ACOUSTIC VALUE OF THE SEVERAL COMPONENTS OF THE AUDITORY SYSTEM IN CATS

Abstract

Cats were tested at 3 frequencies (125, 1000 and 8000 cycles) with a newly developed device for measuring conditioned responses, to determine the loss in hearing after operative removal of various components of the acoustic system. Destruction of a single cochlea is followed by a hearing-loss of 3 to 4 decibels, destruction of both cochleae by total deafness to air-borne sounds. Ablation of one-half of the cortex brings a loss of 3 to 5 decibels; the left half may be slightly superior in acoustic value to the right. Despite their numerical inferiority, the uncrossed fibers of the lateral lemnisci are equal in acoustic significance to the crossed components. The evidence discloses a safety-factor of 2 or more in the acoustic mechanisms. These observations confirm and extend previously published material from dogs.