During its 25-year history the Laboratory has focussed on a number of research areas including: 

• Acoustic injury in young animals 
• Hearing in the parakeet
• The middle ear and its development
• The structure and function of hair cells
• Acoustic injury and the recovery of function

Susceptibility to Acoustic Trauma by Young Animals 
Between 1973 and 1982 a series of papers appeared which asked if there was a critical period in the auditory development of mammals when the ear was particularly susceptible to damage from loud sound. The conclusion from this work was that the cochlea, immediately after it achieved adult-like structure and function was at greatest risk to damage from loud sounds. These observations were summarized in several articles. [Back to Top] 

1. Saunders, J. C.  The physiological effect of priming for audiogenic seizure in mice.  The Laryngoscope, 1974, 84, 750 - 756. 
2. Saunders, J. C. & Bock, G. R.  Influence of early auditory trauma on auditory development.  In:  G. Gottlieb (Ed.),  Studies on the Development of Behavior and the Nervous System.  Vol. 4.  Early Influences.  New York:  Academic Press, 1978, 249 - 287.
3. Saunders, J. C. & Tilney, L. G.  Species difference in susceptibility to noise exposure.  In:  R. P. Hamernik, D. Henderson & R. Salvi (Eds.), New perspectives on noise-induced hearing loss.  New York:   Raven Press, 1982, 229 - 248.
4. Saunders, J. C. & Chen, C. -S.  Developmental periods of enhanced susceptibility to auditory trauma in laboratory animals.  In:  A. Wallace Hayes (Ed.), Toxicology of the Eye, Ear and Other Special Senses.  New York:  Raven Press, 1985, 145 - 154. 

Frequency Resolution in the Avian Ear 
From 1976 to 1980 another series of papers explored the frequency resolving power of the budgerigar (parakeet) ear.  Using behavioral conditioning methods and a variety of masking paradigms, critical ratios, critical bands and psychophysical tuning curves were measured.  This work demonstrated that in a narrow range of hearing, the frequency resolving power of this bird ear was as frequency selective as the mammalian ear. These observations were summarized in several places. [Back to Top] 

1. Saunders, J. C.  The psychophysical analysis of pure-tone masking in the parakeet.  In:  S. K. Hirsch, I. J. Hirsh, D. H. Eldredge & S. R. Silverman (Eds.), Hearing and Davis:  Essays Honoring Hallowell Davis.  Washington University Press, 1976, 199 - 211.
2. Saunders, J. C. & Henry, W. J.  The peripheral auditory system of birds:  Structural and functional contributions to auditory perception.  In:  R. J. Dooling & W. M. Hulse (Eds.), Contributions to Auditory Perception in Animals.  Collingswood, N. J.:  L. Earlbaum, 1988, 31 - 62.

The Middle Ear 
Studies of the conductive apparatus were a consistent theme of the Laboratory between 1979 and 1997.  The bulk of the middle ear efforts were directed toward elucidating the contribution of middle-ear development to the overall  development of hearing.   Using tympanometry, acoustic impedance measures, laser interferometry, and morphologic measures of middle-ear structure, the developing structure and function of the middle ear were examined in a variety of laboratory animals.  In mice, rats, and hamsters, there was clear evidence that the improving efficiency of sound transmission through the middle ear limited the rate of overall hearing maturation in these species.  The background and evidence supporting this idea has been summarized in several articles. [Back to Top] 

1. Saunders, J. C., Kaltenbach, J. & Relkin, E. M.  The development of the middle ear.  In:  R. Romond (Ed.),  The Development of the Auditory and Vestibular System.  Academic Press, 1983, pp. 3 - 25.
2. Saunders, J. C., Doan, D. E. & Cohen, Y. E.  The contribution of middle-ear sound conduction to auditory development.  Comparative Biochemistry and Physiology, 1993, 106A, 7 - 13.

Hair Cell Structure and Function 
Beginning in 1980 and continuing to the present a variety of studies have examined the structural and functional aspects of hair cells.  Early work undertaken with Dr. Lewis G. Tilney in the Department of Biology described the cytoskeletal organization of actin in chick stereocilia.  The first report of cytoskeletal damage following intense sound exposure appeared in 1982. Changes in the stiffness of guinea pig sensory hair bundles following in vitro overstimulation was undertaken with Drs. Flock and Canlon in 1985, and replicated on chick hair cells with Drs. Szymko and Nelson in 1996.  The role of intra- and exra-cellular calcium on hair bundle stiffness was reported in 1994 by Dr. Pae.  Most recently, the role of the tip links in determining relative and asymmetric hair bundle motion has been reported.  Several overviews of this hair cell work has been presented. [Back to Top] 

1. Saunders, J. C. & Dear, S. P.  Comparative morphology of stereocilia.  In:  R. Fay and G. Gourevitch (Eds.), Essays in Hearing in Honor of E. G. Wever.  Groton, Connecticut:  Amphora Press, 1983, pp. 175 - 197. 
2. Saunders, J. C., Schneider, M. E. & Dear, S. P.  The structure and function of actin in hair cells.  Journal of Acoustical Society of America, 1985, 78, 299 - 311. 
3. Saunders, J. C. & Coppa, N.  The contributions of stereocilia, rootlet and cuticular plate injury to sensorineural hearing loss.  In:  M. J. Collins, T. J. Glattke & L. A. Harker (Eds.)  Sensorineural Hearing Loss:  Mechanisms, Diagnosis, Treatment.  Iowa City:  University of Iowa Press, 1986, pp. 29 - 58.
4. Saunders, J. C., Canlon, B. & Flock, A.  Mechanical changes in stereocilia following overstimulation.  In:  R. Henderson et al., (Eds.), Basic and Applied Research on Noise Induced Hearing Loss.  New York: Plenum Press, 1986, pp. 11 - 29.
5. Saunders, J. C.  Stereocilia injury and repair.  In:  T. van de Walter & R. J. Rubin (Eds.)  The Biology of Change in Otolaryngology.  New York:  Elsevier, 1987, 319 - 330.

Acoustic Injury and the Recovery of Function. 
The effects of loud sounds on hearing is a long standing recurrent theme of the Laboratory. The work of Doug Cotanche when he was a Post-Doctoral Fellow at Penn in the mid 1980’s paved the way for the discovery of hair cell regeneration in the chick ear.  In the late 1980s the Lab traced the replacement of hair cells over time and correlated it with the recovery of function.  Quantitative measures of functional loss and recovery have led to numerous ideas about how acoustic trauma leads to the loss and restoration of hearing in the bird ear.  The remarkable conclusion from this work is that hair cell regeneration contributes little to the recovery of function.  This conclusion is specific to the sound damaged chicken ear and attests to the complexity of this animal model.  The most recent work has demonstrated the loss and recovery of tip links on tall hair cell sensory hair bundles after exposure to intense sound. Various aspects of the acoustic injury research has been summarized in various papers. [Back to Top] 

1. Saunders, J. C., Dear, S. P. & Schneider, M.  The anatomical consequences of acoustic trauma:  A review and tutorial.  Journal of the Acoustical Society of America, 1985, 78, 833 - 860.
2. Saunders, J. C., Cohen, Y. E. & Szymko, Y. M.  The structural and functional consequences of acoustic injury in the cochlea and peripheral auditory system:  A five year update.  Journal of the Acoustical Society of America, 1991, 90, 136 - 146.

Saunders, J. C., Doan, D. E., Cohen, Y. E., Adler, H. J. & Poje, C. P.  Recent observations on the recovery of structure and function in the sound-damaged chick ear.  In:  R. J. Salvi et al. (Eds.),  Auditory System Plasticity and Regeneration.  Thieme, New York:  1996, pp. 62 – 83.