Morphology and distribution of retinal ganglion cells projecting to different layers of the dorsal lateral geniculate nucleus in normal and Siamese cats

AG Leventhal
1982 Journal of Neuroscience  
Electrophoretic injections of horseradish peroxidase were made into physiologically characterized sites within the different layers of the dorsal lateral geniculate nuclei (LGNd) of normal and Siamese cats. The histochemical procedures used stained the cell bodies, dendrites, and axons of retrogradely labeled ganglion cells. In both normal and Siamese cats, only (Y and /3 ganglion cells are labeled by injections restricted to the A laminae. In normal cats, the (Y/P ratios (number of labeled LY
more » ... mber of labeled LY cells/number of labeled (Y + /3 cells) resulting from injections into lamina A increase from about 0.045 at 0.5 mm from the area centralis to about 0.12 in the far periphery. The a/P ratios observed outside of the area centralis in normal cats following injections into different parts of lamina Al were lower at each eccentricity than those resulting from injections into corresponding parts of lamina A. Also, the cell bodies and dendritic fields of (Y and /3 cells projecting to lamina Al are somewhat larger than those projecting to corresponding parts of lamina A. Outside of the area centralis, the relative numbers of (Y and /3 cells projecting to Siamese lamina A are normal. However, (Y cells comprise an abnormally small proportion of ganglion cells projecting to the normal segments of Siamese lamina Al and an abnormally large proportion of cells projecting to the abnormal segments of lamina Al. In Siamese cats, (Y and p cells projecting to lamina Al are distributed continuously throughout virtually all of the ipsilateral and contralateral temporal retinas. Since large parts of the ipsilateral and contralateral hemifields are not represented in Siamese lamina Al, it seems that some of the retinal afferents to this lamina are being suppressed. Injections into the C laminae of the LGNd show that the same morphological classes of ganglion cells project to these laminae in normal and Siamese cats. The classes projecting to the contralateral C laminae (laminae C and C2) include (Y, p, y, and E as well as two other groups of cells referred to as gl and g2 cells. y, E, gl, and g2 cells project to the ipsilateral C lamina (lamina Cl). In Siamese, but not in normal cats, examples of a.ll of these types are found far into the contralateral temporal retina following injections involving lamina Cl. This indicates that all classes projecting to the ipsilateral C lamina misproject in Siamese cats. The retinas of a variety of species, including cats and ing retinal afferents differ, reflecting, in large part, differmonkeys, contain a number of different classes of retinal ences in their ganglion cell inputs. The receptive field ganglion cells. The receptive field properties and mor-properties of cells in different parts of nuclei receiving phologies of each of these classes are distinctive. The retinal afferents also differ from each other. For example, patterns of central projection of these classes are also cells in lateral portions of the dorsal lateral geniculate distinctive, and different visual relays receive inputs from nucleus (LGNd) subserve the peripheral retina, have different complements of retinal ganglion cells. (For re-larger receptive fields, and are more sensitive to rapid view, see Rodieck, 1979; Stone et al., 1979.) stimulus motion than are medial LGNd cells which sub-The receptive field properties of cells in nuclei receiv-serve the central retina. Also, in the LGNd A laminae, the number of Y cells relative to X cells is higher in ' This work was supported by National Institutes of Health Grant regions subserving the peripheral than in those subserv-PHS 1ROl EY03427. ing the central retina (Cleland et al., 1971; Hoffman et
doi:10.1523/jneurosci.02-08-01024.1982 pmid:6180147 fatcat:uwfyh6gcangvze5vx22v5z2w5y