The effects of age, exposure, preexposure, and noise conditions on variable interval performance

The present study was designed to investigate the differential effects of environmental factors on performance in young and aged rats. Specifically, within- and between-session habituation, environmental preexposure, and noise conditions were examined. Consistent age differences were found in response to environmental change and sensory condition. Variable-interval response rates of the well-habituated old animal were well below those of the young. Stimulus change and increments in noise elevated these behaviors in the aged to levels well above those seen in the young. Aged animals appeared incapable of maintaining higher response rates without corresponding conditions of novelty, contextual change, or increments in ambient sensory conditions. Preexposure to sensory conditions similar to those used in the operant chamber reduced response rates in the old, as did habituation with repeated exposure to the chamber.