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Biomedical subjects

V H Perry

Publications and source records attributed to V H Perry.

At least 199 records · Page 11Linked to original sources
PubMed1983

The long-term effects of removal of sensorimotor cortex in infant and adult rhesus monkeys.

A comparison is made between the long-term effects of the unilateral removal of sensorimotor cortex in infant and adult rhesus monkeys. Both infants and adults recovered to a remarkable extent. They walked, climbed and jumped with ease. However, neither infant nor adult monkeys could grip food by using thumb and forefinger independently of the other fingers. It was demonstrated in the adults that there was a permanent impairment in the use not only of the fingers but also the wrist and forearm. The results do not support the claim made by Kennard (1942) that infants recover more completely than adults from the effects of brain lesions. An analysis of the relevant evidence suggests that compensation occurs only when the animal is very immature at the time of operation. The brain is much more mature in a neonatal monkey than a rat or hamster. True compensation can probably only occur in monkeys if the lesion is made well before birth.

Animals↗
PubMed1982

Effects on visual acuity of neonatal or adult tectal ablation in rats.

Tectal ablation in neonatal rats leads to retrograde degeneration of retinal ganglion cells whereas similar damage in adults does not. We show here that the behavioral effects are comparably different. When rats with neonatal tectal ablation are tested as adults they are impaired in learning a discrimination between vertical and horizontal stripes and their visual acuity for square-wave gratings is slightly but significantly reduced.

Aging↗
PubMed1982

A sensitive period for ganglion cell degeneration and the formation of aberrant retino-fugal connections following tectal lesions in rats.

Rats of 0, 3, 5, 10 and 30 days of age received unilateral tectal lesions. After surviving for 150 days the retinal ganglion cell layer of the contralateral eye was examined for evidence of a ganglion cell loss. The retino-fugal projections of the eye contralateral to the lesion were studied in autoradiographs. In the animals operated at 0 days of age, 33% of the ganglion cells had degenerated but in animals operated at 5 days of age, 67% of the ganglion cells had degenerated. The animals operated at 30 days of age show no significant cell loss. An aberrant retinal projection to the lateral posterior nucleus of the thalamus was found only in animals operated at 0 and 3 days of age. The retinal projection to the thalamus was investigated in normal rats of 0, 3, 5 and 10 days of age using the anterograde transport of horseradish peroxidase. There was a conspicuous projection to the lateral posterior nucleus in animals of 0 and 3 days of age, but in the 5-day-old rat the retinal projection to the lateral posterior nucleus was very small and similar to the adult pattern. We conclude that transecting the tectal terminals of retinal ganglion cells causes the ganglion cells to degenerate, unless they are old enough to have formed sustaining collaterals. In addition, the tectal lesion removes a major tectal input to the lateral posterior nucleus and, if carried out within the first few days, leads to the preservation of the normally transient retinal projection to the lateral posterior nucleus, presumably by reducing competition between axon terminals.

Animals↗
PubMed1982

Ganglion cell death within the developing retina: a regulatory role for retinal dendrites?

The effects of neonatal midbrain lesions on populations of retinal ganglion cells with ipsilateral or contralateral projections were investigated in hooded rats with the use of horseradish peroxidase. After bilateral lesions of the superior colliculus performed at birth, the number of contralaterally projecting ganglion cells is reduced but the number of ipsilaterally projecting cells is increased. Bilateral tectal lesions performed 5 days after birth reduce the number of both contralaterally and ipsilaterally projecting ganglion cells. Unilateral tecto-pretectal lesions performed at birth lead to extensive retrograde degeneration of contralaterally projecting ganglion cells in the opposite retina: but both the ipsilateral terminal fields of the same retina and its population of ipsilaterally projecting ganglion cells are increased. Cells located at the border between the temporal crescent and the nasal areas of the retina opposite an unilateral tecto-pretectal lesion were found to have their dendrites pointing towards the severely depleted nasal areas more frequently than in normal rats. These observations suggest that competitive interactions between retinal dendrites may play a role in regulating ganglion cell death in the developing retina. The increased population of ipsilaterally projecting ganglion cells would reflect the survival of neurones which would otherwise normally degenerate, resulting from reduced local interactions as a consequence of the massive removal of neighbouring contralaterally projecting cells.

Animals↗
PubMed1981

The morphological correlates of X- and Y-like retinal ganglion cells in the retina of monkeys.

The morphology of the ganglion cells of the monkey's retina was revealed by filling the cells with horseradish peroxidase from their cut axons in the optic nerve. This procedure gave much more consistent results than the Golgi method, was much quicker and filled dendrites just as extensively. Quantitative measures of the dendritic tree of two types of ganglion cell, P alpha and P beta, suggest that they correspond to the physiologically defined Y- and X-cells, respectively.

Animals↗
PubMed1981

Spatial contrast sensitivity of cells in the lateral geniculate nucleus of the rat.

1. The responses to visual stimuli of cells in the dorsal lateral geniculate nucleus of the rat were recorded with micro-electrodes. 2. Maps made with small spots of light showed that most units had concentrically organized receptive fields. Some units gave 'on-off' responses to spots flashed anywhere within the receptive field. These units were not directionally selective. 3. By the use of grating patterns as stimuli, units with concentrically organized receptive fields could be divided into groups that showed linear or non-linear spatial summation. Those unit showing linear spatial summation behaved like the 'X' cells of the cat, those showing non-linear summation like 'Y' cells. 4. 'On-off' units showed non-linear spatial summation of a kind that readily distinguished them from Y cells. 5. Measurements of spatial contrast sensitivity made with moving gratings showed, for both X and Y cells, peak sensitivities for spatial frequencies between 0.05 and 0.09 c/deg X and Y cells were not distinguished by their preferred spatial frequencies at any eccentricity.

Action Potentials↗
PubMed1980

Amacrine cells, displaced amacrine cells and interplexiform cells in the retina of the rat.

The amacrine cells in the retina of the rat are described in Golgi-stained whole-mounted retinae. Nine morphologically distinct types of cell were found: one type of diffuse cell, five types of unistratified cell, two types of bistratified cell, and one type of stratified diffuse cell. Measurements show that the largest unistratified cells have a dendritic field 2 mm across. One type of interplexiform cell is also described. Wide-field diffuse amacrine cells and unistratified amacrine cells were found with their somata located in either the inner nuclear layer or the ganglion cell layer. It is clear that there may be an amacrine cell system in the ganglion cell layer of the rat retina.

Age Factors↗
PubMed1980

Morphology of cells in the ganglion cell layer during development of the rat retina.

The development of the cells in the ganglion cell layer in the rat retina has been studied from 3 to 30 days of age postnatal by means of Golgi-stained whole-mounted retinae. The retina grows rapidly from birth to ten days of age and then more slowly from 10 to 30 days of age. The different classes of ganglion cell can be clearly recognized by 10 days of age, but type I ganglion cells with a size comparable to those found in the adult rat retina are not seen until thirty days of age. Type II cells may attain their adult size before type I cells do. The growth of the retina and the resulting decrease in cell density in the ganglion cell layer occur with the same time course as the increase in the size of the cell soma and their dendritic fields.

Age Factors↗
PubMed1979

The ganglion cell layer of the retina of the rat: a Golgi study.

In whole-mounts of Golgi stained rat retinae four cell types are described in the ganglion cell layer. Three of these cell types are considered to be analogous to the alpha, delta and gamma cells described in the cat retina by Boycott & Wässle (1974). The fourth cell type is thoughtt to be a displaced amacrine cell. All the cell types described are present in all parts of the retina. There is no evidence for an increase in dendritic field size with increasing distance from the optic disk.

Animals↗
PubMed1979

The projection of the temporal retina in rats, studied by retrograde transport of horseradish peroxidase.

Horseradish peroxidase (HRP) was injected unilaterally into the lateral geniculate nucleus or tectum, or both, in 26 hooded rats in order to mark the exact extent of the retina from which uncrossed optic axons arise. This region occupied about a quarter of the retina, in the temporal periphery, following thalamic injections, but a much smaller region following tectal injections. By comparing the proportions of HRP positive neurones in nasal and temporal retinae of both eyes it was shown that: (1) within the region supplying uncrossed axons the majority of the ganglion cells nevertheless project contralaterally, (2) a large proportion of the ganglion cells from the temporal crescent project bilaterally, which does not occur from the remainder of the retina, (3) ganglion cells of all sizes contribute to both ipsilateral and contralateral projections. The results also support earlier suggestions that the smallest neurones in the ganglion cell layer do not send an axon into the brain, and are therefore not ganglion cells.

Animals↗
PubMed1979

The effects of unilateral cortical and tectal lesions on retinal ganglion cells in rats.

The ganglion cell layer of the retina was examined for retrograde transneuronal degeneration after removing the striate cortex unilaterally in infant or adult rats. No significant degeneration occurred, even after a survival time of 15 months, and the rat is therefore unlike other mammals in which the phenomenon has been studied. A possible explanation that most optic axons bifurcate in rats and that the tectal branch can sustain the ganglion cell after the branch to the dorsal lateral geniculate nucleus has degenerated following removal of striate cortex was ruled out by the demonstration that combined unilateral removal of striate cortex and superior colliculus in adults was similarly ineffective. Unilateral removal of the superior colliculus alone also failed to affect ganglion cells of adult rats but produced conspicuous degeneration in infants. The greater vulnerability of the infantile developing visual system casts doubt on the common assumption that the effects of brain damage are less severe in infants than adults.

Animals↗
PubMed1979

Changes in the retino-fugal pathways following cortical and tectal lesions in neonatal and adult rats.

Several months after unilateral removal of the striate cortex or superior colliculus, or both, in infant and adult rats the retinal projections were studied autoradiographically. The retinal projection areas in adult-operated animals were not different from those of unoperated controls, but aberrant pathways were found in the infant group. Following removal of striate cortex there was a small aberrant pathway to the lateral posterior nucleus of the thalamus (LP) and possibly to the pretectum. After removal of the superior colliculus there was a conspicuous aberrant projection to LP, which was even more prominent after combined removal of striate cortex and superior colliculus. The results support the proposal that when the normal field of termination is damaged, either directly by a tectal lesion or indirectly by a cortical lesion, axons grow and innervate LP, which has been partly deafferented by the lesion and which consequently possesses vacant synaptic space. Although the different consequences of early and late lesions may indicate that only infantile damaged terminals can redistribute themselves an alternative is that in infants many axons have not yet reached their normal terminal sites at the time of operation and that only those axons have the ability to continue growing and to form an aberrant pathways. The role of the aberrant pathway in vision is unknown.

Age Factors↗