Aging and exercise effects on motor learning and spatial memory

Abstract

The aim of this experiment was to determine whether low impact forced exercise improved learning and memory in middle aged and older mice. The effects of 12 weeks of low impact, forced running on motor learning and spatial memory were compared in 32 C57BL/6 mice in three age groups with a mean age of 13, 17, and 25 months. Motor learning was assessed with the rotorod, and spatial memory was assessed with the Morris water maze (MWM). Mice were randomly assigned to the forced exercise or sedentary control group and were treated for 60 min/day (2 30-min sessions) for 12 weeks. Significant age differences were observed on the rotorod (15 and 25 RPM) with the 13-month-old mice outperforming 17- and 25-month-old mice. Age differences were also observed on the MWM, with 25-month mice impaired in latency to escape and distance covered. The effect of exercise on rotorod performance did not attain statistical significance, but the mean performance of runners was higher than that of controls. Exercise improved spatial memory retention in the MWM and led to significant improvement in acquisition distance. Low impact forced exercise did not have strong effects on motor learning as assessed by the rotorod. However, low impact forced exercise did improve retention of spatial memory in 13-month-old mice. Slight improvements in spatial memory were seen in the oldest runners, though this experiment suggested that the beneficial effect of exercise and plasticity in memory was generally limited to 13-month-old middle aged mice, with significant age-related differences in motor and spatial learning occurring in the 4- month period between 13 and 17 months.