bluuebunny/crossref_metadata_2025_split huggingface dataset:
Eye alignment and cortical binocularity in strabismic kittens: A comparison between tenotomy and recession
Authors: Sireteanu Ruxandra , Singer Wolf , Fronius Maria , Greuel Joachim M. , Best Johannes , Fiorentini Adriana , Bisti Silvia , Schiavi Costantino , Campos Emilio 
Published: June 2009

AbstractInterocular alignment was assessed by corneal light reflex photography in 15 normal and 26 strabismic kittens. Strabismus was induced at 3–4 weeks of age by severing one extraocular muscle (tenotomy), by cutting and reinserting the muscle at another position on the ocular globe (recession), or by combining recession of the medial rectus muscle with resection of the lateral rectus muscle of the same eye. Nineteen strabismic and five normal kittens were followed longitudinally from 12 days to about 6 months of age.Three out of the six longitudinally followed tenotomized cats and six out of the 13 recessed cats conserved their postoperative ocular deviation throughout the testing period (“large-angle strabismics”). Three tenotomized and seven recessed cats showed a transient deviation for 1–2 weeks after surgery, after which the interocular deviation diminished to values found in normal cats (“microstrabismic” cats). Both recessed-resected cats showed a transient interocular deviation.In spite of their different developmental histories, all cats showed a clear breakdown of binocularity in area 17. Large-angle strabismics showed a dominance of the non-operated eye, while in microstrabismic cats, both eyes were equally effective in driving cortical cells. It thus appears that a transient strabismus is sufficient to produce a reduction of binocularity in area 17.
Subcortical connections of subdivisions of inferior temporal cortex in squirrel monkeys
Authors: Steele G. E. , Weller R. E. 
Published: June 2009

AbstractOn the basis of cortical connections and architectonics, inferior temporal (IT) cortex of squirrel monkeys consists of a caudal, prestriate-recipient region, ITC; a rostral region, ITR; and possibly an intermediate region along the border of ITC and ITR, ITI (Weller & Steele, 1992). ITC contains dorsal (ITCd) and ventral (ITCv) areas. The subcortical connections of these subdivisions of IT cortex were determined in the present study from the results of cortical injections of wheat-germ agglutinin conjugated to horseradish peroxidase, [3H]-amino acids and fast blue. ITC and ITR receive afferents from the locus coeruleus, dorsal raphe, nucleus annularis, central superior nucleus, pontine reticular formation, lateral hypothalamus, paracentral nucleus, and central medial nucleus; send efferents to the superior colliculus, reticular nucleus, and striatum; and have both afferent and efferent connections with the pretectum, pulvinar, claustrum, amygdala, and basal nucleus of Meynert. ITC and ITR have different patterns of connections with a number of subcortical structures, including the pulvinar and amygdala. Injections in ITC strongly label multiple nuclei of the inferior pulvinar and the medial division of the lateral pulvinar (PLM), and moderately label the medial pulvinar (PM), whereas injections in ITR strongly label PM and moderately label PLM. Injections in ITC label sparse projections to the lateral nucleus of the amygdala, in contrast to injections in ITR that label strong projections to the lateral and basal nuclei of the amygdala. Injections in “IT” produce a pattern of subcortical label that has some features of that observed from injections in ITC and that observed from injections in ITR. Although most of the connections of ITCd and ITCv appear similar, only injections involving ITCd label the middle nucleus of the inferior pulvinar (PIM).Comparison of the subcortical connections of subdivisions of IT cortex in squirrel monkeys and what is presently known of the subcortical connections of subdivisions of IT cortex in macaque monkeys supports the previous suggestion that ITC of squirrel monkeys may be comparable to area TEO of macaques, IT, may be comparable to posterior area TE, and ITR may be comparable to anterior area TE (Weller & Steele, 1992).
A molecular basis for Weber's law
Authors: Dawis Stevan M. 
Published: June 2009

AbstractA mathematical model is presented that obeys a strong form of Weber's law – over a range of adapting and stimulus intensities, equal contrast stimuli evoke identical responses. To account for the strong Weber's law, the adaptive stage in the proposed model employs a “delayed” reverse reaction along with a power-law input. It is suggested that this Weber's law mechanism is responsible for a slow, voltage-uncorrelated component of adaptation in the vertebrate photoreceptor. A plausible biochemical mechanism is the G-protein cycle with phosphorylation of photoactivated photopigment (and binding of arrestin to the phosphorylated photopigment) as the adaptive process. In an Appendix, features of the general model and implications of a specific biochemical model are examined by computer simulation.
Effects of monocular deprivation on the development of visual inhibitory interactions in kittens
Authors: Speed Harriet D. , Morrone M. Concetta , Burr David C. 
Published: June 2009

AbstractA visual-evoked-potential (VEP) masking technique was used to assess the effects of short- and long-term monocular deprivation on the development of visual inhibitory interactions in kittens. VEP contrast-response curves were recorded in response to contrast-reversed sinusoidal gratings, both with and without superimposed high-contrast masks. The contrast-response curves measured from the nondeprived eye were similar to those of normal cats: with no mask VEP amplitudes increase with contrast up to saturation at about 10% contrast; parallel masks shift the curves to the right, decreasing thresholds; and orthogonal masks decrease the slope of the contrast-response curves without affecting thresholds. After monocular deprivation (either brief or extensive), the contrast-response curves without mask did not show the typical response saturation, and neither parallel nor orthogonal mask had any effect on the contrast-response curves. The masking effects did not return after 100 days of normal vision, although contrast sensitivity and acuity recovered to about half of the normal levels during that period. The results indicate that the inhibitory intracortical circuitry that mediates the orientation-dependent masking effects are highly vulnerable to visual experience.
Habituation-like decrease in the responses of neurons in inferior temporal cortex of the macaque
Authors: Miller Earl K. , Gochin Paul M. , Gross Charles G. 
Published: June 2009

AbstractIn both anesthetized and behaving macaques, we examined the responses of neurons in the inferior temporal cortex (IT) to repeated presentation of a visual stimulus. In anesthetized animals, the responsiveness of IT neurons decreased with repeated stimulus presentation at interstimulus intervals (ISIs) of 2–12 s but not at 20 s. Responsiveness recovered after a 5-min period of no stimulus presentation. The response decrement was similar in anesthetized and awake animals at a 2-s ISI, but at a 6-s ISI, response decrement in the awake animal was much less.
Segregated thalamocortical pathways to inferior parietal and inferotemporal cortex in macaque monkey
Authors: Baleydier Christine , Morel Anne 
Published: June 2009

AbstractInferior parietal and inferotemporal cortex, which process different aspects of visual information through largely segregated pathways from the visual cortex, both receive thalamic afferents from the pulvinar complex. We examined the topography of pulvinar projections to these two cortical regions by placing multiple injections of different tracers (fluorescent dyes, horseradish peroxidase) in the inferotemporal and inferior parietal cortex of macaque monkeys.The patterns of label observed after injections in inferotemporal gyrus indicate that area TEO and the ventral part of area V4 receive a major input from the ventral part of the lateral pulvinar (PuLv) while area TE has strong connections with the caudal pole of the medial pulvinar (PuM) and only minor connections with PuLv. In contrast, injections in the caudal inferior parietal cortex demonstrate that area PGc, on the lateral surface of the inferior parietal gyrus, and area POa, in the ventral bank of intraparietal sulcus, receive strong projections from PuM and the adjacent fringe of the dorsal part of the lateral pulvinar (PuLd).Paired injections of two different tracers in the inferotemporal and inferior parietal cortex of the same hemisphere revealed a nearly complete segregation of the two populations of labeled neurons in the pulvinar, with only a small region of overlap in PuM, close to the PuM/PuLd border. These results demonstrate a clear separation of the thalamic afferents to the inferior parietal and inferotemporal cortex which parallels the separation of prestriate afferents to these two cortical territories (Morel & Bullier, 1990).
Three types of GABA-immunoreactive cone horizontal cells in teleost retina
Authors: Van Haesendonck Eduarda , Missotten Luc 
Published: June 2009

AbstractPeroxidase-anti-peroxidase immunocytochemistry, applied on serial semithin epoxy resin sections, was used to examine the localization of endogenous GABA in horizontal cells in the retina of a marine teleost, the dragonet (Callionymus lyra L.). The immunostaining shows that not only the external H1 cone horizontal cells label with antibodies against GABA, but also the H2 and H3 cone horizontal cells in the inner nuclear layer. The distribution of the H1 cells corresponds to that of the single cones. They are square-patterned and in the dorsal retina their density equals 20,000 cells/mm2. The estimated density of the immunostained H2 and the H3 cells in the dorsal retina is 9500 and 1300 cells/mm2, respectively. The H2 and H3 cells are not geometrically arranged, but nearest-neighbor analysis shows that these horizontal cell types do have a very regular disposition. We suggest that GABA is the likely neurotransmitter substance used by all cone horizontal cell types in teleost retina.
Ocular dominance columns in area 17 of Old World macaque and talapoin monkeys: Complete reconstructions and quantitative analyses
Authors: Florence S. L. , Kaas J. H. 
Published: June 2009

AbstractThe effects of monocular deprivation on cytochrome-oxidase (CO) expression were used to reveal ocular dominance columns in flatmounts of the striate cortex in macaque (Macaca fascicularis) and talapoin (Miopithecus talapoin) monkeys. This procedure allowed the first direct visualization of the complete pattern of ocular dominance bands in macaque monkeys, and less complete reconstructions in talapoin monkeys. In a second macaque monkey, the ocular dominance organization was revealed by injecting wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP) into one eye.The organization of ocular dominance columns in the macaque monkeys conforms to previous descriptions, but the flat-mounted hemispheres provide accurate details on (1) the arrangement of columns, (2) the orientation of the representation of the optic disc, and (3) the breakdown of the bands in the cortex between the optic disc and monocular representations into a pattern of dots activated by the ipsilateral eye and larger surrounds related to the contralateral eye.Talapoin monkeys, the smallest of Old World monkeys, have sharply segregated ocular dominance bands. The columns in talapoins are narrower than those in macaques, so that even with less striate cortex than macaques, talapoins have more ocular dominance hypercolumns.
Blockers of potassium channels reduce the outward dark current in rod photoreceptor inner segments
Authors: Yan Kun , Matthews Gary 
Published: June 2009

AbstractThe dark current of single isolated toad rods was monitored by drawing either the inner segment or the outer segment into a suction electrode. The potassium-channel blockers tetraethylammonium (TEA) and 3,4-diaminopyridine (DAP) reduced the amplitude of the dark current when applied to the inner segment. Both drugs were less effective when applied to the outer segment, suggesting that they act at the inner segment to block part of the outward path for the dark current. In addition, DAP affected the kinetics of the light response, possibly by affecting internal pH.
Topography of the evoked potential to spatial localization cues
Authors: Steinman Scott B. , Levi Dennis M. 
Published: June 2009

AbstractVisual tasks that are perceptually diverse might be expected to elicit unique evoked-potential waveforms that exhibit differing topographic maps. To investigate this possibility, multichannel visual-evoked potentials (VEPs) were recorded in response to several dot spatial localization stimuli that are physically similar yet produce different percepts (vernier offsets, stereoscopic disparity, bisection, orientation, and relative displacement) to determine if the unique percepts arising from these stimuli reflect the activation of different cortical neural populations. The resulting evoked potentials were all similar in waveform, although the stereoscopic VEPs were relatively delayed. Topographic maps of the evoked-potential activity to each stimulus revealed a late major component with two independent foci: one 7 or more centimeters above the inion lateral to the midline, and the other at least 6 cm lateral to Oz. The scalp localization of both peaks was independent of both the position of the stimulus in the visual field and the particular stimulus cue presented. An asymmetric response to pattern appearance vs. disappearance indicated strong pattern specificity for each stimulus type except unreferenced motion. The timing of the VEP responses and relative insensitivity to retinal locus of stimulation suggest the involvement of higher cortical areas. The two map foci might be interpreted as activation of inferotemporal and parietal cortices whose roles are thought to be visual object interpretation and spatial attention and localization, respectively.
Ganglion cell types of the turtle retina that project to the optic tectum: Intracellular HRP injections of retrogradely, rhodamine-marked cell bodies
Authors: Guiloff Gloria D. , Kolb Helga 
Published: June 2009

AbstractThe turtle retina has been shown to have a variety of different morphological ganglion cell types as well as distinct physiological ganglion cell types. The major projection of the retina to the brain in nonmammalian vertebrates is to the optic tectum. In this study, we address the question of which retinal ganglion cell types project to the optic tectum in the turtle.Fluorescent rhodamine-labeled microspheres were used to trace the retinal ganglion cell projection to the superficial layers of the optic tectum. The fluorescent ganglion cell somata, retrogradely marked by transport from the contralateral optic tectum, were impaled with micropipettes containing rhodamine-horseradish peroxidase solution and this dye was iontophoresed into the cells under visual control.Most of the morphological ganglion cell types described in Golgi studies (Kolb, 1982; Kolb et al., 1988) were stained. Thus, the small cell types G1, G2, G3, G5, G6, and G7; the medium-sized types G10, G11, G12, G13, and G14; and the large-sized types G15, G16, G19, G20, and G21 project to the optic tectum in the turtle. We have added a new type, G2a, which proves to have some differences from the original G2 in branching pattern. We were unable to stain the small type G4, the medium-sized types G8 and G9, and the large cell types G17 and G18; this suggests that they might not project to the superficial layers of the dorsolateral optic tectum, at least, in the turtle.
Development of functional calcium channels in cultured avian photoreceptors
Authors: Gleason Evanna , Mobbs Peter , Nuccitelli Richard , Wilson Martin 
Published: June 2009

AbstractVertebrate photoreceptors are unusual neurons in that they are capable of continuous calcium-mediated release of neurotransmitter (Trifonov, 1968; Hagins et al., 1970). In this study, we have examined the development and characteristics of calcium currents in chick cone cells placed in culture on embryonic day 8. Cone cells were identified by their lectin-binding properties, rhodopsin-like immunoreactivity, and the presence of an oil droplet. Using the whole-cell patch-clamp method, we have seen calcium currents in these cells after three days in culture, slightly before the appearance of synapses (Gleason & Wilson, 1989). Because cone calcium currents are blocked by cadmium and nifedipine but are enhanced by Bay K 8644, they most closely resemble L-type current (Nowycky et al., 1985). An unexpected feature of these currents is that their gating ranges varied widely between cells so that some cells showed the foot of their activation range at —70 mV and others as positive as —25 mV. Calcium imaging of fura-2 loaded cells was used to confirm the time course of calcium current development and describe the distribution of cytosolic calcium. As expected, depolarization of young cells failed to increase cytosolic calcium but in older cells an increase of threefold to fourfold was usually observed. Both at rest and during depolarization, most cone cells showed regional differences in internal calcium concentration. In the most mature cones, depolarization strongly elevated cytosolic calcium at the terminal end of the cell while producing a lesser change around the oil droplet and the ellipsoid region, suggesting that calcium channels are localized to the terminal.
Electrophysiological recordings in solitary photoreceptors from the retina of squid,Loligo pealei
Authors: Nasi Enrico , Gomez Maria 
Published: June 2009

AbstractA protocol was developed to isolate enzymatically photoreceptors from the retina of the squid,Loligo pealei. The procedure routinely results in a high yield of intact cells. Examination of solitary photoreceptors under Nomarski optics revealed that the fine morphological features described in anatomical studies of retinal sections are retained. The distal segment is up to 250 μm long, 4–7 μm wide, covered in part by short microvilli; the inner segment and the cell body, with the initial portion of the axon, are also clearly discernible in solitary cells. Suction electrode measurements performed from the cell body confirmed that responsiveness to light survived cell isolation. Macroscopic membrane currents were measured using the whole-cell tight-seal technique, and the perforated-patch method. Step depolarizations of membrane voltage administered in the dark elicited a slowly activating, sustained outward current. Light stimulation evoked an inward current graded with stimulus intensity; the peak current could amply exceed 1000 pA. Intense photostimulation gave rise to a prolonged inward aftercurrent that lasted for tens of seconds. On-cell patch recording along the intermediate segment and most of the smooth areas of the distal segment showed a large incidence of silent patches, with the occasional presence of voltage-dependent channels. On the other hand, channel activity could be recorded more frequently from electrode placements near the apical tip of the cell, where the presence of microvilli could be confirmed visually. Some patches were unresponsive to voltage Stimulation applied in the dark but produced distinct bursts of channel openings after illumination. The feasibility of single-cell electrophysiology in isolated photoreceptors, together with the growing body of biochemical information on cephalopod preparations, makes squid an attractive model system to investigate the visual process in invertebrates using multiple experimental approaches.
Neural elements of the pineal complex of the frog, rena esculenta, I: Centrally projecting neurons
Authors: Ekström Peter , Meissl Hilmar 
Published: June 2009

AbstractThe pineal complex of anuran &amp;hibians is a directly photosensory organ, encompassing both an extracranial portion, the frontal organ, and an intracranial portion, the pineal organ proper. The projection neurons of the frontal organ respond differentially according to the wavelengths of the light stimuli. The pineal organ, on the other hand, functions mainly as a luminosity meter. Most of its centrally projecting neurons respond to all increases in ambient illumination with decreases in spontaneous firing of action potentials, although some neural units in the pineal organ may respond according to wavelength. This difference in responses to light stimulation may be reflected in the neural organization of the two parts of the pineal complex. In the present study, we have analyzed the morphology of the projection neurons of the frontal and pineal organs of the frog,Rana esculenta, by backfilling of the neurons with horseradish peroxidase through their cut axons. In the pineal organ, several types of centrally projecting neurons were observed: peripherally situated unipolar and multipolar neurons, the dendrites of which extend into a superficial axon plexus that surrounds the pineal epithelium; smaller unipolar, bipolar, or multipolar neurons situated close to the central pineal tract; and radially oriented bipolar neurons, with short dendritic processes oriented towards the lumen of the pineal organ. This latter type was strongly reminiscent of photoreceptor cells. The centrally projecting neurons of the frontal organ were multipolar, and situated in the ventral part of the organ. One photoreceptor-like bipolar neuron was observed in one frontal organ. The neurons of the frontal organ did not form a superficial plexus of neurites. This difference may relate to the different ratio of chromaticity/luminosity units in the frontal and pineal organs.
Behavioral determination of the spatial selectivity of contrast adaptation in cats: Some evidence for a common plan in the mammmlian visual system
Authors: Berkley M.A. 
Published: June 2009

AbstractAn aftereffects paradigm was used to behaviorally measure contrast sensitivity of cats to gratings of three different test spatial frequencies after adaptation to gratings of various spatial frequencies, contrasts, and durations. Post-adaptation reductions in sensitivity occurred even after short periods of adaptation (&lt;7 s) and could be as large as 1.0 log unit under some conditions. The magnitude of the adaptation effect varied monotonically with (1) adaptation grating contrast, (2) duration, and (3) the contrast sensitivity for the test grating. Average half-width (at half-height) of the spatial-frequency tuning curves constructed from the data was 1.4 octaves, and was not dependent upon the level of adaptation or the spatial frequency of the test grating. Post-adaptation psychometric functions of the cats showed reduced slopes and maxima suggesting that, unlike humans, in cats apparent contrast grows more slowly with increases in physical contrast after contrast adaptation. All of the characteristics observed are in excellent agreement with electrophysiologically measured properties of neurons in striate cortex of cats. In addition, there was a remarkable similarity of the cat tuning functions, both in shape and bandpass, to those measured in man with a similar paradigm suggesting that (1) the two visual systems are sufficiently similar to make the cat a useful spatial vision model and (2) there is a common functional plan to all mammalian visual systems despite significant anatomical differences between species.