Disentangling the Enigmatic Slowing Effect of Microgravity on Sensorimotor Performance

Abstract

The success of many space missions depends on astronauts’ performance. Yet, prior research documented that sensorimotor performance is impaired in microgravity, e.g. aimed arm movements are slowed down and are less accurate. Several explanatory approaches for this phenomenon have been discussed, such as distorted proprioception or stress-related attentional deficits. In the current work, sensorimotor performance was investigated during aimed joystick-controlled motions in a simulation. The task included rapid as well as fine matching motions. Results of two different studies were compared: 1) a study utilising a dual-task paradigm to investigate the impact of attentional distraction (N = 19) and 2) a study investigating the impact of microgravity during spaceflight (N = 3). In both studies, an overall slowing effect was found. However, results diverged when comparing feedforward vs. feedback controlled parts of aiming. Reduced attentional resources mainly affected feedforward control, which was reflected in significantly longer response times and longer rapid motion times. Microgravity, however, did not affect response times at all, but rapid aiming times as well as fine matching times substantially increased. These findings provide evidence that impaired attention is not the main trigger behind the slowing effect, but rather it is distorted proprioception which impairs feedback controlled motions.