"Novelty" neurons in the frog auditory system

Some neurones in the torus semicircularis of paralyzed lake frogs (Rana ridibunda) exhibited strong response habituation to tonal bursts following with interstimuli intervals of 1 to 5 sec. The habituation became less evident with a devrease of the repetition rate or increase of the stimulus intensity. These units revealed the phenomenon of "postzero" habituation. The frequency selectivity of the units exhibited by their responses to the first stimulus presentation was very poor. Usually the habituation occurred within a wide frequency band, although there were some exceptions. Afther the habituation was completed, the unit's response could be elicited by tones of a different frequency. The more distant on the frequency scale the tones were, the more vigorous was the reaction. Some properties of these "novelty" units can be explained by assuming that they are multipolar neurones located in the nucleus magnocellularis of the torus.