 His lab also discovered and developed methods for the purification and culturing of retinal ganglion cells and the glial cells with which they interact, including the oligodendrocytes and astrocytes of the optic nerve.Near the turn of the 21st century he continued his study of glial cells and the mechanisms behind their ability to generate new neurons.He studied control of synapses by glia, and the differentiation of astrocytes by endothelial cells.