Evidence of sub-collicular auditory projections to the medial geniculate nucleus in the cat: an autoradiographic and horseradish peroxidase study.

Connection of a posteromedial region of the ventral nucleus of the lateral lemniscus were examined in the cat using the autoradiographic tracing method. This sub-collicular region previously had been shown, using retrograde transport of horseradish peroxidase, to send axons to the superior colliculus. The autoradiographic findings revealed that many axons from the posteromedial region of the ventral nucleus of the lateral lemniscus that entered the superior colliculus continued into the midbrain reticular formation. Moreover, other axons traced rostral to the interior colliculus into the thalamus ended in the medial geniculate nucleus, bilaterally. Experiments in which horseradish peroxidase was placed in the medial geniculate nucleus retrogradely labeled the large neurons in the posteromedial region supporting the autoradiographic observations. Other sub-collicular regions also contained labeled cells in these cases, including the main body of the ventral nucleus of the lateral lemniscus and scattered cell groups around the superior olivary complex.