THE DORSAL LATERAL GENICULATE NUCLEUS OF THE SHEEP AND ITS RETINAL CONNECTIONS

¹ Institut d'Anatomie, Rue du Bugnon 9, 1005, Lausanne, Switzerland
² MRC Unit for Anatomical Neuropharmacology, Department of Pharmacology, Oxford
³ 31 Thoniayappan Street, Roya-pettah, Madras 600014

Layers 1 and 2 of the sheep's LGN have similar properties to layers A and A1 in the cat. In layer 3 of the sheep the cell size is the same as that of the main group in layers 1 and 2, and it is contralaterally driven but has no sublamination. There is a medial interlaminar nucleus in the sheep which consists of two incomplete laminae, each driven by one eye. Scattered cells from the whole of the retina temporal to the decussation line project to the contralateral LGN. There is only a band of cells 1·5 mm wide nasal to the decussation line which project to the ipsilateral LGN. Cells with corresponding ipsilateral fields are found on the medial side of the nucleus in layers 1 and 2. A few cells with orientation sensitivity have been seen in the LGN. The area of the greatest cell density in the retina, the streak, is accommodated in the LGN by expansion vertically, not horizontally.