Tonotopic map reorganization and spectral weights in high-frequency sensorineural hearing loss

Abstract

Owing to reduced afferent input from high characteristic‐frequency hair cells, high‐frequency sensorineural hearing loss (SNHL) reorganizes the tonotopic maps in the central auditory nervous system: Map expansion is observed in the midfrequencies and map contraction in the high frequencies. Does the relative weighting of mid and high frequency information depend on this reorganization? With complex tones consisting of a 1,000‐ and a 3,127‐Hz sinusoid, 80 and 60 ms each, the resolution of simultaneous increments in frequency (IF) at 1,000 Hz and in duration (IT) at 3,127 Hz was studied in participants having either normal hearing or moderate‐to‐severe SNHL above 2,000 Hz. In both groups, the sensation level at 1,000 Hz (1.5–8 dB) was 17–38 dB lower than at 3,127 Hz (25–39 dB). In normal‐hearing participants, IF resolution was inferior to that of IT, suggesting stronger weighting for the more audible component. In hearing‐impaired participants, IF resolution was superior or equal to that of IT, suggesting stronger weighting for the lower sensation level 1,000‐Hz component impinging on the expanded tonotopic map region; in addition, IT resolution improved significantly following extensive training. [Work supported by PHF and NIH grants.]