Crossed and descending projections to the inferior colliculus.

Crossed and descending projections to the inferior colliculus of the cat were studied following injections of horseradish peroxidase. Earlier injections of large (about 1 microliter) volumes and diaminobenzidine histochemistry were fully confirmed with later small volume injections and tetramethylbenzidine histochemistry. Emphasis was placed on describing the cell types projecting to the colliculus and 16 cell types were described. These were found in the contralateral inferior colliculus, the ipsilateral superior colliculus, central gray, substantia nigra, parabrachial region, medial geniculate and bilaterally in the hypothalamus and auditory cerebral cortex.