Is Implicit Motor Learning Preserved after Stroke? A Systematic Review with Meta-Analysis

Abstract

Many stroke patients experience difficulty with performing dual-tasks. A promising intervention to target this issue is implicit motor learning, as it should enhance patients’ automaticity of movement. Yet, although it is often thought that implicit motor learning is preserved post-stroke, evidence for this claim has not been systematically analysed yet. Therefore, we systematically reviewed whether implicit motor learning is preserved post-stroke, and whether patients benefit more from implicit than from explicit motor learning. We comprehensively searched conventional (MEDLINE, Cochrane, Embase, PEDro, PsycINFO) and grey literature databases (BIOSIS, Web of Science, OpenGrey, British Library, trial registries) for relevant reports. Two independent reviewers screened reports, extracted data, and performed a risk of bias assessment. Overall, we included 20 out of the 2177 identified reports that allow for a succinct evaluation of implicit motor learning. Of these, only 1 study investigated learning on a relatively complex, whole-body (balance board) task. All 19 other studies concerned variants of the serial-reaction time paradigm, with most of these focusing on learning with the unaffected hand (N = 13) rather than the affected hand or both hands (both: N = 4). Four of the 20 studies compared explicit and implicit motor learning post-stroke. Meta-analyses suggest that patients with stroke can learn implicitly with their unaffected side (mean difference (MD) = 69 ms, 95% CI[45.1, 92.9], p < .00001), but not with their affected side (standardized MD = -.11, 95% CI[-.45, .25], p = .56). Finally, implicit motor learning seemed equally effective as explicit motor learning post-stroke (SMD = -.54, 95% CI[-1.37, .29], p = .20). However, overall, the high risk of bias, small samples, and limited clinical relevance of most studies make it impossible to draw reliable conclusions regarding the effect of implicit motor learning strategies post-stroke. High quality studies with larger samples are warranted to test implicit motor learning in clinically relevant contexts.

Motor learning in post stroke subjects: the effects of practice conditions on the temporal synchronization

“…Therefore, long term transfer tests are indicated to assess the random effect on motor learning processes 1 , being the adaptability, assessed by this test, an important issue for neurorehabilitation sessions 9 . After a unilateral stroke, the neural areas related to motor learning can be affected 10 , in special those areas responsible for implicit learning demands 11 . Considering the peculiarity of the areas that can be affected, and given that sensorial 12 , motor 13 , and cognitive 14 and memory impairment 15 contribute to the functional disability in 75% of post-stroke survivors 10 .…”

“…A few studies have investigated the process of skill acquisition in subjects with neurological lesions 17,18 and concluded that, in functional motor tasks, practice schedule may influence the functional performance and learning of hemiparetic subjects. Recent studies have been done in order to investigate motor performance after a stroke; however the investigation about motor learning process and the effects of practice on this process is still needed 11,19,20 . In sum, because of divergence in the results, it remains unclear whether the effects of practice schedule were a consequence of the learning process, and/or of aspects that are related to the effector control of the hemiparetic limb.…”

Retraining Automaticity: Recovering the Procedural Memory of Walking after Stroke

“…Similar effects are possible for walking among people who have experienced a stroke. Kal and colleagues conducted a meta-analysis looking at the effects of procedural learning in people who experienced strokes [12]. The authors concluded that there is good theoretical support for the hypothesis that procedural learning can lead to improvements after a stroke, they asserted that there is a need for additional empirical evidence in this area.…”

The Effects of Implicit and Explicit Motor Learning in Gait Rehabilitation of People After Stroke: Protocol for a Randomized Controlled Trial (Preprint)

“…There however, seems to be a need for knowledge about the application of optimal motor learning conditions for and within clinical relevant environments and the acquisition of everyday, functional tasks 18,56 . A recent systematic review on implicit motor learning in people after stroke pointed out that studies performed within clinical settings is limited 18 . Of the 20 included studies only one study involved a clinically relevant task 22 , whereas the other remaining studies primarily used (versions of) the serial reaction time task (SRT), a non-functional computer task.…”

“…Studies have demonstrated that individuals who learned motor skills implicitly, have a more robust performance of the motor skill under pressure, perform better in dual task situations and perform better over time compared to their explicit counterparts 12,16,17 . However, these studies have primarily been conducted within the healthy population, while implicit learning may also be advantageous for the patient population 18,19 . For example, implicit motor learning may be of extra benefit to those with cognitive deficits 20 …”