bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preoccipital cortex receives a differential input from the frontal eye field and projects to the pretectal olivary nucleus and other visuomotor-related structures in the rhesus monkey
Authors: Leichnetz G. R. 
Published: June 2009

AbstractThe bidirectional axonal transport capabilities of the horseradish peroxidase (HRP) technique facilitated the study of the frontal-eye-field (FEF) input and pretectal output of two regions of extrastriate preoccipital cortex (POC). Following horseradish peroxidase (HRP) gel implants into the middle and dorsal POC in two rhesus monkeys, the middle POC implant demonstrated retrograde frontal cortical labeling largely restricted to the inferior frontal eye field (iFEF) and adjacent inferior prefrontal convexity, whereas the dorsal POC implant showed labeling in the caudal ventral bank of the superior ramus of the arcuate sulcus (sas) and middle-to-dorsal region of the rostral bank of the concavity of the arcuate sulcus (dorsal FEF). Prominent anterogradely labeled efferent preoccipital projections were observed to the ipsilateral pretectal olivary nucleus (PON) and to a lesser extent the anterior pretectal nucleus. Although the middle POC case had heavier projections to the lateral PON, the dorsal case projected more heavily to the medial PON. In addition, both implants demonstrated subcortical connections with the lateral and dorsal inferior pulvinar nuclei, central superior lateral thalamic intralaminar nucleus, caudate nucleus, and middle-to-ventral claustrum. However, while the middle POC implant had efferent projections to the superficial superior colliculus (SC), pregeniculate nucleus (PGN), lateral terminal accessory optic nucleus (LTN), and dorsolateral pontine nucleus (DLPN), resembling those previously reported for the middle temporal (MT) visual area (Maunsell & Van Essen, 1982; Ungerleider et al., 1984), the dorsal implant had projections to the lateral intermediate SC, zona incerta (ZI), PGN, a notably lesser projection to the LTN, and basilar pontine projections to the lateral and lateral dorsal pontine subnuclei (not including the extreme dorsolateral DLPN).These preliminary results suggest that the preoccipital cortex, which reportedly functions in pupillary constriction, accommodation, and convergence, entertains connections with the PON and other visuomotorrelated structures, and thus could act as an intermediary in the pathway between the iFEF and PON, and provide a possible explanation for pupillary effects that occur with stimulation of the FEF (Jampel, 1960) and within the context of other oculomotor activities. The findings shed light on certain differences in connections of middle vs. dorsal POC with visuomotor-related nuclei, and appear to suggest that the middle region, which receives input from the iFEF, has greater access to the optokinetic (OKN) system by virtue of its projection to the LTN, and to the smooth-pursuit system by virtue of its projection to the DLPN.
Multi-microelectrode investigation of monkey striate cortex: Link between correlational and neuronal properties in the infragranular layers
Authors: Krüger J. 
Published: June 2009

AbstractRecordings were taken from infragranular layers of area 17 of anesthetized monkeys with an array of 30 microelectrodes matching about one hypercolumn. From intracortical spike-train correlations, the novel neuronal property “delay scale position” related to retino-cortical delays, was derived. Relationships were established to the degree of spike isolation and to classical response properties. Direction selectivity, spike rate, spike-isolation quality, delay scale, and color selectivity could be linked to an underlying factor upon which the latter variables depend in a fixed way. Neurons with similar factors were characterized by non-delayed correlations. The link was more strict in layer VI than in layer V, and it was related to the parvo/magnocellular subdivision of the visual system.
Differences between ipsilaterally and contralaterally evoked potentials in the visual wulst of the zebra finch
Authors: Bredenkötter Manfred , Bischof Hans-Joachim 
Published: June 2009

AbstractThe telencephalic target of the thalamofugal visual pathway in birds, the visual wulst, is part of the hyperstriatum accessorium/dorsale in the bird's brain. In this study, we tried to determine the exact location of the visually responsive area in the zebra finch by recording visually evoked potentials (VEPs) from different sites throughout the hyperstriatum and calculating current source densities (CSDs). In addition, we examined the influence of ipsilateral and contralateral stimuli on stimulus processing within this area, and tried to get insight into the neuronal machinery of the thalamofugal pathway by application of drugs such as tetrodotoxin (TTX) and picrotoxin.About two-thirds of the hyperstriatum is responsive to contralateral stimuli but only a small portion responds to ipsilateral stimuli. Contralateral visual information arrives in the hyperstriatum dorsale (HD) and is processed further to the hyperstriatum accessorium (HA).The small influence of ipsilaterally evoked potentials is not due to inhibition by the activity of the contralateral eye, as could be demonstrated previously for the ectostriatum. Instead, our results show that ipsilaterally evoked potentials are inhibited at least in part by a projection from the contralateral visual wulst.
Cortical connections of MT in four species of primates: Areal, modular, and retinotopic patterns
Authors: Krubitzer Leah A. , Kass Jon H. 
Published: June 2009

AbstractCortical connections were investigated by restricting injections of WGA-HRP to different parts of the middle temporal visual area, MT, in squirrel monkeys, owl monkeys, marmosets, and galagos. Cortex was flattened and sectioned tangentially to facilitate an analysis of the areal patterns of connections. In the experimental cases, brain sections reacted for cytochrome oxidase (CO) or stained for myelin were used to delimit visual areas of occipital and temporal cortex and visuomotor areas of the frontal lobe. Major findings are as follows: (1) The architectonic analysis suggests that in addition to the commonly recognized visual fields, area 17 (V-I), area 18 (V-II), and MT, all three New World monkeys and prosimian galagos have visual areas DL, DI, DM, MST, and FST. (2) Measurements of the size of these areas indicate that about a third of the neocortex in these primates is occupied by the eight visual areas, but they occupy a somewhat larger proportion of neocortex in the diurnal marmosets and squirrel monkeys than the nocturnal owl monkeys and galagos. The diurnal primates also have proportionally more neocortex devoted to areas 17, 18, and DL and less to MT. These differences are compatible with the view that diurnal primates are more specialized for detailed object and color vision. (3) In all four primates, restricted locations in MT receive major inputs from short meandering rows of neurons in area 17 and several bands of neurons in area 18. (4) Major feedforward projections of MT are to two visual areas adjoining the rostral half of MT, areas MST and FST. Other ipsilateral connections are with DL, DI, and in some cases DM, parts of inferotemporal (IT) cortex, and posterior parietal cortex. (5) In squirrel monkeys, where injection sites varied from caudal to rostral MT, caudal parts of MT representing central vision connect more densely to DL and IT than other parts. Both DL and IT cortex emphasize central vision. (6) In the frontal lobe, MT has dense connections with the frontal ventral area (FV), but not with the frontal eye field (FEF). (7) Callosal connections of MT are most dense with matched locations in MT of the other hemisphere, rather than with the outer boundary of MT representing the vertical meridian. Targets of sparser callosal connections include FST, MST, and DL.The results support the conclusions that (1) prosimian primates and New World monkeys have at least ten visual and visuomotor areas in common, (2) the connections of MT are remarkably consistent across four species of primates, (3) the anatomical segregation of visual subsystems in areas 17 and 18 is common to all primates, (4) connections from the part of MT representing central vision with visual areas emphasizing central vision are more dense, and (5) MT and the associated fields MST and FST occupy proportionally more cortex in nocturnal than diurnal primates.
Function of the corpus callosum in the representation of the visual field in cat visual cortex
Authors: Payne B. R. 
Published: June 2009

AbstractInterposed between areas 17 and 18 of cat cerebral cortex is an architectonically distinct zone that represents a substantial portion of the ipsilateral visual field. The extent of this representation was assessed following severance of the corpus callosum by recording the activities of neurons and plotting their receptive fields. The results show that, even after the hemispheres are disconnected, the transition zone still contains a representation of part of the ipsilateral visual hemifield, albeit a reduced one. The extent of this representation is contracted towards the midline so that just one-half to one-third of the azimuths mapped in intact cats can be plotted. As in the intact cat, the width of the region represented is not equal at all elevations, for it extends to only −1.4 deg near the visual axis whereas it extends to −6.6 deg at an elevation of −20 deg. The retention of this representation after the transition zone neurons have been disconnected from the opposite hemisphere indicates that other pathways make a functional contribution to the representation of the ipsilateral field in this region of cortex.
Neural gradient models for the measurement of image velocity
Authors: Jin Z. Fei , Srinivasan M. V. 
Published: June 2009

AbstractAlthough gradient schemes for detecting the motion of images and measuring their velocities are commonly used in computer vision, and although there is increasing evidence to support the existence of such schemes in biological vision, little attention has been directed to suggesting how such computations might be realized by neural hardware. This paper proposes two simple models, consisting of physiologically realistic networks of neurons, that approximate the gradient scheme. Computer simulations demonstrate that the models measure the speed of an object or pattern independently of its structural properties.
Rearing in darkness changes visually-guided choice behavior in Drosophila
Authors: Hirsch Helmut V.B. , Potter Doreen , Zawierucha Dariusz , Choudhri Tanvir , Glasser Adrian , Murphey Rodney K. , Byers Duncan 
Published: June 2009

AbstractTo test whether visual experience can affect development of visual behavior in the fruitfly, Drosophila, we measured the visually-guided choice behavior of groups of flies reared in complete darkness, compared with controls reared in a normal light/dark cycle. We used a simple visual preference test, i.e. choice among four different visual targets each consisting of vertical black lines of a particular width on a white background, using a blind testing procedure so that the individual rearing histories were not known by the tester. Both groups of flies were strongly attracted to the vertical lines; however, generally the dark-reared flies were more attracted to the wider stimulus lines than were the control flies. Control experiments in which normally reared adults were kept for several days in darkness showed that the effects of dark-rearing were not simply due to being in darkness, but depended upon the timing of the deprivation. The results indicate that the development of visual behavior can be affected by visual experience in Drosophila and thus open the possibility of using Drosophila for genetic dissection of mechanisms of visual plasticity.
Duplicity theory and ground squirrels: Linkages between photoreceptors and visual function
Authors: Jacobs Gerald H. 
Published: June 2009

AbstractThe presence of rod and cone photorceptors has traditionally been linked to well-defined classes of visual capacity by the generalization known as duplicity theory. This paper summarizes results obtained from studies of vision and the visual system in ground squirrels (Spermophilus sp.) that reveal instances where structure/function linkages depart from expectations based in duplicity theory. The details of these exceptions are reviewed and their possible mechanisms discussed.
Macaque vision after magnocellular lateral geniculate lesions
Authors: Merigan William H. , Maunsell John H.R. 
Published: June 2009

AbstractIbotenic-acid lesions of the magnocelluar portion of the macaque lateral geniculate nucleus were used to examine the role of the M-cell pathway in spatio-temporal contrast sensitivity. A lesion was place in layer 1 of the lateral geniculate of each of two monkeys. Physiological mapping in one animal demonstrated that the visual-field locus of the lesion was on the horizontal meridian, approximately 6 deg in the temporal field. Visual thresholds were tested monocularly in the contralateral eye, and fixation locus was monitored with a scleral search coil to control the retinal location of the test target.Three threshold measures were clearly disrupted by the magnocellular lesions. Contrast sensitivity for a 1 cycle/deg grating that drifted at 10 Hz was reduced from about twofold greater than, to about the same as, that for 10-Hz counterphase modulated gratings. Sensitivity for a very low spatial frequency (Gaussian blob), 10-Hz flickering stimulus was reduced so severely that no threshold could be measured. In addition, flicker resolution was greatly reduced at lower modulation depths (0.22), but not at higher depths (1.0). Two of the measured thresholds were unaffected by the lesions. Contrast sensitivity for 2 cycle/deg stationary gratings remained intact, and little or no effect on sensitivity was found for 1 cycle/deg, 10-Hz counterphase modulated gratings.Together, these results suggest that the magnocellular pathway makes little contribution to visual sensitivity at low to moderate temporal frequencies. On the other hand, some contribution to detection sensitivity is evident at lower spatial and high temporal frequencies, especially for drifting stimuli. It appears that a major role of the magnocellular pathway may be to provide input to cortical mechanisms sensitive to rapid visual motion.
Intact “biological motion” and “structure from motion” perception in a patient with impaired motion mechanisms: A case study
Authors: Vaina Lucia M. , Lemay Marjorie , Bienfang Don C. , Choi Albert Y. , Nakayama Ken 
Published: June 2009

AbstactA series of psychophysical tests examining early and later aspects of image-motion processing were conducted in a patient with bilateral lesions involving the posterior visual pathways, affecting the lateral parietal-temporal-occipital cortex and the underlying white matter (as shown by magnetic resonance imaging studies and confirmed by neuro-ophthalmological and neuropsychological examinations). Visual acuity, form discrimination, color, and contrast-sensitivity discrimination were normal whereas spatial localization, line bisection, depth, and binocular stereopsis were severely impaired. Performance on early motion tasks was very poor. These include seeing coherent motion in random noise (Newsome &amp; Paré, 1988), speed discrimination, and seeing two-dimensional form from relative speed of motion. However, on higher-order motion tasks the patient was able to identify actions from the evolving pattern of dots placed at the joints of a human actor (Johansson, 1973) as well as discriminating three-dimensional structure of a cylinder from motion in a dynamic random-dot field. The pattern of these results is at odds with the hypothesis that precise metrical comparison of early motion measurements is necessary for higher-order “structure from motion” tasks.
Slow light and dark adaptation of horizontal cells in the Xenopus retina: A role for endogenous dopamine
Authors: Witkovsky Paul , Shi Xiao-Ping 
Published: June 2009

AbstractA role for endogenous dopamine in the control of rod and contributions to a second-order retinal neuron, the horizontal cell (HC) was studied in theXenopusretina. Relative rod and cone contributions were estimated from HC responses to scotopically balanced 491- and 650-nm flashes. In eyecups prepared in light then placed in darkness, cone input to the HC slowed and diminished on a time scale of hours. The decline in cone input was balanced by a slow growth of rod input to the HC. Administration of D-amphetamine, a dopamine releasing agent, restored the light-adapted waveform.The kinetics of slow light adaptation were examined by recording HC responses from eyecups that had been dark-adapted previously for 11–14 h. When test flashes fell on a dark field, cone input to the HC grew for 2–4 h, reached a plateau, and later declined. If, however, flashes were superimposed on a weak background field, cone input to the HC continued to increase monotonically at about 10%/h. This increase was abolished by superfusion with a nonspecific dopamine receptor blocker, cis-flupenthixol (50 μM), resulting in the complete suppression of cone-to-horizontal cell synaptic transfer and the enhancement of rod-to-horizontal cell communication. Subcutaneous injection of reserpine, a drug that depletes dopamine stores (2 mg/kg on 1–4 successive days), or intraocular injection of the dopamine neurotoxin, 6-hydroxydopamine (10–30 μg) slowed and reduced the amplitude of cone input to the HC, even in completely light-adapted eyes. Subsequent treatment with D-amphetamine (5–50 μM) or dopamine (10 μM) partially restored the normal response.Our experimental findings are consistent with the following hypothesis. Weak light is sufficient to stimulate dopamine release; dopamine augments cone-to-horizontal cell synaptic transfer and reduces rod-to-horizontal cell communication. The rapid kinetics of the fully light-adapted response depend on the presence of dopamine. Thus, dopamine appears to be an intraretinal signal for slow light adaptation.
Microphotometric, ultrastructural, and electrophysiological analyses of light-dependent processes on visual receptors in white-eyed wild-type and norpA (noreceptor potential) mutant Drosophila
Authors: Zinkl Gregory M. , Maier Linnette , Studer Kent , Sapp Randall , Chen De-Mao , Stark William S. 
Published: June 2009

AbstractWe examined a white-eyed strain of the norpA mutant (norpA;cn bw) and white (w)norpA+ controls using microspectrophotometry (MSP), electron microscopy (EM), and electroretinography (ERG). These studies revealed that light mediates receptor demise in norpA even though norpA lacks phototransduction. Rhodopsin and the rhabdomere which houses it decrease with increasing age in norpA but not in w with rearing on a 12 h light/12-h dark cycle or in constant light. At higher temperature in norpA;cn bw and w reared in constant light, visual pigment decreases, rhabdomeres diminish, and cells die. Importantly, dark rearing blocked visual pigment loss in norpA;cn bw; the M-potential, an ERG reflection of visual pigment level, corroborated this finding. MSP showed that norpA's visual pigment loss was not due to acute loss of metarhodopsin, rhodopsin's photoproduct. NorpA blocks certain processes expected to be light elicited. The alteration of visual pigment as a function of time of day, present in w controls, is absent in white-eyed norpA, suggesting that light-induced depolarization may be necessary to entrain the rhythm. Microspectrofluorometry using the fluorescent dye, Lucifer yellow, suggested that norpA lacks a light-induced uptake mechanism; using control flies, we determined the stimulus parameters required for uptake in vivo. An attempt to “cure” norpA;cn bw by replacement “therapy” using phospholipase C, missing in norpA's phototransduction cascade, was largely unsuccessful.
Somatostatin and prosomatostatin in the retina of the rat: An immunohistochemical, in-situ hybridization, and chromatographic study
Authors: Larsen Jens Nicolai Brink , Bersani Maurizio , Olcese James , Holst Jens Juul , Møller Morten 
Published: June 2009

AbstractSpecific antisera, raised in rabbits, against somatostatin 1-14, somatostatin 1-28, the fragment 1-12 of somatostatin 1-28, and prosomatostatin 20-36 were used for immunohistochemistry and gel filtration of the rat retina.With all antisera, immunoreactive perikarya could be located in the inner nuclear and ganglion cell layers. In the inner nuclear layer, amacrine cells with processes extending predominantly into the first sublayer of the inner plexiform layer were observed. Some processes extended also to the ganglion cell layer. In addition, somatostatin-immunoreactive interplexiform cells were present in the inner nuclear layer.In the ganglion cell layer, perikarya were found located in the midperiphery and in the far periphery of the retina. The neurons located in the midperiphery of the retina possessed a round perikaryon from which processes could be followed going into the inner plexiform layer, where they dichotomized in the third and first sublayers. The perikarya in the far periphery of the retina near the ora serrata exhibited an ovoid-shaped cell body from which processes extended horizontally in a bipolar manner in the layer itself.By use of an [35S]-labeled antisense oligonucleotide probe,in situhybridization of the rat retina showed the presence of perikarya in the inner nuclear layer and ganglion cell layer containing mRNA encoding for prosomatostatin.Gel filtration of the retinal extracts followed by radioimmunoassay showed the presence of somatostatin 1-14, the fragment 1-12 of somatostatin 1-28, and prosomatostatin 1-64. However, somatostatin 1-28 was not detected.The results obtained in this study verify the presence of somatostatin 1-14 in the rat retina located in perikarya and processes in the inner nuclear and ganglion cell layers. The positivein-situhybridization signals show that the intraneuronal somatostatin immunoreactivity is due to synthesis of the peptide and not uptake in the neurons. The presence of the somatostatin propeptide and fragments of this propeptide, in both intraretinal perikarya and fibers, indicate a posttranslational modification of this neuropeptide in the perikarya and the processes as well.