Cerebellar vermis: essential for long-term habituation of the acoustic startle response.

The acoustic startle response in rats shows both short-term habituation, which recovers in seconds or minutes, and long-term habituation, which is effectively permanent. Lesions of the cerebellar vermis significantly attenuated long-term habituation without affecting the short-term process or altering initial response levels. In this response system the cerebellar vermis is part of an essential circuit for long-term habituation.