Background and Purpose-Understanding brain plasticity after stroke is important in developing rehabilitation strategies.Active movement therapies show considerable promise but depend on motor performance, excluding many otherwise eligible patients. Motor imagery is widely used in sport to improve performance, which raises the possibility of applying it both as a rehabilitation method and to access the motor network independently of recovery. Specifically, whether the primary motor cortex (M1), considered a prime target of poststroke rehabilitation, is involved in motor imagery is unresolved. Summary of Review-We review methodological considerations when applying motor imagery to healthy subjects and in patients with stroke, which may disrupt the motor imagery network. We then review firstly the motor imagery training literature focusing on upper-limb recovery, and secondly the functional imaging literature in healthy subjects and in patients with stroke. Conclusions-The review highlights the difficulty in addressing cognitive screening and compliance in motor imagery studies, particularly with regards to patients with stroke. Despite this, the literature suggests the encouraging effect of motor imagery training on motor recovery after stroke. Based on the available literature in healthy volunteers, robust activation of the nonprimary motor structures, but only weak and inconsistent activation of M1, occurs during motor imagery. In patients with stroke, the cortical activation patterns are essentially unexplored as is the underlying mechanism of motor imagery training. Provided appropriate methodology is implemented, motor imagery may provide a valuable tool to access the motor network and improve outcome after stroke.

Objective-Neuroplasticity is essential for recovery after stroke and is the target for new stroke therapies. During recovery from subcortical motor stroke, brain activations associated with movement may appear normal despite residual functional impairment. This raises an important question: how far does recovery of motor performance depend on the processes that precede movement execution involving the premotor and prefrontal cortex, rather than recovery of the corticospinal system alone?Methods-We examined stroke patients with functional magnetic resonance imaging while they either imagined or executed a finger-thumb opposition sequence. In addition to classical analyses of regional activations, we studied neuroplasticity in terms of differential network connectivity using structural equation modeling. The study included 8 right-handed patients who had suffered a left-hemisphere subcortical ischemic stroke with paresis, and 13 age-matched healthy controls.Results-With good functional recovery, the regional activations had returned to normal in patients. However, connectivity within the extended motor network remained abnormal. These abnormalities were seen predominantly during motor imagery and correlated with motor performance.Interpretation-Our results indicate that neuroplasticity can manifest itself as differences in connectivity among cortical areas remote from the infarct, rather than in the degree of regional activation. Connection strengths between nodes of the cortical motor network correlate with motor outcome. The altered organization of connectivity of the prefrontal areas may reflect the role of the prefrontal cortex in higher order planning of movement. Our results are relevant to the assessment and understanding of emerging physical and neurophysiological therapies for stroke rehabilitation.The human brain reorganizes itself throughout life, in health and disease. This neuroplasticity not only underpins human adaptation and learning, 1 but is especially important for recovery after brain injury. Understanding and influencing the processes of neuroplasticity are therefore crucial in providing more effective therapies for patients. Functional neuroimaging can reveal the alterations in large-scale brain networks following brain injury, 2,3 physical training, 4-6 and pharmacological therapy. 7 After a subcortical stroke, functional magnetic resonance imaging (fMRI) during movement reveals cortical reorganization that is associated with the recovery of function. [8][9][10] The reorganization includes overactivity of cortical motor areas, 11 alterations in the interhemispheric balance, 4,9,[12][13][14][15] However, the cortical activation patterns associated with some motor tasks may appear normal in patients despite residual functional impairment. 11,13,14,[17][18][19] An explanation for this paradox is that hemiparetic stroke disrupts both corticospinal output and important motor processes prior to the execution of movement, for example, motor attention, imagination, preparation, or planning....

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A life course approach to ageing relies on maintaining participation rates in national birth cohorts and other long-term longitudinal studies. This reduces the risk of selective attrition biasing associations between lifetime risk factors and health outcomes in later life and ensures the studies remain as representative as possible of the original population. We report the participation patterns for a postal questionnaire and home visit at 68–69 years of study members in the MRC National Survey of Health and Development, the oldest and longest-running British birth cohort study. We investigated how participation varied by lifetime and recent contact, health status, previous clinical feedback and study engagement, taking account of prior socioeconomic and cognitive characteristics. Overall participation and home visit participation remained high (94 and 80%, respectively) and there were no gender differences. Participation was higher in those with higher levels of prior contact and lower in those with the poorest health status. Having previously received clinical feedback on actionable blood results was associated with reduced home visit participation but other forms of clinical feedback were not associated with subsequent participation. Activities that fostered study engagement were associated with increased home visit participation. These findings inform strategies to maintain participation in life course studies.Electronic supplementary materialThe online version of this article (doi:10.1007/s10654-016-0217-8) contains supplementary material, which is available to authorized users.