Recent findings in auditory research have significantly changed our vi
ews of the processes involved in hearing. Novel techniques and new app
roaches to investigate the mammalian cochlea have expanded our knowled
ge about the mechanical events occurring at physiologically relevant s
timulus intensities. Experiments performed in the apical, low-frequenc
y regions demonstrate that although there is a change in the mechanica
l responses along the cochlea, the fundamental characteristics are sim
ilar across the frequency range. The mechanical responses to sound sti
mulation exhibit tuning properties comparable to those measured intrac
ellularly or From nerve fibres. Non-linearities in the mechanical resp
onses have now clearly been observed at all cochlear locations. The me
chanics of the cochlea are vulnerable, and dramatic changes are seen e
specially when the sensory hair cells are affected, for example, follo
wing acoustic overstimulation or exposure to ototoxic compounds such a
s furosemide. The results suggest that there is a sharply tuned and vu
lnerable response related to the hair cells, superimposed on a more ro
bust, broadly tuned response. Studies of the micromechanical behaviour
down to the cellular level have demonstrated significant differences
radially across the hearing organ and have provided new information on
the important mechanical interactions with the tectorial membrane. Th
ere is now ample evidence of reverse transduction in the auditory peri
phery, i.e. the cochlea does not only receive and detect mechanical st
imuli but can itself produce mechanical motion. Hence, it has been sho
wn that electrical stimulation elicits motion within the cochlea very
similar to that evoked by sound. In addition, the presence of acoustic
ally-evoked displacements of the hearing organ have now been demonstra
ted by several laboratories. (C) 1997 Elsevier Science Ltd.