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Introduction: Tripping over an obstacle is one of the most common causes of falls among older adults. However, the effects of aging, obstacle height and anticipation time on negotiation strategies have not been systematically evaluated.Methods: Twenty older adults (ages: 77.7±3.4years; 50% women) and twenty young adults (age: 29.3±3.8years; 50% women) walked through an obstacle course while negotiating anticipated and unanticipated obstacles at heights of 25mm and 75mm. Kinect cameras captured the: (1) distance of the subject's trailing foot before the obstacles, (2) distance of the leading foot after the obstacles, (3) clearance of the leading foot above the obstacles, and (4) clearance of the trailing foot above the obstacles. Linear-mix models assessed changes between groups and conditions.Results: Older adults placed their leading foot closer to the obstacle after landing, compared to young adults (p<0.001). This pattern was enhanced in high obstacles (group*height interaction, p=0.033). Older adults had lower clearance over the obstacles, compared to young adults (p=0.007). This was more pronounced during unanticipated obstacles (group*ART interaction, p=0.003). The distance of the leading foot and clearance of the trailing foot after the obstacles were correlated with motor, cognitive, and functional abilities.Conclusions: These findings suggest that there are age-related changes in obstacle crossing strategies that are dependent on the specific characteristics of the obstacle. The results have important implications for clinical practice, suggesting that functional exercise should include obstacle negotiation training with variable practice of height and available response times. Further studies are needed to better understand the effects of motor and cognitive abilities. [ABSTRACT FROM AUTHOR]

Introduction: Behavioral studies suggest that deficits in cognitive domains and sensory-motor processes associated with Parkinson's disease (PD) impair the ability to walk in complex environments. However, the neural correlates of locomotion in complex environments are still unclear.Methods: Twenty healthy older adults (mean age 69.7 ± 1.3 yrs) and 20 patients with PD (mean age 72.9 ± 1.6 yrs; disease duration: 6.8 ± 1.3 yrs; UPDRSIII: 29.8 ± 2.4) were asked to imagine themselves walking while in the MRI scanner. Three imagined walking tasks, i.e., usual walking, obstacle negotiation, and navigation were performed. Watching the same virtual scenes without imagining walking served as control tasks. Whole brain analyses were used.Results: Compared to usual walking, both groups had increased activation during obstacle negotiation in middle occipital gyrus (MOG) (pFWEcorr<0.001), middle frontal gyrus (MFG) (pFWEcorr<0.005), and cerebellum (pFWEcorr<0.001). Healthy older adults had higher activation in precuneus and MOG (pFWEcorr<0.023) during navigation, while no differences were observed in patients with PD. Between group comparisons revealed that patients with PD had a significantly higher activation in usual walking and obstacle negotiation (pFWEcorr<0.039) while during navigation task, healthy older adults had higher activation (pFWEcorr<0.047).Conclusions: Patients with PD require greater activation during imagined usual walking and obstacle negotiation than healthy older adults. This increased activation may reflect a compensatory attempt to overcome inefficient neural activation in patients with PD. This increased activation may reduce the functional reserve needed during more demanding tasks such as during navigation which may contribute to the high prevalence of falls and dual tasking difficulties among patients with PD. [ABSTRACT FROM AUTHOR]

Highlights: [•] Introduce a new definition of a near fall. [•] Evaluate the intra and inter-rater reliability of traditional and new definitions of a near fall. [•] Demonstrate the potential utility of a new definition by adding five compensatory mechanisms. [•] Help to develop automatic algorithms to detect near falls and quantify fall risk. [ABSTRACT FROM AUTHOR]

The electroencephalogram (EEG) can be a useful tool to investigate the neurophysiology of gait during walking. Our aims were to develop an approach that identify and quantify event related potentials (ERPs) during a gait cycle and to examine the effects of aging and dual tasking on these gait related potentials (GRPs). 10 young and 10 older adults walked on a treadmill while wearing a wireless 20-channels EEG and accelerometers on the ankles. Each heel strike extracted from the accelerometers was used as an event to which the electrical brain activity pattern was locked. The subjects performed usual and dual task walking that included an auditory oddball task. GRPs amplitude and latency were computed, and a new measure referred to as Amplitude Pattern Consistency (APC) was developed to quantify the consistency of these GRP amplitudes within a gait cycle. The results were compared between and within groups using linear mixed model analysis. The electrical pattern during a gait cycle consisted of two main positive GRPs. Differences in these GRPs between young and older adults were observed in Pz and Cz. In Pz, older adults had higher GRPs amplitude (p = 0.006, p = 0.010), and in Cz lower APC (p = 0.025). Alterations were also observed between the walking tasks. Both groups showed shorter latency during oddball walking compared to usual walking in Cz (p = 0.040). In addition, the APC in Cz was correlated with gait speed (r = 0.599, p = 0.011) in all subjects and with stride time variability in the older adults (r = −0.703, p = 0.023). This study is the first to define specific gait related potentials within a gait cycle using novel methods for quantifying waveforms. Our findings show the potential of this approach to be applied broadly to study the EEG during gait in a variety of contexts. The observed changes in GRPs with aging and walking task and the relationship between GRPs and gait may suggest the neurophysiologic foundation for studying walking and for developing new approaches for improving gait. • Gait related potentials (GRPs) can be applied to quantify the EEG pattern during walking. • The GRP includes two main, positive potential waves. • A new measure, Amplitude Pattern Consistency, is lower in Cz among older adults. • Dual-task reduces the latency and increases the Amplitude Pattern Consistency in Cz. • Amplitude Pattern Consistency is correlated with gait variability in older adults. [ABSTRACT FROM AUTHOR]

Background: Previous reports indicate that patients with Parkinson's disease (PD) activate the prefrontal cortex (PFC) during complex activities such as obstacle negotiation to compensate for impaired motor function. However, the influence of disease severity on PFC activation has not been systematically evaluated. Here, we examined the effects of disease severity on PFC activation during obstacle negotiation.Methods: 74 patients with PD (age 68.26 ± 7.54 yrs; 62.2% men) were divided into three groups based on Hoehn and Yahr stages. All patients walked along an obstacle course while negotiating anticipated and unanticipated obstacles (long/low available response time) at heights of 50 mm and 100 mm. PFC activation was measured using functional near-infrared spectroscopy (fNIRS) and was compared between groups and tasks using mixed model analyses.Results: Participants with more advanced PD (i.e., Hoehn & Yahr 3) had higher PFC activation levels when negotiating anticipated obstacles, compared to participants with milder PD (i.e., Hoehn & Yahr 1, 2) (p < 0.001). Moreover, higher LEDD correlated with higher prefrontal activation during the higher anticipated obstacle. In contrast, during the negotiation of unanticipated obstacles, the differences in PFC activation were not associated with disease severity in a linear manner.Conclusions: The present study suggests that with increased disease severity, patients with PD rely more on the PFC when negotiating anticipated obstacles, perhaps to compensate for attention and motor deficits. These findings support the role of cognition in fall risk and the need to improve attention and cognition in fall prevention programs, especially among patients with more advanced disease. [ABSTRACT FROM AUTHOR]

Background: Previous reports show that patients with Parkinson's disease (PD) rely on prefrontal activation to compensate for impaired motor function during complex activities such as obstacle negotiation. However, the influence of the properties of the obstacles on prefrontal activation has not been systematically evaluated. Here, we examined the effects of obstacle height and anticipation time on prefrontal activation in patients with PD and older adults.Methods: 34 patients with PD (age: 67.4 ± 5.7 years; 14 women) and 26 older adults (age: 71.3 ± 8.9 years; 11 women) walked in an obstacle course while negotiating anticipated and unanticipated obstacles (long/short available time response, ART) at heights of 50 mm and 100 mm. Prefrontal activation was measured using functional Near-Infrared Spectroscopy (fNIRS); obstacle negotiation performance was measured using Kinect cameras.Results: PD patients showed greater increases in prefrontal activation during and after obstacle crossing compared to the older adults (p < 0.001). Obstacle height affected prefrontal activity only when crossing anticipated obstacles (ARTxheight interaction, p = 0.011), in which case higher obstacles were accompanied by higher prefrontal activity. PD patients showed higher levels of activation during unanticipated obstacles, compared to older adults (groupXART: p = 0.015). Different correlations between prefrontal activation and obstacle negotiation strategies were observed in patients and controls.Conclusions: These results point to the use of prefrontal activation as a compensatory mechanism in PD. Moreover, the higher activation observed when negotiating more challenging obstacles suggests that there is greater reliance on cognitive resources in these demanding situations that may contribute to the higher risk of falls in PD patients. [ABSTRACT FROM AUTHOR]