bluuebunny/crossref_metadata_2025_split huggingface dataset:
Area 17 lesions deactivate area MT in owl monkeys
Authors: Kaas Jon H. , Krubitzer Leah A. 
Published: June 2009

AbstractThe middle temporal visual area, MT, is one of three major targets of the primary visual cortex, area 17, in primates. We assessed the contribution of area 17 connections to the responsiveness of area MT neurons to visual stimuli by first mapping the representation of the visual hemifield in MT of anesthetized owl monkeys with microelectrodes, ablating an electrophysiologically mapped part of area 17, and then immediately remapping MT. Before the lesions, neurons at recording sites throughout MT responded vigorously to moving slits of light and other visual stimuli. In addition, the relationship of receptive fields to recording sites revealed a systematic representation of the contralateral visual hemifield in MT, as reported previously for owl monkeys and other primates. The immediate effect of removing part of the retinotopic map in area 17 by gentle aspiration was to selectively deactivate the corresponding part of the visuotopic map in MT. Lesions of dorsomedial area 17 representing central and paracentral vision of the lower visual quadrant deactivated neurons in caudomedial MT formerly having receptive fields in the central and paracentral lower visual quadrant. Most neurons at recording sites throughout other parts of MT had normal levels of responsiveness to visual stimuli, and receptive-field locations that closely matched those before the lesion. However, neurons at a few sites along the margin of the deactivated zone of cortex had receptive fields that were slightly displaced from the region of vision affected by the lesion into other parts of the visual field, suggesting some degree of plasticity in the visual hemifield representation in MT. Subsequent histological examination of cortex confirmed that the lesions were confined to area 17 and the recordings were in MT. The results indicate that the visually evoked activity of neurons in MT of owl monkeys is highly dependent on inputs relayed directly or indirectly from area 17.
Neuronal basis for parallel visual processing in the fly
Authors: Strausfeld Nicholas J. , Lee Jong-Kyoo 
Published: June 2009

AbstractBehavioral and electrophysiological studies of insects demonstrate both spectrally independent and chromatically dependent behaviors and interneurons. This account describes the neuroanatomical identification of two parallel retinotopic subsystems, one supplying descending channels to spectrally independent neck and flight motor circuits, the other supplying polychromatic channels to neuropils associated with leg motor circuits in the thoracic ganglia. In the compound eye, two classes of photoreceptors contribute to each of several thousand sampling units. High-sensitivity, chromatically uniform short-axon photoreceptors (R1-R6) supply the lamina's external plexiform layer and are presynaptic to L1, L2 efferents. These project in parallel with a second system of trichromatic long-axon receptors and the L3 efferent. Both pathways supply columns of the medulla, equal in number to ommatidia. Golgi and cobalt-silver impregnation demonstrates that neurons from the medulla diverge to two deeper regions, the lobula plate and lobula, the former a thin tectum of neuropil dorsal to the more substantial lobula. Layer relationships between medulla neurons and their afferent supply suggest that the lobula plate and lobula are each supplied by one or the other, but not both, of the two parallel subsystems. Independence of the two parallel pathways is suggested by ablation of the photoreceptor layer leading to selective degeneration of the motion-sensitive lobula plate neuropil. In addition, octets of small-field neurons associated with the R1-R6/L1, L2 pathway give rise to synaptic complexes with motion-sensitive neurons of the lobula plate. A variety of behavioral and electrophysiological studies provide supporting evidence that certain insects possess parallel visual pathways comparable to the magnocellular and parvocellular subsystems of primates.
Induction of retinal degeneration in a crab by light and okadaic acidin vitro: Comparison with theDrosophilalight-dependent retinal degeneration mutantw rdgBKS222
Authors: Blest A. D. , Carter M. , Clausen J. A. , Stowe S. , Trowell S. C. , Tsukitani Y. 
Published: June 2009

AbstractRetinae of the crabLeptograpsuswhich had been maintained on a 12-h light/12-h dark cycle were culturedin vitroand exposed to 1 μM okadaic acid (OKA) at 0.75 h before light onset. Control retinae were subjected to the same routine and sampled at the same times without OKA treatment. At the concentration used, OKA totally inhibits types 1 and 2A protein phosphatases, minimally inhibits type 2B, and does not affect type 2C. 1 μM OKA provoked a diminution of rhabdom diameter measured at the level of the photoreceptor nuclei in the dark, some ommatidial cartridges being stripped of rhabdomeral microvilli altogether. After 1-h illumination (225–320 lux), further reduction of rhabdom diameter was modest in control retinae but precipitate in those treated with OKA. After 2 h, control rhabdom diameters showed a further, not significant, decline, but OKA had induced a resynthesis of massive structures with the light-microscopic appearance of rhabdoms. Electron microscopy revealed that they were heterogeneous and of the following kinds: (1) a minority of rhabdoms with normally disposed but distorted microvilli; (2) rhabdoms in the throes of events that parody normal assembly; and (3) rhabdomal volumes occupied by saccular organelles or by pleats or ruffles of irregular architecture. The cytoplasm of all such receptors was packed with free and bound ribosomes and endomembranes. The sequence of events parallels that seen during light-induced degeneration of photoreceptors of theDrosophilamutantw rdgBKS222. Preliminary experiments show that a protein kinase activator SC-9 mimics many of these effects in the dark in the presence of 1 μM OKA. As a working hypothesis, it is proposed that light activates protein kinasesviadiacylglycerols generated by the phototransduction cascade, and that in both crab retinas challenged with OKA and retinas ofrdgBKS222activation of a nuclear regulatory protein by hyperphosphorylation provokes a runaway transcription whose selectivity and extent remain to be determined.
Anatomical pathways for color vision in the human retina
Authors: Kolb Helga 
Published: June 2009

AbstractThe major neurons and neural circuits that are involved in the transmission of color signals through the human retina to produce the color and spatially opponent P cell or midget ganglion cell responses are described. The older findings of single cone to midget bipolar connectivity is reviewed, and the single midget bipolar cell to midget ganglion cell connectivity as revealed by a recent serial section electron microscope study is described in detail. Our present knowledge concerning the discrimination of the blue-cone subtype from the other longer wavelength cones in the human at the outer plexiform layer is summarized, and our most recent findings concerning horizontal cell connectivity to the different spectral types of cones are discussed. Finally, a hypothetical pathway is proposed for color-opponent surrounds of midget ganglion cells using both horizontal cells at the outer plexiform layer and amacrine cell pathways at the inner plexiform layer.
Red-green interactions in the spectral sensitivity of primates as derived from ERG and behavioral data
Authors: Sperling Harry G. , Mills Stephen L. 
Published: June 2009

AbstractDifferent techniques were used to manipulate the inhibitory interaction between the red and green photoreceptors (R and G cones) of rhesus and human primates. The response techniques that were used were the corneal electroretinogram (ERG) and psychophysical increment-threshold spectral sensitivity functions. Red-green opponency, as measured by the depth of the notch at 580 nm, is removed by intravitreal injection of bicuculline but not by strychnine. Therefore, red-green opponency is mediated by GABA and not glycine. The depth of the notch is dependent upon stimulus size. Between 30' and 15' test light diameters, this sign of red-green opponency disappears. Psychophysical increment thresholds are shown to produce the notch while decrements do not and intravitreal APB is shown to reduce the notch, evidence that red-green opponency is carried by the “ON” and not the “OFF” bipolar pathways of the retina. Red and green annuli are shown to selectively reduce red and green inhibition, as though there were selective reduction of the surround response in center-surround organized red-green receptive fields.
Retinal neuromodulation: The role of dopamine
Authors: Dowling John E. 
Published: June 2009

AbstractDopamine exerts multiple effects on retinal horizontal cells. Dopamine, via cyclic AMP and protein kinase A, reduces the light responsiveness of horizontal cells and the electrical coupling between the cells. The gating kinetics of both gap-junctional and glutamate channels are altered as a result of phosphorylation by protein kinase A. Dopamine also causes a reversible retraction of neurites of horizontal cells maintained in culture. Diacylglycerol analogues as well as phorbol esters mimic this effect of dopamine, but not cyclic AMP analogues or Forskolin. The results suggest that dopamine causes neurite retraction by the activation of protein kinase C via diacylglycerol.
The rod bipolar cell of the mammalian retina
Authors: Wässle Heinz , Yamashita Masayuki , Greferath Ursula , Grünert Ulrike , Müller Frank 
Published: June 2009

AbstractThree approaches to study the function of mammalian rod bipolar cells are described. Extracellular recordings from the intact cat eye under light- and dark-adapted conditions showed that in dark-adapted retina all light responses can be blocked by 2-amino-4-phosphonobutyrate (APB). Immunocytochemical staining with an antibody against protein kinase C (PKC) labeled rod bipolar cells in all mammalian retinae tested. When rat retinae were dissociated, PKC immunoreactivity was also found in isolated bipolar cells and could be used for their identification as rod bipolars. Patch-clamp recordings were performed from such dissociated rod bipolar cells and their responses to APB were measured. APB closed a nonselective cation channel in the cell membrane. The actions of GABA and glycine were also tested and both opened chloride channels in dissociated rod bipolar cells. These results suggest that rod bipolar cells are depolarized by a light stimulus and that GABA as well as glycine modulate their light responses.
The organization of dopaminergic neurons in vertebrate retinas
Authors: Witkovsky Paul , Schütte Michael 
Published: June 2009

AbstractA survey of the shapes of dopaminergic (DA) neurons in the retinas of representative vertebrates reveals that they are divisible into three groups. In teleosts and Cebus monkey, DA cells are interplexiform (IPC) neurons with an ascending process that ramifies to create an extensive arbor in the outer plexiform layer (OPL). All other vertebrates studied, including several primate species, have either DA amacrine cells or IPCs with an ascending process that either does not branch within the OPL or does so to a very limited degree. DA neurons of non-teleosts exhibit a dense plexus of fine caliber fibers which extends in the distal most sublamina of the inner plexiform layer (IPL). Teleosts lack this plexus. In all vertebrates, DA cells are distributed more or less evenly and at a low density (10–60 cells/mm2) over the retinal surface. Dendritic fields of adjacent DA neurons overlap. Most of the membrane area of the DA cell is contained within the plexus of fine fibers, which we postulate to be the major source of dopamine release. Thus, dopamine release can be modeled as occurring uniformly from a thin sheet located either in the OPL (teleosts) or in the distal IPL (most other vertebrates) or both (Cebus monkey). Assuming that net lateral spread of dopamine is zero, the fall of dopamine concentration with distance at right angles to the sheet (i.e. in the scleral-vitreal axis) will be exponential. The factors that influence the rate of fall – diffusion in extracellular space, uptake, and transport – are not yet quantified for dopamine, hence the dopamine concentration around its target cells cannot yet be assessed. This point is important in relation to the thresholds for activation of D1 and D2 dopamine receptors that are found on a variety of retinal cells.
Some visual and neurochemical correlates of refractive development
Authors: Laties Alan M. , Stone Richard A. 
Published: June 2009

AbstractIncreasing evidence indicates that the retina takes part in the postnatal regulation of eye growth, functioning in this respect to minimize refractive error. The evidence derives both from clinical observations in man and from experiments in animals. The discovery that visual form deprivation leads to an axial overgrowth of the eye and to myopia has opened the way to many current research initiatives. Neurochemical and immunocytochemical experiments in chick and monkey suggest that definable retinal neurons participate in the regulatory pathway controlling eye growth. The most comprehensive data presently implicate dopaminergic amacrine cells. Other important issues to be addressed include the relevance of an intact connection to the central nervous system and the precise retinal mechanism by which eye growth is regulated.
An enzymatically enhanced recording technique forLimulusventral photoreceptors: Physiology, biochemistry, and morphology
Authors: Zhang Hui-Juan , Jinks Robert N. , Wishart Anne C. , Battelle Barbara-Anne , Chamberlain Steven C. , Fahrenbach Wolf H. , Kass Leonard 
Published: June 2009

AbstractEnzymatic treatments that facilitated whole-cell electrophysiological recordings were used onLimulusventral photoreceptor cells. Ventral optic nerves were treated with either collagenase or collagenase, papain, and trypsin. Either treatment greatly increased the ease of making whole-cell recordings of transmembrane potentials. Light responses obtained from enzyme-treated photoreceptor cells were nearly identical to results obtained without enzyme treatment and compared favorably toin vivorecordings of light responses from the compound lateral eye. Enzyme-treated cells also responded to applied octopamine, as do untreated cells, with an increased phosphorylation of a 122-kD protein. This suggests that the external receptors and internal biochemical machinery required for at least one second-messenger cascade are present after enzyme treatment. The morphological integrity of enzyme-treated photoreceptor cells was examined with light microscopy as well as with scanning and transmission electron microscopy. In general, we found that each enzyme treatment greatly reduced the integrity of the layers of glial cells that surround the photoreceptor cells thereby making these cells easily accessible for whole-cell recordings of transmembrane potentials. The morphology of the rhabdomere was normal after enzymatic degradation of the adjacent glial covering.
Bipolar cells of the chick retina containing α-bungarotoxin-sensitive nicotinic acetylcholine receptors
Authors: Hamassaki-Britto Dânia E. , Brzozowska-Prechtl Agnieszka , Karten Harvey J. , Lindstrom Jon M. 
Published: June 2009

AbstractTwo cDNA clones for nicotinic acetylcholine receptor (nAChR) subunits sensitive to α-bungarotoxin (α-Bgt) have been isolated, the so-called α-Bgt binding proteins α1 (or α7 nAChR subunit) and α2 (or α8 nAChR subunit). Immunohistochemical experiments have shown that both α7 and α8 subunits, as well as subunits insensitive to α-Bgt (β2 and α3), are present in amacrine and ganglion cells of the chick retina. However, only the α8 subunit was observed in presumptive bipolar cells. The present study investigated in detail the pattern of distribution of the bipolar cells containing the α8 nAChR subunit and its relation to the pattern of distribution of bipolar cells immunoreactive to protein kinase C (PKC). Presumptive α8-and PKC-like immunoreactive (α8-LI and PKC-LI) bipolar cells were observed sending their dendrites to the outer plexiform layers and their axons to the inner plexiform layer. Where as α8-LI bipolar cells corresponded to 40–53% of the whole population of bipolar cells, PKC-LI bipolar cells represented only 6–8% of the same population. The soma sizes of the α8-LI bipolar cells were slightly smaller (mean ± s.d.; 4.9 ± 0.8 μm) than the soma sizes of the PKC-LI bipolar cells (5.4 ± 0.9 μm). Double-labeling experiments indicated that probably all PKC-LI bipolar cells also contain α8-LI. This indicates that two distinct groups of cholinoceptive bipolar cells exist in the chick retina, one that contains PKC-LI, and another one that does not.
The postnatal development of geniculocortical axon arbors in owl monkeys
Authors: Pospichal Marcie W. , Florence Sherre L. , Kaas Jon H. 
Published: June 2009

AbstractTo characterize the postnatal development of geniculocortical axon arbor morphology in owl monkeys at a series of ages from birth to adulthood, individual arbors were bulk-filled with HRP in brain slice preparations and were reconstructed from serial sections. At all ages, cortical layers and sublayers were obvious. Presumed M or magnocellular arbors were largely confined to layer IVα, but they also extended into layer IIIc (IVB of Brodmann, 1909); presumed P or parvocellular arbors were almost exclusively confined to layer IVβ. Other axons that may reflect feedback projections from MT terminated in layer IIIc. Overall, M axon arbors increased in size and complexity from birth to adulthood with mean surface-view arbor areas ranging from 0.08 ± 0.01 mm2 in newborns to 0.24 ± 0.02 mm2 in adults. The developing P arbor areas were, on average, as large or larger than adult (newborn = 0.07 ± 0.01 mm2, adult = 0.047 ± 0.01 mm2; n.s.) but the arbors were somewhat less complex. Since the brain and area 17 increase in size postnatally, the proportion of area 17 subserved by each P arbor would decrease in postnatal development. Terminal boutons with immature features were evident in both M and P populations at all developmental ages. The results indicate that, while both LGN axon types in monkeys undergo morphological changes postnatally, M arbors appear to mature by increasing arbor size and terminal branching complexity, whereas P arbors increase in complexity but not in size. These distinct programs of axon arbor development suggest that the periods of susceptibility of geniculocortical axon arbors to postnatal influences of the environment, and the types of plastic responses they potentially exhibit, are class-specific.
Opponent-color detection threshold asymmetries may result from reduction of ganglion cell subpopulations
Authors: Billock Vincent A. , Vingrys Algis J. , King-Smith P. Ewen 
Published: June 2009

AbstractThresholds for psychophysically opposite stimuli—light and dark, or equiluminous red and green, or equiluminous blue and yellow—are usually nearly equal. This color threshold symmetry is sometimes violated in subjects who have optic nerve hypoplasia, a congenital loss of retinal ganglion cells. We describe a subject who has optic nerve hypoplasia, who exhibits large red-green and blue-yellow detection threshold asymmetries for equiluminous spots. Temporal and spatial integration for equiluminous red and green test spots also differed from normal; static perimetric thresholds for equiluminous green, blue, and yellow (but not red) spots lacked the normal “V” shaped minimum at the fovea. These asymmetries may relate to a developmental paucity of some ganglion cell subtypes. Optic nerve hypoplasia may allow the contributions to detection made by individual ganglion cell subtypes to be isolated psychophysically, in analogy to the study of cone spectral sensitivity in dichromats.
Cortical projections to anterior inferior temporal cortex in infant macaque monkeys
Authors: Rodman Hillary R. , Consuelos Michael J. 
Published: June 2009

AbstractInferior temporal (IT) cortex is a “high-order” region of extrastriate visual cortex important for visual form perception and recognition in adult primates. The pattern of cortical afferents from both ipsilateral and contralateral hemispheres to anterior IT cortex was determined in infant macaque monkeys 7–18 weeks of age following injections of wheat-germ agglutinin-HRP. Within the ipsilateral hemisphere, the locations and laminar distribution of labeled cells were similar to those observed after comparable injections in adult monkeys. Specifically, ipsilateral afferents derived from visual areas V4, TEO, anterior and posterior IT, and STP, from parahippocampal, perirhinal, and parietal zones, and from several anterior zones including lateral and ventral frontal cortex, the insula, and cingulate cortex. Within the contralateral hemisphere, we observed labeled cells in homotopic regions of IT and in parahippocampal and perirhinal areas, as has been reported for adult monkeys. However, we also identified additional contralateral regions not previously known to provide input to anterior IT, including lateral and ventral frontal cortex, cingulate cortex, and STP. Overall, the strongest and most widespread projections from outside the temporal lobe were found in the youngest monkey, suggesting that some of these projections may represent transient circuitry necessary for the development of complex visual response properties in anterior IT.
Variability of responses to sinusoidal modulation
Authors: Levine Michael W. 
Published: June 2009

AbstractMany studies of visual neurons make use of stimuli that are sinusoidally modulated in time, and take as the response the fundamental Fourier component of the firing. This is a study of the variability of the fundamental sinusoidal components.A theoretical analysis shows that the variance of sinusoidal components should be nearly independent of their amplitudes; this is expected despite the observation that variance of firing rate increases with increasing firing rate. However, this result applies only to the variance of the complex amplitude, defined as the complex Fourier amplitude in response to each stimulus cycle. This variance is called the complex variance. The variance of the scalar amplitude, which is simply the amplitude in response to each stimulus cycle disregarding phase (scalar variance) is expected to shrink by a factor of up to 2⅓ as the response magnitude approaches zero.If the relationship between variance of rate and rate is linear, complex variance should be independent of amplitude. If the relationship between variance of rate and rate is characterized by a compressive nonlinearity (as has been observed), the complex variance should very slightly decrease with increased amplitude, despite the main trend of increased variance of rate with increased rate.Data from cat ganglion cells stimulated with sinusoidally modulated lights of various contrasts agree with the theory, although some individual cases show trends that may be indicative of nonlinearity in the relationship between variance of rate and rate.