African jewel fish reared with eyeless cave fish, but without visual-tactile contact with conspecifics, exhibit hyperresponsive behavior after release in community aquaria. Because the optic tectum might be affected by these restraints on visual experience, unreleased members of the same social isolate group were compared histologically with controls reared in community aquaria. Using the rapid Golgi method, we counted dendritic spines and branches on pyriform interneurons between 402 and 529 days of age. As compared with isolates, control group interneurons exhibited significantly more spines and primary branches on apical dendrites in deep tectal layers. Our focus is the relation between experiential differences in rearing conditions and synaptic changes in the deep tectal layers.