Using signal detection theory, we can relate the thresholds determined in these studies to the imprecision or noise associated with the underlying sensory signal ( Green and Swets 1966 Merfeld 2011). 2012) have been determined by repeatedly exposing subjects to small motions to the left or right in the dark and asking them to report their perceived motion direction. On the other hand, vestibular perceptual thresholds in humans ( Benson et al. Perceptual precision has been characterized by measuring intertrial variability in subjective visual vertical tasks in humans ( De Vrijer et al. The precision of afferent signals has been characterized by measuring variability in firing rate in squirrel monkeys ( Fernandez and Goldberg 1971) and macaque monkeys ( Jamali et al. Thus we use the term “vestibular,” while recognizing that our self-motion perception and control tasks involve other sensory contributors to some degree.Ī number of studies have measured the precision of vestibular responses at varying levels (i.e., neuronal, perceptual, motor). 2012), the predominant role of the vestibular organs has been demonstrated for whole body motion perception with the head held so that the neck is straight ( Valko et al.
Although other sources of sensory information play a role in motion sensation in the dark ( Mittelstaedt 1996 Valko et al. The vestibular system includes the semicircular canals, which sense angular rotation, and the otolith organs, which sense the combination of inertial acceleration and gravity. In this study, we aimed to focus on imprecision arising in the vestibular system. Imprecision includes trial-by-trial and temporal variations in sensations, as opposed to overall systematic errors such as bias. Sensorimotor responses and perception are inherently imprecise because of noise in neural systems ( Faisal et al.
Precise and accurate motion control is important for survival, such as in older individuals climbing stairs in the dark or pilots landing an aircraft or spacecraft.
#Orbiter 2016 manual manual
Furthermore, using an altered-gravity centrifuge configuration, we found that manual control precision was improved in “hypergravity” and degraded in “hypogravity.” These results have potential relevance for postural control, aviation, and spaceflight. We found a significant correlation between subjects’ vestibular perceptual thresholds and performance in a manual control task (using a joystick to keep their chair upright), consistent with sensory imprecision negatively affecting functional precision. NEW & NOTEWORTHY The functional implications of imprecise motion sensation are not well understood. The decrement in manual control performance observed in 0.5 G C and in subjects with high thresholds suggests potential risk factors for piloting and locomotion, both on Earth and during human exploration missions to the moon (0.16 G) and Mars (0.38 G). Furthermore, compared with 1.0 G C manual control was more precise in 1.33 G C (−18.3%, P = 0.005) and less precise in 0.5 G C (+39.6%, P < 0.001). A significant intersubject correlation was found between manual control performance (defined as the standard deviation of chair tilt) and thresholds, consistent with sensory imprecision negatively affecting functional precision. Roll-tilt vestibular precision was quantified with roll-tilt vestibular direction-recognition perceptual thresholds, the minimum movement that one can reliably distinguish as leftward vs. Subjects performed the manual control task while supine during short-radius centrifugation, with roll tilts occurring relative to centripetal accelerations of 0.5, 1.0, and 1.33 G C (1 G C = 9.81 m/s 2). Our second objective was to examine the influence of altered gravity on manual control performance. Our first objective was to study the relationship between intersubject differences in manual control performance and sensory precision, determined by measuring vestibular perceptual thresholds. We studied a “vestibular” manual control task in which subjects attempted to keep themselves upright with a rotational hand controller (i.e., joystick) to null out pseudorandom, roll-tilt motion disturbances of their chair in the dark. Motion sensation is inherently imprecise, and the functional implications of this imprecision are not well understood. Precise motion control is critical to human survival on Earth and in space.