British Medical Bulletin 43:780-801 (1987)
© 1987 The British Council
research-article |
Anatomical features of the auditory pathway from cochlea to cortex
Department of Communication and Neuroscience, University of Keele Keele, Staffs
Abstract
The hair cells of the organ of Corti transduce vibrations within the cochlea into neural signals. Outer hair cells are contractile and may contribute to mechanical feedback processes, whilst the inner hair cells are apparently the primary sensory cells being innervated by the majority of the afferent fibres. These run in the auditory nerve to the brain stem where they bifurcate, projecting cochleotopically to the dorsal and ventral cochlear nuclei, a divergence continued in the main routes taken by the ascending pathways. One runs bilaterally from the ventral cochlear nucleus to the superior olivary complex and then to the inferior colliculi. The other runs from the dorsal cochlear nucleus to the contralateral inferior colliculus. Fibres from the brainstem nuclei travelling to each inferior colliculus form a tract, the lateral lemniscus, and may make contact with one of the nuclei within it. The pathway continues to the medial geniculate bodies and on to the auditory cortex, preserving its cochleotopicity at all levels. A descending system parallels the ascending system throughout. The presence of commissural and decussating connections from the level of the brainstem onwards, provides the anatomical basis for the analysis of binaural information. The division of the pathway forms the anatomical substrate for the parallel processing of different features of the auditory environment.