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PubMed2001

Development of the visual pathway is disrupted in mice with a targeted disruption of the calcium channel beta(3)-subunit gene.

Refinement of the retinal pathways to the superior colliculus (SC) and dorsal lateral geniculate nucleus (dLGN) is mediated by nitric oxide (NO). Long-term depression (LTD) can also be induced in SC and LGN during the time at which these pathways are refined, and this LTD is partially dependent on NO and L-type Ca(2+) channel function. In an effort to determine whether NO-mediated pathway refinement is also mediated by Ca(2+) channel function, we have examined the refinement of the retinocollicular and retinogeniculate pathways in mice which lack the gene for the Ca(2+) channel beta(3) subunit (CCKO) and which have significantly reduced L-type Ca(2+) currents. Injections of the anterograde tracer cholera toxin subunit B/HRP were made into one eye of these knockout animals and in wild-type mice ages postnatal day (P) 13, P19, and P26. After 48 hours, mice were perfused and sections processed by using tetramethylbenzidine histochemistry. Labeling distribution in some animals was analyzed quantitatively. Obvious differences in the distribution of the ipsilateral retinocollicular pathway were observed at P15, with the pathway being more exuberant in CCKO mice. This difference was statistically significant. More subtle differences were seen at P21 and P28. Obvious differences were also seen in the contralateral retinogeniculate pathway which in CCKO mice filled most of the domain normally occupied by ipsilateral eye fibers. This difference was also statistically significant. We conclude that reduction in L-type Ca(2+) currents has an effect on axonal refinement similar to that which occurs in NO knockout mice, which supports the possibility that L-type Ca(2+) channel-dependent LTD mediates NO-dependent axonal refinement.

Aging↗
PubMed1992

Disconnected optic axons persist in the visual pathway during regeneration of the retino-tectal projection in the frog.

In this study, we crushed one optic nerve in the frog Litoria (Hyla) moorei and at intervals thereafter anterogradely labelled optic axons with horseradish peroxidase (HRP). For one series, HRP was applied between the eye and the crush site and in a second series between the crush site and the chiasm. A tectal projection of regenerating axons was seen in both series but, in addition, up to 12 weeks post-crush, the second series displayed an additional projection. Its appearance matched that of the disconnected, but persisting, optic axon terminals which are found after enucleation or optic nerve ligation. We conclude that, in the frog, many disconnected optic axons persist throughout the period of optic nerve regeneration and of restoration of an orderly retino-tectal map.

Animals↗
PubMed1980

[Electro-ophthalmological responses in inflammations of various sections of the orbital visual pathways (author's transl)].

In a study of electro-ophthalmological responses of the EOG, the photopic and scotopic ERG, the OP and the VECP, in combination with fluorescein angiography and computerized perimetry, in 34 patients suffering from uveitis, chorioretinitis (lesions near the macula and at the periphery), papillitis or retrobulbar neuritis, the following results were obtained: Uveitis and chorioretinitis with lesions either near the macula or at the retinal periphery produce different responses; generally, pathologic responses of the EOG and ERG and normal VECP are obtained in cases of uveitis. Peripheral chorioretinal lesions lead to a diminution of the scotopic ERG, OP and EOG, in contrast to lesions near the macula, in which pathologically diminished amplitudes of the photopic ERG and VECP are found. In papillitis and retrobulbar neuritis, however, the most important peculiarity is the increase in latency and the decrease in amplitudes of the VECP, especially in retrobulbar neuritis.

Chorioretinitis↗
PubMed1976

The pattern-evoked potential in compression of the anterior visual pathways.

Pattern evoked responses have been recorded in 19 patients with compression of the optic nerve, chiasm or tract, verified at operation. These included 4 patients with orbital tumours, 5 with intracranial meningiomas, 2 with craniopharyngiomas and 8 with pituitary tumours. The evoked response was abnormal in all except one of these patients. The pattern of abnormalities in the response, however, differed from that in the earlier series of patients with primary demyelinating disease. The incidence of delayed responses was much lower, and the magnitude of the delays was smaller. Absent responses were particularly characteristic of patients with intracranial meningiomas. Tumours arising in the region of the sella turcica were associated with a high incidence of abnormalities of the waveform of the response, and asymmetry of the field of the occipital evoked potential was especially characteristic of this group. Most, but not all, asymmetric cases were associated with field defects.

Adult↗
PubMed1991

Texture segregation by chromatic and achromatic visual pathways: an analogy with motion processing.

We present results to show that texture segregation can be obtained through the so-called coherent spatial grouping of local shape (orientation) and of local color under both nonequiluminant and equiluminant conditions. Color grouping entails texture segregation independent of orientation grouping, while the reverse is not true under equiluminant conditions. The experiments permit the isolation of chromatic- and luminance-oriented mechanisms, as well as of chromatic nonoriented mechanisms, all of which contribute to texture discrimination. As a general rule, the present results (including the asymmetry between color and orientation grouping) are similar to those obtained by us in a series of motion-perception experiments. This similarity suggests that the perceptual rules governing spatial grouping are analogous (if not identical) to those governing spatiotemporal grouping. As in the case of directional discrimination, texture-discrimination performances may be accounted for by the activation of higher-order units receiving inputs from subunits, all of which display similar tuning properties within a multidimensional space.

Color Perception↗
PubMed1988

Objective evidence for phase-independent spatial frequency analysis in the human visual pathway.

Electrophysiological responses in human index an interaction between responses to two gratings that is relatively independent of the distribution of light in the retinal image. Two 5 cycle/deg sinewave gratings were superimposed, one counterphase-modulated at F1 Hz and the other at F2 Hz. Nonlinear interaction terms of frequency (nF1 +/- mF2) were recorded that could not be produced by superimposing the F1 Hz grating on blank-field 7 Hz flicker. A local luminance origin could be excluded for the (2F1 + 2F2) term and for the suppression of 2F1 and 4F1, but not for the (F1 + F2), (F1 + 3F2) and (5F2 - F1) terms. The relative spatial phase of the two gratings was varied, thus altering the light distribution in the retinal image without changing its spatial power spectrum. The (2F1 + 2F2) Hz contrast-specific grating-grating interaction term was almost unaffected by these substantial changes in retinal image light distribution providing that the spatial frequency power spectrum of the retinal image was held constant. The (2F1 + 2F2) term and the suppression of 2F1 were both tuned to spatial frequency.

Evoked Potentials, Visual↗
PubMed1984

58,000 dalton intermediate filament proteins of neuronal and nonneuronal origin in the goldfish visual pathway.

A group of proteins in the goldfish optic nerve with a molecular weight of 58K daltons was analyzed by two-dimensional gel electrophoresis. Results show that the proteins are differentially phosphorylated and found exclusively in a cytoskeletal-enriched fraction. The proteins from this fraction can be reconstituted into typical intermediate filament structures, as shown by electron microscopy. Two components which are of neuronal origin are transported within the slow phase of transport. The 58K proteins are the most abundant proteins in the optic nerve, and they are distinct from actin and tubulin. It was concluded that they are intermediate filament proteins. Cytoskeletal preparations of rat spinal cord, rat optic nerve, and goldfish optic nerve were compared by one-dimensional gel electrophoresis. The rat spinal cord contains glial fibrillary acidic protein (GFAP), and the rat optic nerve contains vimentin and GFAP, in addition to the neurofilament triplet. A typical mammalian neurofilament triplet is not detected in the goldfish optic nerve, while the major cytoskeletal constituent is a 58K band which coelectrophoreses with vimentin in the rat optic nerve by one-dimensional gel electrophoresis.

Animals↗
PubMed1989

Motion processing by chromatic and achromatic visual pathways.

We describe a family of stimuli consisting of colored bars of different orientations, which, when presented in rapid succession, may elicit unambiguous motion perception. These stimuli permitted the isolation of directional spatiotemporal information extracted from oriented luminance clues, from nonoriented chromatic-plus-luminance clues, or, when the stimuli were presented under equiluminant conditions, from pure chromatic clues. As a general rule, matching of orientation induces weaker motion-detection performances than does matching of color. When the orientation clues are in competition with the chromatic ones, motion perception based on the former is always overridden by motion perception based on the latter. We indirectly isolated an oriented chromatic mechanism that also contributes to motion perception. We finally showed that, under equiluminant conditions, matching of orientation across different colors is inefficient in eliciting motion perception, either because motion information is extracted poorly across different chromatic channels or because such channels show little orientational selectivity. Because motion strength determined by each of the manipulated attributes follows different functions with the displacement (or velocity) of the stimuli, we propose the existence of three underlying mechanisms, a luminance mechanism, a chromatic-plus-luminance mechanism, and a pure chromatic mechanism, each of which provides motion information.

Attention↗
PubMed1977

Putative neurotransmitters of the avian visual pathway.

The ability of homogenates of the chick optic lobe to accumulate a series of possible neurotransmitters has been studied. High affinity uptake of several possible neurotransmitters was examined in optic lobes of 21-day-old embryos that had a single eye removed on the third day of incubation and in 23-day-old chicks that had an eye removed at hatch. Embryonic enucleation resulted in severe reduction of development of the ability of the contralateral optic lobe to take up tritiated GABA, dopamine, choline, serotonin and glutamate from solutions around 10(-8)M. Unilateral eye removal of new-hatched chicks caused failure of the denervated optic lobe to grow, but only the uptake capacity for glutamate was significantly recuced. This deficit was apparent as early as 4 days after enucleation. The transport of other compounds was unimpaired. The uptake of glutamate by homogenates of the optic tract was 43% of that or the optic lobe. This was a much greater fraction than the corresponding value for other postulated neurotransmitters. These data suggest that glutamate may be the primary neurotransmitter of the fibers of the optic tract originating in the retinal ganglion cells.

Age Factors↗
PubMed1998

Disruption of the activity-rest cycle by MAOI treatment: dependence on light and a secondary visual pathway to the circadian pacemaker.

The disruptive effects on the activity-rest cycle of the monoamine oxidase inhibitor (MAOI) clorgyline and of continuous light were examined in Syrian hamsters. When administered in dim and moderate light intensities, clorgyline delayed the daily onset of wheel-running. When administered in bright light, it dissociated the circadian rhythm of wheel-running. This dissociation was prevented by lesions of the intergeniculate leaflet of the ventral lateral geniculate nucleus. Constant darkness restored the circadian rhythm of wheel-running in hamsters with disrupted circadian rhythms. The phase of the restored rhythm of wheel-running was shifted 6-12 h later than the phase of wheel-running prior to dissociation. Our results suggest that MAOI treatment weakens the coupling between oscillators that comprise the circadian pacemaker, and augments the disruptive effects of continuous light acting via the intergeniculate leaflet region of the ventral lateral geniculate nucleus. These effects on the circadian pacemaker may be responsible for disruptions of the sleep-wake cycle that occur as side effects when MAOIs are used clinically to treat depression and might play a role in the induction of mania and rapid cycling by antidepressants.

Analysis of Variance↗
PubMed1973

Distribution coding in the visual pathway.

Although a variety of types of spike interval histograms have been reported, little attention has been given to the spike interval distribution as a neural code and to how different distributions are transmitted through neural networks. In this paper we present experimental results showing spike interval histograms recorded from retinal ganglion cells of the cat. These results exhibit a clear correlation between spike interval distribution and stimulus condition at the retinal ganglion cell level. The averaged mean rates of the cells studied were nearly the same in light as in darkness whereas the spike interval histograms were much more regular in light than in darkness. We present theoretical models which illustrate how such a distribution coding at the retinal level could be "interpreted" or recorded at some higher level of the nervous system such as the lateral geniculate nucleus. Interpretation is an essential requirement of a neural code which has often been overlooked in modeling studies. Analytical expressions are derived describing the role of distribution coding in determining the transfer characteristics of a simple interaction model and of a lateral inhibition network. Our work suggests that distribution coding might be interpreted by simply interconnected neural networks such as relay cell networks, in general, and the primary thalamic sensory nuclei in particular.

Animals↗
PubMed1997

Visual pathways for postural control and negative phototaxis in lamprey.

The functional roles of the major visuo-motor pathways were studied in lamprey. Responses to eye illumination were video-recorded in intact and chronically lesioned animals. Postural deficits during spontaneous swimming were analyzed to elucidate the roles of the lesioned structures for steering and postural control. Eye illumination in intact lampreys evoked the dorsal light response, that is, a roll tilt toward the light, and negative phototaxis, that is a lateral turn away from light, and locomotion. Complete tectum-ablation enhanced both responses. During swimming, a tendency for roll tilts and episodes of vertical upward swimming were seen. The neuronal circuitries for dorsal light response and negative phototaxis are thus essentially extratectal. Responses to eye illumination were abolished by contralateral pretectum-ablation but normal after the corresponding lesion on the ipsilateral side. Contralateral pretectum thus plays an important role for dorsal light response and negative phototaxis. To determine the roles of pretectal efferent pathways for the responses, animals with a midmesencephalic hemisection were tested. Noncrossed pretecto-reticular fibers from the ipsilateral pretectum and crossed fibers from the contralateral side were transected. Eye illumination on the lesioned side evoked negative phototaxis but no dorsal light response. Eye illumination on the intact side evoked an enhanced dorsal light response, whereas negative phototaxis was replaced with straight locomotion or positive phototaxis. The crossed pretecto-reticular projection is thus most important for the dorsal light response, whereas the noncrossed projection presumably plays the major role for negative phototaxis. Transection of the ventral rhombencephalic commissure enhanced dorsal light response; negative phototaxis was retained with smaller turning angles than normal. Spontaneous locomotion showed episodes of backward swimming and deficient roll control (tilting tendency). Transections of different spinal pathways were performed immediately caudal to the brain stem. All spinal lesions left dorsal light response in attached state unaffected; this response presumably is mediated by the brain stem. Spinal hemisection impaired all ipsiversive yaw turns; the animals spontaneously rolled to the intact side. Bilateral transection of the lateral columns impaired all yaw turns, whereas roll control and dorsal light response were normal. After transection of the medial spinal cord, yaw turns still could be performed whereas dorsal light response was suppressed or abolished, and a roll tilting tendency during spontaneous locomotion was seen. We conclude that the contralateral optic nerve projection to the pretectal region is necessary and sufficient for negative phototaxis and dorsal light response. The crossed descending pretectal projection is most important for dorsal light response, whereas the noncrossed one is most important for negative phototaxis. In the most rostral spinal cord, fibers for lateral yaw turns travel mainly in the lateral columns, whereas fibers for roll turns travel mainly in the medial spinal cord.

Animals↗
PubMed1988

Regenerated optic fibers in goldfish reestablish a crude sectoral order in the visual pathway.

The goldfish optic pathway is regenerated after an optic nerve crush. We have examined the axonal topography of the regenerated pathway by labeling, with horseradish peroxidase (HRP), axons originating from retinal sectors or annuli. The positions of the labeled axons in the cross section of the pathway were compared to the normal and related to the factors that may influence axonal pathfinding. The positions of retinal axons in the cross section of the normal pathway are predictable from the retinal addresses of the ganglion cells described by the polar coordinates r (the distance from the optic disc) and theta (the sectoral or clockface position). The two coordinates map orthogonally onto the cross section of the pathway; r varies monotonically along one axis; theta varies along a perpendicular axis. The normal r-order, present in the nonregenerated stump of the experimental nerve, was severely degraded and perhaps lost entirely in the regenerated optic nerve, tract, and brachia. Sectoral order was also lost as the axons passed the crush site, but it was reestablished, albeit crudely, in the regenerated tract and brachia where axons tended to occupy positions appropriate to their dorsal, ventral, nasal, and temporal retinal origins. The exit sequence of the regenerated axons from the stratum opticum into the tectal neuropil was normal: temporal first, nasal last. These results suggest that the regenerating fibers followed some theta-specific cue located in the nonaxonal environment. It seems likely that the original axons probably followed the same cue. In contrast, the absence of r-order suggests that there is no r-specific cue for the regenerates to follow. It seems likely that the original r-order was a consequence of nonspecific influences--the orderly spatiotemporal growth of the retina and the existence of a permissive region for axonal growth.

Animals↗
PubMed1999

The performance of synapses that convey discrete graded potentials in an insect visual pathway.

Synapses from nonspiking neurons transmit small graded changes in potential, but variability in their postsynaptic potential amplitudes has not been extensively studied. At synapses where the presynaptic signal is an all-or-none spike, the probabilistic manner of neurotransmitter release causes variation in the amplitudes of postsynaptic potentials. I have measured the reliability of the operation of synapses that convey small graded potentials between pairs of identified large, second-order neurons in the locust ocellar system. IPSPs are mediated by small rebound spikes, which are graded in amplitude, in the presynaptic neuron. A transfer curve plotting amplitudes of spikes against amplitudes of IPSPs has a characteristic S shape with a linear central portion where IPSP amplitude is between -0.2 and -0.6 as large as spike amplitude but shows appreciable scatter. Approximately half of the scatter is attributable to background noise, most of which originates in photoreceptors and persists in darkness. The remaining noise is intrinsic to the synapse itself and is usually 0.3-0.7 mV in amplitude. It limits the resolution with which two spike amplitudes can be distinguished from one another to approximately 2 mV and, because the linear part of the transfer curve occupies approximately 10 mV in spike amplitudes, limits the number of discrete signal levels that can be conveyed across the synapse to approximately five. The amplitude of the noise is constant throughout the synaptic operating range, which means it is unlikely that presynaptic membrane potential controls transmitter release by setting a single probability level for quantal release.

Animals↗
PubMed1990

Anatomical segregation of two cortical visual pathways in the macaque monkey.

A number of lines of evidence suggest that, in the macaque monkey, inferior parietal and inferotemporal cortices process different types of visual information. It has been suggested that visual information reaching these two subdivisions follows separate pathways from the striate cortex through the prestriate cortex. We examined directly this possibility by placing injections of the retrograde fluorescent tracers, fast blue and diamidino yellow, in inferior parietal and inferotemporal cortex and examining the spatial pattern of cortical areas containing labeled cells in two-dimensional reconstructions of the cortex. The results of injections in inferotemporal cortex show that TEO receives afferents from areas V2, ventral V3, V3A, central V4, V4t, and DPL in prestriate cortex and from areas IPa, PGa, and FST in the superior temporal sulcus (STS). Area TEp receives afferents only from V4 in prestriate cortex and from IPa, PGa, and FST in the anterior STS. Area TEa receives no prestriate input and is innervated by IPa, PGa, FST, and TPO in the anterior STS. The results of injections in inferior parietal cortex demonstrate that POa receives afferents from dorsal V3, V3A, peripheral V4, DPL, and PO in prestriate cortex, from MST and *VIP and from IPa, PGa, TPO, and FST in anterior STS. Area PGc (corresponding to 7a) is innervated by PO, MST, and by TPO in the anterior STS. Examination of the two-dimensional reconstructions of the pattern of labeling after combined injections of fast blue and diamidino yellow in areas POa and TEO revealed that these areas are principally innervated by different prestriate areas. Only a small region, centered on area V3A and extending into V4 and DPL, contained cells labeled by either injection as well as a small number of double-labeled cells. In contrast, areas POa and TEO receive afferents from extensive common regions in the anterior STS corresponding to areas IPa, PGa, and FST. These results directly demonstrate that visual information from the striate cortex reaches inferior parietal and inferotemporal cortices through largely separate prestriate cortical pathways. On the other hand, both parietal and inferotemporal cortices receive common inputs from extensive regions in the anterior STS which map play a role in linking the processing occurring in these two cortical subdivisions of the visual system.

Amidines↗
PubMed1991

Retinal projections in the freshwater butterfly fish, Pantodon buchholzi (Osteoglossoidei). I. Cytoarchitectonic analysis and primary visual pathways.

The freshwater butterfly fish, Pantodon buchholzi, is a member of the most primitive radiation of teleosts. The retinofugal projections were studied in this fish with autoradiographic and horseradish peroxidase (HRP) methods, and the cytoarchitecture of the retinorecipient regions in the diencephalon and pretectum was analyzed with Bodian-, cresylecht-violet- and acetylcholinesterase-reacted sections. The rostral diencephalon of Pantodon contains a large retinorecipient nucleus, not previously identified in any other fish, i.e. nucleus rostrolateralis. Other nuclei that are described correspond to those previously recognized in other species. The majority of retinorecipient nuclei are positive for acetylcholinesterase, particularly those in the pretectum, as has been found in other species of teleosts. Most of the retinofugal fibers decussate in the optic chiasm. Some fibers project via the axial optic tract to preoptic nuclei and a region in the rostral hypothalamus. Fibers leave the medial optic tract to terminate in nucleus rostrolateralis and in dorsal and ventral thalamic nuclei, accessory optic and tubercular nuclei, periventricular and central pretectal nuclei, and sparsely in the deep tectal fascicle and terminal field. Dorsal optic tract fibers project to the dorsal accessory optic nucleus, superficial and central pretectal nuclei, and superficial and deep tectal layers. Ventral optic tract fibers project to the superficial pretectum, accessory optic nuclei, posterior tuberculum, nucleus corticalis in the central pretectum, and superficial tectal layer. Fibers that remain in the ipsilateral optic tract project to most of the targets reached by contralaterally projecting fibers. A few fibers in the contralateral medial optic tract redecussate via the posterior commissure to reach the ipsilateral periventricular pretectum. No labeled retinopetal cells caudal to the olfactory bulb were identified in any of the HRP cases.

Acetylcholinesterase↗
PubMed1988

Aberrant optic axons in the retinal pigment epithelium during chick and quail visual pathway development.

Examination of a large number of retinal pigment epithelia revealed that, in a small proportion, optic axons in chick and quail eyes aberrantly entered the pigment cell layer between embryonic day (E) 7 to E14. The aberrant retinal axons originated from the main stream of retinal fibers in the optic nerve and invaded the pigment layer from various positions of the optic nerve head or fissure by growing along the basal side of the pigment epithelium. The axon bundles grew several millimeters into the epithelial sheet and arborized at the margin of the eye. As shown by electron microscopy the nerve fibers occurred as bundles of three to several hundred axons. They always were located at the basal side of the epithelium, and were enveloped by processes of epithelial cells. Very large bundles of axons, however, displaced the epithelial cells from the basal matrix. These retinal axons contacted the pigment epithelial basal lamina. The basal extracellular matrix from the retinal pigment epithelium was isolated and used as substratum for in vitro cultures of various types of neural explants. The matrix preparations consisted of a sheet of a 50 nm thick basal lamina with a central lamina densa, two laminae rarae, and a 15 micron thick stroma. Axons from avian retina explants, as well as sensory ganglia, grew on the basal lamina side of the pigment cell matrix with the same growth rate and with the same fiber density as on similarly prepared basal laminae from the neural retina. These experiments show that the matrix from the pigment epithelium of the avian eye does not have negative effects on axonal growth and indicate that a basal lamina from a normally non-innervated tissue can provide a favorable matrix for axonal growth.

Animals↗