Abstract
Abstract: :
Purpose: To evaluate the controversial hypothesis that projections from P On retinal ganglion cells from the central visual field are segregated from the projections from P Off retinal ganglion cells to the upper layers of the macaque LGN. Methods: Small injections were made of one of two fluorescent tracers into selected locations in the P layers of the central visual field portion of the macaque LGN. The exact placement of the lesions was controlled by physiological mapping of the characteristic retinotopy and eye dominance of these layers. After retrograde transport of the fluorescent label to the retina, the filled portion of the dendritic arbor of labeled retinal ganglion cells was examined to determine if they branched in inner (On) or outer (Off) portions of the inner plexiform layer (IPL). Results: P retinal ganglion cells labeled from injections in single upper P cell layers of the LGN showed branching in both the inner and outer portions of the IPL. Conclusions: The separation of LGN P layers 6 from 4 and 5 from 3 do not reflect separation of On from Off P cell pathways.
Keywords: retina: proximal (bipolar, amacrine, and ganglion cells) • receptive fields • ganglion cells