Abstract
Motor imagery has been considered a substitute for overt motor execution to study post-stroke motor recovery. However, motor imagery abilities at the acute stage (<3 weeks) are poorly known. The aim of this study was to compare explicit and implicit motor imagery abilities in stroke patients and healthy subjects, correlate them with motor function, and investigate the role of right or left hemisphere lesions on performance. Twenty-four stroke patients at the acute stage and 24 age- and gender-matched healthy volunteers performed implicit (Hand Laterality Judgment Task) and explicit (number of imagined/executed hand movements) motor imagery tasks and a clinical motor assessment. Differences between healthy subjects and patients as well as the impact of lesion side on motor imagery were studied using ANOVA. We analyzed the relationship between motor executed and imagined movements (temporal congruence) using Pearson correlations. Our study shows that for implicit imagery, stroke patients had slower reaction times [RTs, t(46) = 1.7, p = 0.02] and higher error rates for the affected hand [t(46) = 3.7, p < 0.01] yet shared similar characteristics [angle effect: F(1,46) = 30.8, p ≤ 0.0001] with respect to healthy subjects. For the unaffected hand, right-sided stroke patients had a higher error rate and similar RTs whereas left sided stroke had higher RTs but similar error rate than healthy subjects. For explicit imagery, patients exhibited bilateral deficits compared to healthy subjects in the executed and imagined condition (p < 0.0001). Patients and healthy subjects exhibited a temporal congruence between executed and imagined movements (p ≤ 0.04) except for right-sided strokes who had no correlation for both hands. When using motor imagery as a tool for upper limb rehabilitation early after stroke, caution must be taken related to the side of the lesion.
Highlights
Motor imagery shares a number of similarities with overt movement execution such as behavioral (Jeannerod, 1995), physiological parameters (Kranczioch et al, 2009), and perhaps more importantly, certain functional neuroanatomical correlates
In order to better characterize the abilities of stroke patients in implicit and explicit motor imagery, we performed a behavioral study in acute stroke patients and healthy individuals
Patients exhibited similar results compared to healthy subjects for the Kinesthetic and Visual Imagery Questionnaire (KVIQ) in both visual and kinesthetic scores (p > 0.05 for all items)
Summary
Motor imagery shares a number of similarities with overt movement execution such as behavioral (Jeannerod, 1995), physiological parameters (Kranczioch et al, 2009), and perhaps more importantly, certain functional neuroanatomical correlates (e.g., recruitment of brain motor networks; Confalonieri et al, 2012). Implicit motor imagery concerns the ability to perform mental rotation, usually with one part of the body, by a first person perspective It can be tested by the Hand Laterality Judgment Task (HLJT) in which a subject has to determine the laterality (handedness) of pictures of hands (De Vries et al, 2011; Yan et al, 2013). In the context of explicit imagery, the number of executed and imagined movements in a given amount of time (temporal congruence) has been suggested to be altered in stroke patients (Di Rienzo et al, 2014) It is, worth noting that studies investigating these performances have been performed at the chronic phase (>3 months) except in one study (De Vries et al, 2011). We correlated the motor imagery performance with motor function in patients
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