PSYCHOPHYSICAL TUNING CURVES IN SUBJECTS WITH TINNITUS SUGGEST OUTER HAIR CELL LESIONS

A study by Penner (J Speech Hear Res 1980;23:779-86) found evidence fo r impaired lateral suppression in subjects with tinnitus and sensorine ural hearing loss. If lateral suppression is related to tuning curve s harpness and lateral suppression is impaired, the shape of the tuning curve should be affected, The purpose of this study was to determine w hether subjects with tinnitus have psychophysical tuning curves that a re different from those of subjects without tinnitus. Psychophysical t uning curves and hearing thresholds were obtained from 18 subjects, 7 with tinnitus and 11 without tinnitus. Only subjects with normal audio grams (through 8 kHz) were selected for this study. In subjects with t innitus psychophysical tuning curves were obtained in the region pitch -matched to their tinnitus, In nontinnitus subjects psychophysical tun ing curves were determined at the same frequencies as for the tinnitus subjects in a yoked-control design. The slopes of the tails and tips and the Q(10) and other measures were calculated for each tuning curve . The psychophysical tuning curves in subjects with tinnitus were sign ificantly different (0.01 level) from those of control subjects and of ten had hypersensitive tails and some elevated tips, These shapes of t uning curves are consistent with cochlear lesions involving the loss o f outer hair cells without damage to the inner hair cells or nerve fib ers.