MOSAIC ARRANGEMENT OF GANGLION-CELL RECEPTIVE-FIELDS IN RABBIT RETINA

The arrangement of ganglion cell receptive fields on the retinal surfa ce should constrain several properties of vision, including spatial re solution. Anatomic and physiological studies on the mammalian retina h ave shown that the receptive fields of several types of ganglion cells tile the retinal surface, with the degree of receptive field overlap apparently being similar for the different classes. It has been diffic ult to test the generality of this arrangement, however, because it is hard to sample many receptive fields in the same preparation with con ventional single-unit recording. In our experiments, the response prop erties and receptive fields of up to 80 neighboring ganglion cells in the isolated rabbit retina were characterized simultaneously by record ing with a multielectrode array. The cells were divided into 11 classe s on the basis of their characteristic light responses and the tempora l structures of their impulse trains. The mosaic arrangement of recept ive fields for cells of a given class was examined after the spatial p rofile of each receptive field was fitted with a generalized Gaussian surface. For eight cell classes the mosaic arrangement was similar: th e profiles of neighboring cells approached each other at the I-a borde r. Thus field centers were 2 sigma apart. The layout of fields for the remaining three classes was not well characterized because the fields were poorly fitted by a single Gaussian or because the cells responde d selectively to movement. The 2-sigma center-center spacing may be a general principle of functional organization that minimizes spatial al iasing and confers a uniform spatial sensitivity on the ganglion cell population.