RESUMEN
This internal representation of movement of part(s) of the body is involved during Implicit Motor Imagery tasks (IMI); the same representations are employed in the laterality judgment task. Few studies have looked at the consequences of aging, Alzheimer's disease (AD) and mild cognitive impairment (MCI) on the processes of motor preparation but none showed evidence of an alteration of action representation in patient with amnestic MCI. In the present study, the IMI task was used to assess the action representation abilities in MCI patients and healthy counterparts. A total of 24 elderly participants aged between 65 and 90 years old (12 women, 73.4 ± 6 years, mean ± S.D.) were recruited: 12 patients with MCI (MCI group) and 12 healthy aged adults (HAA group). The results showed that MCI patients have significantly a greater response time (RT) than HAA subjects only in IMI task and more precisely when performing their mental rotation at the challenging conditions. Furthermore, the IMI task related to the non-dominant hand induced a significant increase of RT only in MCI subjects. At the light of these results, we assume that MCI patients are able to engage themselves in IMI processes, still showing a compelling impairment of this mental ability across its complexity.
RESUMEN
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.