Anatomical characteristics and three‐dimensional model of the dog dorsal lateral geniculate body

Abstract

The morphological and laminar characteristics of the dorsal lateral geniculate nucleus (LGN) and medial interlaminar nucleus (MIN) of the domestic dog (Canis familiaris) were studied by three-dimensional computer reconstruction of labeled retinal afferents following intraocular HRP injections. As previously reported, the dog LGN consisted of layers A, A1, C, C1, C2, and C3. Layers A, C, and C2 receive contralateral-eye inputs, and layers A1 and C1 ipsilateral inputs. The dog MIN was found to have four orderly interdigitating layers; layers 1, 2, 3, and 4, medial to lateral. MIN layers 1 and 3 received contralateral inputs, and layers 2 and 4 ipsilateral inputs. Layer 1 had the largest soma of all LGN/MIN layers. LGN layer A was partially separated into medial and lateral subdivisions by a cleft free of somata. The overall three-dimensional shape of the lateral geniculate body was like the letter C, with the convex part of the C directed posteriorly. The relative volume of the MIN was smaller than in the cat; the canine MIN comprised 8.3% of the combined volume of layers A, A1 and the MIN, while that of the cat comprised 14.2% as estimated from Sanderson's map. The volume of all contralateral-eye layers, combining both LGN and MIN, was 31.2 mm3 (78%), and that for ipsilateral layers was 8.6 mm3 (22%). The ratio of ipsilateral to contralateral laminar volumes is much lower in the dog than in the cat. Anat Rec 256:29–39, 1999. © 1999 Wiley-Liss, Inc.