Cytoarchitecture and visual receptive neurons in the Wulst of the Japanese quail (Coturnix coturnix japonica).

The cellular organization of the Wulst was studied in Nissl- and Golgi-stained brain sections in order to identify the visual receptive neurons. Golgi-impregnated neurons were divided into four types according to their soma size, dendritic configuration, and density of spine distribution. Type I neurons, the largest cells in the Wulst, have long, straight dendrites with many spines. Type II neurons are medium-sized cells with long, straight dendrites. These dendrites have numerous spines. Type III neurons are medium-sized or small cells with spine-free dendrites. Type IV neurons, the smallest cells in the Wulst, have short dendrites with sparse spines. The projections of the nucleus dorsolateralis anterior thalami pars lateralis (DLL) to the Wulst were determined by the Fink-Heimer method. After lesions of the DLL, degenerating terminals are seen in a dorsolateral portion of the nucleus intercalatus hyperstriatum accessorium where the types II, III, and IV neurons are distributed. Postsynaptic elements to the DLL axons were identified by reconstruction of electron microscopic serial sections. Most of the postsynaptic elements were dendritic spines of the type II and IV neurons and a few were dendritic shafts of the type III neurons.