Retrograde transneuronal degeneration in a basal ganglia target, the lateral spiriform nucleus, induced by anterograde transneuronal degeneration following eye removal in the chicken.

The chicken lateral spiriform nucleus (Spl) receives its major input from the paleostriatum primitivum of the forebrain, projects almost exclusively upon the optic tectum, but receives no projections from the tectum. In the present study we show that not only do tectal ablations reduce the volume of the Spl, the cross-sectional area, and the number of Spl neurons, but eye removal also produces a statistically significant reduction in Spl volume, cross-sectional area, and neuron number. Because the retina does not project upon the Spl directly, and because both the retina and the Spl project upon the optic tectum, we propose that the retina produces its effects upon the Spl by an anterograde transneuronally induced retrograde transneuronal mechanism.