Relationships among age, conditioned stimulus-unconditioned stimulus interval, and neuropsychological test performance

To evaluate the effect of age at various conditioned stimulus (CS)-uncondit ioned stimulus (US) intervals, 144 young, middle-aged, and older adults wer e tested on eyeblink classical conditioning at CS-US intervals of 500, 1,00 0, or 1,500 ms. Reaction time, response timing, motor learning, declarative memory, and attention were assessed to identify correlates of conditioning at various CS-US intervals. Previously reported middle-aged and older adul ts were impaired at a 400-ms CS-US interval, but the addition of 100 ms to the CS-US interval in this study enabled equal conditioning in middle-aged and young adults. At a 1,000-ms CS-US interval, older adults remained signi ficantly impaired. It was only at the 1,500-ms; CS-US interval that conditi oning was equal for the 3 age groups. Measures of reaction time, timing, an d motor learning were not correlated systematically with conditioning. Wher eas the results of age differences at various CS-US intervals were clear an d striking, patterns of relationships among neuropsychological and conditio ning variables were not consistent in indicating sources of age differences .