“…For example, the saccule may respond to both auditory and vestibular stimuli, with different regions responding best to different frequencies [e.g., Enger, 1981] and different directions of particle motion [e.g., Piatt and Popper, 1981]. Although it is not yet possible to relate specific functions to specific ear regions, several investigations provide evidence for variation in response within individual epithelia: (a) hair cell orientation patterns [e.g., Piatt, 1977;Popper, 1977Popper, , 1981; (b) lengths of cilia on hair cells and related tuning properties from epithelial regions with hair cells having different length ciliary bundles [e.g., Piatt and Popper, 1984]; (c) the presence of at least two physiologically distinct hair cell 'types 1 within individual end organs [e.g., Sugihara and Furukawa, 1989;Steinacker and Romero, 1992]; and (d) the presence of two ultrastructurally distinct hair cell 'types' within a single end organ [e.g., Chang et al, 1992]. Indirect evidence supporting this hypothesis also comes from studies showing that there are clear regional differences in innnervation in the various otic end organs [e.g., Bell, 1981;Wegner, 1982;Saidel and Popper, 1983;Mathiesen and Popper, 1987;Popper and Saidel, 1990;Presson et al, 1992], suggesting differences in peripheral processing or central projections (see section on Innervation below).…”