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Biomedical subjects

S M Sherman

Publications and source records attributed to S M Sherman.

At least 127 records · Page 7Linked to original sources
PubMed1975

Behavioral and morphological evidence for binocular competition in the postnatal development of the dog's visual system.

Two normally-reared dogs and five dogs reared with monocular eyelid closure were studied. The two normal dogs and three of the deprived dogs were tested with a perimetry technique for the extent of behavioral visual field, and all of the dogs were studied histologically to determine the size of cell somata in the lateral geniculate nucleus. Behaviorally, the normal dogs saw with each eye approximately from 120 degrees ipsilateral to 30 degrees contralateral. The deprived dogs had a normal field of view for the non-deprived eye, but with the deprived eye they saw only in the monocular segment (i.e., approximately 120 degrees to 30 degrees ipsilateral). Histologically, geniculate cells in the monocular segment of deprived dogs were of normal size. In the deprived laminae of the binocular segment, however, cells averaged about two-thirds normal size, and in non-deprived laminae of this segment, neurons were hypertrophied. The hypertrophy was greater for cells in lamina A (40%) than for those in lamina A1 (17%). These data indicate that in monocularly deprived dogs, the monocular segment of the visual system develops normally, but the binocular segment does not. Therefore, we conclude that binocular competition operates in the developing dog's visual system much as it does in the cat's.

Age Factors↗
PubMed1975

Effects of early binocular deprivation on visual input to cat superior colliculus.

1. Recent work has demonstrated at least three distinct inputs to the superior colliculus in normal cats: a) the W-direct retinotectal pathway; b) the Y-direct retinotectal pathway; and c) the Y-indirect pathway which involves Y-cells in retina and lateral geniculate nucleus plus complex cells in cortex, the last being the corticotectal cells. 2. We investigated these inputs in five cats raised with binocular eyelid closure by studying the electrophysiological properties of 164 collicular neurons. After such binocular deprivation, the Y-indirect pathway was missing and the Y-direct pathway appeared reduced, although the W-direct input seemed unaffected. 3. Despite the loss of the Y-indirect input, collicular activation to electrical stimulation of cortex seemed normal in these cats. This suggested that the Y-indirect loop was affected between the optic tract and cortex, and this, in turn, correlated to the previously described reduction in recordable Y-cells from the lateral geniculate nucleus of binocularly deprived cats. 4. We found receptive-field correlates to this loss of Y-direct and Y-indirect input in the binocularly deprived cats. Compared to collicular neurons in normal cats, those in deprived cats exhibited abnormally strong dominance by the contralateral eye, loss of directional selectivity, and loss of responsiveness to fast visual stimuli. 5. These and other data lead to the suggestion that in normal and monocularly deprived cats, the corticotectal input dominates collicular receptive-field properties, whereas in binocularly deprived cats, the remaining retinotectal input dominates these properties.

Animals↗
PubMed1974

Monocularly deprived cats: improvement of the deprived eye's vision by visual decortication.

Monocularly deprived cats were tested for visual perinetry before and after visual cortex lesions. Such a lesion greatly enhances the deprived eye's performance and impairs that of the nondeprived eye so that the pronounced preoperative interocular asymmetry is lost postoperatively. Apparently this destruction of abnormal corticotectal pathways allows the expression of previously suppressed, normal retinotectal pathways.

Animals↗
PubMed1974

Visual fields of cats with cortical and tectal lesions.

When cats were tested for visual field perimetry, the field of vision for each eye separately was from 45 degrees contralateral to 90 degrees ipsilateral. After either bilateral occipitotemporal lesions (with a split of the tectal commissure) or bilateral area 17, 18, and 19 lesions, the cats could see with each eye only from the midline to 90 degrees ipsilateral. A cat that became nearly totally blind as a result of bilateral occipitotemporal decortication had a subsequent tectal split which enabled it to see with each eye from the midline to 90 degrees ipsilateral.

Animals↗