Topography of cells responding with long latencies to flashes and cells projecting to layer I of area 17 in the rat dorsal lateral geniculate nucleus.

After deposition of horseradish peroxidase (HRP) crystals on the surface of cortical area 17 in 7 adult Wistar albino rats only relay cells were found to be labelled retrogradually in the caudal two thirds of the dorsal lateral geniculate nucleus (dLGN). From these results it can be concluded that cells projecting to the cortical layer I are concentrated in this part of the nucleus. Single cell recordings in the rat dLGN have shown that cells responding to light stimuli with long latencies are very frequent in this part of the dLGN, likewise. These findings support the idea that W-cells dominate in the caudal region of the rat dLGN, which is characterized by a population of relatively small geniculo-cortical relay neurons (GCR-neurons).