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Search Results: 1 - 10 of 297839 matches for " Janis J. Daly "
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Construction of Efficacious Gait and Upper Limb Functional Interventions Based on Brain Plasticity Evidence and Model-Based Measures For Stroke Patients
Janis J. Daly,Robert L. Ruff
The Scientific World Journal , 2007, DOI: 10.1100/tsw.2007.299
Abnormal Leg Muscle Latencies and Relationship to Dyscoordination and Walking Disability after Stroke
Janis J. Daly,Kristen Roenigk,Roger Cheng,Robert L. Ruff
Rehabilitation Research and Practice , 2011, DOI: 10.1155/2011/313980
Abstract: The purpose was to determine timing characteristics of leg muscle latencies for patients following stroke ( 12 months) who had persistent coordination and gait deficits, and to determine the relationships among abnormal latencies, dyscoordination, and gait deficits. We compared nine healthy controls and 27 stroke survivors. Surface electromyography measured activation and deactivation latencies of knee flexor and extensor muscles during a ballistic knee flexion task, consistency of latencies across repetitions, and close coupling between agonist and antagonist muscle latencies. We measured Fugl-Meyer (FM) coordination and the functional gait measure, six minute walk test (6MWT). For stroke subjects, there were significant delays of muscle activation and deactivation, abnormal inconsistency, and abnormal decoupled agonist and antagonist activations. There was good correlation between activation latencies and FM and 6MWT. Results suggest abnormal timing characteristics underlie coordination impairment and dysfunctional gait. These abnormal muscle activation and deactivation timing characteristics are important targets for rehabilitation. 1. Introduction Lower limb coordination deficits persist after stroke rehabilitation. Timing characteristics of muscle activation are integral to coordinated movement and normal gait. Though abnormal timing characteristics for upper limb dyscoordination have been reported, there is little information regarding the nature of lower limb muscle activation abnormalities and their relationship to coordinated movement and functional gait. Because the mechanisms underlying coordination impairments and gait deficits are poorly understood, it is difficult to accurately target rehabilitation interventions. The purpose of this study was twofold. First, we identified the abnormal timing characteristics of muscle activation and deactivation for knee flexor and extensor muscles for patients following stroke who had persistent coordination and gait deficits in the swing phase of gait. Second, we determined the association between muscle activation latency and coordination impairment and dysfunctional gait. In the swing phase of gait, complex and precisely coordinated muscle activation and deactivation timings are critical for safe, coordinated walking. There are relatively few studies that characterize in stroke survivors, the precision of muscle activation and deactivation latencies that are demanded during gait-swing phase. In an attempt to study flexion and extension limb movements, one study utilized a cycle pedaling task to study
Guest Editorial: Gait coordination protocol for recovery of coordinated gait, function, and quality of life following stroke
Janis J. Daly, PhD, MS,Jessica P. McCabe, MPT,Jennifer Gansen, DPT,Jean Rogers, PT
Journal of Rehabilitation Research and Development , 2012, DOI: 10.1682/jrrd.2012.07.0127
Abstract: The Gait Coordination Protocol (GCP) was successful in producing clinically and statistically significant gains in impairment, function, and life-role participation for those in the chronic phase after stroke who had exhibited persistent moderate to severe gait deficits.
Functional Brain Correlates of Upper Limb Spasticity and Its Mitigation following Rehabilitation in Chronic Stroke Survivors
Svetlana Pundik,Adam D. Falchook,Jessica McCabe,Krisanne Litinas,Janis J. Daly
Stroke Research and Treatment , 2014, DOI: 10.1155/2014/306325
Abstract: Background. Arm spasticity is a challenge in the care of chronic stroke survivors with motor deficits. In order to advance spasticity treatments, a better understanding of the mechanism of spasticity-related neuroplasticity is needed. Objective. To investigate brain function correlates of spasticity in chronic stroke and to identify specific regional functional brain changes related to rehabilitation-induced mitigation of spasticity. Methods. 23 stroke survivors (>6 months) were treated with an arm motor learning and spasticity therapy (5?d/wk for 12 weeks). Outcome measures included Modified Ashworth scale, sensory tests, and functional magnetic resonance imaging (fMRI) for wrist and hand movement. Results. First, at baseline, greater spasticity correlated with poorer motor function ( ) and greater sensory deficits ( ). Second, rehabilitation produced improvement in upper limb spasticity and motor function ( ). Third, at baseline, greater spasticity correlated with higher fMRI activation in the ipsilesional thalamus ( , ). Fourth, following rehabilitation, greater mitigation of spasticity correlated with enhanced fMRI activation in the contralesional primary motor ( , ), premotor ( , ), primary sensory ( , ), and associative sensory ( , ) regions while controlling for changes in motor function. Conclusions. Contralesional motor regions may contribute to restoring control of muscle tone in chronic stroke. 1. Introduction Motor rehabilitation is a challenging task especially for individuals who exhibit spasticity along with motor impairment. Spasticity can limit effective practice of coordinated movement and hinder functional recovery and rehabilitation [1–3]. In fact, a more complete restoration of motor function is achieved when spasticity is absent [4]. The obstacle that spasticity creates for upper limb rehabilitation is due to restriction of movement, in opposition to the spastic muscle activity, as in practice of wrist and finger extension when wrist and finger flexors exhibit spasticity. Spasticity burdens a significant portion of patients with chronic motor deficits, secondary to stroke and other types of brain injury. Up to 42% of stroke survivors exhibit abnormal hypertonia [4–8]. This abnormally elevated muscle tone is likely to impact quality of life because it affects many aspects of everyday function, produces pain and discomfort, and prevents normal movements [3, 9]. Spasticity can be improved to some degree. Currently available treatment modalities for spasticity include pharmacological agents (oral preparations, neuromuscular blockade
Promoting School Based Cohorts in Distance/Online Learning  [PDF]
Janis McKinley, D. J. Champagne
Creative Education (CE) , 2013, DOI: 10.4236/ce.2013.48A003
Abstract: Successful cohort online learning requires three important components: Community, Collaboration, and Content. Looking at how to develop these components is discussed as a result of what is known by the authors’ active engaging in the cohort online learning model.
Causality vs. Ward identity in disordered electron systems
V. Janis,J. Kolorenc
Physics , 2003, DOI: 10.1142/S0217984904007591
Abstract: We address the problem of fulfilling consistency conditions in solutions for disordered noninteracting electrons. We prove that if we assume the existence of the diffusion pole in an electron-hole symmetric theory we cannot achieve a solution with a causal self-energy that would fully fit the Ward identity. Since the self-energy must be causal, we conclude that the Ward identity is partly violated in the diffusive transport regime of disordered electrons. We explain this violation in physical terms and discuss its consequences.
A mean-field theory of Anderson localization
V. Janis,J. Kolorenc
Physics , 2004, DOI: 10.1103/PhysRevB.71.033103
Abstract: Anderson model of noninteracting disordered electrons is studied in high spatial dimensions. We find that off-diagonal one- and two-particle propagators behave as gaussian random variables w.r.t. momentum summations. With this simplification and with the electron-hole symmetry we reduce the parquet equations for two-particle irreducible vertices to a single algebraic equation for a local vertex. We find a disorder-driven bifurcation point in this equation signalling vanishing of diffusion and onset of Anderson localization. There is no bifurcation in $d=1,2$ where all states are localized. A natural order parameter for Anderson localization pops up in the construction.
A consistent description of diffusion and its vanishing in disordered electron systems
V. Janis,J. Kolorenc
Physics , 2015,
Abstract: We address the problem of vanishing of diffusion in noninteracting disordered electron systems and its description by means of averaged Green functions. Since vanishing of diffusion, Anderson localization, cannot be identified by means of one-electron quantities, one must appropriately approximate two-particle functions. We show how to construct nontrivial and self-consistent approximations for irreducible vertices and to handle them so that the full dynamical Ward identity and all macroscopic conservation laws are obeyed. We derive an approximation-free low-energy representation of the full two-particle vertex that we use to calculate the critical part of the electron-hole correlation function, the diffusion pole and the dynamical diffusion constant. We thereby pave the way for a systematic and controllable description of vanishing of diffusion in disordered systems.
Absence of the diffusion pole in the Anderson insulator
V. Janis,J. Kolorenc
Physics , 2004,
Abstract: We discuss conditions for the existence of the diffusion pole and its consequences in disordered noninteracting electron systems. Using only nonperturbative and exact arguments we find against expectations that the diffusion pole can exist only in the diffusive (metallic) regime. We demonstrate that the diffusion pole in the Anderson localization phase would lead to nonexistence of the self-energy and hence to a physically inconsistent picture. The way how to consistently treat and understand the Anderson localization transition with vanishing of the diffusion pole is presented.
Mean-field theories for disordered electrons: Diffusion pole and Anderson localization
V. Janis,J. Kolorenc
Physics , 2005, DOI: 10.1103/PhysRevB.71.245106
Abstract: We discuss conditions to be put on mean-field-like theories to be able to describe fundamental physical phenomena in disordered electron systems. In particular, we investigate options for a consistent mean-field theory of electron localization and for a reliable description of transport properties. We argue that a mean-field theory for the Anderson localization transition must be electron-hole symmetric and self-consistent at the two-particle (vertex) level. We show that such a theory with local equations can be derived from the asymptotic limit to high spatial dimensions. The weight of the diffusion pole, i. e., the number of diffusive states at the Fermi energy, in this mean-field theory decreases with the increasing disorder strength and vanishes in the localized phase. Consequences of the disclosed behavior for our understanding of vanishing of electron diffusion are discussed.
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