Transneuronal retrograde degeneration of retinal ganglion cells following restricted lesions of striate cortex in the monkey

Transneuronal retrograde degeneration of retinal ganglion cells follows extensive striate cortical removal in macaque monkeys. Its extent depends on the age of the monkey at operation, post-operative survival, species and retinal eccentricity. Some studies of human patients with occipital lobe injury have found no evidence for transneuronal retrograde degeneration, suggesting that either degeneration may not occur or, if present, it is caused directly by secondary damage impinging upon the underlying white matter or the blood supply to the dorsal lateral geniculate nucleus and optic tract. We therefore studied retinal ganglion cell degeneration in three macaques in which only the striate cortex corresponding to the macular retina had been removed, thereby sparing extrastriate cortex and precluding interruption of the vascular supply to the thalamus and optic tract. There was extensive loss of ganglion cells in the central retina, corresponding to the central 10 degrees of vision. As the cortical lesion was too small to affect the thalamus or optic tract directly, the retinal degeneration must be transneuronal. Quantitative analysis showed a 65-80% loss of ganglion cells in the corresponding perifoveal retinae along the horizontal meridian. The results confirm that the loss of retinal ganglion cells following striate cortical lesions is predominantly transneuronal.