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Force Variability during Dexterous Manipulation in Individuals with Mild to Moderate Parkinson's Disease.

Ko NH, Laine CM, Fisher BE, Valero-Cuevas FJ - Front Aging Neurosci (2015)

Bottom Line: The more-affected hand exhibited significantly lower F and lower F_LF than those in the less-affected hand.The more-affected hand showed significant negative correlations between F_LF and the Unified Parkinson's Disease Rating Scale motor scores for both total and hand-only, suggesting that greater force variability in the voluntary range was associated with less clinical motor impairment.We conclude the nature of force variability in the voluntary range during this dynamic and dexterous task may be a biomarker of greater motor capability/flexibility/adaptability in PD.

View Article: PubMed Central - PubMed

Affiliation: Brain-Body Dynamics Laboratory, Department of Biomechanical Engineering, Division of Biokinesiology and Physical Therapy, University of Southern California Los Angeles , Los Angeles, CA , USA ; Neuroplasticity and Neuroimaging Laboratory, Division of Biokinesiology and Physical Therapy, University of Southern California Los Angeles , Los Angeles, CA , USA.

ABSTRACT
Parkinson's disease (PD) is a progressive neurodegenerative disease affecting about 1-2% of the population over the age of 65. Individuals with PD experience gradual deterioration of dexterous manipulation for activities of daily living; however, current clinical evaluations are mostly subjective and do not quantify changes in dynamic control of fingertip force that is critical for manual dexterity. Thus, there is a need to develop clinical measures to quantify those changes with aging and disease progression. We investigated the dynamic control of fingertip forces in both hands of 20 individuals with PD (69.0 ± 7.4 years) using the Strength-Dexterity test. The test requires low forces (<3 N) to compress a compliant and slender spring prone to buckling. A maximal level of sustained compression is informative of the greatest instability the person can control, and thus is indicative of the integrity of the neuromuscular system for dexterous manipulation. Miniature sensors recorded fingertip force (F) during maximal sustained compressions. The force variability during sustained compression was quantified in two frequency bands: low (<4 Hz, F_LF) and high (4-12 Hz, F_HF). F_LF characterizes variability in voluntary fluctuations, while F_HF characterizes variability in involuntary fluctuations including tremor. The more-affected hand exhibited significantly lower F and lower F_LF than those in the less-affected hand. The more-affected hand showed significant negative correlations between F_LF and the Unified Parkinson's Disease Rating Scale motor scores for both total and hand-only, suggesting that greater force variability in the voluntary range was associated with less clinical motor impairment. We conclude the nature of force variability in the voluntary range during this dynamic and dexterous task may be a biomarker of greater motor capability/flexibility/adaptability in PD. This approach may provide a more quantitative clinical assessment of changes of sensorimotor control in individuals with PD.

No MeSH data available.


Related in: MedlinePlus

The Strength–Dexterity test and raw force data examples of three trials from the more-affected hand of two PD participants with different UPDRS hand motor scores. (A) Participants compress a slender spring prone to buckling as much as they can to its solid length, sustain the compression for 5 s, and release the compression. The force data were recorded from miniature load cells at the tips of spring. (B)Orange lines: the top three force traces during a hold phase from PD2 with UPDRS (more-affected) hand motor score, 7. Purple lines: the top three force traces during a hold phase from PD12 with UPDRS (more-affected) hand motor score, 15.
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Figure 1: The Strength–Dexterity test and raw force data examples of three trials from the more-affected hand of two PD participants with different UPDRS hand motor scores. (A) Participants compress a slender spring prone to buckling as much as they can to its solid length, sustain the compression for 5 s, and release the compression. The force data were recorded from miniature load cells at the tips of spring. (B)Orange lines: the top three force traces during a hold phase from PD2 with UPDRS (more-affected) hand motor score, 7. Purple lines: the top three force traces during a hold phase from PD12 with UPDRS (more-affected) hand motor score, 15.

Mentions: The Strength–Dexterity test was used to measure dynamic sensorimotor control of fingertip force from the thumb and index finger. The test required compressing a slender spring with the thumb and index fingers without allowing it to buckle (Figure 1) (Valero-Cuevas et al., 2003; Dayanidhi et al., 2013). The specifications of the custom spring (Century Springs Corp., Los Angeles, CA, USA) were the following: (1) free length = 3.96 cm, (2) solid length = 0.69 cm, (3) force range = 0–2.84 N, (4) stiffness = 0.86 N/cm, and (5) the diameter of end caps were 0.95 cm (Figure 1) (Dayanidhi et al., 2013). The spring was designed to be impossible to compress fully, and thus the maximal compression participants could achieve was less than 3N (Dayanidhi et al., 2013). As the spring is compressed, it becomes increasingly unstable in a non-linear way (Venkadesan et al., 2007), making it unpredictable and also making the particular dynamics of each sustained compression unique. The maximal level of compression that is sustained reflects the integrity of the sensorimotor system, which controls fingertip force and direction during object manipulation (Dayanidhi et al., 2013; Dayanidhi and Valero-Cuevas, 2014; Lawrence et al., 2014).


Force Variability during Dexterous Manipulation in Individuals with Mild to Moderate Parkinson's Disease.

Ko NH, Laine CM, Fisher BE, Valero-Cuevas FJ - Front Aging Neurosci (2015)

The Strength–Dexterity test and raw force data examples of three trials from the more-affected hand of two PD participants with different UPDRS hand motor scores. (A) Participants compress a slender spring prone to buckling as much as they can to its solid length, sustain the compression for 5 s, and release the compression. The force data were recorded from miniature load cells at the tips of spring. (B)Orange lines: the top three force traces during a hold phase from PD2 with UPDRS (more-affected) hand motor score, 7. Purple lines: the top three force traces during a hold phase from PD12 with UPDRS (more-affected) hand motor score, 15.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4530309&req=5

Figure 1: The Strength–Dexterity test and raw force data examples of three trials from the more-affected hand of two PD participants with different UPDRS hand motor scores. (A) Participants compress a slender spring prone to buckling as much as they can to its solid length, sustain the compression for 5 s, and release the compression. The force data were recorded from miniature load cells at the tips of spring. (B)Orange lines: the top three force traces during a hold phase from PD2 with UPDRS (more-affected) hand motor score, 7. Purple lines: the top three force traces during a hold phase from PD12 with UPDRS (more-affected) hand motor score, 15.
Mentions: The Strength–Dexterity test was used to measure dynamic sensorimotor control of fingertip force from the thumb and index finger. The test required compressing a slender spring with the thumb and index fingers without allowing it to buckle (Figure 1) (Valero-Cuevas et al., 2003; Dayanidhi et al., 2013). The specifications of the custom spring (Century Springs Corp., Los Angeles, CA, USA) were the following: (1) free length = 3.96 cm, (2) solid length = 0.69 cm, (3) force range = 0–2.84 N, (4) stiffness = 0.86 N/cm, and (5) the diameter of end caps were 0.95 cm (Figure 1) (Dayanidhi et al., 2013). The spring was designed to be impossible to compress fully, and thus the maximal compression participants could achieve was less than 3N (Dayanidhi et al., 2013). As the spring is compressed, it becomes increasingly unstable in a non-linear way (Venkadesan et al., 2007), making it unpredictable and also making the particular dynamics of each sustained compression unique. The maximal level of compression that is sustained reflects the integrity of the sensorimotor system, which controls fingertip force and direction during object manipulation (Dayanidhi et al., 2013; Dayanidhi and Valero-Cuevas, 2014; Lawrence et al., 2014).

Bottom Line: The more-affected hand exhibited significantly lower F and lower F_LF than those in the less-affected hand.The more-affected hand showed significant negative correlations between F_LF and the Unified Parkinson's Disease Rating Scale motor scores for both total and hand-only, suggesting that greater force variability in the voluntary range was associated with less clinical motor impairment.We conclude the nature of force variability in the voluntary range during this dynamic and dexterous task may be a biomarker of greater motor capability/flexibility/adaptability in PD.

View Article: PubMed Central - PubMed

Affiliation: Brain-Body Dynamics Laboratory, Department of Biomechanical Engineering, Division of Biokinesiology and Physical Therapy, University of Southern California Los Angeles , Los Angeles, CA , USA ; Neuroplasticity and Neuroimaging Laboratory, Division of Biokinesiology and Physical Therapy, University of Southern California Los Angeles , Los Angeles, CA , USA.

ABSTRACT
Parkinson's disease (PD) is a progressive neurodegenerative disease affecting about 1-2% of the population over the age of 65. Individuals with PD experience gradual deterioration of dexterous manipulation for activities of daily living; however, current clinical evaluations are mostly subjective and do not quantify changes in dynamic control of fingertip force that is critical for manual dexterity. Thus, there is a need to develop clinical measures to quantify those changes with aging and disease progression. We investigated the dynamic control of fingertip forces in both hands of 20 individuals with PD (69.0 ± 7.4 years) using the Strength-Dexterity test. The test requires low forces (<3 N) to compress a compliant and slender spring prone to buckling. A maximal level of sustained compression is informative of the greatest instability the person can control, and thus is indicative of the integrity of the neuromuscular system for dexterous manipulation. Miniature sensors recorded fingertip force (F) during maximal sustained compressions. The force variability during sustained compression was quantified in two frequency bands: low (<4 Hz, F_LF) and high (4-12 Hz, F_HF). F_LF characterizes variability in voluntary fluctuations, while F_HF characterizes variability in involuntary fluctuations including tremor. The more-affected hand exhibited significantly lower F and lower F_LF than those in the less-affected hand. The more-affected hand showed significant negative correlations between F_LF and the Unified Parkinson's Disease Rating Scale motor scores for both total and hand-only, suggesting that greater force variability in the voluntary range was associated with less clinical motor impairment. We conclude the nature of force variability in the voluntary range during this dynamic and dexterous task may be a biomarker of greater motor capability/flexibility/adaptability in PD. This approach may provide a more quantitative clinical assessment of changes of sensorimotor control in individuals with PD.

No MeSH data available.


Related in: MedlinePlus