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At least 1,135 records · Page 63Linked to original sources
PubMed2003

[The value of VEP assessment and immunological csf analysis in the diagnosis of childhood and juvenile MS].

Multiple sclerosis (MS) in children and adolescents is a rare disease. In such cases additional evidence from visual evoked potential (VEP) recordings, cerebrospinal fluid (CSF) analysis may be helpful in attaining security about the definite diagnosis of this disease. The VEP assessment and the immunological investigation of CSF were performed in 42 patients with MS at the age of 4-22 years. The diagnosis of this disease was based on the clinical and MR findings according to the recommended criteria by Mc Donald and al. VEP recordings were performed with Multiliner equipment in accordance to the IFCN recommendations and CSF analysis including IgG index and the oligoclonal IgG bands by using isoelectric focusing. Abnormal VEP typical of MS (delayed but with well-preserved wave form) was observed in 100% of MS patients with optic neuritis (ON). Changes in VEP indicating clinically silent lesions in the visual pathway were found at the initial period of disease in 86% of patients in whom a diagnosis of clinically definite MS was established. The increased IgG index, testifying the intrathecal IgG synthesis was found only in 52% cases, whereas the oligoclonal IgG bands were visible in 50% of patients. This indicated the limited value of immunological studies of CSF in diagnosis of childhood and juvenile MS in contrast to VEP, which was the most helpful method especially in the detection of clinically silent lesions in the visual pathway. Nevertheless, only close and careful evaluation of the neurological symptoms together with paraclinical investigations may be fundamental for early diagnosis of the disease in young patients.

Adolescent↗
PubMed2006

Reading impairment and visual processing deficits in schizophrenia.

Individuals with schizophrenia show magnocellular visual pathway abnormalities similar to those described in dyslexia, predicting that reading disturbance should be a common concomitant of schizophrenia. To date, however, reading deficits have not been well established, and, in fact, reading is often thought to be normal in schizophrenia based upon results of tests such as the WRAT, which evaluate single word reading. This study evaluated "real world" reading ability in schizophrenia, relative to functioning of the magnocellular visual pathway. Standardized psychoeducational reading tests and contrast sensitivity measures were administered to 19 patients and 10 controls. Analyses of between group differences were further refined by classification of participants into reading vs. non-reading impaired groups using a priori and derived theoretical models. Patients with schizophrenia, as a group, showed highly significant impairments in reading (p<0.04-p<0.001), with particular deficits on tests of rate, comprehension and phonological awareness. Between 21% and 63% of patients met criteria for dyslexia depending upon diagnostic model vs. 0-20% of the controls. The degree of deficit correlated significantly with independent measures of magnocellular dysfunction. Reading impairment in schizophrenia reaches the level of dyslexia and is associated with compromised magnocellular processing as hypothesized. Findings related to symptoms, functioning and recommendations for reading ability assessment are discussed.

Adolescent↗
PubMed1999

The cerebellum and cognition: cerebellar lesions do not impair spatial working memory or visual associative learning in monkeys.

Anatomical studies in non-human primates have shown that the cerebellum has prominent connections with the dorsal, but not the ventral, visual pathways of the cerebral cortex. Recently, it has been shown that the dorsolateral prefrontal cortex (DPFC) and cerebellum are interconnected in monkeys. This has been cited in support of the view that the cerebellum may be involved in cognitive functions, e.g. working memory. Six monkeys (Macaca fascicularis) were therefore trained on a classic test of working memory, the spatial delayed alternation (SDA) task, and also on a visual concurrent discrimination (VCD) task. Excitotoxic lesions were made in the lateral cerebellar nuclei, bilaterally, in three of the animals. When retested after surgery the lesioned animals were as quick to relearn both tasks as the remaining unoperated animals. However, when the response times (RT) for each task were directly compared, on the SDA task the monkeys with cerebellar lesions were relatively slow to decide where to respond. We argue that on the SDA task animals can prepare their responses between trials whereas this is not possible on the VCD task, and that the cerebellar lesions may disrupt this response preparation. We subsequently made bilateral lesions in the DPFC of the control animals and retested them on the SDA task. These monkeys failed to relearn the task. The results show that, unlike the dorsal prefrontal cortex, the cerebellum is not essential for working memory or the executive processes that are necessary for correct performance, though it may contribute to the preparation of responses.

Animals↗
PubMed2006

The generation of receptive-field structure in cat primary visual cortex.

Cells in primary visual cortex show a remarkable variety of receptive-field structures. In spite of the extensive experimental and theoretical effort over the past 50 years, it has been difficult to establish how this diversity of functional-response properties emerges in the cortex. One of the reasons is that while functional studies in the early visual pathway have been usually carried out in vivo with extracellular recording techniques, investigations about the precise structure of the cortical network have mainly been conducted in vitro. Thus, the link between structure and function has rarely been explicitly established, remaining a well-known controversial issue. In this chapter, I review recent data that simultaneously combines anatomy with physiology at the intracellular level; trying to understand how the primary visual cortex transforms the information it receives from the thalamus to generate receptive-field structure, contrast-invariant orientation tuning and other functional-response properties.

Animals↗
PubMed1986

Modification of the discharge of lateral geniculate neurons during visual learning.

Visually conditioned heart rate change in the pigeon has been developed as a vertebrate model system for cellular analysis of associative learning. Previous studies have characterized the behavior, largely delineated the neural circuitry mediating the conditioning, and estimated the central processing time for the conditioned response. Most recently, this system has been used to investigate neuronal activity during conditioning along the visual pathways that transmit the conditioned stimulus (CS) information. It was first shown that neither maintained nor CS-evoked discharge of retinal ganglion cells changes during conditioning. Subsequently, we found that the thalamic and telencephalic components of the ascending tectofugal pathway show associative modification. We report here studies of the thalamofugal pathway, the avian homolog of the mammalian geniculocortical system. Single-cell activity was recorded in the thalamic relay of this pathway, the dorsal lateral geniculate equivalent (LGNe). This provided an opportunity to evaluate the generality of the training-induced modification found along the tectofugal pathway, and to determine if such modification occurs as peripherally as retinorecipient neurons. The results show that almost all LGNe neurons (97%) respond phasically to the onset of whole-field illumination. Most (94%) also respond to the unconditioned stimulus (US), footshock, some with increased and others with decreased discharge. Of cells receiving convergent input, those responding with decreased discharge to the US showed associative change (52%). Neurons that did not respond to both the CS and US, or that responded to the US with increased discharge, did not show associative modification. These findings suggest that the visual pathways transmitting CS information are not merely input lines, but undergo training-induced modification; such modification can occur as peripherally as the retinorecipient neurons of these pathways; and CS-US convergence is necessary but not sufficient for associative modification, since modifiability is apparently contingent on specific US response properties.

Analysis of Variance↗
PubMed2001

Memory-driven movements in limb apraxia: is there evidence for impaired communication between the dorsal and the ventral streams?

Memory-driven reaching and grasping movements were analysed in patients with left cerebral hemispheric damage and impaired gesture imitation. The dorsal and ventral streams of the visual pathway model of Milner and Goodale (Milner and Goodale, The Visual Brain in Action, 1995) are thought to operate relatively independently. However, cross-connections between the areas of each pathway are likely to enable interactions essential for higher-level praxis. Apraxic errors such as seen in gesture imitation can possibly be understood as arising from a disconnection of the two visual pathways. If the integrated action of the perceptual and visuomotor systems in patients with apraxia is compromised, then we would expect to find indications of impaired motor programming and misreaching in these patients when making movements driven by stored representations. Such a pattern, however, was not found in our sample of apraxic patients. Patients with limb apraxia produced normal movement kinematics and normal end-point accuracy when making memory-driven reaching movements with or without visual guidance of movement. Furthermore, perceptual information about object size and object distance were incorporated as normal in memory-driven grasping movements of these patients.

Aged↗
PubMed1983

A clinicopathologic study of optic neuropathies associated with intracranial mass lesions with quantification of remaining axons.

We examined three patients with intracranial mass lesions that damaged the anterior visual pathway and studied this damage histologically after the patients died. Estimation of the number of surviving axons in the six optic nerves generally showed the greatest atrophy to be in the temporal sector in cross sections immediately behind the globe. More posterior to the globe, atrophy appeared greatest in the center of several nerves. This pattern of damage may result from particular vulnerability of macular axons to damage along the anterior visual pathway. Optic disk pallor was present in two eyes that had less than 40% of the normal number of axons remaining, while one optic disk appeared to be normal with 70% of the axons intact. Afferent pupillary defects were observed in two patients who had two to three times as many remaining axons in the contralateral optic nerve as in the nerve on the side of the defect.

Adenoma↗
PubMedDate not supplied

[Chiasmatic cavernoma].

Hemorrhage into the structures of the anterior visual pathway, apoplexy of the chiasma or optic nerves, is a rare pathology that can be caused by different pathological processes among which cavernous angioma and arteriovenous malformation are more frequently mentioned. The cause of chiasmatic apoplexy may be also hemorrhage into the tumor--chiasmatic glioma of blood penetration into the chiasma in pituitary apoplexy. The authors describe a rare case of chiasmatic apoplexy whose cause was chiasmatic cavernoma. In addition to acute visual disorders suggesting the involvement of the left optic nerve, chiasma, and left visual pathway, 23-year-old patient had endocrine disorders as polyuria, polydipsia, which first suggests craniopharyngioma and glioma of the chiasma. A capsule and hematomic clots were removed from the thickened left optic nerve and left chiasmatic half during surgery. Only did a morphological study involving immunohistochemical analysis permit identification of the process as hemorrhage from cavernous micromalformation with the formation of hematoma.

Adult↗
PubMed1998

Clinical and radiologic evaluation of optic pathway lesions.

The clinical evaluation can often suggest the level of a visual pathway lesion; however, several different types of pathological processes, can produce the same visual field deficit. Imaging evaluation with CT and/or MRI can help to localize and characterize these diverse types of pathology. A radiological differential diagnosis can then be suggested which, in turn, facilitates patient management. In certain instances, the specific cause of a visual field defect can be identified with the radiological evaluation.

Brain Diseases↗
PubMed1999

Developmental expression of dynamin in the chick retinotectal system.

Dynamin I, a GTPase involved in the endocytic cycle of synaptic vesicle membranes, is believed to support axonal outgrowth and/or synaptogenesis. To explore the temporal and spatial patterns of dynamin I distribution in neuronal morphogenesis, we compared the developmental expression of dynamin with the expression of presynaptic membrane proteins such as SV2, synaptotagmin, and syntaxin in the chick primary visual pathway. Western blots of retina and tectum revealed a steady increase of synaptotagmin and syntaxin from embryonic Day 7 (E7) to E11, whereas for the same time frame no detectable increase of dynamin was found. Later stages showed increasing amounts of all tested proteins until the first postnatal week. Immunofluorescence revealed that SV2, synaptotagmin, and syntaxin are present in retinal ganglion cell axons from E4 on. In later stages, the staining pattern in the retina and along the visual pathway paralleled the formation and maturation of axons. In contrast, dynamin is not detectable by immunofluorescence in the developing retina and optic tectum before synapse formation. Our data indicate that, in contrast to the early expression of synaptotagmin, SV2, and syntaxin during axonal growth, dynamin is upregulated after synapse formation, suggesting its function predominantly during and after synaptogenesis but not in axonogenesis.(J Histochem Cytochem 47:1297-1306, 1999)

Aging↗
PubMed1985

[Use of visual evoked potentials in neurology--a review. II].

Visual potentials evoked by whole-field pattern reversal (PRVEP) are most frequently used for the diagnosis of damage of the optic nerve. Already in monocular whole-field stimulation typical PRVEP findings could also be observed in case of a damage of the visual pathway in its further course (chiasm or lesion of the optic tract). The application of a hemi-field stimulation led to a distinct improvement of the information value with respect to the presence of a damage of the optic chiasm. A reduction of the amplitudes at the beginning of the disease, the subsequent extension of the P100 latency and the disappearance of a response to the stimulus are considered to be typical. In recent time, the combined application of whole- and hemi-field stimulation also in the diagnosis of lesions of the posterior visual pathway (especially in the region of the occipital lobe) has brought about a certain advance. The results still are contradictory in some respects and require further clarification. The introduction of the VEP into clinical practice as a non-invasive neurophysiological method involving hardly any stress has led to a considerable enrichment of clinical diagnostics and one can still expect a strengthening of this position in conjunction with the increasing perfection of the examination technique.

Dominance, Cerebral↗
PubMed1998

Effects of early discordant binocular vision on the postnatal development of parvocellular neurons in the monkey lateral geniculate nucleus.

The effects of early discordant binocular vision on the fidelity of signal transfer in parvocellular neurons of the lateral geniculate nucleus (LGN) were investigated in rhesus monkeys reared with ocular misalignment (strabismus). Unilateral convergent strabismus (esotropia) was surgically induced in four infant monkeys between 20 and 30 days of age and the animals were reared in a normally lighted environment until they were adults. Extracellular microelectrode recordings were made in individual units of anesthetized and paralyzed subjects. Drifting sinusoidal gratings were used as visual stimuli. Within-unit comparisons of the LGN action potentials (LGN output) and S potentials (retinal input) were performed to determine the accuracy of signal transfer in the LGN. Contrary to the previous findings in the cat LGN, the signal transfer characteristics of parvocellular units in strabismic monkeys were normal regardless of stimulus spatial frequency, temporal frequency, or contrast. The differences between cats and monkeys in LGN circuitry and the relative maturity of the central visual pathway at the onset of strabismus may have contributed to the apparent species differences in the functional development of the LGN.

Action Potentials↗
PubMed1998

The metabolic pathway of visual pigment chromophore formation in Drosophila melanogaster--all-trans (3S)-3-hydroxyretinal is formed from all-trans retinal via (3R)-3-hydroxyretinal in the dark.

Carotenoid-depleted fruit flies, Drosophila melanogaster, were reared on yeast/glucose medium containing lipid-depleted white corn grits and cholesterol. After rearing for more than a year, the yield of flies remained constant and the content of 3-hydroxyretinal in a head was three logarithmic units less than that of normal flies reared on medium containing yellow corn grits. When all-trans retinal was supplied as the sole source of retinoids, the flies formed and accumulated all-trans 3-hydroxyretinal in the dark. To examine the metabolic pathway to produce (3S)-3-hydroxyretinal in Drosophila, all-trans retinal was supplemented for two hours to carotenoid-depleted flies in the dark, and the subsequent changes in the composition of 3-hydroxyretinal enantiomers were analyzed using a chiral column on HPLC. The results indicated initial formation of (3R)-3-hydroxyretinal followed by isomerization into the 3S enantiomer. In another set of experiments, the membrane fraction was obtained from the head homogenate of retinoid-depleted flies and an in vitro assay of 3-hydroxyretinal formation from retinal was performed. The 3-hydroxyretinal produced was the 3R enantiomer, supporting the result obtained from the in vivo experiment whereby (3S)-3-hydroxyretinal is produced from retinal via (3R)-3-hydroxyretinal. Addition of NADPH enhanced 3-hydroxyretinal formation and the presence of carbon monoxide inhibited it, suggesting that hydroxylation at the C3 position of retinal occurred via the monooxygenase activity of cytochrome P-450.

Animals↗
PubMed2002

Reorganization of human cortical maps caused by inherited photoreceptor abnormalities.

We describe a compelling demonstration of large-scale developmental reorganization in the human visual pathways. The developmental reorganization was observed in rod monochromats, a rare group of congenitally colorblind individuals who virtually lack cone photoreceptor function. Normal controls had a cortical region, spanning several square centimeters, that responded to signals initiated in the all-cone foveola but was inactive under rod viewing conditions; in rod monochromats this cortical region responded powerfully to rod-initiated signals. The measurements trace a causal pathway that begins with a genetic anomaly that directly influences sensory cells and ultimately results in a substantial central reorganization.

Adult↗
PubMed1977

[Recording of visual evoked potentials in the diagnosis of multiple sclerosis].

The authors report the results of recording EVP obtained by pattern reversal in 20 controls and 43 patients with "established", "probable" or "possible" MS on the basis of MacAlpine's criteria. Whilst the latency of the wave 1 of the EVP appeared stable in the controls (107.5 msec +/- 7.46), lengthening of the latency of the EVP was seen in 77p. 100 of cases, confirming involvement of the visual pathways, though bulbar neuritis had been known clinically in only 28 p. 100 of patients. The value of this method of recording EVP in contributing to the diagnosis of DS is discussed.

Adolescent↗
PubMed1987

[Modification of visual perception by vision training].

The course of the visual pathway as far as the sulcus temporalis superior is described and the change in the shape of the receptive fields is pointed out. The transformation of action potentials into conscious perception is interpreted as it was by Eccles. A connection is made between the problem of learning and the plasticity of the spine synapses, the capacity of which can be considerably increased. In conclusion, it is pointed out that in cases of macular disease it is possible to stimulate peripheral areas of the visual field by special training and thus to help the visual field by special training and thus to help the patient.

Aged↗
PubMed1988

Brainstem auditory and visual evoked potential studies in patients with chronic cervical pain.

Brainstem auditory evoked potential (BAEP) and visual evoked potential (VEP) studies were undertaken in 8 patients with chronic cervical pain associated with auditory and visual symptoms of more than 6 months duration. The purpose of the study was to ascertain possible central abnormalities, including posterior cervical sympathetic syndrome (Barre-Lieou syndrome), in their auditory and/or visual pathways. Patients who had been treated surgically for cervical pain were excluded from the study group. All patients had normal cervical radiographs and electromyographic findings. Six also had normal CT scans and myelograms. A criterion of the study was that abnormal results would be considered significant only if ophthalmological and/or otolaryngological work-ups failed to reveal an underlying organic abnormality. The TECA-TE 42 was used throughout the study, as well as the international Ten-Twenty System of Electrode Placement. The results showed no abnormalities in the latency, amplitude, or waveform morphology of the evoked potentials. BAEP and VEP studies do not appear to reveal central abnormalities of the auditory and visual pathways in this group of patients. However, in view of the small number of patients included in the study, no conclusions can be made with certainty and the study is continuing.

Adult↗
PubMed2003

Maternal docosahexaenoic acid supplementation during pregnancy and visual evoked potential development in term infants: a double blind, prospective, randomised trial.

AIM: To test the hypothesis that maternal docosahexaenoic acid (DHA) supplementation during pregnancy enhances maturation of the visual evoked potential (VEP) in healthy term infants. METHODS: One hundred women were supplemented with either fish oil capsules rich in DHA (n = 50) or placebo capsules (n = 50) from week 15 of pregnancy until delivery. Total fatty acids in red blood cells and plasma were measured at weeks 15, 28, and 40 of pregnancy and at delivery in umbilical cord blood. Infant visual pathway development was assessed using VEPs recorded to flash stimuli shortly after birth and to both flash and pattern-reversal stimuli at 50 and 66 weeks post-conceptional age (PCA). RESULTS: Maternal supplementation did not significantly elevate the level of DHA in umbilical cord blood. Moreover, there were no significant differences in any of the VEP measures observed between supplementation groups. However, maturity of the pattern-reversal VEP at 50 and 66 weeks PCA was associated with DHA status of the infants at birth. Infants with higher DHA status, both as a concentration and as a percentage of total fatty acids, showed shorter P100 peak latencies of the pattern-reversal VEP than those with lower DHA status. CONCLUSIONS: Maternal DHA supplementation during pregnancy did not enhance VEP maturation in healthy term infants. However, these results show an association between the DHA status of infants at term and early postnatal development of the pattern-reversal VEP, suggesting that DHA status itself may influence maturation of the central visual pathways.

Body Height↗