Ely Rabin

Precision contact of the fingertip reduces postural sway of individuals with bilateral vestibular loss.

Abstract Contact of the hand with a stationary surface attenuates postural sway in normal individuals even when the level of force applied is mechanically inadequate to dampen body motion. We studied whether subjects without vestibular function would be able to substitute contact cues from the hand for their lost labyrinthine function and be able to balance as well as normal subjects in the dark without finger contact. We also studied the relative contribution of sight of the test chamber to the two groups. Subjects attempted to maintain a tandem Romberg stance for 25 s under three levels of fingertip contact: no contact; light-touch contact, up to 1 N (≈100 g) force; and unrestricted contact force. Both eyes open and eyes closed conditions were evaluated. Without contact, none of the vestibular loss subjects could stand for more than a few seconds in the dark without falling; all the normals could. The vestibular loss subjects were significantly more stable in the dark with light touch of the index finger than the normal subjects in the dark without touch. They also swayed less in the dark with light touch than when permitted sight of the test chamber without touch, and less with sight and touch than just sight. The normal subjects swayed less in the dark with touch than without, and less with sight and touch than sight alone. These findings show that during quiet stance light touch of the index finger with a stationary surface can be as effective or even more so than vestibular function for minimizing postural sway.

Haptic feedback from manual contact improves balance control in people with Parkinson's disease

Parkinsons disease (PD) degrades balance control. Haptic (touch and proprioception) feedback from light contact with a stationary surface inadequate to mechanically stabilize balance improves balance control in healthy people. In this study we tested whether PD impairs use of haptic cues independent of mechanical support to control balance. We measured postural sway in thirteen individuals with PD (H&Y 1-3, median=2, Q1=2, Q3=2) and thirteen age-matched controls balancing in a widened, sharpened Romberg stance in four conditions: eyes-closed, no manual contact; eyes-closed light-touch contact (<1N), eyes-closed, unrestricted contact; and eyes-open, no contact. To determine whether PD-severity affects any of these balance strategies, PD participants were tested on- and off-medication, and using the more- and less-affected body side in the stance and manual contact. Individuals with PD simultaneously maintained non-supportive fingertip contact and balance in this task without practice. PD participants swayed more than control participants (ML CP p=0.010; shoulder p<0.001), but manual contact reduced sway. Non-supportive manual contact stabilized balance more than vision (p<0.05). PD-severity factors had no significant effect (p>0.05). We conclude the effect of PD on balance is not specific to vision or haptic feedback. Nevertheless, haptic cues from manual contact, independent of mechanical support, improve balance control in individuals with PD. We discuss the implication that PD or associated dopaminergic pathways do not directly affect haptic feedback balance control mechanisms, including arm/posture coordination and proprioceptive integration.

Tactile/proprioceptive integration during arm localization is intact in individuals with Parkinson's disease.

It has been theorized that sensorimotor processing deficits underlie Parkinsons disease (PD) motor impairments including movement under proprioceptive control. However, it is possible that these sensorimotor processing deficits exclude tactile/proprioception sensorimotor integration: prior studies show improved movement accuracy in PD with endpoint tactile feedback, and good control in tactile-driven precision-grip tasks. To determine whether tactile/proprioceptive integration in particular is affected by PD, nine subjects with PD (off-medication, UPDRS motor=19-42) performed an arm-matching task without visual feedback. In some trials one arm touched a static tactile cue that conflicted with dynamic proprioceptive feedback from biceps brachii muscle vibration. This sensory conflict paradigm has characterized tactile/proprioceptive integration in healthy subjects as specific to the context of tactile cue mobility assumptions and the intention to move the arm. We found that the individuals with PD had poorer arm-matching accuracy than age-matched control subjects. However, PD-group accuracy improved with tactile feedback. Furthermore, sensory conflict conditions were resolved in the same context-dependent fashion by both subject groups. We conclude that the somatosensory integration mechanism for prioritizing tactile and proprioception feedback in this task are not disrupted by PD, and are not related to the observed proprioceptive deficits.

Parkinsonian gait ameliorated with a moving handrail, not with a banister.

OBJECTIVE To determine whether haptic (touch and proprioception) cues from touching a moving handrail while walking can ameliorate the gait symptoms of Parkinson disease (PD), such as slowness and small stride length. DESIGN Nonrandomized, controlled before-after trial. SETTING Physical therapy clinic. PARTICIPANTS People with PD (n=16) and healthy age-matched control subjects (n=16) with no neurologic disorders volunteered. No participants withdrew. INTERVENTIONS We compared gait using a moving handrail as a novel assistive aid (speed self-selected) versus a banister and unassisted walking. Participants with PD were tested on and off dopaminergic medication. MAIN OUTCOME MEASURES Mean gait speed, stride length, stride duration, double-support duration, and medial-lateral excursion. RESULTS With the moving handrail, participants with PD increased gait speed relative to unassisted gait by 16% (.166m/s, P=.009, d=.76; 95% confidence interval [CI], .054-.278m/s) and increased stride length by 10% (.053m, P=.022, d=.37; 95% CI, .009-.097m) without significantly changing stride or double-support duration. The banister reduced speed versus unassisted gait by 11% (-.097m/s, P=.040, d=.40; 95% CI, .002-.193m/s) and reduced stride length by 8% (.32m, P=.004, d=.26; 95% CI, .010-.054m), whereas it increased stride duration by 3% (.023s, P=.022, d=.21; 95% CI, .004-.041s) and double-support duration by 35% (.044s, P=.031, d=.58; 95% CI, .005-.083s). All medication × condition interactions were P>.05. CONCLUSIONS Using haptic speed cues from the moving handrail, people with PD walked faster by spontaneously (ie, without specific instruction) increasing stride length without altering cadence; banisters slowed gait. Haptic cues from the moving handrail can be used by people with PD to engage biomechanical and neural mechanisms for interpreting tactile and proprioception changes related to gait speed to control gait better than static cues afforded by banisters.

Effects of Exercise and B Vitamins on Homocysteine and Glutathione in Parkinson’s Disease: A Randomized Trial

Background: Individuals with Parkinson’s disease (PD) have decreased glutathione levels and elevated homocysteine levels. These substances are considered markers of health, and an inverse relationship has been suggested through the transsulfuration pathway. This experiment tested the effects of exercise and B vitamin supplementation on homocysteine and glutathione levels, and if a relationship was present between these two markers in those with PD. Secondary aims included examining the impact of the interventions on aerobic efficiency and strength. Methods: Thirty-six subjects were randomly assigned to 4 groups. The Vit group received vitamins B6, B12 and folic acid daily for 6 weeks. The Ex group received aerobic and strength training twice weekly for 6 weeks. The Vit + Ex group received both interventions. A control group received no intervention. Subjects were tested prior to and after intervention on the following measures: glutathione and homocysteine levels, strength measures and oxygen consumption. Results: Subjects who received 6 weeks of B vitamin supplementation had lowered homocysteine levels. Subjects who received 6 weeks of exercise training had increased glutathione levels, strength and aerobic capacity. The combination of vitamin and exercise did not yield greater changes than the separate intervention. The control subjects did not change on any measures. Conclusion: Positive results were realized with each intervention; however, the expected relationship between glutathione and homocysteine was not found in this sample of subjects with PD. Homocysteine and glutathione levels can be improved independently in individuals with PD with exercise or vitamins B6, B12 and folic acid supplementation.

Wireless body area sensor network for posture and gait monitoring of individuals with Parkinson's disease

This paper presents a wireless body area sensor network that detects and records real-time posture and gait kinematic data from individuals with Parkinsons disease. The network comprises wearable sensors placed at lower limbs and back of a human body to measure users kinematics. The collected data are transmitted wirelessly to a receiver and stored in cloud-based database. The time series kinematic data is interpreted with adaptive fractal analysis (AFA) to differentiate a healthy subject from another with PD. We use frequency analysis to differentiate spontaneous movement from cued movement of clinical evaluations of several persons with Parkinson disease (PD).

Effects of Tyrosine on Parkinson's Disease: A Randomized, Double-Blind, Placebo-Controlled Trial

Individuals with Parkinsons disease (PD) can suffer from orthostatic hypotension (OH) resulting from reduced levels of norepinephrine (NE), which inhibits the sympathetic nervous system. Levodopa reduces NE levels even further, leading to a greater decrease in blood pressure (BP) and increased OH. Tyrosine is a nonessential amino acid that is the major precursor to NE. Reduced levels of tyrosine have been shown after administration of l‐dopa. This study was a single‐center, randomized, double‐blind, placebo‐controlled trial to test the effects of supplementing l‐tyrosine on BP, plasma tyrosine, NE levels, and autonomic responses to exercise in PD. Thirty‐six subjects with PD receiving l‐dopa medication that suffer from OH participated. Random assignment was to a placebo group or l‐tyrosine 1,000 mg (500 mg of 2× daily) group for 7 days. OH testing and exercise testing was performed pre‐ and postsupplementation. There was no effect of tyrosine on BP after OH testing postsupplementation (tyrosine, n = 17; placebo, n = 19). There was an increase in plasma tyrosine in the tyrosine group (P > 0.05). There were no significant changes in any of the secondary outcome measures. l‐tyrosine at 1,000 mg (500 mg/2× day) for 7 days is safe and well tolerated in PD. Our results were inconclusive as to whether an increase in plasma tyrosine has an effect on OH in subjects with PD. An increase in plasma tyrosine had no effect on BP or autonomic responses in subjects with PD during acute exercise stress. (Trial registration: ClinicalTrials.gov.; identifier: NCT01676103)

Gait parameter control timing with dynamic manual contact or visual cues

We investigated the timing of gait parameter changes (stride length, peak toe velocity, and double-, single-support, and complete step duration) to control gait speed. Eleven healthy participants adjusted their gait speed on a treadmill to maintain a constant distance between them and a fore-aft oscillating cue (a place on a conveyor belt surface). The experimental design balanced conditions of cue modality (vision: eyes-open; manual contact: eyes-closed while touching the cue); treadmill speed (0.2, 0.4, 0.85, and 1.3 m/s); and cue motion (none, ±10 cm at 0.09, 0.11, and 0.18 Hz). Correlation analyses revealed a number of temporal relationships between gait parameters and cue speed. The results suggest that neural control ranged from feedforward to feedback. Specifically, step length preceded cue velocity during double-support duration suggesting anticipatory control. Peak toe velocity nearly coincided with its most-correlated cue velocity during single-support duration. The toe-off concluding step and double-support durations followed their most-correlated cue velocity, suggesting feedback control. Cue-tracking accuracy and cue velocity correlations with timing parameters were higher with the manual contact cue than visual cue. The cue/gait timing relationships generalized across cue modalities, albeit with greater delays of step-cycle events relative to manual contact cue velocity. We conclude that individual kinematic parameters of gait are controlled to achieve a desired velocity at different specific times during the gait cycle. The overall timing pattern of instantaneous cue velocities associated with different gait parameters is conserved across cues that afford different performance accuracies. This timing pattern may be temporally shifted to optimize control. Different cue/gait parameter latencies in our nonadaptation paradigm provide general-case evidence of the independent control of gait parameters previously demonstrated in gait adaptation paradigms.