Projection from the pretectal nuclei to the dorsal lateral geniculate nucleus in the cat: a wheat germ agglutinin-horseradish peroxidase study.

To study the projection from the pretectum to the dorsal lateral geniculate nucleus (LGNd) in the cat, we used anterograde and retrograde transport of wheat germ agglutinin-horseradish peroxidase (WGA-HRP). Special attention was directed to the retinotopic maps of the pretectum and LGNd. Multiple restricted injections were made into different parts of the pretectum or LGNd. The pretectogeniculate pathway terminates mostly in the medial interlaminar nucleus (MIN) and layers A and A1, and to some extent in the lamina C within the ipsilateral LGNd. The lateral part of the nucleus of the optic tract (NTO) receives afferents from the superior retina, and the medial part of NTO and posterior pretectal nucleus (NPP) receives afferents from the inferior retina. There is no topographic organization in the retinal projection to the olivary pretectal nucleus (NOL). The lateral part of NTO projects ipsilaterally to the rostral portion of LGNd, which receives afferents from the superior retina. The medial part of NTO projects ipsilaterally to the caudal portion of LGNd, which receives afferents from the inferior retina. The NOL projects to all laminar parts of LGNd, ipsilaterally. The NPP projects largely to the ipsilateral MIN, which receives afferents from the pericentral and peripheral retina. These results suggest that similar parts of the retinotopic maps present in the pretectum and LGNd are connected.