RECEPTIVE-FIELDS AND DENDRITIC STRUCTURE OF DIRECTIONALLY SELECTIVE RETINAL GANGLION-CELLS

We studied the relationship between the receptive fields of directiona lly selective retinal ganglion cells and the dendritic arbors of the s ame cells. The cells were recorded from extracellularly under visual c ontrol and then injected with Lucifer yellow. The arbor of Lucifer-fil led dendrites could then be directly compared with the properties of t he receptive field. A large population of on-off directionally selecti ve cells was injected and drawn. The directionally selective ganglion cells had bistratified receptive fields similar to those previously de scribed by others in the central retina. in the periphery, the dendrit ic fields became larger, rounder, and sparser than centrally. The diam eters of the dendrites were measured in living or lightly fixed retina s; they were found to be somewhat larger than previously estimated by electron microscopy. The local structure of the dendritic arbor bore n o obvious relation to the directional properties of the cen. The recep tive fields of most cells were centered symmetrically around their den dritic fields. For about 10% of the cells, however, the receptive fiel d was displaced. The displacement was always toward the preferred dire ction, relative to the dendritic field. The meaning of these shifts is not clear. In both cases, the diameter of the receptive field exceede d the diameter of the dendritic field only slightly; in our sample, th e diameters of the receptive fields averaged 6% larger than the dendri tic fields. This means that the neurons afferent to the directionally selective ganglion cells must either have narrow dendritic fields or, if they are wide spreading, have dendrites that do not conduct effecti vely along their length. It also means that the observed spread of neu robiotin between DS ganglion cells (Vaney, 1991) must be due to a very few gap junctions, or to some mechanism other than a gap junction.