Deep brain stimulation enhances movement complexity during gait in individuals with Parkinson's disease.

Deep brain stimulation (DBS) is associated with substantial improvements in motor symptoms of PD. Emerging evidence has suggested that nonlinear measures of complexity may provide greater insight into the efficacy of anti-PD treatments. This study investigated sample entropy and complexity index values in individuals with PD when DBS was OFF compared to ON.

Normalizing EMG to Background Muscle Activation Masks Medication-Induced Reductions in Reflex Amplitudes in Parkinsonian Rigidity.

Objectives: Exaggerated reflex responses to passive stretch and shortening contribute to parkinsonian rigidity. Studies have reported medication-induced reductions in rigidity in the absence of attenuated reflex magnitudes. The purpose of this study was to determine if normalization procedures mask medication-induced reductions in reflex responses in Parkinson's disease.

A Comparison of the Effects of Continuous versus Discontinuous Movement Patterns on Parkinsonian Rigidity and Reflex Responses to Passive Stretch and Shortening.

Objective: Quantify the effect of a continuous compared to discontinuous movement trajectory on parkinsonian rigidity and reflex responses to passive stretch and shortening.

Methods: Eighteen participants with Parkinson's disease (PD) performed passive wrist flexion and extension movements through a 90° range of motion at 50 °/sec using continuous (CONT) and discontinuous (DISC) movement trajectories. Participants were tested in both the OFF-MED and ON-MED states.

Quantification of neural reflex and muscular intrinsic contributions to parkinsonian rigidity.

Parkinson's disease (PD) is a progressive neurodegenerative disease characterized by rigidity, bradykinesia, resting tremor, and postural instability. Rigidity, defined as an increased resistance to passive movement of a joint, progresses faster than other motor signs in PD. Rigidity is attributable to both exaggerated neural reflex and altered muscle mechanical properties.

Promoting Community Health and Eliminating Health Disparities Through Community-Based Participatory Research.

In physical therapy, there is increasing focus on the need at the community level to promote health, eliminate disparities in health status, and ameliorate risk factors among underserved minorities. Community-based participatory research (CBPR) is the most promising paradigm for pursuing these goals. Community-based participatory research stresses equitable partnering of the community and investigators in light of local social, structural, and cultural elements.

Parkinson's disease is associated with greater regularity of repetitive voluntary movements.

Bradykinesia is a cardinal symptom of Parkinson's disease (PD). Both aging and disease are shown to be associated with decreased adaptability to environmental stresses characterized by reduced complexity (or increased regularity) of biorhythms. The purpose of this study was to investigate the regularity of movement in individuals with PD, and the effect of dopaminergic medication.

Progression of motor symptoms in Parkinson's disease.

Parkinson's disease (PD) is a chronic progressive neurodegenerative disease that is clinically manifested by a triad of cardinal motor symptoms - rigidity, bradykinesia and tremor - due to loss of dopaminergic neurons. The motor symptoms of PD become progressively worse as the disease advances. PD is also a heterogeneous disease since rigidity and bradykinesia are the major complaints in some patients whereas tremor is predominant in others.

Amplitude- and velocity-dependency of rigidity measured at the wrist in Parkinson's disease.

Objective: Quantify the effects of increased amplitude and rate of muscle stretch on parkinsonian rigidity.

Methods: Eighteen subjects with Parkinson's disease participated in this study. Subjects' tested hand was passively displaced through 60° and 90° ranges of wrist flexion and extension at velocities of 50°/s and 280°/s in both treated and untreated conditions.

Differentiation between the contributions of shortening reaction and stretch-induced inhibition to rigidity in Parkinson's disease.

Parkinsonian rigidity is characterized by an increased resistance of a joint to externally imposed motion that remains uniform with changing joint angle. Two candidate mechanisms are proposed for the uniformity of rigidity, involving neural-mediated excitation of shortening muscles, i.e.

Enhancement of parkinsonian rigidity with contralateral hand activation.

Objective: Quantify the enhancement of parkinsonian rigidity associated with a contralateral activation maneuver.

Methods: Twelve subjects with PD and eight controls participated in the study protocol. Subjects' tested hand was displaced by a servo-motor throughout wrist flexion and extension motions of 60° without and with a concurrent gripping activation in the contralateral hand, referred to as Passive and Active conditions, respectively.

Human strategies in balancing an inverted pendulum with time delay.

The strategy of human manual control is investigated in balancing an inverted pendulum under time-delay constraints. Experiments show that as the task becomes more difficult due to the increase in time delay, the human operator adopts a more discrete-like strategy. Interpretation of the discrete-control mechanism is provided by relating the observed human responses with a human-performance model.

Analysis of interactive effect of stretch reflex and shortening reaction on rigidity in Parkinson's disease.

Objective: To examine the correlation between rigidity and interaction of stretch reflex and shortening reaction during passive movements of the wrist and to compare this correlation with that between rigidity and stretch reflex alone.

Methods: Twelve subjects with Parkinson's disease participated in the study in Off-medication and On-medication states. A servomotor imposed wrist flexion and extension within +/-30 degrees at velocities 50 and 280 degrees/s, while joint torque and EMG of the wrist flexors and extensors were recorded.

Modulation of reflex responses in hand muscles during rhythmical finger tasks in a subject with writer's cramp.

The objective of this study was to examine phase- and task-dependent modulation of stretch reflexes during repetitive finger movements in writer's cramp, and compare them with normal controls from our previous study. A subject with writer's cramp conducted two rhythmic tasks, index finger abduction (RFA) and a pen-squeezing (RPS) task akin to handwriting. Stretch reflexes were evoked by mechanical perturbations at random phases of each task.

Phase-dependent and task-dependent modulation of stretch reflexes during rhythmical hand tasks in humans.

Phase-dependent and task-dependent modulation of reflexes has been extensively demonstrated in leg muscles during locomotory activity. In contrast, the modulation of reflex responses of hand muscles during rhythmic movement is poorly documented. The objective of this study was to determine whether comparable reflex modulation occurs in muscles controlling finger motions during rhythmic, fine-motor tasks akin to handwriting.

The role of shortening reaction in mediating rigidity in Parkinson's disease.

Rigidity in Parkinson's disease (PD) is defined as an increased resistance to passive movement of a joint. The plastic-type rigidity is uniform and constant throughout the entire range of motion, whereas the cogwheel-type rigidity is accompanied by tremor. Rigidity in PD has been understudied.

Oculomanual Coordination in Tracking of Pseudorandom Target Motion Stimuli.

Oculomanual coordination was investigated in 9 healthy subjects during tracking of pseudorandom motion stimuli. Each subject was required to track visual stimuli under eye-hand (EH) and eye-alone (EA) conditions. Subjects were exposed to 3 types of mixed sinusoidal stimulus with varying frequency or amplitude of the highest frequency component, or various degrees of irregularity.