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At least 361 records · Page 20Linked to original sources
PubMed1990

Damage to the anterior visual pathway and brain parenchyma following external pituitary irradiation.

Three cases of damage to the optic nerves and chiasma following pituitary irradiation with Co60 teletherapy are described. All of them presented with progressive visual impairment months following irradiation and simulated recurrence of the tumour. CT scan was also not helpful in differentiating radionecrosis from tumour recurrence. On exploration the optic nerves and chiasma appeared discoloured and scarred. One case, who also had diffuse radionecrosis of brain parenchyma, died. No satisfactory therapy is currently available for this grave complication but proper safeguards can prevent it.

Adult↗
PubMed1992

5-HT1 receptors in the structures of visual pathway of normal and monocularly deprived kittens.

The density and pattern of distribution of 5-HT1 receptor sites was examined using quantitative in vitro autoradiography with [3H]5-HT as a ligand in the visual structures of 5 weeks old kittens. One group of animals had normal binocular vision, the other was monocularly deprived during the last three days of life. The density of 5-HT1 receptor sites and the pattern of their distribution in the visual structures showed distinct regional, areal and laminar differences. In the primary visual cortex (area 17) a high labelling density was found as compared with other cortical areas investigated. Three bands of high binding density were observed corresponding to cortical layers II-III, IV c and VI. This pattern distinguished area 17 from other cortical areas investigated. In subcortical visual structures very high labelling was present in the superficial visual layers of superior colliculus, but LGN showed rather weak labelling although the lamination of LGN was also seen in the pattern of distribution of 5-HT1 sites. Neither density nor pattern of 5-HT1 sites in the visual cortex and superior colliculus were affected by 3 days of monocular deprivation. High density of labelling and the distinct pattern of 5-HT1 receptor sites in the primary visual cortex suggest the important role of serotonergic transmission in the modulation of visual afferent input activity.

Animals↗
PubMed1989

Separable evoked retinal and cortical potentials from each major visual pathway: preliminary results.

Single cell experiments in primates show that there are two major parallel pathways named after the lamination in the lateral geniculate nucleus. Each of these systems can be preferentially excited by appropriate stimuli. Here we report that in man the polarity of the evoked potentials both in retina and in cortex depends on which of these pathways is stimulated. The identification of the resulting waveforms is thereby simplified--a matter of practical importance. The fact that at retina and cortex there are characteristic potentials may reflect the different cell biology of the two pathways.

Color Perception↗
PubMedDate not supplied

[Impairment of visual pathway function in right hemisphere in patients with arteriovenous malformation of the parietooccipital area of left hemisphere].

Marked arteriovenous malformation in the left parietooccipital area manifested only by symptoms of associative migraine involving changes of visual fields indicative of impaired functions of symmetrical compartments of the other brain hemisphere. Visual evoked potentials were changed in this patient because of dysfunction of both hemispheres and largely because of disorders in brain structures symmetrical to the site of arteriovenous malformation. This can be regarded as a manifestation of the so-called stealing phenomenon, when blood supply to one brain compartment is decreased because of excessive blood delivery to other regions of the brain. The results permit us to hypothesize regulation of blood supply to symmetrical compartments of brain hemispheres.

Cerebral Angiography↗
PubMed2002

Morphological characteristics and central projections of two types of interneurons in the visual pathway of Hermissenda.

The synaptic interactions between photoreceptors in the eye and second-order neurons in the optic ganglion of the nudibranch mollusk Hermissenda are well characterized. However, the higher-order neural circuitry of the visual system, consisting of cerebropleural interneurons that receive synaptic input from photoreceptors and project to pedal motor neurons that mediate visually guided behaviors, is only partially understood. In this report we have examined the central projections of two identified classes of cerebropleural interneurons that receive excitatory or inhibitory synaptic input from identified photoreceptors. The classification of the interneurons was based on both morphological and electrophysiological criteria. Type I interneurons received monosynaptic excitatory or inhibitory synaptic input from identified photoreceptors and projected to postsynaptic targets within the cerebropleural ganglion. Type II interneurons, characterized here for the first time, received polysynaptic excitatory or inhibitory synaptic input from identified photoreceptors and projected to postsynaptic targets in either the ipsilateral pedal ganglion or the contralateral cerebropleural ganglion. Type I interneurons exhibited unique intraganglionic projections to different regions of the cerebropleural ganglion, depending on whether they received excitatory or inhibitory synaptic input from identified photoreceptors. Type I interneurons that received monosynaptic excitatory input from identified B photoreceptors terminated near the cerebropleural commissure and had multiple regions of varicosities located at branches that projected from the primary axon. Type I interneurons that received monosynaptic inhibitory input from identified B photoreceptors projected to the anterior cerebropleural ganglion and exhibited varicosities localized to the terminal region of the primary axonal process. Type II interneurons that received polysynaptic inhibitory input from identified photoreceptors projected to the contralateral cerebropleural ganglion. Most type II interneurons that projected to the pedal ganglia received polysynaptic excitatory input from identified photoreceptors. These results indicate that there is at least one additional interneuron in the higher-order visual circuit between type I interneurons and pedal motor neurons responsible for the generation of phototactic locomotion in Hermissenda.

Action Potentials↗