5-YEAR RETENTION OF THE CLASSICALLY-CONDITIONED EYEBLINK RESPONSE IN YOUNG-ADULT, MIDDLE-AGED, AND OLDER HUMANS

Human participants who 5 years earlier participated in studies of acqu isition of the classically conditioned eyeblink response to a tone con ditioned stimulus (CS) and an air puff unconditioned stimulus (UCS) re turned to the laboratory to test for retention of the conditioned resp onse (CR). Retention consisted of 20 tone CS-alone presentations. Youn g adult participants (23-31 years of age at the lime of retention test ing) showed good retention of the CR (45%), middle-aged participants ( 45-52 years) showed reduced retention (28%), and older participants (6 9-78 years) showed little evidence of retention (<5%). Retention testi ng was followed by reacquisition of the CR in which the CS and the UCS were again paired. The ability to reacquire the CR also showed a decl ine with age. The data suggest that the CR can be retained over long i ntervals and that the degree of retention is age dependent.