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Neural Mechanisms of Hearing/ 6 : 4 



enter the brain; it is often called the eighth cranial nerve. As shown in 

 Figure 7, several additional synapses occur within the brain stem. 

 Some of the pulses cross over to the opposite half of the brain stem so 



Medial 

 Geniculate Body 



Ihferior- 

 Colliculus 



Midbrain- 

 Level 



Nuclei of 

 Lateral Lemnisci 



Medulla, 

 Level 



Vestibular Membrane 



.Cochlear 

 Duct 



.Sea la 

 Tympani 



Olivary 

 Complex 



Cochlear 

 Nerve 



Inner \ ' Outer 

 Pillar \ Pillar 



Basilar Membrane 



Phalangeal Cells 



Figure 7. Auditory pathways of the central nervous system. 

 Copyright The CIBA Collection of Medical Illustrations, by Frank 

 H. Netter, M.D., Vol. I, "The Nervous System," 1953. 



that those starting at either ear are represented in both halves of the 

 brain. Finally, at least in unconscious animals, the pulses are con- 

 ducted to specific areas on the surface of the temporal lobes of the 

 cerebral hemisphere. This latter projection is believed to be necessary 

 for conscious hearing. 



In humans and other primates, this auditory area on the temporal 



