Matching Items (23)
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- All Subjects: Biomedical Engineering
- Creators: Abbas, James
Description
Between 20%-30% of stroke survivors have foot drop. Foot drop is characterized by inadequate dorsiflexion required to clear the foot of the ground during the swing phase of gait, increasing the risk of stumbles and falls (Pouwels et al. 2009; Hartholt et al. 2011). External postural perturbations such as trips and slips are associated with high rate of falls in individuals with stroke (Forster et al. 1995). Falls often results in head, hip, and wrist injuries (Hedlund et al 1987; Parkkari et al. 1999). A critical response necessary to recover one’s balance and prevent a fall is the ability to evoke a compensatory step (Maki et al. 2003; Mansfield et al. 2013). This is the step taken to restore one’s balance and prevent a fall. However, this is difficult for stroke survivors with foot drop as normal gait is impaired and this translates to difficulty in evoking a compensatory step. To address both foot drop and poor compensatory stepping response, assistive devices such as the ankle-foot-orthosis (AFO) and functional electrical stimulator (FES) are generally prescribed to stroke survivors (Kluding et al. 2013; S. Whiteside et al. 2015). The use of these assistive devices improves walking speed, foot clearance, cadence, and step length of its users (Bethoux et al. 2014; Abe et al. 2009; Everaert et al. 2013; Alam et al. 2014). However, their impact on fall outcome in individuals with stroke in not well evaluated (Weerdesteyn et al. 2008). A recent study (Masood Nevisipour et al. 2019) where stroke survivors experienced a forward treadmill perturbation, mimicking a trip, reports that the impaired compensatory stepping response in stroke survivors in not due to the use of the assistive devices but to severe ankle impairments which these devices do not fully address. However, falls can also occur because of a slip. Slips constitute 40% of outdoor falls (Luukinen et al. 2000). In this study, results for fall rate and compensatory stepping response when subjects experience backward perturbations, mimicking slips, reveal that these devices do not impair the compensatory stepping response of its users.
ContributorsAnnan, Theophilus (Author) / Honeycutt, Claire (Thesis advisor) / Abbas, James (Committee member) / Peterson, Daniel (Committee member) / Arizona State University (Publisher)
Created2021
Description
Motor skill learning is important to rehabilitation, sports, and many occupations. When attempting to learn or adapt a motor skill, some individuals learn slower or less compared to others despite the same amount of motor practice. This dissertation aims to understand the factors that contributed to such variability in motor learning, and thereby identify viable methods to enhance motor learning. Behavioral evidence from our lab showed that visuospatial ability is positively related to the extent of motor learning. Neuroimaging studies suggest that motor learning and visuospatial processes share common frontoparietal neural structures, and that this visuospatial-motor relationship may be more pronounced in the right hemisphere compared to the left. Thus, the overall objective of this dissertation is to determine if aspects of motor learning (such as the rate and extent of skill acquisition) may be modifiable through neuromodulation of the right frontoparietal network. In Aim 1, anodal transcranial direct current stimulation (tDCS) was used to test whether modulating the right parietal area affects visuospatial ability and motor skill acquisition. A randomized, three-arm design was used, which added a no-tDCS control group to the double-blinded sham-control protocol to address placebo effects. No tDCS treatment effect was observed, likely due to low statistical power to detect any treatment effects as the study is still ongoing. However, the current results revealed a unique finding that the placebo effect of tDCS was stronger than its treatment effect on motor learning, with implications that tDCS and motor studies should measure and control for placebo effects.
In Aim 2, right frontoparietal connectivity during resting-state EEG was estimated via alpha band imaginary coherence to test whether it correlated with visuospatial performance and motor skill acquisition. As a preliminary step towards leveraging the frontoparietal network for EEG-neurofeedback applications, this work found that alpha imaginary coherence was positively correlated with visuospatial function, but not with motor skill acquisition during a limited dose of motor practice (only 5 trials). This work establishes a premise for developing frontoparietal alpha IC-based neurofeedback for cognitive training in rehabilitation, while warranting future studies to test the relationship between alpha IC and motor learning with a more extensive motor training regimen.
ContributorsWang, Peiyuan (Author) / Schaefer, Sydney Y (Thesis advisor) / Buneo, Christopher A (Committee member) / Abbas, James (Committee member) / Lohse, Keith R (Committee member) / Wyckoff, Sarah N (Committee member) / Arizona State University (Publisher)
Created2021
Description
The use of a non-invasive form of energy to modulate neural structures has gained wide spread attention because of its ability to remotely control neural excitation. This study investigates the ability of focused high frequency ultrasound to modulate the excitability the peripheral nerve of an amphibian. A 5MHz ultrasound transducer is used for the study with the pulse characteristics of 57msec long train burst and duty cycle of 8% followed by an interrogative electrical stimulus varying from 30μsecs to 2msecs in pulse duration. The nerve excitability is determined by the compound action potential (CAP) amplitude evoked by a constant electrical stimulus. We observe that ultrasound's immediate effect on axons is to reduce the electrically evoked CAP amplitude and thereby suppressive in effect. However, a subsequent time delayed increased excitability was observed as reflected in the CAP amplitude of the nerve several tens of milliseconds later. This subsequent change from ultrasound induced nerve inhibition to increased excitability as a function of delay from ultrasound pulse application is unexpected and not predicted by typical nerve ion channel kinetic models. The recruitment curve of the sciatic nerve modified by ultrasound suggests the possibility of a fiber specific response where the ultrasound inhibits the faster fibers more than the slower ones. Also, changes in the shape of the CAP waveform when the nerve is under the inhibitive effect of ultrasound was observed. It is postulated that these effects can be a result of activation of stretch activation channels, mechanical sensitivity of the nerve to acoustic radiation pressure and modulation of ion channels by ultrasound.
The neuromodulatory capabilities of ultrasound in tandem with electrical stimulation has a significant potential for development of neural interfaces to peripheral nerve.
The neuromodulatory capabilities of ultrasound in tandem with electrical stimulation has a significant potential for development of neural interfaces to peripheral nerve.
ContributorsChirania, Sanchit (Author) / Towe, Bruce (Thesis advisor) / Abbas, James (Committee member) / Muthuswamy, Jitendran (Committee member) / Arizona State University (Publisher)
Created2016