Age-related changes in classical (Pavlovian) conditioning in the New Zealand albino rabbit.

The groups of New Zealand albino rabbits of approximately six and forty months of age respectively were subjected to Pavlovian conditioning in which a 1216 Hz, 75 dB tone served as the conditioning stimulus and a brief paraorbital electric shock train served as the unconditioned stimulus. Eyeblink and heart rate responses were assessed. Older animals revealed acquisition deficits in the somatomotor eyelid conditioning task compared to the young animals: however, the magnitude of the concomitantly occurring heart rate change was greater in older than in younger animals. These age-related changes appeared to be enhanced in males and were unrelated to general activity differences, or to the unconditioned response to unpaired tones or electric shocks.