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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

Correlations between magnitudes of voluntary force fluctuations and UPDRS total and hand-only motor scores for both hands. (A) Greater voluntary force fluctuations correlated with less total motor impairment in the more-affected hand. (B) No significant correlation between voluntary force fluctuations and UPDRS total motor score in the less-affected hand. (C) Greater voluntary force fluctuations associated with less hand-related motor impairment in the more-affected hand. (D) No significant correlation between voluntary force fluctuations and UPDRS hand-only motor score in the less-affected hand. (*p < 0.05, Statistical significance of each Spearman’s coefficient was determined by a 10,000 iteration permutation test. The linear fit was only for visual representations.)
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Figure 2: Correlations between magnitudes of voluntary force fluctuations and UPDRS total and hand-only motor scores for both hands. (A) Greater voluntary force fluctuations correlated with less total motor impairment in the more-affected hand. (B) No significant correlation between voluntary force fluctuations and UPDRS total motor score in the less-affected hand. (C) Greater voluntary force fluctuations associated with less hand-related motor impairment in the more-affected hand. (D) No significant correlation between voluntary force fluctuations and UPDRS hand-only motor score in the less-affected hand. (*p < 0.05, Statistical significance of each Spearman’s coefficient was determined by a 10,000 iteration permutation test. The linear fit was only for visual representations.)

Mentions: For the UPDRS hand-only motor score, we considered a set of seven hand-related items from the full assessment list: rigidity, finger tapping, hand movements, pronation/supination, postural tremor, kinetic tremor, and resting tremor amplitude. The UPDRS hand-only motor score for the more-affected hands ranged from 4 to 17, and from 0 to 12 for the less-affected hand. Once again, only F_LF (ρ = −0.52, p = 0.016) showed a significant correlation in the more-affected hand (Figure 2). That is, greater variability of voluntary force fluctuations was associated with less motor impairment measured by UPDRS total and hand-only motor scores.


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)

Correlations between magnitudes of voluntary force fluctuations and UPDRS total and hand-only motor scores for both hands. (A) Greater voluntary force fluctuations correlated with less total motor impairment in the more-affected hand. (B) No significant correlation between voluntary force fluctuations and UPDRS total motor score in the less-affected hand. (C) Greater voluntary force fluctuations associated with less hand-related motor impairment in the more-affected hand. (D) No significant correlation between voluntary force fluctuations and UPDRS hand-only motor score in the less-affected hand. (*p < 0.05, Statistical significance of each Spearman’s coefficient was determined by a 10,000 iteration permutation test. The linear fit was only for visual representations.)
© Copyright Policy
Related In: Results  -  Collection

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

Figure 2: Correlations between magnitudes of voluntary force fluctuations and UPDRS total and hand-only motor scores for both hands. (A) Greater voluntary force fluctuations correlated with less total motor impairment in the more-affected hand. (B) No significant correlation between voluntary force fluctuations and UPDRS total motor score in the less-affected hand. (C) Greater voluntary force fluctuations associated with less hand-related motor impairment in the more-affected hand. (D) No significant correlation between voluntary force fluctuations and UPDRS hand-only motor score in the less-affected hand. (*p < 0.05, Statistical significance of each Spearman’s coefficient was determined by a 10,000 iteration permutation test. The linear fit was only for visual representations.)
Mentions: For the UPDRS hand-only motor score, we considered a set of seven hand-related items from the full assessment list: rigidity, finger tapping, hand movements, pronation/supination, postural tremor, kinetic tremor, and resting tremor amplitude. The UPDRS hand-only motor score for the more-affected hands ranged from 4 to 17, and from 0 to 12 for the less-affected hand. Once again, only F_LF (ρ = −0.52, p = 0.016) showed a significant correlation in the more-affected hand (Figure 2). That is, greater variability of voluntary force fluctuations was associated with less motor impairment measured by UPDRS total and hand-only motor scores.

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