Abstract
Position sense refers to an aspect of proprioception crucial for motor control and learning. The onset of neurological diseases can damage such sensory afference, with consequent motor disorders dramatically reducing the associated recovery process. In regular clinical practice, assessment of proprioceptive deficits is run by means of clinical scales which do not provide quantitative measurements. However, existing robotic solutions usually do not involve multi-joint movements but are mostly applied to a single proximal or distal joint. The present work provides a testing paradigm for assessing proprioception during coordinated multi-joint distal movements and in presence of kinaesthetic perturbations: we evaluated healthy subjects' ability to match proprioceptive targets along two of the three wrist's degrees of freedom, flexion/extension and abduction/adduction. By introducing rotations along the pronation/supination axis not involved in the matching task, we tested two experimental conditions, which differed in terms of the temporal imposition of the external perturbation: in the first one, the disturbance was provided after the presentation of the proprioceptive target, while in the second one, the rotation of the pronation/ supination axis was imposed during the proprioceptive target presentation. We investigated if (i) the amplitude of the perturbation along the pronation/supination would lead to proprioceptive miscalibration; (ii) the encoding of proprioceptive target, would be influenced by the presentation sequence between the target itself and the rotational disturbance. Eighteen participants were tested by means of a haptic neuroergonomic wrist device: our findings provided evidence that the order of disturbance presentation does not alter proprioceptive acuity. Yet, a further effect has been noticed: proprioception is highly anisotropic and dependent on perturbation amplitude. Unexpectedly, the configuration of the forearm highly influences sensory feedbacks, and significantly alters subjects' performance in matching the proprioceptive targets, defining portions of the wrist workspace where kinaesthetic and proprioceptive acuity are more sensitive. This finding may suggest solutions and applications in multiple fields: from general haptics where, knowing how wrist configuration influences proprioception, might suggest new neuroergonomic solutions in device design, to clinical evaluation after neurological damage, where accurately assessing proprioceptive deficits can dramatically complement regular therapy for a better prediction of the recovery path.
Highlights
The term “proprioception,” introduced in the early twentieth century, refers to the self-perception of position, motion and orientation of the body or body segments (Goldscheider, 1898; Sherrington, 1907; Evarts, 1981)
As evidenced by the repeated measures analyses of variance (rANOVA) results, for both outcomes, we did not find any significant difference between the two conditions
Understanding how proprioceptive information is encoded at distal joints, has multiple intersections across different fields involving physiology, motor learning, sensorimotor recovery as well as those applications in haptics where proprioception is predominantly involved in a robot mediated manipulation
Summary
The term “proprioception,” introduced in the early twentieth century, refers to the self-perception of position, motion and orientation of the body or body segments (Goldscheider, 1898; Sherrington, 1907; Evarts, 1981). Two submodalities of proprioception are distinguished: (i) kinaesthesia, the sense of limb movement; (ii) joint position sense, the sense of limb position (Proske, 2006) These two senses constitute the sensory stream colloquially referred to as conscious proprioception. Neurological pathologies, such as stroke (Carey, 1995) or Parkinson’s disease (Konczak et al, 2012), can permanently deprive the brain of its main sources of dynamogenic information from skin and muscles (Debert et al, 2012), leading to a compromised coding of the proprioceptive information, with negative consequences in motor control and the associated recovery progress (Marchal-Crespo and Reinkensmeyer, 2009; Schabrun and Hillier, 2009). Accurate assessment and quantification of proprioceptive function becomes a leading factor in the diagnosis and treatment of neurological diseases
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