Organization of connections underlying the processing of auditory information in the dog

1. The canine temporal cortex includes the ectosylvian, composite posterior and sylvian gyri. 2. The distinctive features of the canine temporal cortex include the ectosylvian sulcus closed in its dorsal side and the substantial development of neocortex located within the posterior composite gyrus. 3. Thalamofugal connections from particular nuclei of the medial geniculate body, posterior thalamus and lateromedial-suprageniculate complex project to specific areas of the canine temporal cortex and are arranged as dominant and non-dominant projections. 4. Local intracortical connections distinguish the ectosylvian and posterior composite areas as unimodal auditory cortex. Long distant connections and polymodal convergence indicate that the composite ectosylvian area of the anterior ectosylvian gyrus and the anterodorsal sylvian areas are higher order association cortex. 5. Analysis of both thalamo-cortical and intracortical connections indicate that auditory processing in the cortex occurs in successive, hierarchically organized stages and in two main, anterior and ventral pathways.