[Relation between the spontaneous activity and dynamic characteristics of primary afferents of the lateral semicircular canal in frogs].

Spontaneous activity (SA) and responses of 68 primary afferents of frog lateral semicircular canal to sinusoidal vibration (frequency band: 0.04-200 Hz, double peak amplitude up to 10 microns) of canal wall were studied in immobilized frogs. The regularity of SA was evaluated by coefficient of variation (CV). 12 units (17.6%) constituted the regular group (CV less than 0.3), 9 units (13.2%)--the irregular group (CV approximately equals 1.0), and 47 units (69.1%)--the intermediate one (CV =0.4-0.9). The correlation between background activity and responses is most clear for the regular group whose dynamic characteristics are: responses only "all round" type; narrow (0.04-0.4 Hz) band of effective vibration frequencies; large (up to 9 sec) time constant to step stimulus. The two other groups are clearly different in their frequency possibilities. The wide range afferents (identified as intermediate) are able to respond to wide band of vibration (0.04-180 Hz) and have the largest gain among the three groups. Their dynamic range is also wide. For high frequency (irregular) units effective band is from 20-60 Hz (from below) up to 120-180 Hz (from above). They may be identified as real vibroreceptors. The other characteristics (CV, time constant to step stimulus, etc.) in the two last groups smoothly pass on from one group to another.