The corticofugal projection from auditory relating area to the inferior colliculus (IC) is one of top-down stream and modurate auditory perception as attention or contextual information. We have reported abundant projection was originated from posterodorsal auditory area of the neocortex into the dorsal cortex (DC) and the external nucleus of the IC (EN) with anterograde tracing study. These areas of IC are located around the central nucleus of IC (ICC) and known to project into the suprageniculate nucleus (SG)or surrounding nucei such as the marginal zone, the posterior intralaminar thalamic nucleus, and the posterior limitans nucleus. This ascending pathway is parallel to the main auditory ascending projection from ICC to the vental part of the medial geniculate body (MGv). Thus the projecting neurons in DC or EN which involved in this pathway might receive direct and strong input from the corticofugal projection from auditory relating area. We designed an investigation with triple labeling of presynaptic and postsynaptic neurons respectively and synaptic marker vesicular glutamate transporter 1 (vGluT1) in order to estimate synapse formation between them. As a result, we successfully labeled DC and EN neuron involved in parallel ascending pathway with A555 conjugated Choleratoxin B subunit injected into SG. Corticocollicular projecting axons were labeled with recombinant Sindbis virus infection which make infected cell express palmytoilated GFP. We found some labeled neurons in both DC and EN which were contacted with anterogradely labeled corticocollicular projecting axons. In many cases synaptic marker collocalization were positive, which suggested the synaptic formation between them. These results suggest that corticocollicular projection have influence on the main auditory pathway via DC and EN neurons and more directly enhance the parallel ascending pathway formed by themselves.