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At least 55 records · Page 3Linked to original sources
PubMed1975

Use of the Pulfrich pendulum for detecting abnormal delay in the visual pathway in multiple sclerosis.

(1) Pulfrich's pendulum has been developed as a method for detecting abnormal delay in the visual pathway of patients with suspected multiple sclerosis. (2) Forty-one normal subjects gave a mean interocular latency difference of 2-4 +/- 1-8 msec on Pulfrich's pendulum. This mean +2 SD (6 msec) was taken as the limit of normal interocular latency difference by this method. (3) The test was assessed on 58 patients. Eighteen of these had definite multiple sclerosis, 9 had probable multiple sclerosis, and 8 had possible multiple sclerosis, according to clinical criteria. The remaining 23 patients did not conform with clinical criteria for multiple sclerosis, and served as neurological controls. Thirteen of these 23 patients had abnormal signs in the visual system. All the 58 patients also had visual evoked responses (VERs) recorded. (4) Interocular latency difference was outside the normal range in 9/18 with definite multiple sclerosis, in 3/9 with probably multiple sclerosis and in 2/8 with possible multiple sclerosis. (5) Interocular latency difference was outside the normal range in 2/23 patients with other neurological disorders. (6) There was a strong correlation between abnormality on the Pulfrich pendulum and on the VER for the multiple sclerosis group. (7) Individual results are compared with those from the VER. There was no significant correlation of the size and direction of the interocular latency difference obtained from the Pulfrich pendulum with that obtained from the VER, for any group. Possible reasons for this are discussed. (8) It is concluded that Pulfrich's pendulum is an easily performed and potentially useful subjective test for detecting abnormal dealy in the visual pathway in multiple sclerosis.

Adolescent↗
PubMed1991

Sensitivity and integration in a visual pathway for circadian entrainment in the hamster (Mesocricetus auratus).

1. Light-induced phase shifts of the circadian rhythm of wheel-running activity were used to measure the photic sensitivity of a circadian pacemaker and the visual pathway that conveys light information to it in the golden hamster (Mesocricetus auratus). The sensitivity to stimulus irradiance and duration was assessed by measuring the magnitude of phase-shift responses to photic stimuli of different irradiance and duration. The visual sensitivity was also measured at three different phases of the circadian rhythm. 2. The stimulus-response curves measured at different circadian phases suggest that the maximum phase-shift is the only aspect of visual responsivity to change as a function of the circadian day. The half-saturation constants (sigma) for the stimulus-response curves are not significantly different over the three circadian phases tested. The photic sensitivity to irradiance (1/sigma) appears to remain constant over the circadian day. 3. The hamster circadian pacemaker and the photoreceptive system that subserves it are more sensitive to the irradiance of longer-duration stimuli than to irradiance of briefer stimuli. The system is maximally sensitive to the irradiance of stimuli of 300 s and longer in duration. A quantitative model is presented to explain the changes that occur in the stimulus-response curves as a function of photic stimulus duration. 4. The threshold for photic stimulation of the hamster circadian pacemaker is also quite high. The threshold irradiance (the minimum irradiance necessary to induce statistically significant responses) is approximately 10(11) photons cm-2 s-1 for optimal stimulus durations. This threshold is equivalent to a luminance at the cornea of 0.1 cd m-2. 5. We also measured the sensitivity of this visual pathway to the total number of photons in a stimulus. This system is maximally sensitive to photons in stimuli between 30 and 3600 s in duration. The maximum quantum efficiency of photic integration occurs in 300 s stimuli. 6. These results suggest that the visual pathways that convey light information to the mammalian circadian pacemaker possess several unique characteristics. These pathways are relatively insensitive to light irradiance and also integrate light inputs over relatively long durations. This visual system, therefore, possesses an optimal sensitivity of 'tuning' to total photons delivered in stimuli of several minutes in duration. Together these characteristics may make this visual system unresponsive to environmental 'noise' that would interfere with the entrainment of circadian rhythms to light-dark cycles.

Animals↗
PubMed1988

Sarcoidosis of the anterior visual pathway: successes and failures.

Four patients with progressive visual deterioration were found to have sarcoidosis involving the anterior visual pathway. They all developed chiasmal dysfunction and bilateral optic neuropathy, which responded to megadose corticosteroid therapy. When an attempt was made to withdraw the corticosteroids, the patients experienced a recrudescence of visual dysfunction and were subsequently unable to tolerate the corticosteroid dose levels necessary to maximise their visual potential. Each patient was treated with high-voltage radiation therapy, totalling up to 4500 rads. The beneficial response obtained was temporary, and immunosuppressive therapy with azathioprine or chlorambucil was instituted, preventing further deterioration.

Adrenal Cortex Hormones↗
PubMed1986

A second ascending visual pathway from the optic tectum to the telencephalon in the pigeon (Columba livia).

Previous studies in the pigeon (Karten and Revzin: Brain Res. 2:368-377, '66; Karten and Hodos: J. Comp. Neurol. 140:35-52, '70) have described an ascending tectofugal visual pathway from the optic tectum to the ectostriatum by way of the nucleus rotundus of the thalamus. This present study used anterograde autoradiographic and retrograde horseradish peroxidase pathway-tracing techniques to investigate another ascending tectofugal pathway in the pigeon. Injections of 3H-proline/leucine confirmed a previous report that the optic tectum projects to the nucleus dorsolateralis posterior of the thalamus (DLP). This projection is predominantly ipsilateral and is confined to a large-celled caudal region of the nucleus (DLPc); the rostral region of the nucleus (DLPr) is not tectorecipient. Injections of horseradish peroxidase in DLPc labeled cells predominantly ipsilaterally in layers 8-15 of the optic tectum. Injections of 3H-proline/leucine placed in the DLPc labeled a discrete region of the ipsilateral telencephalon. Similar injections of DLPr labeled a contiguous, but more rostral, region of the neostriatum intermedium. Nissl- and silver-stained material indicated that the region in which DLP terminates is cytoarchitecturally distinct from ventromedial ectostriatal core and belt. Injections of horseradish peroxidase at various locations in the neostriatal DLP terminal field demonstrated a rostrocaudal ordering of the DLP projection upon the neostriatum intermedium. Single-unit recording demonstrated that cells in DLPc respond to whole-field illumination at the same latency as cells in the nucleus rotundus, indicating that the tecto-DLPc-neostriatal pathway transmits visual information to the telencephalon. We suggest that comparable pathways may exist in both reptiles and mammals.

Animals↗
PubMed1981

Sensitivity deficits consistent with aberrant crossed visual pathways in human albinos.

There is both anatomical and electrophysiological evidence that human albinos have abnormally crossed visual pathways. The present study examined some perceptual consequences of such pathways on the visual abilities of 12 oculocutaneous albinos and one ocular albino. Measurements were made of visual fields in all subjects. For seven subjects, contrast sensitivity functions were obtained for the central, nasal, and temporal retinas. There was a wide variation in the dimensions of the visual fields, but there was no evidence for a loss corresponding to the origin of the aberrant projections. On the basis of their contrast sensitivity functions, however, it was possible to classify the albinos into two groups. One group, with higher overall sensitivity, showed no differences between central, nasal, and temporal retina. The other group showed a marked depression in sensitivity for the temporal retina, indicating that in some albinos, information from the retinal region corresponding to the aberrant pathway is degraded.

Adult↗
PubMed1985

[Value of visual evoked potentials (VEP) in compression of the anterior visual pathway, especially in the area of the chiasm].

We investigated 86 patients by pattern half-field stimulation presenting clinically with temporal field-defects or with a mass causing compression of the visual pathways found by C.T.-scanning. Pattern half-field stimulation proved to be a very sensitive method for detecting a compression of the anterior visual pathways. In 65 cases the results of perimetry and VEP were congruent, 6 times the evoked potential was pathologic the perimetry showing no abnormalities, only 1 false negative VEP was observed. Thus we stress the importance of an investigation by VEP including half-field stimulation in all patients with suspected compression of the anterior visual pathways.

Evoked Potentials, Visual↗
PubMedDate not supplied

Corticofugal feedback influences the generation of length tuning in the visual pathway.

In the feline visual system, neurons exhibiting sensitivity to the length of a moving contour were first observed in the cortex and described as 'hypercomplex cells'. In these cells an increase in stimulus length beyond an optimal value leads to a rapid decline in response. This decline has been attributed to an intracortical inhibitory input which may be driven by layer VI cells with very long receptive fields. It is now clear, however, that cells in the dorsal lateral geniculate nucleus (dLGN), exhibit a degree of length tuning similar to that of cortical 'hypercomplex cells', suggesting that this response property could be generated subcortically. Alternatively, as the dLGN receives a massive corticofugal projection from layer VI cells in the visual cortex, it is possible that this input has a function in generating length tuning in the dLGN. We have investigated this issue by comparing the length tuning of dLGN cells with and without corticofugal feedback. The data show that corticofugal feedback makes a highly significant contribution to the length tuning of dLGN cells. This raises the possibility that length tuning is an emergent property of the geniculo-cortical loop.

Animals↗
PubMed1994

Immunocytochemical localization of the alpha-, beta I-, beta II- and gamma-subspecies of protein kinase C in the monkey visual pathway.

We examined the distribution of alpha-, beta I-, beta II- and gamma-subspecies of protein kinase C (PKC) in the monkey visual pathway, including the retina, the lateral geniculate nucleus (LGN) and the visual cortex (area 17). In the retina, alpha-PKC immunoreactivity was found in cone photoreceptor and in bipolar cells. beta I-PKC immunoreactivity was present in the ganglion cell layer and the optic nerve fibers. The beta II- and gamma-PKCs were not found in the retina. In the LGN, intense gamma-PKC immunoreactivity was found in a part of magno and parvo cells. The LGN was negative for the alpha-, beta I- and beta II-PKC. All four PKC subspecies were present in the visual cortex but the distribution was distinct. The beta I-PKC immunoreactive cells were scattered in all layers, while the alpha-PKC immunoreactive cells were prominent in layers II, III, IVb, IVc and VI, and the beta II-PKC immunoreactive cells were found in layers II, III, IVb and VI. The intense gamma-PKC immunoreactivity was present in the neuropils in layers I, IVa, IVc and VI and also in soma and dendrites in layers II and VI. It thus seems likely that each subspecies plays a specific role in neuronal transmission in the visual pathway.

Amino Acid Sequence↗
PubMed1982

Somatostatin-like immunoreactivity in the central visual pathway of the prenatal rat.

Somatostatin (SRIF)-like immunoreactivity was localized in the central visual pathway of near-term prenatal rats using light-microscopic immunocytochemistry and a highly specific antibody to the peptide. SRIF was demonstrable in neuronal perikarya and fibers of the lateral geniculate nucleus, superior colliculus and visual cortex. At this stage the distribution of these elements had not attained the pattern seen in the adult. The presence of SRIF in the central visual pathway prior to maturation suggests a role for this peptide in the development of visual function.

Animals↗
PubMed1982

WGA-HRP as a transneuronal marker in the visual pathways of monkey and rat.

Wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP) was injected intraocularly in monkeys and rats. All known primary visual pathways were labeled and, in addition, ocular dominance columns in visual cortex were labeled in monkey, and in rat, parabigeminal, oculomotor, thalamic reticular, and visual cortical areas were labeled as well as neuronal soma in superior colliculus. We conclude that WGA-HRP is a useful transneuronal marker for visual pathways.

Animals↗
PubMed1990

The influence of action potentials on the development of the central visual pathway in mammals.

The development of the mammalian visual system begins prenatally at distributed sites, where cells generated at different embryonic ages are destined to interconnect and form the visual pathways, and ends postnatally with the functional tuning of neuronal receptive-field properties. It is reasonable to assume that the earliest stages in this developmental sequence are completed prior to the onset of neural activity, and also that activity may play only a minor role or even none at all in primary axon outgrowth and pathway finding (Harris, 1981; Harris and Holt, 1990). However, recent evidence indicates that subsequent events in development, such as the sorting of axons at their targets, the cellular differentiation of target cells and the formation of synaptic contacts by developing axons, are all influenced by action potentials. Action potentials in the developing retino-geniculo-cortical pathway can be eliminated by blocking the voltage-gated sodium channel with tetrodotoxin. Prenatal blockade prevents the laminar segregation of retinogeniculate axons. Postnatal blockade interrupts the formation of retinogeniculate synaptogenesis, slows the cytoarchitectonic differentiation of the lateral geniculate nucleus and produces abnormalities in the responses of lateral geniculate neurons. In the visual cortex, the development of cells and synapses is retarded and the eye-specific separation of geniculocortical axons is halted, thereby blocking the formation of ocular dominance columns. While the cellular mechanisms underlying these effects are not understood, a partial restoration of normal development can be produced by stimulating blocked axonal pathways electrically.

Action Potentials↗
PubMed1994

Effect of endoscopic white light on the developing visual pathway: a histologic, histochemical, and behavioral study.

OBJECTIVE: We examined the potential teratogenic effect of endoscopic white light on the developing visual pathways. STUDY DESIGN: The right eye of chicken embryos (n = 22) was exposed to maximal endoscopic light intensity on day 10 of development. At day 17 of development the histologic characteristics of the light-exposed retinas were compared with those of the control embryos (n = 4). Normal functioning of the light-exposed eye was assessed by intravitreal injection of wheat germ agglutinin-horseradish peroxidase and observation of its axonal transport pattern to the diencephalic and mesencephalic visual centers. Axonal transport patterns were compared with those found in previous studies of normal embryos. Behavioral feeding patterns were compared between two groups of newly hatched chickens, one exposed to endoscopic light after hatching (n = 13) and the other, an unexposed control group (n = 12). RESULTS: No evidence of retinal damage, altered axonal transport or altered feeding patterns could be found between control and experimental animals. CONCLUSION: Endoscopic white light does not appear to be harmful to the developing retina and visual pathway.

Animals↗
PubMedDate not supplied

MR of visual pathways in patients with neurofibromatosis.

MR was performed on six patients clinically diagnosed as having neurofibromatosis. Owing to its multiplanar capability, MR greatly helped determine the extent of visual pathway disease. We attempted to find specific optimal pulse sequences for evaluating the prechiasmatic, chiasmatic, and retrochiasmatic visual system at 0.35 T. Using spin-echo techniques, we evaluated a T1-weighted sequence (TR 300 msec/TE 35 msec), an intermediate T2-weighted sequence (TR 1500 msec/TE 35 msec), and a T2-weighted sequence (TR 1500 msec/TR 70 msec). We found that the orbital and intracanalicular optic nerves were most accurately and easily seen with the T1-weighted sequence axially and coronally; the chiasm was best seen with the intermediate T2-weighted coronal sequence; and the retrochiasmatic visual pathway was optimally evaluated with T2-weighted spin-echo technique.

Child↗
PubMed1989

Glial fibrillary acidic protein (GFAP) from goldfish: its localisation in visual pathway.

An intermediate filament fraction, isolated from goldfish brain, contains a prominent protein having a molecular weight of 51 kDa. In normal goldfish visual pathway, this protein is present in tectum and tract, but not in optic nerve. A polyclonal antibody raised to this protein clearly labels ependymal glial profiles in tectum and parallel processes in the tract, whereas optic nerve is unlabelled; Müller fibres in the retina are also labelled. A similar, but less prominent, pattern of staining is observed with antibodies, raised elsewhere, against glial fibrillary acidic protein from human and porcine. These results suggest that the 51 kDa protein is a GFAP, demonstrate the heterogeneity of astrocytes in goldfish visual pathway, and are consistent with the idea that GFAP is well conserved in vertebrate phylogeny.

Animals↗
PubMed1975

[A light-independent function of the retina of rabbits. Examination on the energetic part of the visual pathway (author's transl)].

In this study a light-independent function of the retina of rabbits could be proved. For this purpose, the energetic part of the visual pathway was utilized, and its influence on the maturation of the testicles was examined. As a criterion of maturation, the pattern of the phosphatid-fatty acids was ascertained. The subdivision of the energetic part of the visual pathway into a photo-energetic and an autonomic-energetic component is proposed.

Animals↗
PubMed1984

Dissociated vertical deviation: evidence of abnormal visual pathway projection.

Abnormalities in visually evoked responses have been used to demonstrate abnormal optic nerve fibre projections in human albinos, who have anomalous nystagmoid movements. Using visually evoked potentials we tested the hypothesis that patients with dissociated vertical deviation (another group with anomalous nystagmoid movements) may have abnormal visual evoked responses similar to those of albinos. Patients with dissociated vertical deviation (both unilateral and alternating), patients with congenital esotropia without dissociated vertical deviation, and normal subjects were investigated. The results showed a very high incidence of abnormal visual evoked responses in patients with dissociated vertical deviation, while recordings from the other groups were normal. As well as suggesting the possibility of abnormalities of optic nerve fibre projections, the visual evoked responses showed a marked increase in latency in all patients with dissociated vertical deviation. These results occurred regardless of the visual acuity or amblyopia of the eyes tested. The possible existence of abnormal pathway projection in the presence of dissociated vertical deviation is discussed.

Evoked Potentials, Visual↗
PubMed1983

[Morphological development of the primary visual pathway in the child].

This study concerns the development of the human primary visual pathway. The lateral geniculate nucleus (LGN), the principle thalamic relay to the visual cortex (area 17), has a population of neurons similar to that of the monkey, as identified by Golgi impregnation. Commonest neuron is the multipolar with a radiate or tufted dendritic tree, followed by the bipolar neuron with two or three diametrically opposed dendritic trunks and, more rarely, neurons with beaded dendrites and those with fine, axon-like dendritic processes, possibly interneurons. The dendritic tree of all neurons remains generally within a lamina, but some dendrites cross interlaminar zones. These zones contain neurons whose dendrites enter adjacent laminae. LGN neurons are identifiable at birth, and even earlier, and differ from their adult form by the presence of immature features (growth cones and numerous dendritic and somatic spines), most frequent at four months but disappearing completely by nine months post-natally, when the LGN has reached its "adult" volume. Two stages in the development of area 17 can be defined. The first is marked by rapid growth to its "adult" volume at about four months, and by intense synaptogenesis beginning in the foetus and reaching a maximum around eight months. The second stage is one of stabilization of volume of area 17 and loss of synapses to reach "adult" synaptic density around 11 years, at about 60 p. cent of maximum values. The formation of transitory morphological features in the first year coincides with a period of visual plasticity in the infant. Our observations can be correlated with clinical evaluations of visual activity during the preverbal stage, a period of great importance in the establishment of visual acuity, of stereopsis, and of oculomotor function, all very sensitive to the numerous forms of visual deprivation.

Animals↗
PubMed1981

Labelling by axonal transport of myelin-associated proteins in the rabbit visual pathway.

After intraocular injections of [3H]leucine, six regions of the visual pathway of adult rabbit were used to study the spatio-temporal pattern of the slow anterograde axonal transport of radioactive proteins associated with the particulate fraction, the water-soluble fraction and the myelin fraction. Unlike other fractions, myelin-associated labelled proteins represented a time-constant (for a given region) percentage of total tissue radioactivity. This percentage increased from the first half to the second half of the optic nerve and remained high in the chiasma and tract. The peak specific radioactivity of myelin decreased in the same direction. Myelin proteins were separated by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis and the labelling patterns obtained in different regions and at different survival times were compared. At the peak of myelin radioactivity of a given region the label was typically associated with four protein bands, L1, L2, L3 and L4, of 40000, 44000, 62000, and 68000 mol.wts. respectively. The basic protein, the proteolipid protein and the W1 component (mol.wt. 51000-53000) of the Wolfgram proteins were not significantly labelled. The radioactivity associated with the W2 component (mol.wt 60000) of the Wolfgram proteins could be derived from the closely migrating L3 component. At shorter survival times no clear labelling pattern could be detected. At longer survival times radioactivity was almost totally localized around band L3. The results presented underline the importance of choosing appropriate experimental conditions to obtain a consistent labelling pattern of myelin-associated proteins and to investigate the possible mechanism responsible for this phenomenon.

Animals↗