 
Published: June 2009

AbstractConnections of the rabbit suprageniculate pretectal nucleus (SP) with the superior colliculus were explored by means of retrograde transport of horseradish peroxidase or Fluorogold. Large injections centered in the superficial and intermediate tectal layers resulted in bilateral retrograde transport to the medium-size multipolar neurons of the suprageniculate pretectal nucleus. Horseradish peroxidase was also transported anterogradely into the ipsilateral and contralateral neuropiles of the suprageniculate pretectal nucleus. The labeled cells in SP were dispersed throughout the nucleus, including its dorsal, wedge-shaped, internal portion. Labeling was mainly ipsilateral, and less abundant on the contralateral side.
Motion defined exclusively by second-order characteristics does not evoke optokinetic nystagmus
Authors: Harri Laurence R. , Smith Andrew T. 
Published: June 2009

AbstractWe showed high-contrast, second-order motion stimuli to subjects whilst recording their horizontal eye movements. These stimuli were very poor at evoking optokinetic nystagmus. Smooth-pursuit eye movements and fixation were reduced by a masking band ±2.5 deg above and below an imaginary fixation point. First-order stimuli evoked vigorous optokinetic nystagmus (OKN) under identical conditions and also when matched for apparent contrast. These findings are discussed in terms of the site of detection of second-order motion.
Visual responsiveness and direction selectivity of cells in area 18 during local reversible inactivation of area 17 in cats
Authors: Casanova C. , Michaud Y. , Morin C. , McKinley P.A. , Molotchnikoff S. 
Published: June 2009

AbstractWe have investigated the effects of inactivation of localized sites in area 17 on the visual responses of cells in visuotopically corresponding regions of area 18. Experiments were performed on adult normal cats. The striate cortex was inactivated by the injection of nanoliters of lidocaine hydrochloride or of γ-aminobutyric acid (GABA) dissolved in a staining solution. Responses of the simple and complex cells of area 18 to optimally oriented light and dark bars moving in the two directions of motion were recorded before, during, and after the drug injection. Two main effects are described.First, for a substantial number of cells, the drug injection provoked an overall reduction of the cell's visual responses. This nonspecific effect largely predominated in the complex cell family (76% of the units affected). This effect is consistent with the presence of long-range excitatory connections in the visual cortex.Second, the inactivation of area 17 could affect specific receptive-field properties of cells in area 18. The main specific effect was a loss of direction selectivity of a number of cells in area 18, mainly in the simple family (more than 53% of the units affected). The change in direction selectivity comes either from a disinhibitory effect in the nonpreferred direction or from a reduction of response in the preferred direction. It is proposed that the disinhibitory effects were mediated by inhibitory interneurones within area 18. In a very few cases, the change of directional preference was associated with a modification of the cell's response profile.These results showed that the signals from area 17 are necessary to drive a number of units in area 18, and that area 17 can contribute to, or at least modulate, the receptive-field properties of a large number of cells in the parastriate area.
The interstitial nucleus of the superior fasciculus, posterior bundle (INSFp) in the guinea pig: Another nucleus of the accessory optic system processing the vertical retinal slip signal
Authors: Benassi C. , Biral G. P. , Lui F. , Porro C. A. , Corazza R. 
Published: June 2009

AbstractAs in rabbit, gerbil, and rat, the guinea pig interstitial nucleus of the superior fasciculus, posterior bundle (INSFp) is a sparse assemblage of neurons scattered among the fibers forming the fasciculus bearing this name. Most of the INSFp neurons are small and are ovoid in shape. Interspersed among these, are a few larger, elongated neurons whose density becomes greater and whose shape becomes fusiform in correspondence to the zone of transition from the superior fasciculus to the ventral part of the medial terminal nucleus (MTN). Like the MTN, the INSFp is activated by retinal-slip signals evoked by whole-field visual patterns moving in the vertical direction, as shown by the increase of 14C-2-deoxyglucose (2DG) uptake into this nucleus. At the same level of luminous flux, neither pattern moving in the horizontal direction nor the same pattern held stationary can elicit increases in the INSFp 2DG assumption. The specificity of the observed increases in metabolic rates in INSFp following vertical whole-field motion suggests that this assemblage of neurons relays visual signals used in the control of vertical optokinetic nystagmus.
The amount of information transmitted about contrast by neurones in the cat's visual cortex
Authors: Tolhurst D. J. 
Published: June 2009

AbstractThe responses of neurones in the cat's visual cortex are very variable in amplitude. Thus, although the average response amplitude of a single neurone depends closely upon the contrast of a sinusoidal grating, the instantaneous amplitude of the response can convey little information about the grating's contrast. This paper shows that a typical cortical neurone can convey less than one bit of information about contrast in 0.5 s. The amount of information that a neurone can convey is closely correlated with the neurone's responsivity.
X- and Y-mediated synaptic potentials in neurons of areas 17 and 18 of cat visual cortex
Authors: Ferster David 
Published: June 2009

AbstractWhen a cuff-shaped electrode is placed on the optic nerve of the cat, X and Y axons, by virtue of their different diameters, exhibit different thresholds to electrical stimulation. Large-diameter Y axons have low thresholds, while smaller-diameter X axons have high thresholds. There is very little overlap between the two populations. Given this segregation, the strength of stimulation of the optic nerve required to evoke synaptic potentials in cortical neurons becomes a reliable indicator of the type of visual input a cortical neuron receives. Potentials with thresholds below the thresholds of X axons must be mediated by Y cells of the retina and LGN. Potentials with thresholds above the Y axons of the optic nerve must be mediated by X cells. From previous experiments, one would expect ot find &amp;le input via both types of axon to are 17 of the visual cortex. This was not the case. Of 58 neurons distributed throughout the layers of area 17 from which intracellular records were taken, in only four could substantial Y excitation be detected. Three of these four were located near the border with area 18. All four received large X inputs as well. The 24 neurons studied in area 18 all received large Y inputs but no detectable X input.
Development of morphological types and distribution patterns of amacrine cells immunoreactive to tyrosine hydroxylase in the cat retina
Authors: Wang Hou-Hua , Cuenca Nicolas , Kolb Helga 
Published: June 2009

AbstractUsing an antibody against tyrosine hydroxylase on newborn to 30-day kitten retinas, we have been able to follow the development of the dopaminergic amacrine cells of the cat retina by light-microscopical investigations of retinal wholemounts. The Type 1 or large Toh+ amacrine cells described by others (Oyster et al., 1985; Törk &amp; Stone, 1979) and named A18 from a Golgi study (Kolb et al., 1981), is at birth (P1) an immature neuron with a small cell body and two or three simple thick radiating dendrites stratifying in stratum 1 with many of the dendrites ending in enlarged growth cones. With increasing postnatal age, the cell body size increases from 12.5 μm diameter to reach 15.5 μm diameter at P30. The dendritic fields also increase in size and complexity. At P1, cells of the central area exhibit dendritic appendages which then develop progressively until at P13 (after eye opening) they are part of rudimentary rings and by P30 the dendritic plexus of Toh+ dendrites and rings in stratum 1, typical of the adult cells, are complete. Toh+ stained processes with growth cones that run deep in stratum 5 of the inner plexiform layer and processes passing to the outer plexiform layer first become apparent at P1 in cells of central inferior retina but not till after P13 are these processes clearly expressed. At P1, the total number of Toh+ Type 1 cells is approximately 4000 and this number remains unchanged to the adult retina. However, the retina increases in size over the Pl–P30 stage and thus the mean density of Type 1 Toh+ cells decreases from 30/mm2at P1 to 18/mm2at P30. The maximum density of Type 1 Toh+ cells occurs in central retina 2–4 mm superior temporal to the area centralis, corresponding to the maximum rod photoreceptor concentration.A second type of small Toh+ amacrine cell can be visualized at P1. This Type 2 cell is characterized by a much smaller cell body than Type 1 cells (9 μm diameter), and with faintly stained dendrites located in stratum 3 of the inner plexiform layer. During later postnatal days, Type 2 cells gradually become unstainable and only few are still seen in far peripheral retina by P23. Type 2 Toh+ cells form a total population of 40,000 cells at P1 with their highest density occurring in peripheral retina. By P13, they cannot be seen in central retina and are reduced to a total population of cells staining for the antibody of 7400 cells in far peripheral retina. Their density decreases from 233/mm2at P1 to 0/mm2at P30. The transiently staining population of Type 2 Toh+ immunoreactive cells probably correspond to the small THI-CA-cell seen in rat retina (Nguyen–Legros et al., 1983), and the second type of dopaminergic amacrine cell seen in macaque retina (Mariani &amp; Hokoc, 1988).
Cholera toxin mapping of retinal projections in pigeons (Columba livia), with emphasis on retinohypothalamic connections
Authors: Shimizu Toru , Cox Kevin , Karten Harvey J. , Britto Luiz R. G. 
Published: June 2009

AbstractAnterograde transport of cholera toxin subunit B (CTb) was used to study the retinal projections in birds, with an emphasis on retinohypothalamic connections. Pigeons (Columba livia) were deeply anesthetized and received unilateral intraocular injections of CTb. In addition to known contralateral retinorecipient regions, CTb-immunoreactive fibers and presumptive terminals were found in several ipsilateral regions, such as the nucleus of the basal optic root, ventral lateral geniculate nucleus, intergeniculate leaflet, nucleus lateralis anterior, area pretectalis, and nucleus pretectalis diffusus. In the hypothalamus, CTb-immunoreactive fibers were observed in at least two contralateral cell groups, a medial hypothalamic retinorecipient nucleus, and a lateral hypothalamic retinorecipient nucleus. To compare retinorecipient hypothalamic nuclei in pigeons with the mammalian suprachiasmatic nucleus, double-label experiments were conducted to study the existence of neurophysin-like immunoreactivity in the retinorecipient avian hypothalamus. The results showed that only cell bodies in the medial hypothalamic nucleus contained neurophysin-like immunoreactivity. The results demonstrate CTb to be a sensitive anterograde tracer and provide further anatomical information on the avian equivalent of the mammalian suprachiasmatic nucleus.
Does early enucleation affect the decussation pattern of alpha cells in the ferret?
Authors: Reese Benjamin E. , Urich Janal L. 
Published: June 2009

AbstractNaturally occurring cell death has been hypothesized to sculpt various features of the organization of the mature visual pathways, including the recent proposal that the selective elimination of ganglion cells in the temporal retina shapes the formation of decussation patterns. Through a class-specific interocular competition, ganglion cells in the two temporal hemiretinae are selectively lost to produce the decussation patterns characteristic of each individual cell class (Leventhal et al., 1988). The present study has tested this hypothesis by asking whether the removal of one retina in newborn ferrets, which should disrupt binocular interactions at the level of the terminals, alters the decussation pattern of the alpha cells, a cell class that is entirely decussating in the normal adult ferret. Enucleation on the day of birth was found to increase the uncrossed projection by ≈50%, but not a single uncrossed alpha cell was found in the temporal retina. Either alpha cells never project ipsilaterally during development, or if they do, they cannot be rescued by early enucleation. While naturally occurring cell death plays many roles during development, creating the decussation pattern of the ferreth's alpha cell class via a binocular competition at the level of the targets is unlikely to be one of them.
Chromatic properties of neurons in macaque MT
Authors: Gegenfurtner Karl R. , Kiper Daniel C. , Beusmans Jack M. H. , Carandini Matteo , Zaidi Qasim , Movshon J. Anthony 
Published: June 2009

AbstractWe have studied the responses of MT neurons to moving gratings, spatially modulated in luminance and chromaticity. Most MT neurons responded briskly and with high contrast sensitivity to targets whose luminance was modulated, with or without added chromatic contrast. When luminance modulation was removed and only chromatic stimulation was used, the responses of all MT neurons were attenuated. Most were completely unresponsive to stimulation with targets whose modulation fell within a “null” plane in color space; these null planes varied from neuron to neuron, but all lay close to the plane of constant photometric luminance. For about a third of the neurons, there was no color direction in which responses were completely abolished; almost all of these neurons had a definite minimum response for chromatic modulation near the isoluminant plane. MT neurons that responded to isoluminant targets did so inconsistently and with poor contrast sensitivity, so that only intensely modulated targets were effective. Whereas the best thresholds of MT neurons for luminance targets are close to behavioral contrast threshold, the thresholds for isoluminant targets lie considerably above behavioral contrast threshold. Therefore, although some MT neurons do give responses to isoluminant targets, they are unlikely to be the source of the chromatic motion signals revealed behaviorally.
Distribution and coverage of A- and B-type horizontal cells stained with Neurobiotin in the rabbit retina
Authors: Mills Stephen L. , Massey Stephen C. 
Published: June 2009

AbstractBoth A- and B-type horizontal cells in the rabbit retina were labeled by brief in vitro incubations of the isolated retina in the blue fluorescent dye 4,6–diamino-2–phenylindole. Intracellular injection of Lucifer Yellow into the somata revealed the morphology of the individual cells. Dye-coupling with Lucifer Yellow was seen only between A-type horizontal cells. By contrast, injection of the tracer Neurobiotin showed dye-coupling between both A- and B-type horizontal cells. There also appeared to be coupling between the axon terminals of B-type horizontal cells.The extensive dye-coupling seen following injection of Neurobiotin into a single horizontal cell soma can be used to obtain population counts of each cell type. Staining of large numbers of each cell type across the retina showed that each type increased in number and declined in dendritic diameter as the visual streak was approached, such that relatively constant coverage across the retina was maintained. In the visual streak, A-type horizontal cells numbered 555 cells/mm2 and averaged 120 μm in diameter, compared to 1375 cells/mm2 and 100 μm for B-type horizontal cells. In the periphery, the A- and B-types numbered 250 cells/mm2 and 400 cells/mm2, respectively. The average diameters of the dendritic trees at these locations were 225 μm for the A-type and 175 μm for the B-type. Coverage across the retina averaged almost six for A-type horizontal cells and 8–10 for the B-type. A-type horizontal cells in the visual streak whose elliptical dendritic fields were shown by Bloomfield (1992) to correlate physiologically with orientation bias were shown to be dye-coupled to cells with symmetrical dendritic fields.
Similar properties of cGMP-activated channels between cones and rods in the carp retina
Authors: Watanabe Shu-Ichi , Murakami Motohiki 
Published: June 2009

AbstractUsing patch-clamp techniques, properties of cGMP-activated channel were studied at a single-channel level in order to examine (1) whether any differences are recognized between the cGMP-activated channels of rods and cones in the same animal species, and (2) whether the channel properties of the same photoreceptor class differ in different animal species. Experiments were performed on inside-out membrane patches excised from outer segments of rods and morphological subtypes of cones in the carp retina. Single-channel activities could be recorded when the patches were perfused with low concentrations of cGMP (<10 μM). Throughout five morphological subtypes of cones and rod, single-channel currents showed no significant rectification at membrane hyperpolarization in a low divalent cation solution, and single-channel conductances were almost the same: 13.8 ± 0.2 pS (mean ± s.e.m., n = 23) in cones and 12.7 ± 0.8 pS (n = 3) in rods. These values were significantly smaller than that reported in catfish cones (about 50 pS), and that in rods of the toad and the tiger salamander (about 25 pS). In rods and all subtypes of cones of the carp, open durations of cGMP activated channels were brief. In addition, kinetic parameters of channel openings and closings showed no differences throughout all subtypes of cones and rod.
Experimental stray light in retinal densitometry
Authors: Baker Howard D. , Watson Adieren J. , Coile D. Caroline 
Published: June 2009

AbstractThe effects of stray light upon retinal pigment densitometric measurements were evaluated by adding specified amounts of stray light to fundus reflections. To allow for interpolations and extrapolations, a computer simulation was devised and validated against the empirical data. The results demonstrate that measured density is greatly decreased by increases in stray light but the time constant of pigment regeneration is little affected.
A physiological model of binocular rivalry
Authors: Mueller T. J. 
Published: June 2009

AbstractThis paper presents a modified reciprocal inhibition model for the temporal dynamics of binocular rivalry. The model is based on neurophysiological mechanisms and is derived from human psychophysical data. A simple reciprocal inhibition oscillator may be described with a set of four coupled differential equations with a neurophysiological interpretation. However, such a circuit does not account for some aspects of the temporal behavior of binocular rivalry, including the effects of contrast change on alternation rate and on the magnitudes of changes in duration of the suppressed and dominant phases. To better account for these phenomena, the equations and their simulation are modified to include three new components: (1) presynaptic inhibition of the reciprocal inhibition by the input, (2) the motor delays that occur when a human observer tracks rivalry and (3) a minimum threshold for each neuron's state variable. The result is a much improved fit to psychophysically-obtained data on the temporal behavior of binocular rivalry. Finally, the model is incorporated into a larger model to suggest how rivalry might occur in a network that usually exhibits binocular fusion.