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PubMed1986

Evaluation of visual pathways in multiple sclerosis. I. After-images compared to visual evoked potentials.

The value of flight of colours (FOC), i.e. the succession of coloured afterimages following light stimulation, in diagnosing and following visual impairment was evaluated in 65 patients with multiple sclerosis (MS). Previous optimistic reports of the use of a pocket flashlight (PFL) method could not be confirmed, and are ascribed to inadequate methods. An electronic flashlight (EFL) method developed by us, proved a significantly better diagnostic tool (61% abnormal versus 18% abnormal). The EFL method was diagnostically less sensitive than pattern reversal visual evoked potential (PR-VEP) (80% abnormal). It did, however, add to PR-VEP by diagnosing 16 eyes with normal PR-VEP latency. The EFL method reflected the degree of degenerative changes in the central visual pathways and may be of value in following the disease activity in MS. The potential of the EFL method may be further improved by proposed modifications.

Afterimage↗
PubMed1989

Pattern electroretinography in patients with delayed pattern visual evoked potentials due to distal anterior visual pathway dysfunction.

Between March 1983 and January 1988 delayed pattern visual evoked potentials (PVEP) were observed in 67 patients with distal visual pathway dysfunction. Many of these patients had been referred for neurophysiological examination because of possible optic nerve dysfunction. These patients also had pattern electroretinography (PERG) performed which in all cases showed an abnormality of the main positive P50 component. None of these patients had an abnormality confined to the negative N95 component, the type of abnormality usually found if the PERG is abnormal in optic nerve disease. It is suggested that PERG recording should now be a routine adjunct to the PVEP in the assessment of anterior visual pathway dysfunction.

Adolescent↗
PubMed1989

Reorganization of visual pathways following posthatching removal of one retina in pigeons.

Organization of visual pathways was studied in 2-month-old pigeons that underwent unilateral retinal removal on either the day of hatching (ERA, i.e., early retinal ablated) or the 9th day after hatching (LRA, i.e., late retinal ablated). A general size reduction of visual areas contralateral to the removed retina was found in ERA pigeons, which additionally showed an altered differentiation of thalamic visual targets as well as a different cytoarchitectonic arrangement of the superficial layers of the optic tectum. No comparable modifications were found in LRA pigeons. The retinal projections of the remaining eye were studied following intraocular injections of 3H-proline. Both in ERA and LRA pigeons, the distribution of retinofugal afferents to primary visual regions contralateral to the injected eye was similar to that of control pigeons. Anomalous ipsilateral projections from the remaining retina to primary retinorecipient regions were found in ERA pigeons only. Effects of early ablation of one retina on second-order visual connections were also studied. Following injections of wheat germ agglutinin-conjugated horseradish peroxidase (WGA-HRP) into the visual Wulst contralateral to the operated eye, a smaller number of ipsilateral projecting thalamo-Wulst neurons was found as compared with control pigeons. In contrast, the contralateral thalamo-Wulst projections were increased. No changes in thalamo-Wulst projections were found following tracer injections into the opposite Wulst, i.e., ipsilateral to the operated eye. The present study demonstrates a substantial anatomical reorganization of both primary and secondary visual pathways following unilateral retinal removal immediately after hatching, when maturation of the visual system is not yet completed.

Animals↗
PubMedDate not supplied

Visual pathway abnormalities in albinism and infantile nystagmus: VECPs and stereoacuity measurements.

The visual pathway of albinos is characterized by abnormal optic nerve fiber decussation with increased contralateral projection. This results in hemispheric asymmetry of monocular visually evoked cortical potentials (VECPs) and may be related to lack of stereopsis. Flash VECP, Random Dot E (RDE), and Titmus stereotest data were collected from 40 nystagmus patients, 19 albino and 21 with normal pigmentation. Data were compared with results obtained from 19 race- and age-matched normal subjects. All albino patients demonstrated hemispheric VECP asymmetries exceeding +/- 2.0 standard deviations from the normal mean, showing either delayed ipsilateral P latency (88%), reduced ipsilateral P amplitude (59%), or both (47%). None of the normally pigmented infantile nystagmus patients exceeded this criteria on either VECP measure. While only one albinotic patient showed positive RDE and stereofly results, 86% of normally pigmented nystagmus patients passed the stereofly test, 60% demonstrated 400 sec (Titmus) stereopsis, and 66% showed positive RDE results. These findings reveal that normally pigmented infantile nystagmus patients have variable degrees of stereopsis and no excessive abnormalities of optic nerve fiber decussation as evidenced by flash VECP. Additionally, this study verifies visual pathway abnormalities and the lack of stereopsis in albino nystagmus patients.

Albinism↗
PubMed1991

Different susceptibilities of the geniculate and extrageniculate visual pathways to human Creutzfeldt-Jakob disease (a combined neurophysiological-neuropathological study).

Flash evoked visual potentials (FEPs) of 7 patients with advanced Creutzfeldt-Jakob disease (CJD) were compared with those recorded in 7 patients with senile dementia of the Alzheimer type (SDAT), in 13 age- and sex-matched healthy volunteers and in 7 neuropsychiatrically normal subjects whose occipital evoked responses were increased in amplitude (amplitude controls). Post-mortem examination was performed in 4 of 7 CJD patients in order to map pathological changes along the visual pathways, including the retino-geniculo-striate and extrageniculate pathways. Normal FEPs were typified by 2 constant early components (P1 and N2) followed by several (3 or more) late components that were characterized by marked interindividual variability. Amplitude controls had enlarged (from 14 to 44.8 microV, mean 25.7) P1 component. Both SDAT and CJD patients had normal early FEP waves (P1 and N2) and important alterations of the late FEP components. Moreover, a late positive component was responsible for abnormally enlarged FEPs (52.6 and 58.2 microV) in 2 CJD patients. Finally, electroretinograms, recorded in 1 CJD patient, were normal. These findings suggested relative functional integrity of the retino-geniculo-striate pathway associated with important dysfunction of the cortical visual processing in both SDAT and CJD patients. Pathological studies disclosed preservation of optic nerves, chiasmas, lateral geniculate nuclei and Gennari's strip of the striate cortex but associated with important spongiform change, neuronal loss and gliosis in the superior colliculi (layer II), pulvinar, extrastriate cortex and layers II-III, V and VI of the striate cortex. We conclude that different visual pathways have different susceptibilities to CJD: important functional and anatomical alterations of the intracortical and extrageniculate pathways contrast with relative preservation of the retino-geniculo-striate pathway.

Adult↗
PubMed1992

Electrophysiologic evaluation of the visual pathway in children. Case reports.

Clinical findings and results of electrophysiologic evaluation of the visual pathway were studied in seven children ranging in age from 10 months to 13 years. Using skin electrodes for electroretinographic and visual evoked potential testing, we obtained reliable results without sedation or pupil dilation. The half-field stimulation was indispensable for localizing lesions along the visual pathway and thus for specific diagnosis.

Adolescent↗
PubMed1990

Spread of Creutzfeldt-Jakob disease virus along visual pathways after intraocular inoculation.

We studied the targeting of spongiform lesions within the visual pathways after intraocular injection with the Fujisaki strain of Creutzfeldt-Jakob disease (CJD) virus. The first lesions were observed 18 weeks postinoculation in the most superficial layer of the superior colliculus and in the lateral geniculate body contralateral to the side of the inoculation. Asymmetrical lesions in the superior colliculus were found also in mice sacrificed at 19, 22, and 27 weeks postinoculation. These results demonstrate that CJD virus spreads within the CNS via central axons of the visual pathways following intraocular inoculation.

Animals↗
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↗
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↗
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↗
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↗