Processing of intensity-correlated information in an acoustic-autonomic reflex system

The extraction and utilization of sound level changes in acoustic-autonomic reflex systems were studied on a vasoconstriction response in the tail of nonanesthetized rats. The vasoconstriction was found to depend on sound level and changes of level in the following ways. (a) It increased as a linear function of sound level (in dB) of short noise bursts. (b) It habituated during stimulation with a constant sound. (c) It was re-elicited by changes in the level of ongoing sound. (d) Its size, in response to a 10 dB increase in an on-going sound, was determined by the total level reached, and not by the size of the change. (e) Its size, in response to an increase varying from 5 to 50 dB, was equal if the total level reached was the same. (f) It gradually decreased if the stimulus steps were of less than 5 dB. The results are interpreted to show the existence of sound level specific information channels and level-specific habituation phenomena.