Quantification DOES NOTHING to get survivors recovered! I'd fire you all for absolute stupidity! I can do no reaching with left arm until spasticity is cured.
A robot-based interception task to quantify upper limb impairments in proprioceptive and visual feedback after stroke
Journal of NeuroEngineering and Rehabilitation volume 20, Article number: 137 (2023)
Abstract
Background
A key motor skill is the ability to rapidly interact with our dynamic environment. Humans can generate goal-directed motor actions in response to sensory stimulus within ~ 60-200ms. This ability can be impaired after stroke, but most clinical tools lack any measures of rapid feedback processing. Reaching tasks have been used as a framework to quantify impairments in generating motor corrections for individuals with stroke. However, reaching may be inadequate as an assessment tool as repeated reaching can be fatiguing for individuals with stroke. Further, reaching requires many trials to be completed including trials with and without disturbances, and thus, exacerbate fatigue. Here, we describe a novel robotic task to quantify rapid feedback processing in healthy controls and compare this performance with individuals with stroke to (more) efficiently identify impairments in rapid feedback processing.
Methods
We assessed a cohort of healthy controls (n = 135) and individuals with stroke (n = 40; Mean 41 days from stroke) in the Fast Feedback Interception Task (FFIT) using the Kinarm Exoskeleton robot. Participants were instructed to intercept a circular white target moving towards them with their hand represented as a virtual paddle. On some trials, the arm could be physically perturbed, the target or paddle could abruptly change location, or the target could change colour requiring the individual to now avoid the target.
Results
Most participants with stroke were impaired in reaction time (85%) and end-point accuracy (83%) in at least one of the task conditions, most commonly with target or paddle shifts. Of note, this impairment was also evident in most individuals with stroke when performing the task using their unaffected arm (75%). Comparison with upper limb clinical measures identified moderate correlations with the FFIT.
Conclusion
The FFIT was able to identify a high proportion of individuals with stroke as impaired in rapid feedback processing using either the affected or unaffected arms. The task allows many different types of feedback responses to be efficiently assessed in a short amount of time.
Introduction
A key feature of our motor system is the ability to use sensory feedback for the online control of movement, such as responding when your arm is accidentally bumped when reaching for an object [1]. A broad range of studies highlight how proprioceptive and visual feedback can be used to generate goal-directed motor corrections and initiate new motor actions within 100ms [2, 3]. Impressively, even responses requiring cognitive functions such as aborting an on-going motor action can be generated within 200ms [4]. This use of proprioceptive and visual feedback for goal-directed motor actions is supported by highly distributed circuits including both cortical and subcortical structures [1, 5].
Previous studies highlight how stroke can impair an individual’s ability to generate rapid and accurate motor corrections [6,7,8,9,10,11]. Marsden et al. studied individuals with brain damage and identified delays in generating responses to mechanical perturbations applied during thumb movements [9]. Schaefer and colleagues examined responses to visual perturbations while participants reached towards a goal. They found individuals with stroke had delayed response initiation when compared to healthy controls [7]. Of note, ~ 30% of individuals with stroke display these impairments with their ‘unaffected’ arm [8, 12]. Identifying impaired corrective responses after stroke is crucial as reaction time impairments have been associated with reduced quality of life and an increased risk of falls [10, 13,14,15,16]. Importantly, the ability to use sensory feedback for motor function is not adequately considered in common clinical tools such as Fugl-Meyer Assessment (FMA) and Chedoke McMaster Stroke Assessment (CMSA) [17, 18].
The present study and associated behavioural task address several aspects of goal-directed feedback control. First, neural circuits associated with feedback processing involve a broad range of cortical and subcortical circuits. Thus, we hypothesize that impairments in using sensory feedback for goal-directed motor actions will be commonly observed in individuals following stroke. Second, neural pathways for proprioceptive and visual feedback overlap, but also involve distinct brain regions [19]. For example, primary somatosensory cortex and parietal area 5 are associated with somatosensory feedback, whereas occipital and posterior parietal regions are associated with visual feedback [20]. Thus, we hypothesize that individuals with stroke may display impairments that are limited to one sensory modality, proprioceptive or visual feedback. Finally, sensory feedback for motor and cognitive functions are also somewhat distinct, such as the involvement of medial regions in the frontal lobe engaged for inhibitory control [21]. Thus, we hypothesize that individuals with stroke may display selective impairment for either motor corrections or cognitive control.
We examined these hypotheses by developing a novel interception task that requires individuals to maintain their hand at a spatial location and were instructed to intercept a target moving rapidly towards them. On random trials, we induce mechanical or visual perturbations that require rapid corrective responses to intercept the moving target, or when instructed by a color cue, to avoid the target. The results highlight that most individuals with stroke are impaired in at least one form of feedback processing, and in some cases, selectively for one form of feedback processing.
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