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

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.

The inclination for conscious motor control after stroke: validating the Movement-Specific Reinvestment Scale for use in inpatient stroke patients.

PURPOSE: Stroke survivors are inclined to consciously control their movements, a phenomenon termed "reinvestment". Preliminary evidence suggests reinvestment to impair patients' motor recovery. To investigate this hypothesis, an instrument is needed that can reliably assess reinvestment post-stroke. Therefore, this study aimed to validate the Movement-Specific Reinvestment Scale (MSRS) within inpatient stroke patients. METHOD: One-hundred inpatient stroke patients (<1 year post-stroke) and 100 healthy peers completed the MSRS, which was translated to Dutch for the study purpose. To assess structural validity, confirmatory factor analysis determined whether the scale measures two latent constructs, as previously reported in healthy adults. Construct validity was determined by testing whether patients had higher reinvestment than controls. Reliability analyses entailed assessment of retest reliability (ICC), internal consistency (Cronbach's alpha), and minimal detectable change. RESULTS: Both structural and construct validity of the MSRS were supported. Retest reliability and internal consistency indices were acceptable to good. The minimal detectable change was adequate on group level, but considerable on individual level. CONCLUSIONS: The MSRS is a valid and reliable tool and suitable to assess the relationship between reinvestment and motor recovery in the first months post-stroke. Eventually, this may help therapists to individualize motor learning interventions based on patients' reinvestment preferences. IMPLICATIONS FOR REHABILITATION: This study showed that the Movement-Specific Reinvestment Scale (MSRS) is a valid and reliable tool to objectify stroke patients' inclination for conscious motor control. The MSRS may be used to identify stroke patients who are strongly inclined to consciously control their movements, as this disposition may hinder their motor recovery. Eventually, the MSRS may enable clinicians to tailor motor learning interventions to stroke patients' motor control preferences.

Stay Focused! The Effects of Internal and External Focus of Attention on Movement Automaticity in Patients with Stroke.

Dual-task performance is often impaired after stroke. This may be resolved by enhancing patients' automaticity of movement. This study sets out to test the constrained action hypothesis, which holds that automaticity of movement is enhanced by triggering an external focus (on movement effects), rather than an internal focus (on movement execution). Thirty-nine individuals with chronic, unilateral stroke performed a one-leg-stepping task with both legs in single- and dual-task conditions. Attentional focus was manipulated with instructions. Motor performance (movement speed), movement automaticity (fluency of movement), and dual-task performance (dual-task costs) were assessed. The effects of focus on movement speed, single- and dual-task movement fluency, and dual-task costs were analysed with generalized estimating equations. Results showed that, overall, single-task performance was unaffected by focus (p = .341). Regarding movement fluency, no main effects of focus were found in single- or dual-task conditions (p's ≥ .13). However, focus by leg interactions suggested that an external focus reduced movement fluency of the paretic leg compared to an internal focus (single-task conditions: p = .068; dual-task conditions: p = .084). An external focus also tended to result in inferior dual-task performance (ß = -2.38, p = .065). Finally, a near-significant interaction (ß = 2.36, p = .055) suggested that dual-task performance was more constrained by patients' attentional capacity in external focus conditions. We conclude that, compared to an internal focus, an external focus did not result in more automated movements in chronic stroke patients. Contrary to expectations, trends were found for enhanced automaticity with an internal focus. These findings might be due to patients' strong preference to use an internal focus in daily life. Future work needs to establish the more permanent effects of learning with different attentional foci on re-automating motor control after stroke.

A long-lasting improvement of somatosensory function after prism adaptation, a case study.

Previous studies have observed a reduction of visual and representational neglect symptoms after visuo-manual adaptation to rightward displacing prisms. Recently, improvements have also been observed on somatosensory tasks, such as locating the centre of a haptically explored circle and tactile double simultaneous stimulation. In the current single case study we assessed whether prism adaptation with the ipsilesional hand improved two aspects of contralesional somatosensory function, pressure sensitivity and proprioception. After the first application of prism adaptation improvements in pressure sensitivity and proprioception were observed. A second prism adaptation confirmed the improvements in contralesional somatosensory function. The effects of prism adaptation on position sense were longer lasting than have been reported previously, but consistent with reductions of visual neglect symptoms after prism adaptation. The current findings suggest that prism adaptation can have a non-spatial effect on neglect-related supra-modal deficits.

Prosthesis motility with and without intraorbital implants in the anophthalmic socket.

Ocular prosthesis motility was measured and compared in 15 patients with a primary baseball implant after enucleation of an eye, in 11 patients with a secondary baseball implant, in 12 patients with an Allen implant, and in 11 patients without any intraorbital implant. In all patients a noticeable lag of movement of the prosthetic eye was measured: in the extreme directions of gaze the excursions of the prosthesis were far less in comparison with the contralateral normal eye. For normal eye movement round the primary position of gaze, however, the prosthesis motility in the primary baseball and Allen implant group appeared to be sufficient to give a lifelike appearance. The average motility of the prostheses in these two groups did not differ. The motility in the secondary baseball group and in the group without an implant was evidently worse. In the last group the prosthesis motility was most impaired. We conclude that the insertion of an implant, even when inserted some time after the enucleation (a secondary implant), improves the motility of the prosthesis markedly. We recommend the primary baseball implant as the correction of choice after enucleation.

Primary and secondary implants in the anophthalmic orbit. Preoperative and postoperative computed tomographic appearance.

Sagittal computed tomographic (CT) scans of 10 anophthalmic orbits with a primary implant, an acrylic ball covered with donor sclera, and 10 anophthalmic orbits before and after insertion of a secondary implant were studied. For each patient, the scans of the anophthalmic and contralateral normal orbit were compared. In the anophthalmic orbits, the anatomy was optimally restored in those with a primary implant, and suboptimal results were achieved in the orbits with a secondary implant. The greatest differences were noticed in the orbits without an implant. Differences were noticed for the position and length of the superior muscle complex and the inferior rectus muscle, the position of the upper eyelid, the depth of the superior sulcus, and the backward tilt of the prosthesis. The authors conclude that the rotatory displacement of the orbital contents after enucleation, which explains the sequelae of the anophthalmic orbit, is grossly circumvented by the insertion of an implant. In achieving this effect, primary implants are better than secondary ones.

Computed tomography in the assessment of the postenucleation socket syndrome.

To gain a deeper insight into the cause of the postenucleation socket syndrome, high-resolution computed tomography (CT) was performed in 22 anophthalmic patients before insertion of an intraorbital implant. The anatomy of the normal and the anophthalmic orbits was compared. Computed tomographic scans were made either in the sagittal and the coronal plane or in the sagittal and transverse plane. The authors discovered a sagging and retraction of the superior muscle complex and a downward and forward redistribution of orbital fat. Finally, an upward displacement of the distal end together with a retraction of the inferior rectus muscle was found. These phenomena were measured and appear to cause a rotatory displacement of orbital contents from superior to posterior and from posterior to inferior which is best demonstrated in the sagittal plane. This redistribution of orbital contents can explain the sequelae of the anophthalmic orbit. No signs of orbital fat atrophy could be demonstrated. With this knowledge, the proper treatment of patients with a postenucleation socket syndrome is ascertained.

Primary versus secondary intraorbital implants.

To compare the results of primary and secondary intraorbital implants after enucleation, we retrospectively studied the surgical outcomes of 114 patients. In 44 patients the implant was inserted immediately after enucleation and in the remaining 70 patients the implant was inserted at a later date. To achieve a satisfactory cosmetic result, additional procedures were needed in 11% of the patients with a primary implant and in 49% of those with a secondary implant. The insertion of an implant at the time of enucleation has distinct advantages over the insertion of the implant at a later date.