Temporal features of imagined locomotion in normal aging.

Motor imagery is the ability to mentally simulate a movement without executing it. Previous investigations have reported a deterioration of this ability during complex arm movements in aged adults. In the present study, we aimed to extend these findings by investigating the temporal features of imagined precision gait in healthy elderly adults. Locomotion is a unique example of imagined movement because it involves simulated full-body movement and the concurrent updating of environmental spatial information. Nine young and nine older adults actually or mentally walked (walking distance: 5m) along three paths having different widths (15cm, 25cm, and 50cm). The narrowest path required balance control and accurate foot placement. We used the mental chronometry paradigm, notably the temporal similarity between actual and imagined movements, as an indicator of the accuracy of the motor imagery process. Our findings indicated that while motor imagery ability was preserved in the young group whatever the width of the path, it was significantly deteriorated in the elderly group. Aged adults systematically overestimated the duration of imagined movements with respect to those of executed movements. Moreover, paths width negatively influenced the motor imagery performances in the elderly group. We assume that motor imagery decline may reflect functional changes in the aging brain, and could be a clinical tool to detect deteriorations in motor planning and prediction in aged adults.