Effects of corpus callosum section on functional compensation in the posteromedial lateral suprasylvian visual area after early visual cortex damage in cats.

A visual cortex lesion made in adult cats leads to a loss of direction selectivity and a loss of response to the ipsilateral eye among cells in posteromedial lateral suprasylvian (PMLS) cortex of cats. However, a visual cortex lesion made in young cats results in normal direction selectivity and normal ocular dominance in PMLS cortex. Thus cats with an early lesion demonstrate functional compensation in PMLS cortex.

Subannular aortic aneurysms in whites. Report of two cases and review of literature.

Subannular aortic aneurysms are a rare entity occurring predominantly in young black men. Five white patients have been reported who underwent surgical correction, but long-term survival occurred in only two. We report two white men, 36 and 45 years old, who survived aortic valve replacement and direct suture of subannular aneurysms, with no symptoms at 29 and 42 postoperative months.

Genesis of interneurons in the dorsal lateral geniculate nucleus of the cat.

Most neurons in the A-laminae of the cat's dorsal lateral geniculate nucleus (LGN) are born between embryonic days 22 and 32. Whereas approximately 78% of these cells are destined to become geniculocortical relay cells, the remaining 22% of LGN neurons do not appear to establish connections with visual cortex, and therefore can be considered interneurons. In the present study we have combined the 3H-thymidine method for labeling dividing neurons with the retrograde horseradish peroxidase (HRP) method for identifying LGN relay cells in order to study specifically the genesis of interneurons in the cat's LGN.

Elimination of action potentials blocks the structural development of retinogeniculate synapses.

Although the influence of electrical activity on neural development has been studied extensively, experiments have only recently focused on the role of activity in the development of the mammalian central nervous system (CNS). Using tetrodotoxin (TTX) to abolish sodium-mediated action potentials, studies on the visual system show that impulse activity is essential both for the normal development of neuronal size and responsivity in the lateral geniculate nucleus (LGN), and for the eye-specific segregation of geniculo-cortical axons. There have been no anatomical studies to investigate the influence of action potentials on CNS synaptic development.

Critical periods for functional and anatomical compensation in lateral suprasylvian visual area following removal of visual cortex in cats.

Previous experiments have found that neurons in the cat's lateral suprasylvian (LS) visual area of cortex show functional compensation following removal of visual cortical areas 17, 18, and 19 on the day of birth. Correspondingly, an enhanced retino-thalamic pathway to LS cortex develops in these cats. The present experiments investigated the critical periods for these changes.

Effects of strabismus on responsivity, spatial resolution, and contrast sensitivity of cat lateral geniculate neurons.

Rearing cats with esotropia is known to cause a number of deficits in visual behavior tested through the deviated eye. These include a loss of orienting response to stimuli presented in the nasal visual field of the deviated eye, a reduction in visual acuity, and a general reduction in contrast sensitivity at all spatial frequencies. To assess the involvement of the lateral geniculate nucleus (LGN) in these deficits, we measured the following: 1) the visual responsiveness of lamina A1 cells with peripheral (more than 10 degrees from area centralis) receptive fields in three esotropic and three normal cats and 2) the spatial resolution and contrast sensitivity of lamina A X-cells with central (within 5 degrees of the area centralis) receptive fields in six esotropic and six normal cats.

Response properties of striate cortex neurons in cats raised with divergent or convergent strabismus.

Recordings were made from striate cortex in five groups of cats that had been raised with strabismus produced by sectioning the extraocular muscles. These groups included animals reared with exotropia, unilateral or bilateral esotropia, and esotropia combined with lid suture of the unoperated eye. In addition, a group of esotropes was studied in which the unoperated eye was removed a few hours prior to recording.

Basal encephalocele presenting with monocular visual loss.

A 23-year-old male was seen with acute onset of decreased vision in the right eye. There was no associated facial abnormality, optic disc abnormality, or previous history of head trauma. A computerized tomography scan of the head revealed a soft tissue density in the right ethmoidal sinus.

The percentage of interneurons in the dorsal lateral geniculate nucleus of the cat and observations on several variables that affect the sensitivity of horseradish peroxidase as a retrograde marker.

Ten cats ranging in age from 4 weeks postnatal to adult received large bilateral injections of horseradish peroxidase (HRP) into cortical areas 17 and 18. In one cat additional unilateral injections of HRP were made into the lateral suprasylvian visual areas (PMLS). The purpose of these injections was to label relay cells in lamina A of the dorsal lateral geniculate nucleus (LGN), in order to distinguish them from neurons that could not be labeled retrogradely.

Visual-evoked responses from strabismic cats. A comparison of esotropes with exotropes.

We examined cortical responses evoked by 8-Hz, phase-shifted sine wave gratings at a range of contrasts and spatial frequencies in normal cats and in cats raised with artificial esotropia or exotropia. There were no significant differences between the amplitudes of the responses evoked through the two eyes of the normal cats, but for some esotropes and exotropes the responses evoked through the unoperated eye were larger than those evoked through the operated eye. Interocular response differences were comparable in all affected cats and were most pronounced at high contrasts.