Book Review

In the present series of publications published over a period of more than 25 years between 1980 and 2006, Eric LePage has concerned himself primarily with the study of the highly complex micromechanics of the inner ear. Already his first paper in 1980 in collaboration with Brian Johnstone demonstrated a then largely unknown phenomenon, namely the non-linear behavior of the mammalian basilar membrane. He refined his studies in later years, succeeding in making direct observations of the electromechanical processes in the cochlea using a capacitive probe. At an early time, namely in 1987, he showed that bias phenomena could be measured at the level of the basilar membrane and suggested that these might contribute to a regulation of sensitivity in the hearing organ. In 1989 he expanded his studies to an examination of the functional role of regulation of the inner ear by the brain. Here he demonstrated a motor-unit-control-system in the cochlea that is controlled by the brain via the olivocochlear bundle. Then he referred to studies of Helmholtz from the 19th century, and on the basis of his mechanical measuring data proposed a physical model for the dynamic control of the tonotopic principle along the cochlea. Importantly then in the year 1992 he observed a hysteresis of cochlear micromechanics. He was able to draw conclusions of clinical relevance by understanding that hysteresis represented a mechanism that might underlie the large variability seen in noise-induced hearing loss. In 1993 he returned to his earlier work on the bias of the basilar membrane by measuring summating baseline shifts using optical displacement sensors and concluded that a mechanical adaptation was occurring.

Last but not least, Eric LePage also dealt with clinically relevant scenarios. In 1994 he was a member of a research group which described that transient endolymph leakage represented a cellular-biological basis for hearing-loss and tinnitus. A contribution to the understanding of how functional losses occur with ageing was a publication from the year 1995 in which the aging processes of the outer hair cells were associated with this same functional loss. He then dealt with the important topic of tinnitus in 1995 when he described the operating point of inner hair cells and suggested an excitatory drift as a possible cause for subjective tinnitus. In 2006 Eric LePage summarized his results as well as the results of other international researchers in a review and established the hypothesis of a servo-loop in the mammalian cochlea.

For more than 25 years Eric LePage has therefore made an outstanding contribution to auditory research whether it be from a methodological, informative or observational perspective. Regarding the micromechanics of the cochlea he has contributed important publications to the international literature that have been built upon further by many other authors. Summarizing his work with the work of many other authors, his papers have allowed a considerably more differentiated view to be acquired for the micromechanical function of the cochlea than was possible 25 years ago.

Professor Dr. Hans-Peter Zenner

Tuebingen, 30/10/2006