Modification of the acoustic startle response in hearing-impaired C57BL/6J mice: Prepulse augmentation and prolongation of prepulse inhibition.

Modification of acoustic startle amplitude by a 10-ms tone prepulse (S1) was evaluated as a function of the interstimulus interval (ISI) between the onset of S1 and the onset of the startle-evoking stimulus (S2). Subjects were normal-hearing 1-month-old C57BL/6J (C57) mice and CBA/CaJ mice and 5-month-old C57 mice with high-frequency hearing loss. With a 2-ms ISI, 5-month-old C57 mice (but not the normal-hearing mice) exhibited pronounced prepulse augmentation (PPA) of startle: Amplitudes were much larger when S1 was present. Prepulse inhibition (PPI) occurred with ISls of 10–100 ms in all subject groups. With long ISls of 200 and 500 ms, however, PPI was strong only in 5-month-old C57 mice and only with S1 frequencies of 8, 12, and 16 kHz. Physiological studies of neural plasticity have shown that frequencies of 8–16 kHz become "over-represented" (more neurons responding) in the central auditory system of C57 mice, suggesting a link with prolonged PPI observed here. (PsycINFO Database Record (c) 2010 APA, all rights reserved)