Receptive-field properties of adult cat's retinal ganglion cells with regenerated axons

Receptive-field properties of retinal ganglion cells (RGCs) that had regene rated their axons were studied by recording single-unit activity from stran ds teased from peripheral nerve (PN) grafts apposed to the cut optic nerve in adult cats. Of the 286 visually responsive units recorded from PN grafts in 20 cats, 49.7% were classified, according to their receptive-field prop erties, as Y-cells, 39.5% as X-cells, 6.6% as W-cells, and 4.2% were unclas sified. The predominant representation of Y-cells is consistent with a corr esponding morphological study (Watanabe et al. 1993a), which identified a-c ells as the RGC type with the largest proportion of regenerating axons. Amo ng the X-cells, we only found ON-center types, whereas both ON-center and O FF-center Y-cells were found. As in intact retinas, the receptive-field cen ter sizes of Y-cells and W-cells were larger than those of X-cells at corre sponding displacements from the area centralis. Within the 10 degrees surro unding the area centralis, the receptive fields of X-cells with regenerated axons were larger than those in intact retinas, suggesting that some rearr angement of retinal circuitry occurred as a consequence of degeneration and regeneration. Receptive-field center responses of Y-, X-, and W-ty-pe unit s with regenerated axons were similar to those found in intact retinas, but the level of spontaneous activity of Y- and X-type units was, in general, less than that of intact RGCs. Receptive-field surrounds were weak or not d etected in more than half of the visually responsive RGCs with regenerated axons.