Intro | Auditory Cortex | Cochlear Nucleus | Inferior Colliculus | Medial Geniculate | Superior Olive
Part 1: Image-Mapped Tutorial
Part 2: Matching Self-Test
Part 3: Multiple-Choice Self-Test
The second site of synapse for the majority of auditory fibers leaving the cochlear nucleus is the Superior Olive, also located in the medulla. The superior olive is composed of a group of nuclei, and is commonly referred to as the superior olivary complex. Each superior olive receives a bilateral projection, from both the ipsilateral (same side) and contralateral (opposite side) cochlear nucleus. The contralateral projection, however, is the largest. The information reaching the primary auditory cortex is therefore primarily representative of information conveyed from the opposite ear.
The medial and lateral superior olive nuclei are involved in the localization of sound. Neurons located in the medial superior olive nucleus respond to differences in the time that a given stimulus reaches each of the ears, whereas neurons located in the lateral superior olive nucleus respond to slight differences in the amplitude of sound waves reaching each ear. This information is then conveyed to the inferior colliculus where an auditory spatial map, aids in the localization of sound.
| Advanced |
The fibers arising from the cochlear nuclei proceed anteriorly according to several general principles (Parent, 1996). All projections between the cochlear nuclei and each structure along the path leading to the auditory cortex are bilateral. Therefore, damage on only one side of the pathway anterior to the cochlear nuclei does not result in deafness for either ear. Since the majority of fibers are contralateral or crossed, however, any subtle hearing loss following damage will affect hearing from the contralateral ear.
| Reference |
Parent, A. (1996). Carpenter's human neuroanatomy (9th ed.). London: Williams & Wilkins.