bluuebunny/crossref_metadata_2025_split huggingface dataset:
Contrast gain control in the primate retina: P cells are not X-like, some M cells are
Authors: Benardete Ethan A. , Kaplan Ehud , Knight Bruce W. 
Published: June 2009

AbstractPrimate retinal ganglion cells that project to the magnocellular layers of the lateral geniculate nucleus (M) are much more sensitive to luminance contrast than those ganglion cells projecting to the parvocellular layers (P). We now report that increasing contrast modifies the temporal-frequency response of M cells, but not of P cells. With rising contrast, the M cells' responses to sinusoidal stimuli show an increasing attenuation at low temporal frequencies while the P cells' responses scale uniformly. The characteristic features of M-cell dynamics are well described by a model originally developed for the X and Y cells of the cat, where the hypothesized nonlinear feedback mechanism responsible for this behavior has been termed the contrast gain control (Shapley & Victor, 1978, 1981; Victor, 1987, 1988). These data provide further physiological evidence that the M-cell pathway differs from the P-cell pathway with regard to the functional elements in the retina. Furthermore, the similarity in dynamics between primate M cells and cat X and Y retinal ganglion cells suggests the possibility that P cells, being different from either group, are a primate specialization not found in the retinae of lower mammals.
Light-sensitive melatonin synthesis by Xenopus photoreceptors after destruction of the inner retina
Authors: Cahill Gregory M. , Besharse Joseph C. 
Published: June 2009

AbstractSeveral lines of evidence indicate that retinal photoreceptors produce melatonin. However, there are other potential melatonin sources in the retina, and melatonin synthesis can be regulated by feedback from the inner retina. To analyze cellular mechanisms of melatonin regulation in retinal photoreceptors, we have developed an in vitro method for destruction of the inner retina that preserves functional photoreceptors in contact with the pigment epithelium. Eyecups, which include the neural retina, retinal pigment epithelium, choroid, and sclera were prepared. The vitreal surface of the retina in each eyecup was washed sequentially with 1% Triton X-100, water, and culture medium. This lysed the ganglion cells and neurons and glia of the inner nuclear layer, causing the retina to split apart within the inner nuclear layer. The damaged inner retina was peeled away, leaving photoreceptors attached to the pigment epithelium. The cell density of the inner nuclear layer was reduced 94% by this method, but there was little apparent damage to the photoreceptors. Lesioned eyecups produced normal melatonin levels in darkness at night, and melatonin production was inhibited by light. These results indicate that the inner retina is not necessary for melatonin production nor for regulation of photoreceptor melatonin synthesis by light. The lesion method used in this study may be useful for other physiological and biochemical studies of photoreceptors.
Retinoids in the lateral eye of Limulus: Evidence for a retinal photoisomerase
Authors: Smith W. Clay , Friedman Matthew A. , Goldsmith Timothy H. 
Published: June 2009

AbstractThe lateral eyes of the horseshoe crab Limulus contain about 80 pmoles of retinal, 30 pmoles of retinol, and 4 pmoles of retinyl esters. More all-trans than 11-cis isomer was found in each category of retinoid. No consistent changes were observed in the amounts of retinal, retinol, or retinyl esters as a function of time of day. No 3,4-dehydro- nor hydroxyretinoids were found.Aqueous extracts of the eye support the stereospecific formation of 11 -cis retinal from a11-trans retinal when irradiated with light. The reaction requires a protein that is apparently recognized by polyclonal antibodies raised against the retinal photoisomerase extracted from honeybee eyes. The isomerase is able to use as substrate either endogenous all-trans retinal in the extract or retinal supplied in vesicles of phospholipid. The spectral efficiency of this isomerization has λmax at 550 nm, but the spectrum appears too narrow compared with the absorbance spectrum of retinoid-binding proteins, probably because of inadequate correction for nonspecific isomerization at short wavelengths.
Synchronization of oscillatory neuronal responses in cat striate cortex: Temporal properties
Authors: Gray Charles M. , Engel Andreas K. , König Peter , Singer Wolf 
Published: June 2009

AbstractPreviously, we have demonstrated that a subpopulation of visual cortical neurons exhibit oscillatory responses to their preferred stimuli at a frequency near 50 Hz (Gray & Singer, 1989). These responses can selectively synchronize over large distances of cortex in a stimulus-specific manner (Gray et al., 1989; Engel et al., 1990a). Here we report the results of a new analysis which reveals the fine temporal structure inherent in these interactions. We utilized pairs of recordings of the local field potential (LFP) activity from area 17 in the anesthetized cat which met two criteria. The LFP was correlated with the underlying unit activity at each site and the recording sites were at least 5 mm apart in cortex. A moving-window technique was applied to compute cross correlograms on 100-ms epochs of data repeated at intervals of 30 ms for a period of 3 s during each direction of stimulus movement. A statistical test was devised to determine the significance of detected correlations. In this way we were able to determine the magnitude, phase difference, frequency, and duration of correlated oscillations as a function of time. The results demonstrate that (1) the duration of synchrony is variable and lasts from 100–900 ms; (2) the phase differences between and the frequencies of synchronized responses are also variable within and between events and range from +3 to —3 ms and 40–60 Hz, respectively; and (3) multiple correlation events often occur within a single stimulus period. These results demonstrate a high degree of dynamic variability and a rapid onset and offset of synchrony among interacting populations of neurons which is consistent with the requirements of a mechanism for feature integration.
Changes in sensitivity of the dark-adapted eye during concurrent light adaptation of the other eye
Authors: Auerbach E. , Dörrenhaus A. , Cavonius C. R. 
Published: June 2009

AbstractThresholds for detection of light by a dark-adapted test eye were measured while the other, non-test eye was either similarly dark adapted or while it was exposed to an intense red adapting field. An interocular effect that depends on the retinal location of the test was found: compared to the threshold during binocular dark adaptation, sensitivity decreased during contralateral light adaptation when the test was presented to the foveola and up to 4 deg above it; but sensitivity increased when the test was between 7 and 12 deg, showing a reversal at 5 deg.
Colocalization of vasoactive intestinal polypeptide and GABA immunoreactivities in a population of wide-field amacrine cells in the rabbit retina
Authors: Casini Giovanni , Brecha Nicholas C. 
Published: June 2009

AbstractVasoactive intestinal polypeptide (VIP) immunoreactive (IR) neurons in the rabbit retina constitute a population of wide-field amacrine cells. To better define this cell population, we examined the coexpression of VIP with other putative retinal transmitters or their biosynthetic enzymes, including γ-aminobutyric acid (GABA), tyrosine hydroxylase (TH), and somatostatin (SRIF). Colchicine-treated retinas were immersion fixed in 4% paraformaldehyde. The retinas were cut either perpendicular or parallel to the vitreal surface and processed by double-label immunofluorescence techniques using antibodies directed to VIP, GABA, TH, and SRIF. The immunoreactive staining patterns obtained with these antibodies were the same as those described in previous studies. GABA-IR neurons were localized to the proximal inner nuclear layer (INL) and ganglion cell layer (GCL) and processes were distributed throughout the inner plexiform layer (IPL). TH- and SR1F-IR neurons were sparsely distributed to the proximal INL and GCL, respectively. TH-IR processes ramified in laminae 1, 3, and 5, and SRIF-1R processes in laminae 1 and 5 of the IPL. Colocalization experiments showed that all VIP-IR neurons contain GABA immunoreactivity. In contrast, colocalization of VIP and TH or SRIF immunoreactivities was never observed. These results demonstrate that VIP-IR wide-field amacrines of the rabbit retina make up a neurochemically and morphologically distinct subpopulation of the GABA-IR amacrine cell population. Furthermore, VIP-IR amacrine cells constitute a distinct group with respect to the TH- and SRIF-IR amacrine cells.
Cycle GMP-activated channels of rod photoreceptors show neither fast nor slow desensitization
Authors: Watanabe Shu-Ichi , Matthews Gary 
Published: June 2009

AbstractDesensitization of cGMP-activated channels was examined in excised, inside-out patches obtained from rod photoreceptors. Cyclic GMP was applied using a rapid-flow system in which concentration jumps are complete within 10–50 ms. In outer-segment patches containing many channels, the cGMP-dependent conductance reached a steady plateau that was maintained for tens of seconds in the presence of cGMP; thus, there was no indication of slow desensitization. However, rapid desensitization on the scale of milliseconds could not be ruled out because of limited speed of access of cGMP to the inner face of the patch membrane. To test for rapid desensitization, inner-segment patches containing only a single cGMP-activated channel were used. In these one-channel patches, there was no change in activity of the channel with time from its earliest onset after application of cGMP, indicating that rapid desensitization also did not occur.
Disparity-tuned channels of the human visual system
Authors: Cormack Lawrence K. , Stevenson Scott B. , Schor Clifton M. 
Published: June 2009

AbstractTraditionally, it has been thought that the processing of binocular disparity for the perception of stereoscopic depth is accomplished via three types of disparity-selective channels – “near,” “far,” and “tuned.” More recent evidence challenges this notion. We have derived disparity-tuning functions psychophysically using a subthreshold summation (i.e. low-level masking) technique. We measured correlation-detection thresholds for dynamic random-element stereograms containing either one or two surfaces in depth. The resulting disparity-tuning functions show an opponent-type profile, indicating the presence of inhibition between disparity-tuned units in the visual system. Moreover, there is clear inhibition between disparities of the same sign, obviating a strict adherence to near-far opponency. These results compare favorably with tuning functions derived psychophysically using an adaptation technique, and with the tuning profiles from published single-unit recordings. Our results suggests a continuum of overlapping disparity-tuned channels, which is consistent with recent physiological evidence as well as models based on other psychophysical data.
Photoreceptor cells dissociated from the compound lateral eye of the horseshoe crab, Limulus polyphemus, I: Structure and ultrastructure
Authors: Jinks Robert N. , Hanna W. J. Brad , Renninger George H. , Chamberlain Steven C. 
Published: June 2009

AbstractIsolated photoreceptors are desirable for whole-cell and patch-clamp studies of functional properties of visual processes that cannot be clearly analyzed when the photoreceptors are coupled. The retina of the compound lateral eye of the horseshoe crab, Limulus polyphemus, was dissociated into individual retinular cells using an enzyme pretreatment consisting of collagenase, papain, and trypsin, and a two-stage mechanical dissociation. These photoreceptors are functionally viable in an organ culture medium for up to 1 week and possess naked arhabdomeral and rhabdomeral segment membranes which are easily accessible for whole-cell recordings. A dissection technique was also developed whereby the retinal epidermis and neural plexus, as well as the second-order eccentric cells, could be separated from the ommatidia of the compound lateral eye in one simple step, providing viable isolated ommatidia attached to the cornea. The enzyme pretreatment used for dissociating the retina was then used to remove the individual ommatidia from the corneal cones.Hoffman modulation contrast microscopy was used to develop a reliable method for sorting and collecting viable isolated retinular cells for morphological and electrophysiological studies. Morphological analysis using light microscopy and scanning and transmission electron microscopy revealed that isolated retinular cells are morphologically nearly identical to retinular cells in situ. Isolated retinular cells possess a normal rhabdomere with no apparent loss of microvillar membrane as a result of the isolation process. Ommatidia can presently be isolated with up to six retinular cells possessing essentially normal structure and ultrastructure including thick rays of rhabdom. Isolated ommatidia possess naked A-segment membranes which are also well suited for whole-cell recording techniques.
Survival of ganglion cells which form the retino-retinal projection during optic nerve regeneration in the frog
Authors: Tennant M. , Bruce S. R. , Beazley L. D. 
Published: June 2009

AbstractDuring optic nerve regeneration in the frog, axons transiently grow along the opposite optic nerve forming a retino-retinal projection. In the present study, we crushed the left optic nerve in the frogLitoria (Hyla) mooreiand later applied horseradish peroxidase (HRP) or diamidino yellow (DY) to the right optic nerve. In one series, retinae were examined 3 days after application of the tracer. The retino-retinal projection was found to be maximal at 5 weeks, fell significantly by 7 weeks, and returned to close-to-normal levels by 24 weeks. In a second series, we applied DY at 5 weeks as before but did not sacrifice the frogs until 7 weeks. Numbers of labeled ganglion cells were not significantly different from those frogs in the first series labeled and examined at 5 weeks. We conclude that ganglion cells giving rise to the retino-retinal projection had not died in appreciable numbers, presumably being sustained by collateral axons in the brain.
Light-evoked changes in near-infrared transmission by the ON and OFF channels of the anuran retina
Authors: Dawis Stevan M. , Rossetto Michelangelo 
Published: June 2009

AbstractWe have developed an optical method to monitor the activity of the ON and OFF channels in the anuran retina. The change in the fraction of near infrared that is transmitted transversely through the retina in an eyecup slice is monitored during stimulation by visible, green light. Near-infrared transmission increases both at the onset and at the termination of a step stimulus. This “ON/OFF” response is maximal in the neural retina. Sodium L-aspartate, which blocks the light-evoked activity of post-photoreceptor neurons, abolishes the “ON/OFF” response. L-AP4, used as a selective blocker of the ON channel, reduces the “ON” component and has little or no effect on the “OFF” component. The “ON” and “OFF” processes observed optically are distinct from those that generate the b– and d–waves of the electroretinogram, and the “ON” and “OFF” components may be superior to the b– and d–waves as indicators of ON and OFF channel activity. The optical method is almost as simple as electroretinography and has the advantage that responses can be spatially localized with ease.
Reduction of a pattern-induced motion aftereffect by binocular rivalry suggests the involvement of extrastriate mechanisms
Authors: Van Der Zwan Rick , Wenderoth Peter , Alais David 
Published: June 2009

AbstractPrevious research suggests that plaid-induced motion aftereffects (MAEs) involve extrastriate mechanisms (Wenderoth et al., 1988). There is evidence also that binocular rivalry occurs beyond VI and that it disrupts the processing of MAEs which are believed to be based upon extrastriate mechanisms (e.g. the spiral MAE) but not MAEs, such as linear MAE induced by a drifting grating, which are thought to arise in striate cortex (Wiesenfelder & Blake, 1990). The logical inference is that binocular rivalry during drifting plaid-induced adaptation should reduce the MAEs which result. We report experiments which confirm this prediction.
Comparison of the responses to light and to GABA of cells postsynaptic to barnacle photoreceptors (I-cells)
Authors: Callaway Joseph C. , Stuart Ann E. 
Published: June 2009

AbstractWe tested the hypothesis that gamma-aminobutyric acid (GABA) is the transmitter released by barnacle photoreceptors onto postsynaptic cells (I-cells). GABA was applied to I-cells either by superfusion or by ejecting it with pressure from a pipette positioned close to the I-cell's soma. The I-cell's response to GABA was compared with its response to light (i.e. to the photoreceptors' transmitter) by recording intracellularly from its soma. Bath-applied (100 µm to 10 mM) and pressure-applied GABA (10 mM in pipette) hyperpolarizes I-cells by increasing their conductance, as does the photoreceptors' transmitter. The response to pressure-applied GABA consists of two components; both persist when Co2+ or Cd2+ are added to the saline to block synaptic transmission in the preparation, indicating that GABA affects the I-cell directly rather than affecting a presynaptic cell. GABA hyperpolarizes the I-cell when applied to the cell over the soma and ipsilateral arbor or over the contralateral arbor. The I-cells' responses to GABA and to light both depend on extracellular K+ and are affected by changes in intracellular and extracellular Cl−. However, picrotoxin and β-guanidinopropionic acid block the response to pressure-applied GABA but do not block the response to light even at an order of magnitude higher concentration. Thus, GABA is not likely to be the transmitter that causes the hyperpolarizing response of the I-cell. It may be a neuromodulator or the transmitter of an unknown input to the I-cell.
Retinal projections in quail (Coturnix coturnix)
Authors: Norren Robert B. , Silver Rae 
Published: June 2009

AbstractThe trajectory of retinal projections and the location of retinorecipient nuclei in the quail brain was examined after application of horseradish peroxidase (HRP) either to the cut end of the optic nerve or following intraocular injection of HRP. Retinal projections to the hypothalamus, dorsalateral anterior thalamus (rostralateral part, magnocellular part, and lateral part), lateral anterior thalamus, lateroventral geniculate nucleus, lateral geniculate intercalated nuclei (rostral and caudal parts), ventrolateral thalamus, superficial synencephalic nucleus, external nucleus, tectal gray, diffuse pretectal area, pretectal optic area, ectomammillary nucleus, and optic tectum were revealed. Retinal projections observed in quail were compared with results obtained in other avian species and considered in relation to possible anatomic pathways underlying photoperiodism and circadian rhythms.
Retinogeniculate EPSPs recorded intracellularly in the ferret lateral geniculate nucleus in vitro: Role of NMDA receptors
Authors: Esguerra Manuel , Kwon Young H. , Sur Mriganka 
Published: June 2009

AbstractWe used an in vitro preparation of the ferret lateral geniculate nucleus (LGN) to examine the role of the NMDA class of excitatory amino acid (EAA) receptors in retinogeniculate transmission. Intracellular recordings revealed that blockade of NMDA receptors both shortened the time course and reduced the amplitude of fast and slow components of excitatory postsynaptic potentials (EPSPs) evoked by optic tract stimulation. The amplitude and width of the EPSPs mediated by NMDA receptors increased as membrane potential was depolarized towards spike threshold. Individual LGN cells were influenced to varying extents by blockade of NMDA receptors; NMDA and non-NMDA receptor blockade together attenuated severely the entire retinogeniculate EPSP. The dependence of all components of retinogeniculate EPSPs (and action potentials) on NMDA receptor activation supports the hypothesis that the NMDA receptor participates in fast (<10 ms) synaptic events underlying conventional retinogeniculate transmission. The voltage dependence of the NMDA receptor-gated conductance suggests strongly that the transmission of retinal information through the LGN is subject to modulation by extraretinal inputs that affect the membrane potential of LGN neurons.
Binocular interactions in the cat's dorsal lateral geniculate nucleus, II: Effects on dominant-eye spatial-frequency and contrast processing
Authors: Tong Lillian , Guido William , Tumosa Nina , Spear Peter D. , Heidenreich Susan 
Published: June 2009

AbstractThe present study tested the hypothesis that nondominant-eye influences on lateral geniculate nucleus (LGN) neurons affect the processing of spatial and contrast information from the dominant eye. To do this, we determined the effects of stimulating the nondominant eye at its optimal spatial frequency on the responses of LGN cells to sine-wave gratings of different spatial frequency and contrast presented to the dominant eye. Detailed testing was carried out on 49 cells that had statistically significant responses to stimulation of the nondominant eye alone.Spatial-frequency response functions to nondominant-eye stimulation indicated that the responses were spatially tuned, as reported previously (Guido et al., 1989). Optimal spatial frequencies through the nondominant eye were significantly correlated with the optimal spatial frequencies through the dominant eye (r = 0.54; P < 0.0001), and the optimal spatial frequencies were fairly similar for the two eyes.Nondominant-eye stimulation changed the maximal amplitude of the fundamental (Fl) response to dominant-eye stimulation for only about 45% (22 of 49) of the cells that responded to nondominant-eye stimulation alone. The response vs. contrast function through the dominant eye was altered for 73% of the cells (51% independent of spatial frequency). Three types of effects were observed: a change in the initial slope of the response vs. contrast function (contrast gain), a change in the response amplitude at which saturation occurred, or an overall change in response at all contrasts. The incidence of these changes was similar for X and Y cells in LGN layers A, Al, and C (only four W cells were tested).Nondominant-eye stimulation had little or no effect on the sizes or sensitivities of the receptive-field centers or surrounds for the dominant eye. In addition, nondominant-eye stimulation had little or no effect on optimal spatial frequency, spatial resolution, or the bandwidth of spatial-frequency contrast sensitivity curves for the dominant eye.Possible functions of binocular interactions in the LGN are considered. The present results suggest a role in interocular contrast-gain control. Interocular contrast differences can occur before the acquisition of binocular fusion, when the two eyes are viewing different aspects of a visual stimulus. Psychophysical and physiological studies suggest that an interocular mechanism exists to maintain relatively constant binocular interactions despite differences in interocular contrast. The present results suggest that at least part of this mechanism occurs in the LGN.