Clinical Determination of Abnormal Auditory Adaptation

Introduction Hallpike and Hood1have clarified the necessity of distinguishing between the initial burst of auditory excitation, known as "on-effect," and the progressive reduction in excitation to continuous stimulation, which is called "adaptation." The normal hearing mechanism exhibits these two phenomena in a manner reminiscent of the neural events characterizing equilibration as observed by Derbyshire and Davis.2However, Hallpike and Hood turn to the work of Matthews3on the behavior of the stretch receptor for both the neurological analogy they accept and the concepts they develop. These British workers have stimulated the clinician to reexamine both his theoretical orientation and his diagnostic practices by claiming that certain types of auditory pathology are characterized by an abnormal balance between "on-effect" and "adaptation." Hallpike and Hood have written that recruitment, which they claim distinguishes end-organ (cochlear) lesions from neural lesions, occurs because the "on-effect" is essentially normal. A tone