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Title:The role of feedback and age-related differences in force production accuracy, variability, and shape across oral and manual effectors
Author(s):Ofori, Edward
Director of Research:Carlton, Les G.
Doctoral Committee Chair(s):Carlton, Les G.
Doctoral Committee Member(s):Sosnoff, Jacob J.; Loucks, Torrey M.J.; Zhu, Weimo; Murphy, Michael R.
Department / Program:Kinesiology & Community Health
Discipline:Kinesiology
Degree Granting Institution:University of Illinois at Urbana-Champaign
Degree:Ph.D.
Genre:Dissertation
Subject(s):Motor Control
Force Variability
Sensory Feedback
Aging
Abstract:The purpose of this dissertation was two-fold: 1) to determine the role of feedback in force production accuracy, variability, and shape and 2) to determine whether sensory feedback mediates age-related difference in force production accuracy, variability, and shape across effectors. The premise of these experiments was that the type of sensory feedback would influence discrete force production. In order to test this premise, two experiments were conducted. Experiment 1 involved 72 college-aged participants (mean=23.4 years old, SD=4.22) randomly assigned to one of four groups (a no feedback, grayscale, auditory, and visual feedback condition). Sensory feedback was equated by determining one’s average ability to discriminate different feedback modalities (i.e., auditory, grayscale, and visual feedback). Participants produced isometric force via elbow flexion to match a Gaussian template waveform with a peak force of 90 N and a time to peak force at 200 ms. Each participant completed 90 trials. Force production accuracy and shape was indexed for each trial. Force production accuracy was assessed with absolute error (AE) of peak force, time to peak force, and mean squared error. Absolute error of peak force was computed by taking the absolute value of the actual peak force minus the criterion peak force (i.e., 90 N). Absolute error of time to peak force was computed by taking the absolute value of the actual time to peak force minus the criterion time to peak force (i.e., 200 ms). Mean squared error (MSE) was computed by taking the summation of squares of the criterion trajectory minus actual trajectory then dividing this value by the number of points. Force variability was assessed using the standard deviation (SD) and coefficient of variation (CV) of impulse, peak force, time to peak force, and peak rate of force production. Force pulse shape was assessed with mean skewness, mean kurtosis and the mean, standard deviation (SD), and coefficient of variation (CV) of the inflection point of a logistic fit. Inflection point is the midpoint of the logistic curve. Results from Experiment 1 indicated feedback influenced AE of peak force, MSE, CV of peak force and time to peak force, skewness, kurtosis, inflection point, and curve length. The type of feedback was found to influence temporal measures. The force shape analysis revealed auditory, grayscale and visual feedback resulted in more symmetric force pulse shapes than without feedback. In Experiment 2, 12 young (mean=23.5±3.3 years) and 11 old (mean=73.2±6 years) produced isometric force with auditory or visual feedback via elbow flexion or jaw elevation to a Gaussian waveform template. The Gaussian waveform template had a peak of 50 N and a time to peak of 200 ms. Each participant performed 70 trials and the last 40 trials were used for analysis. The same dependent variables used in Experiment 1 were used in Experiment 2. Results indicated effector x feedback interactions on force production accuracy and SD of impulse. Results indicated age x feedback interactions on CV of peak force, age x effector interaction on skewness, and age x effector x feedback interaction on SD of peak rate. The force shape analysis revealed the jaw produces more non-symmetric impulses than the elbow. Older adults had difficulty producing a symmetric force-pulse in the elbow in comparison to younger adults. Taken together, results from Experiment 2 indicate that feedback is fundamental to the motor command and age-related differences in force variability depend on the type of feedback and effector.
Issue Date:2013-05-24
URI:http://hdl.handle.net/2142/44499
Rights Information:Copyright 2013 Edward Ofori
Date Available in IDEALS:2013-05-24
2015-05-24
Date Deposited:2013-05


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