The mammalian auditory midbrain, shown above, is part of the ascending auditory pathway, responsible for relaying sensory signals from the ear into the primary auditory cortex deep in the brain. Cajal’s microscopy studies led him to believe that the lateral leminiscus (A) received input from the cochlear and superior olivary nuclei, and carried some of it to the inferior colliculus (B), which integrated the signals necessary for auditory reflexes, while the bulk of the information was sent directly to the medial geniculate body (C), which then relayed the information on to the auditory cortex via the thalamo-cortical path (e).
Modern studies have shown, however, that the inferior colliculus actually processes nearly all the input sent to the medial geniculate body and receives signals from the descending auditory pathway, as well as providing the motor integration necessary for auditory reflexes hypothesized by Cajal, making it a true hub for auditory signaling.
