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Determination of Sound Frequency — The “Place” Principle

المؤلف:  John E. Hall, PhD

المصدر:  Guyton and Hall Textbook of Medical Physiology

الجزء والصفحة:  13th Edition , p677-678

2026-07-01

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From earlier discussions in this chapter, it is apparent that low-frequency sounds cause maximal activation of the basilar membrane near the apex of the cochlea and high frequency sounds activate the basilar membrane near the base of the cochlea. Intermediate-frequency sounds activate the membrane at intermediate distances between the two extremes. Furthermore, there is spatial organization of the nerve fibers in the cochlear pathway, all the way from the cochlea to the cerebral cortex. Recording of signals in the auditory tracts of the brain stem and in the auditory receptive fields of the cerebral cortex shows that specific brain neurons are activated by specific sound frequencies. Therefore, the major method used by the nervous system to detect different sound frequencies is to determine the positions along the basilar membrane that are most stimulated, which is called the place principle for the determination of sound frequency.

Referring again to Figure 1, one can see that the distal end of the basilar membrane at the helicotrema is stimulated by all sound frequencies below 200 cycles/ sec. Therefore, it has been difficult to understand from the place principle how one can differentiate between low sound frequencies in the range of 200 down to 20. These low frequencies have been postulated to be dis criminated mainly by the so-called volley or frequency principle. That is, low-frequency sounds, from 20 to 1500 to 2000 cycles/sec, can cause volleys of nerve impulses synchronized at the same frequencies, and these volleys are transmitted by the cochlear nerve into the cochlear nuclei of the brain. It is further suggested that the cochlear nuclei can distinguish the different frequencies of the volleys. In fact, destruction of the entire apical half of the cochlea, which destroys the basilar membrane where all lower-frequency sounds are normally detected, does not totally eliminate discrimination of the lower-frequency sounds.