Synaptic ring images after silver impregnation.

In view of the contradictory results obtained from a number of studies on the nature of ring images found after neurofibrillar silver impregnation, this question was reinvestigated at the ultrastructural level in the lateral geniculate nucleus of the monkey. The ring images found here are produced by silver deposits on ring-shaped accumulations of neurofilaments in the afferent synapses of retinal origin. Tubular impregnation of axons was not found to be a factor in the genesis of ring images.