Body-centred and Object-centred Motor Imagery in Alzheimer's Disease

Autonomy in patients with Alzheimer's disease (AD) in daily life depends on the preservation of neurocognitive and motor abilities, which decline over time. So far, very few studies have investigated motor representations and their contribution to perception and cognition in AD.

In the present study, we compared the performance of AD patients to age-matched healthy participants in perceptual and cognitive tasks involving motor imagery. Experiment 1 tested explicit motor and visual imagery through an imagined movement task. Experiment 2 tested body-centred implicit motor imagery through a mental rotation of visual hand task. Finally, Experiment 3 tested object-centred implicit motor imagery through a reachability judgment task.

The results showed that, compared to age-matched controls, conscious imagination of a body movement or the movement of a visual stimulus was much longer in AD patients, with no specific difficulty in the motor condition (Experiment 1). Furthermore, response time in AD patients was strongly affected by the angle of rotation of the visual stimuli in the mental rotation of hand task (Experiment 2). Likewise, response time in AD patients increased substantially in the reachability judgment task, but predominantly for stimuli located at the boundary of peripersonal space (Experiment 3).

As a whole, the data suggested a decline in AD of implicit, but not explicit, motor imagery capacities affecting processing time, but not performance accuracy, in motor-related perceptual and cognitive tasks.