Protective postural responses to external perturbations are hypokinetic in people with Parkinson’s disease (PD) and improving these responses may reduce falls. However, the ability of people with PD to improve postural responses with practice is poorly understood. Our objective was to determine whether people with PD can improve protective postural responses similarly to healthy adults through repeated perturbations, and whether improvements are retained or generalize to untrained perturbations. Twelve healthy adults and 15 people with PD underwent 25 forward and 25 backward translations of the support surface, eliciting backward and forward protective steps, respectively. We assessed whether: 1) performance improved over one day of practice, 2) changes were retained 24 hours later, and 3) improvements generalized to untrained (lateral) postural responses. People with PD and healthy adults improved postural response characteristics including center of mass displacement after perturbations (p<0.001), margin of stability at first foot-fall (p=0.001), step latency (p=0.044), and number of steps (p=0.001). However, unlike controls, improvements in people with PD occurred primarily in the first block of trials. Improvements were more pronounced during backward protective stepping than forward, and with the exception of step latency, were retained 24 hours later. Improvements in forward-backward stepping did not generalize to lateral protective stepping. People with PD can improve protective stepping over the course of one day of perturbation practice. Improvements were generally similar to healthy adults, and were retained in both groups. Perturbation practice may represent a promising approach to improving protective postural responses in people with PD, however additional research is needed to understand how to enhance generalization.

The ability to respond quickly and accurately to an external perturbation with a stepping response is critical to avoid falls and this ability is impaired in older, compared to young adults. However, little is known about whether young and older adults improve compensatory stepping responses similarly with practice. This study compares the extent to which young and older adults can improve, retain, and generalize postural compensatory steps in response to external perturbations. Centre of mass displacement, step characteristics and lower leg muscle activation latencies were measured during one training session of compensatory stepping in response to large surface translations in 13 young and 12 older adults. Retention was tested 24 h later. Older adults decreased their center of mass displacements over repeated exposure to large surface translations in both the anterior and posterior directions and retained these improvements. In contrast, young adults only showed adaptation and retention of forward stepping responses. Neither group was able to generalize improvements in stepping responses across directions. These results suggest step training may be beneficial for older adults, however additional, multidirectional training may be necessary to facilitate generalization of postural stepping responses for any direction of a slip or trip.

Background Background: Freezing of gait (FOG) is a common gait deficit in Parkinson's disease. The New Freezing of Gait Questionnaire (NFOG-Q) is a widely used and valid tool to quantify freezing of gait severity. However, its test-retest reliability and minimal detectable change remain unknown. Objective Objective: To determine the test-retest reliability and responsiveness of the NFOG-Q. Methods Methods: Two groups of freezers, involved in 2 previous rehabilitation trials, completed the NFOG-Q at 2 time points (T1 and T2), separated by a 6-week control period without active intervention. Sample 1 (N = 57) was measured in ON and sample 2 (N = 14) in OFF. We calculated various reliability statistics for the NFOG-Q scores between T1 and T2 as well as correlation coefficients with clinical descriptors to explain the variability between time points. Results Results: In sample 1 the NFOG-Q showed modest reliability (intraclass correlation coefficient = 0.68 [0.52-0.80]) without differences between T1 and T2. However, a minimal detectable change of 9.95 (7.90-12.27) points emerged for the total score (range 28 points, relative minimal detectable change of 35.5%). Sample 2 showed largely similar results. We found no associations between cognitive-related or disease severity-related outcomes and variability in NFOG-Q scores. Conclusions Conclusions: We conclude that the NFOG-Q is insufficiently reliable or responsive to detect small effect sizes, as changes need to go beyond 35% to surpass measurement error. Therefore, we warrant caution in using the NFOG-Q as a primary outcome in clinical trials. These results emphasize the need for robust and objective freezing of gait outcome measures.Freezing of gait (FOG) is a prominent and debilitating symptom of Parkinson's disease (PD). It affects up to 80% of PD patients during the course of the disease. 1-3 FOG is defined as the inability to progress forward stepping despite the intention to walk and reach a destination. 4 Furthermore, FOG is one of the most frequent causes of falls in PD, thus contributing to high fall rates ranging from 35% up to 90%. 1,5,6 FOG seriously impedes daily life functioning and overall quality of life. 7,8 So far, the treatment of FOG, including pharmacological, surgical, and rehabilitation interventions, is only partially effective. 4,9 Therefore, new and more personalized rehabilitation approaches are now being developed. To evaluate their effectiveness, valid and reliable assessment is necessary to document FOG severity and its progression.A recent review of Mancini and colleagues 10 highlighted that FOG assessment is hampered by several factors in clinical and laboratory settings. First, the episodic and unpredictable nature of FOG increases the likelihood of missing the event during formal or "online" performance tests of gait. Second, various "testing effects" may be at play that enhance or reduce the occurrence of FOG, such as consciously attending to walking, stepping in broad and well-lit corridors, and experiencing medication effects and...

Functional neuroimaging of human postural control: a systematic review with metaanalysis. NEUROSCI BIOBEHAV REV X(X) XXX-XXX, 2019 Postural instability is a strong risk factor for falls that becomes more prominent with aging. To facilitate treatment and prevention of falls in an aging society, a thorough understanding of the neural networks underlying postural control is warranted. Here, we present a systematic review of the functional neuroimaging literature of studies measuring posture-related neural activity in healthy subjects. Study methods were overall heterogeneous. Eleven out of the 14 studies relied on postural simulation in a supine position (e.g. motor imagery). The key nodes of human postural control involved the brainstem, cerebellum, basal ganglia, thalamus and several cortical regions. An activation likelihood estimation meta-analysis revealed that the anterior cerebellum was consistently activated across the wide range of postural tasks. The cerebellum is known to modulate the brainstem nuclei involved in the control of posture. Hence, this systematic review with meta-analysis provides insight into the neural correlates which underpin human postural control and which may serve as a reference for future neural network and region of interest analyses.