Biomedical subjects

P Godement

Publications and source records attributed to P Godement.

23 records · Page 2Linked to original sources

PubMed1984

Prenatal and postnatal development of retinogeniculate and retinocollicular projections in the mouse.

The development of retinal projections to the dorsal lateral geniculate nucleus (dLGN) and superior colliculus (SC) has been studied in fetal and neonatal mice of the pigmented C57BL/6 strain, using the anterograde transport of tritiated proline and horseradish peroxidase (HRP). Retinal efferents are present contralaterally just beyond the chiasm at E14. By E16 they have grown into both dLGN and SC. Ipsilateral fibers are limited to the proximal optic tract at E16; their growth into dLGN and SC is delayed until E18-birth. During the first 2 postnatal days, an early population of ipsilateral fibers invades the dLGN. Most of these fibers grow in or around the medio-dorsal sector of the dLGN, i.e., the future binocular segment. Fibers are also present, but at lower densities, in the ventral half of the nucleus and thereafter become dispersed or are lost, without at any stage becoming dense. Some denser labeling is also present ipsilaterally in the outer rim of dLGN, just below the optic tract, and later disappears. On the third postnatal day, the ipsilateral fibers establish a deep and denser projection along the medial and dorsal borders of dLGN; this projection overlaps part of the crossed projection, which at this age extends to the whole nucleus. The segregation of each projection starts on the fourth postnatal day, when crossed fibers begin to disappear from the small region of uncrossed projection. This process goes on for another 4 days. During this period, the ipsilateral fibers withdraw from the deepest layer of dLGN, and their terminal density increases gradually; by the eighth postnatal day, both projections are already well separated. Dense crossed projections first appear near the surface of the SC at birth. Prior to this, retinal fibers course throughout neurons of the collicular plate and underneath the pia. The uncrossed fibers invade the SC between birth and P3. They are located preferentially in the anterior and medial aspect of the SC. Subsequently, there occurs a diminution in the laminar and tangential extent of these projections, simultaneously with an intensification of the ipsilateral input to several small, longitudinally oriented clusters located deep to the crossed projections.

Animals↗

PubMed1983

[Physiological and anatomical study of the retinogeniculate projections in the mouse].

A physiological and anatomical study of the dorsal lateral geniculate nucleus (dlGn) in pigmented C57BL/6 Mice is reported. Neurons responding to the ipsilateral eye are clustered in a region near the medial border of dlGn, and are surrounded by contralateral neurons. Electrode penetrations in this part of dlGn show the existence of contra/ipsi/contralateral projection lines. Practically only the contralateral field of vision is represented in each dlGn. Local HRP injections show evidence in the retina of a decussation line for contralateral retinogeniculate projections, the border of which follows the inner border of the region of ipsilateral projection. The mean diameter of ipsilateral retinogeniculate ganglion cells is larger than that of contralateral cells.

Animals↗

PubMed1981

[Absence of ipsilateral retinal projections after very early prenatal destruction of one eye in mice].

Mice embryos underwent unilateral destruction of one eye, in utero between 13 (E 13) and 17 days (E 17) of gestation, or at birth. The extension of the retinal projections from the remaining eye was determined, after birth, using the technique of anterograde transport of HRP. The results show that enucleations performed between E 15 and birth (E 19) result in the formation of an augmented ipsilateral pathway, the terminal extent of which does not depend greatly upon the exact timing of enucleation. However, following enucleations at E 13, the projections from the remaining eye are only crossed, there being practically no projections to the ipsilateral side of the brain.

Aging↗

PubMed1980

The ipsilateral optic pathway to the dorsal lateral geniculate nucleus and superior colliculus in mice with prenatal or postnatal loss of one eye.

The projections, and more particularly the ipsilateral projections, from the retina to the dorsal lateral geniculate nucleus (dlGn) and the superior colliculus have been investigated in adult mice of the C57BL/6J strain after rearing in one of four different conditions: 1) after normal visual experience; 2) after unilateral enucleation at birth; 3) in mice with congenital unilateral anophthalmia (in which only one eye develops) 4) in mice with congenital unilateral microphthalmia (in which one eye is of reduced size while the other is normal). In neonatally enucleated and congenitally monocular mice there is an aberrant uncrossed pathway to regions of the dlGn and the superior colliculus which do not normally receive such a projection. This projection is limited in its distribution; in both the neonatally enucleated and the congenitally monocular animals the uncrossed projection does not reach the lateral and dorsal parts of the dlGn and it only innervates the rostral half of the superior colliculus. The density of the uncrossed pathway in these animals is highest in those regions in which the normal uncrossed pathway terminates. In microphthalmic mice the expansion of the uncrossed pathway is less marked than in monocular mice. In the superior colliculus the aberrant uncrossed projections innervate the stratum griseum superficiale where they are often found distributed in small patches. An intertectal crossing of retinal fibers is described from the contralateral superior colliculus to the deprived ipsilateral superior colliculus.

Animals↗

PubMed1979

Thalamic afferents to the visual cortex in congenitally anophthalmic mice.

Retrograde cell labelling with horseradish peroxidase (HRP) has been used to study the thalamic afferents to the primary visual cortex (area 17) in mutant H1-ZRDCT-An ('eyeless') mice, in which the eyes are missing throughout development. Injections of HRP that were localised to a subregion of area 17, resulted in the labelling of a group of neurons in the ipsilateral dorsal lateral geniculate nucleus, showing the existence of a point-to-point connectivity. Many labelled cells were also found in other posterior thalamic nuclei especially in the lateral posterior nucleus which in normal animals contain very few or no labelled cells.

Animals↗