Long-term retention of the habituation of lick suppression and startle response produced by a single auditory stimulus.

Response decrement produced by a single, 2-sec, 98 dB, auditory stimulus in rats was retained without detectable loss for intervals ranging from approximately 30 sec to 30 days. Response decrements produced by stimulation over these intervals reached an apparent asymptote after 2 or 3 stimulus presentations. These response decrements were unambiguously associated with stimulus presentation for the lick suppression measure, but nonspecific decremental effects may have contributed to the startle response decrements. After these long-term decrements had reached asymptote, 300 stimulus presentations with 1-sec interstimulus intervals produced further response decrements, but these decrements recovered completely within 24 hr., responsiveness returning to the previously established long-term asymptote. The data show that unreinforced stimulus presentations can produce both relatively permanent response decrements and apparently independent short-term decrements. The data also suggest that long-term retention may be more generally characteristic of habituation than is usually assumed.