A topographical representation for frequency has been identified throughout the auditory brain in animals but with limited evidence in humans. Using a midbrain implant, we identified an ordering of pitch percepts for electrical stimulation of sites across the human inferior colliculus (IC) that was consistent with the IC tonotopy shown in animals. Low pitches were perceived by the subject for stimulation of superficial IC sites while higher pitches were perceived for stimulation of deeper sites. Interestingly, this pitch ordering was not initially observed for stimulation across the IC, possibly due to central changes caused by prior hearing loss. Daily implant stimulation for about 4 months altered the pitch percepts from being predominantly low to exhibiting the expected ordering across the stimulated IC. A presumably normal tonotopic representation may have been maintained within the IC or accessible through IC stimulation that helped form this pitch ordering perceived in higher centers.
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We would like to thank the patient for her time and cooperation. We would also like to thank J. Patrick, J. Pesch, and F. Risi for their guidance and assistance in this research, and M. Braun, E. Lorentz, and S. Haumann for their contributions with the audiogram data. S. Offutt, M. Straka, C. Markovitz, B. Smith, C. Gloeckner, and M. Wojtczak provided helpful comments on the manuscript. This work was supported by Cochlear Limited, German Ministry of Education and Research 01GQ0816, and University of Minnesota start-up funds.