Abstract
Impairments in dexterous upper limb function are a significant cause of disability following stroke. While the physiological basis of movement deficits consequent to a lesion in the pyramidal tract is well demonstrated, specific mechanisms contributing to optimal recovery are less apparent. Various upper limb interventions (motor learning methods, neurostimulation techniques, robotics, virtual reality, and serious games) are associated with improvements in motor performance, but many patients continue to experience significant limitations with object handling in everyday activities. Exactly how we go about consolidating adaptive motor behaviors through the rehabilitation process thus remains a considerable challenge. An important part of this problem is the ability to successfully distinguish the extent to which a given gesture is determined by the neuromotor impairment and that which is determined by a compensatory mechanism. This question is particularly complicated in tasks involving manual dexterity where prehensile movements are contingent upon the task (individual digit movement, grasping, and manipulation…) and its objective (placing, two step actions…), as well as personal factors (motivation, acquired skills, and life habits…) and contextual cues related to the environment (presence of tools or assistive devices…). Presently, there remains a lack of integrative studies which differentiate processes related to structural changes associated with the neurological lesion and those related to behavioral change in response to situational constraints. In this text, we shall question the link between impairments, motor strategies and individual performance in object handling tasks. This scoping review will be based on clinical studies, and discussed in relation to more general findings about hand and upper limb function (manipulation of objects, tool use in daily life activity). We shall discuss how further quantitative studies on human manipulation in ecological contexts may provide greater insight into compensatory motor behavior in patients with a neurological impairment of dexterous upper-limb function.
Highlights
Impairments of dexterous upper-limb function are a significant cause of disability following an acquired brain injury or stroke since they affect approximately one half of the patients in this clinical population (Jorgensen et al, 1995)
Byblow et al (2015) demonstrated that these outliers were characterized by severe alterations of the corticospinal tract (CST), demonstrated by anomalies of the motor potentials evoked by transcranial magnetic stimulation (TMS)
When the monosynaptic CST is severely lesioned, fine motor control and hand dexterity are compromised but large-scale changes in brain networks with multiple relays may assure a certain level of motor function at the cost of maladaptive phenomena
Summary
Impairments of dexterous upper-limb function are a significant cause of disability following an acquired brain injury or stroke since they affect approximately one half of the patients in this clinical population (Jorgensen et al, 1995). Most available methods for the evaluation of dexterity do not afford the description of compensatory strategies, with the exception of one recent proposition integrating observational kinematics to appreciate the quality of movement coordination (Alouche et al, 2020) In this text, we shall question the link between consequences of brain lesions, functional impairments, motor strategies and performance in activity, during object handling tasks. This suggests that patients gravitate toward certain motor strategies adapted to their own specific condition (Latash and Anson, 1996) through action-perception cycles (enaction) This description of dexterity is consistent with the theoretical framework of Embodied, Embedded, Enactive, and Extended cognition (4E perspective) suggesting that the shape of individual motor strategies is embodied (dependent of bodily constraints), embedded into the environment (e.g., home), enacted (built through interaction) and potentially extended by assistive devices (Rowlands, 2010). Thereafter, we shall discuss some clinical implications for rehabilitation and some perspectives, with a specific focus on the use of novel technology in this field
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