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Objective. Our objective was to identify the spatial distribution of local atrophy within mobility-related brain regions in relationship with quantitative gait characteristics. Methods. Gray matter volume was obtained from 220 older adults (78.0 years old, 63% women, 77% white) for brain regions of five domains: motor (motor, sensorimotor and supplementary areas, basal ganglia, cerebellum), visuospatial attention (interior and superior posterior parietal lobules), cognitive processing speed/executive control function (dorsolateral prefrontal cortex), memory (hippocampus), and motor imagery (parahippocampus, posterior cingulated cortex) domains. Spatial (step width, step length) and temporal (double support time) gait characteristics were measured using the GaitMat II instrumented walking surface. Multivariable linear regression models were adjusted for demographics, total brain volume, and peripheral (body mass index, ankle arm index, arthritis, vibratory sensation) and central (markers of diffuse brain structural abnormalities and of brain function) risk factors for gait impairment. Results. Shorter steps and longer double support times were associated with smaller sensorimotor regions and also with smaller frontoparietal regions within the motor, visuospatial, and cognitive processing speed domains. The associations between wider step and smaller pallidum and inferior parietal lobule were less robust. None of the gait measures were associated with the cerebellum or with regions of the memory or motor imagery domains. Conclusions. Spatial and temporal characteristics of gait are associated with distinct brain networks in older adults. Addressing focal neuronal losses in these networks may represent an important strategy to prevent mobility disability. Key Words: Brain networks--Gait analysis.

Background. Recent research has explored dual-task deficits during locomotion in older adults, yet the mechanisms underlying these deficits are poorly understood. In the current study, we examined one possible factor contributing to these deficits, the inability to flexibly allocate attention between two tasks. Methods. Twelve healthy young adults and 12 healthy elderly adults performed obstacle avoidance while walking and an auditory Stroop task either alone or simultaneously. Results. Using an attentional allocation index (AAI) to compare performance of healthy young and older adults and to measure the flexibility of allocation of attention, results showed a tendency in older adults toward a decreased ability to flexibly allocate their attention between the two tasks, with small AAI values. The decreased ability to allocate attention in older adults was found to be more prominent in the auditory Stroop task performance than in the obstacle avoidance task. Conclusion. This study suggests that an important factor contributing to decreased dual-task performance in older adults when simultaneously performing a postural and secondary cognitive task is a reduced ability to flexibly allocate attention between the two tasks, with the general ability to switch attention flexibly being predictive of the ability to adhere to a prioritized focus. Key Words: Gait--Attention--Aging.

Background. Cognition influences gait and balance in elderly people. Executive functions seem to play a key role in this mechanism. Previous studies used only a single test to probe executive functions, and outcome measures were restricted to gait variables. We extend this prior work by examining the association between two different executive functions and measures of both gait and balance, with and without two different cognitive dual tasks. Methods. This is a cross-sectional study with randomly selected community-living elderly people. Executive functions were tested with the Trail Making Test Parts A and B and the Stroop Color Word Test; memory with Cambridge Neuropsychological Test Automated Battery (CANTAB) subtests. Patients walked without and with two dual tasks (subtracting serial sevens and animal naming). Main outcomes focused on gait (velocity, stride length, and stride time variability), measured on an electronic walkway, and balance, measured as trunk movements during walking. Associations were assessed with multiple regression models. Results. One hundred elderly people, with a mean age 80.6 years (range 75-93 years) participated. Both dual tasks decreased gait velocity and increased variability and trunk sway. Executive functions were associated with only stride length variability and mediolateral trunk sway during performance of animal naming as the dual task. Memory was not associated with the gait and balance variables. Conclusions. In community-living elderly people, executive functions are associated with gait and balance impairment during a challenging dual-task condition that also depends on executive integrity. Next steps will be to explore the value of executive functions in defining fall-risk profiles and in fall-prevention interventions for frail patients. Key Words: Gait--Balance--Executive functions--Memory--Elderly people.

Background. In older adults, changes in speed and stability during walking are associated with impaired balance and increased fall risk. Narrow-base walking requires increased frontal plane stability and can be used to assess postural control while walking. Performance of a concurrent cognitive task (dual task) may further increase the complexity of walking, potentially allowing identification of individuals with instability that is not detected under single-task conditions. The purpose of this study was to examine age-associated effects of a cognitive task on speed and frontal plane stability during narrow-base walking. Methods. Thirty-four healthy adults participated, categorized by age: Results. Increasing age (p < .001) and the performance of a concurrent cognitive task (p < .001) were both associated with decreased speed, with no interaction between these factors. Frontal plane CoM displacement and velocity increased with increasing age (both p < .001), but dual-task performance had no effect on these variables (both p > .450). Conclusions. Age-associated changes in both speed and stability are observed during narrow-base walking. Among this sample of healthy older adults, the addition of a concurrent cognitive task resulted in reduced speed, with no effect on frontal plane stability. Further research is needed to determine if dual-task, narrow-base walking is a sensitive and specific approach to identifying older adults at risk for falls. Key Words: Dual task--Gait--Frontal plane stability--Falls--Aging.

Two experiments tested 3-and 5-month-old infants' sensitivity to properties of point-light displays of human gait. In Experiment 1, infants were tested for discrimination of point-light displays of a walker and a runner, which, although they differed in many ways, were equivalent with regard to the phasing of limb movements. Results revealed that 3-month-old, but not 5-month-old, infants discriminated these displays. In Experiment 2, the symmetrical phase-patterning of the runner display was perturbed by advancing two of its limbs by 25% of the gait cycle. Both 3-and 5-month-old infants discriminated the walker display from this new phase-shifted runner display. These findings suggest that 3-month-old infants respond to the absolute and relative motions within a single limb, whereas 5-month-old infants respond primarily to the relations between limbs and, in particular, to the bilateral symmetry between the limbs.

We studied the effect of concurrent tasks on motor control of gait with dual-task methodology. Ten healthy subjects were instructed to perform different cognitive and motor tasks during gait on a conductive walkway. Footswitch signals were recorded and stride time and double-support time were calculated. It was assumed that the former reflects gait-patterning mechanisms and the latter relates to balance control. Statistical analysis showed an increase in double-support time when a memory-retention task (digit-span) and a fine motor task (buttoning) were executed simultaneously during gait. During gait performance of the cognitive task declined compared to baseline conditions. Attentional demand of concurrent cognitive and motor tasks appeared to force subjects to modulate their gait strategy to ensure control of balance. Stride time was consistent across task conditions except when subjects performed fast finger-tapping during gait. Then all but one subject showed a decrease in stride time and an increase in stride-frequency that was repeatable on retest. Since different rhythmic movements are likely to share common neurobiological networks, we assumed that the modulation of stride-frequency was due to structural interference.

Tight frequency-to-amplitude relationships are observed in spontaneous human steady gait. If required, however, they can be modified. The following experiments were aimed at the processes underlying this flexibility, which forms the fundamental basis of the intentional adaptive capabilities of locomotion. In Experiment 1, Ss had to intentionally modify the frequency-to-amplitude relationship (leading to preferred or nonpreferred steady states). In Experiment 2, they had to temporarily perturbate the stride-frequency-to-amplitude relationship to intentionally shorten or lengthen 1 stride. Within the important constraints exerted by the head-arm-trunk system on leg movement, the results pointed out 2 main strategies that allow the S to intentionally adapt stride organization on-line: adjustment of the tonic properties of the oscillating leg to achieve nonpreferred steady states and phasic action to ensure temporary movement away from a steady state.

Byline: Mohamed. El-Tamawy, Moshera. Darwish, Mohamed. Khallaf Context : Impairment of initiating sequential movements and processing of proprioception contribute to characteristic Parkinson's disease (PD) gait abnormalities. Many studies have used [...]

Byline: Anne. Ambrose, Mohan. Noone, V. Pradeep, Beena. Johnson, K. Salam, Joe. Verghese Background: Recent reports indicate that gait dysfunction can occur early in the course of cognitive decline suggesting [...]