Plastic changes to dendritic spines in the cerebellar and prefrontal cortices underlie the decline in motor coordination and working memory during successful aging.

Old age is the last stage of life and by taking a multidimensional view of aging, Neuroscientists have been able to characterize pathological or successful aging. Psychomotor and cognitive performance are recognized as two major domains of successful aging, with a loss of motor coordination and working memory deficits two of the most characteristic features of elderly people. Dendritic spines in both the cerebellar and prefrontal cortices diminish in aging, yet the plastic changes in dendritic spines have not been related to behavioral performance neither the changes in the cerebellar or prefrontal cortices. As such, motor coordination and visuospatial working memory (vsWM) was evaluated here in aged, 22-month-old rats, calculating the density of spines and the proportion of the different types of spines. These animals performed erratically and slowly in a motor coordination-related paradigm, and the vsWM was resolved deficiently. Spine density was reduced in aged animals, and the proportional density of each of the spine types studied diminished in both the brain regions studied. The loss of dendritic spines and particularly, the changes in the proportional density of the different spine types could underlie, at least in part, the behavioral deficits observed during aging. To our knowledge, this is the first study of the plastic changes in different dendritic spine types that might underlie the behavioral alterations in motor and cognitive abilities associated with aging. Further neurochemical and molecular studies will help better understand the functional significance of the plastic changes to dendritic spines in both successful and pathological aging.