DOES EARLY ENUCLEATION AFFECT THE DECUSSATION PATTERN OF ALPHA-CELLS IN THE FERRET

Naturally occurring cell death has been hypothesized to sculpt various features of the organization of the mature visual pathways, including the recent proposal that the selective elimination of ganglion cells in the temporal retina shapes the formation of decussation patterns. T hrough a class-specific interocular competition, ganglion cells in the two temporal hemiretinae are selectively lost to produce the decussat ion patterns characteristic of each individual cell class (Leventhal e t al., 1988). The present study has tested this hypothesis by asking w hether the removal of one retina in newborn ferrets, which should disr upt binocular interactions at the level of the terminals, alters the d ecussation pattern of the alpha cells, a cell class that is entirely d ecussating in the normal adult ferret. Enucleation on the day of birth was found to increase the uncrossed projection by approximate to 50%, but not a single uncrossed alpha cell was found in the temporal retin a. Either alpha cells never project ipsilaterally during development, or if they do, they cannot be rescued by early enucleation. While natu rally occurring cell death plays many roles during development, creati ng the decussation pattern of the ferret's alpha cell class via a bino cular competition at the level of the targets is unlikely to be one of them.