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Description
Previous research has shown that a loud acoustic stimulus can trigger an individual's prepared movement plan. This movement response is referred to as a startle-evoked movement (SEM). SEM has been observed in the stroke survivor population where results have shown that SEM enhances single joint movements that are usually performed with difficulty. While the presence of SEM in the stroke survivor population advances scientific understanding of movement capabilities following a stroke, published studies using the SEM phenomenon only examined one joint. The ability of SEM to generate multi-jointed movements is understudied and consequently limits SEM as a potential therapy tool. In order to apply SEM as a therapy tool however, the biomechanics of the arm in multi-jointed movement planning and execution must be better understood. Thus, the objective of our study was to evaluate if SEM could elicit multi-joint reaching movements that were accurate in an unrestrained, two-dimensional workspace. Data was collected from ten subjects with no previous neck, arm, or brain injury. Each subject performed a reaching task to five Targets that were equally spaced in a semi-circle to create a two-dimensional workspace. The subject reached to each Target following a sequence of two non-startling acoustic stimuli cues: "Get Ready" and "Go". A loud acoustic stimuli was randomly substituted for the "Go" cue. We hypothesized that SEM is accessible and accurate for unrestricted multi-jointed reaching tasks in a functional workspace and is therefore independent of movement direction. Our results found that SEM is possible in all five Target directions. The probability of evoking SEM and the movement kinematics (i.e. total movement time, linear deviation, average velocity) to each Target are not statistically different. Thus, we conclude that SEM is possible in a functional workspace and is not dependent on where arm stability is maximized. Moreover, coordinated preparation and storage of a multi-jointed movement is indeed possible.
ContributorsOssanna, Meilin Ryan (Author) / Honeycutt, Claire (Thesis director) / Schaefer, Sydney (Committee member) / Harrington Bioengineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2016-12
Description
The interaction between visual fixations during planning and performance in a
dexterous task was analyzed. An eye-tracking device was affixed to subjects during
sequences of null (salient center of mass) and weighted (non salient center of mass) trials
with unconstrained precision grasp. Subjects experienced both expected and unexpected
perturbations, with the task of minimizing object roll. Unexpected perturbations were
controlled by switching weights between trials, expected perturbations were controlled by
asking subjects to rotate the object themselves. In all cases subjects were able to
minimize the roll of the object within three trials. Eye fixations were correlated with
object weight for the initial context and for known shifts in center of mass. In subsequent
trials with unexpected weight shifts, subjects appeared to scan areas of interest from both
contexts even after learning present orientation.
dexterous task was analyzed. An eye-tracking device was affixed to subjects during
sequences of null (salient center of mass) and weighted (non salient center of mass) trials
with unconstrained precision grasp. Subjects experienced both expected and unexpected
perturbations, with the task of minimizing object roll. Unexpected perturbations were
controlled by switching weights between trials, expected perturbations were controlled by
asking subjects to rotate the object themselves. In all cases subjects were able to
minimize the roll of the object within three trials. Eye fixations were correlated with
object weight for the initial context and for known shifts in center of mass. In subsequent
trials with unexpected weight shifts, subjects appeared to scan areas of interest from both
contexts even after learning present orientation.
ContributorsSmith, Michael David (Author) / Santello, Marco (Thesis advisor) / Buneo, Christopher (Committee member) / Schaefer, Sydney (Committee member) / Arizona State University (Publisher)
Created2017
Description
INTRODUCTION: As people age, they become increasingly susceptible to falls, particularly when their attention is divided. Cognitive domains such as executive functioning and processing speed also decline over time and are associated with falls. A critical aspect to reducing falls are reactive steps, which are used to recover balance after a perturbation. Characterizing the relationship between cognition, dual tasking, and prioritization is necessary in order to decrease fall risk in older adults. Thus, the purpose of this analysis was to determine the effects of baseline cognitive status on dual task interference and prioritization of postural and cognitive tasks while reactive stepping. METHODS: 30 participants (Parkinson's disease (PD) n=16, healthy controls (HC) n=14) were divided into two groups based on their baseline cognitive status: the high-cog group (n=18) or the low-cog group (n=12). All participants experienced 7 perturbation trials where they were solely tasked with reactive stepping, 2 cognitive trials where they were solely tasked with verbally responding to an auditory Stroop test, and 7 trials that combined the two tasks. Cognitive and protective stepping performance was calculated for dual task interference and prioritization across groups. RESULTS: There were no outcome variables that showed the log-cog group performing worse than the high-cog group from single to dual task conditions. While examining the dual task interference between groups, the only significant outcome was that the low-cog group exhibited a subtle improvement in their step length performance under dual task conditions while the high-cog group did not. When comparing the prioritization scores, there was no statistically significant difference in prioritization between the high-cog and low-cog group. Albeit not significant across groups, the prioritization score for all outcomes was negative, indicating a stepping prioritization under dual task conditions for both groups. This analysis provides preliminary evidence that baseline cognitive status does not significantly affect dual task interference nor prioritization while reactive step dual tasking. While these effects should be treated with caution, these results would suggest that baseline cognitive status may not play a critical role in dual task interference or attentional allocation in both people with PD and healthy older adults.
ContributorsBarajas, Jordan (Author) / Peterson, Daniel S (Thesis advisor) / Schaefer, Sydney (Committee member) / Ofori, Edward (Committee member) / Arizona State University (Publisher)
Created2020