The Inferior Colliculus: A Center for Convergence of Ascending and Descending Auditory Information

A major goal in auditory research is to understand completely how we hear, the physiology of the human auditory system and to identify the causes and treatments for hearing impairment. By understanding all the elements of the ‘auditory scaffold’ we will begin to achieve these important goals. The inferior colliculus (IC) occupies a strategic position in the central auditory system and may be considered a central hub or an interface between the lower auditory pathway, the auditory cortex and motor systems. The IC is the site for termination of the ascending fibers of the lateral lemniscus and also receives a heavy innervation from the auditory cortex. Furthermore, the IC receives crossed projections from its counterpart and possesses a dense network of local connections. Thus, the IC is the main site of auditory integration at the midbrain level. Anatomical and physiological experiments demonstrate that the IC is involved in a great diversity of functional roles in the auditory system, and that most of the interesting auditory features might already be extracted from incoming sounds by this midbrain nucleus.