Acoustic coding by the ear of the sunfish (Lepromis gibbosis): Sensitivity, tuning, and directionality of 8th nerve units Free

The auditory system of the sunfish is characteristic of many teleosts, and is unspecialized for sound pressure reception. It is likely that its otolithic ear responds primarily to acoustic particle motion in the manner of an accelerometer. Single units of the lagenar and saccular eighth nerve branches were characterized in response to whole‐body acceleration. Using a three‐dimensional vibration system [Fay et al., J. Acoust. Soc. Am. Suppl. 1 74, S7 (1983)], the directionality of single units were measured in three orthogonal planes, and the cell's best sensitivity axis determined in spherical coordinates. Acceleration tuning curves obtained along a nearly optimal axis were essentially low pass with cutoff frequencies ranging from below 100 to 250 Hz. Best sensitivity varied from −30 to −90 dB re: 1 g (rms). Lagenar units showed a wide range of “best directions,” all roughly in a para‐saggital plane. Saccular units fell into two or more directional groups. Directional patterns for both organs reflect aspects of the organs' orientation in the head, and the orientations of hair cells on the maculae. All cells reponded as if their input (most likely a group of hair cells) were equivalent to a single hair cell of a given three‐dimensional orientation.