Physiological correlates of auditory stimulus periodicity.

Microelectrode studies of single auditory nerve fibers provide information on physiological mechanisms postulated in the two classical theories of pitch perception. The place principle is exemplified by the threshold vs. frequency or tuning curve for a fiber which typically exhibits maximum sensitivity to a narrow band of frequencies. Computer-controlled stimulus presentation has permitted systematic exploration of the supra – threshold response area throughout the entire domain of effective frequencies and SPL's. These studies demonstrate that the assignment of a single characteristic frequency constitutes an inadequate description of the frequency selectivity of a fiber since the frequency of lowest threshold may be appreciably different from the frequency which causes maximal discharge at higher SPL's. In general, the complexity of the response areas is difficult to reconcile with the simplistic concept that each fiber can be associated with a specific pitch.The Volley theory predicts that stimulus per...