6 



Neural Mechanisms of Hearing 



I. Place and Telephone Theories 



Hearing may be approached from various viewpoints. Some of these 

 have been so completely studied it is unlikely that in 50 years our con- 

 cepts will have changed appreciably. These aspects of hearing were 

 presented in Chapter 1. They included the nature of sound trans- 

 mission through the atmosphere, and the gross anatomy and the histology 

 of the ear. Similarly, the role of the outer and middle portions of the 

 ear as pressure amplifiers and mechanical transformers is quite well 

 established. As was discussed in Chapter 1, a maximum amplification 

 of about 35 db can be obtained. 



Other aspects of hearing are far less well understood. Specifically, 

 the conversion of acoustic energy to neural spikes in the inner ear and 

 the analysis of these spikes in the central nervous system are current areas 

 of research. They are discussed in the present chapter. It is assumed 

 that the reader is familiar with the material in Chapter 1 on "Sound 

 and the Ear," as well as in Chapters 4 and 5 on the "Conduction of 

 Impulses by Nerves," and the "Electrical Potentials of the Brain." 



The physicist regards the inner ear as a transducer, that is, as a device 

 which converts one form of energy into another. The inner ear converts 



104 



