CONDITIONED-REFLEX FACILITATION IN YOUNG AND OLDER ADULTS

Young (18-30 years) and elderly (63-88 years) human subjects received 70 trials of single-cue classical eyeblink conditioning (paired group) , or 70 explicitly unpaired presentations of the tone conditioned stim ulus (CS) and airpuff unconditioned stimulus (unpaired group). Before and after conditioning, reflex-eliciting white noise and corneal airpu ff stimuli were presented alone or paired with the CS to investigate t he effects of conditioning on eyeblink reflex amplitude. The results s howed increased conditioned responses in the paired group compared to the unpaired group for the young but not the elderly subjects. There w as, however, evidence of conditioned facilitation of noise-elicited re flexes in both young and elderly subjects. These data indicate that co nditioned facilitation of the startle reflex may be a sensitive indica tor of classical conditioning processes in human subjects.