Increased upper-limb sensory attenuation with age

Abstract

The pressure of our own finger on the arm feels differently than the same pressure exerted by an external agent: the latter involves just touch, whereas the former involves a combination of touch and predictive output from the internal model of the body. This internal model predicts the movement of our own finger and hence the intensity of the sensation of the finger press is decreased. A decrease in intensity of the self-produced stimulus is called sensory attenuation. It has been reported that, due to decreased somatosensation with age and an increased reliance on the prediction of the internal model, sensory attenuation is increased in older adults. In this study, we used a force-matching paradigm to test if sensory attenuation is also present over the arm and if aging increases sensory attenuation. We demonstrated that, while both young and older adults overestimate a self-produced force, older adults overestimate it even more showing an increased sensory attenuation. In addition, we also found that both younger and older adults self-produce higher forces when activating the homologous muscles of the upper limb. While this is traditionally viewed as evidence for an increased reliance on internal model function in older adults because of decreased somatosensory function, somatosensation appeared unimpaired in our older participants. This begs the question of whether the decreased somatosensation is really responsible for the increased sensory attenuation observed in older people. New and NoteworthyForces generated externally (by the environment on the participant) and internally (by the participant on her/his body) are not perceived with the same intensity. Internally-generated forces are perceived less intensely than externally generated ones. This difference in force sensation has been shown to be higher in elderly participants when the forces were applied on the fingers because of their impaired somatosensation. Here we replicated this finding for the arm but suggest that it is unlikely linked to impaired somatosensory function.