The laminar source of efferent projections from the avian Wulst.

Following horseradish peroxidase injections into the pigeon tractus septomesencephalicus, the efferent outflow bundle of the avian Wulst, retrogradely labeled neurons within the Wulst were confined to the superficialmost layer, the hyperstriatum accessorium. These results suggest that the hyperstriatum accessorium is the sole source of Wulst efferent projections. In similarity to the laminar organization of mammalian striate cortex, this efferent layer is juxtaposed to the thalamorecipient layer of Wulst.