Papers by Charles Robinson
Biomedical Engineering Online, Feb 21, 2005
Background: Aging has been shown to slow reflexes and increase reaction time to varied stimuli. H... more Background: Aging has been shown to slow reflexes and increase reaction time to varied stimuli. However, the effect of Type II diabetes on these same reaction times has not been reported. Diabetes affects peripheral nerves in the somatosensory and auditory system, slows psychomotor responses, and has cognitive effects on those individuals without proper metabolic control, all of which may affect reaction times. The additional slowing of reaction times may affect every-day tasks such as balance, increasing the probability of a slip or fall. Reaction times to a plantar touch, a pure tone auditory stimulus, and rightward wholebody lateral movement of 4 mm at 100 mm/s 2 on a platform upon which a subject stood, were measured in 37 adults over 50 yrs old. Thirteen (mean age = 60.6 ± 6.5 years) had a clinical diagnosis of type II diabetes and 24 (mean age = 59.4 ± 8.0 years) did not. Group averages were compared to averages obtained from nine healthy younger adult group (mean age = 22.7 ± 1.2 years). Results: Average reaction times for plantar touch were significantly longer in diabetic adults than the other two groups, while auditory reaction times were not significantly different among groups. Whole body reaction times were significantly different among all three groups with diabetic adults having the longest reaction times, followed by age-matched adults, and then younger adults. Whole body reaction time has been shown to be a sensitive indicator of differences between young adults, healthy mature adults, and mature diabetic adults. Additionally, the increased reaction time seen in this modality for subjects with diabetes may be one cause of increased slips and falls in this group.
Conference proceedings, Aug 1, 2007
This paper presents an innovative technique to study postural control. Our translating platform, ... more This paper presents an innovative technique to study postural control. Our translating platform, the Sliding Linear Investigative Platform For Analyzing Lower Limb Stability and Simultaneous Tracking, EMG and Pressure mapping (SLIP-FALLS-STEPm), makes precise, vibration movements under controlled conditions. We look at the psychophysical thresholds to the perception of a sinusoidally induced sway. In the Sine Lock experiments described, an induced sinusoidal perturbation locks the subject's natural sway pattern at the frequency of the perturbation. The input / output system is treated as an Amplitude Shift Key (ASK) modulated signal modulating a carrier frequency (at or about a subject's natural sway frequency). The Position signal (input) and the Anterior-Posterior Center of Pressure (APCOP) signal (output) or the ankle angle are demodulated by mixing them with the pure sine wave carrier at the frequency of underlying oscillation and then low-pass filtering it to detect the amplitude envelope. These detected envelopes elucidate that the square pulse increase in the position sine wave amplitude yields a triangular increase in APCOP demodulated signal.
IEEE Transactions on Rehabilitation Engineering, Mar 1, 1993
Conference proceedings, Aug 1, 2007
This study modeled ankle angle changes during small forward perturbations of a standing platform.... more This study modeled ankle angle changes during small forward perturbations of a standing platform. A two-dimensional biomechanical inverted pendulum model was developed that uses sway frequencies derived from quiet standing observations on a subject's Anterior Posterior Center of Pressure (APCoP) to track ankle angle changes during a 16 mm anterior displacement perturbation of a platform on which a subject stood. This model used the total torque generated at the ankle joint as one of the inputs, and calculated it assuming a PID controller. This feedback system generated a simulated ankle torque based on the angular position of the center of mass (CoM) with respect to vertical line passing through the ankle joint. This study also assumed that the internal components of the net torque were only a controller torque and a sway-pattern-generating torque. The final inputs to the model were the platform acceleration and anthropometric terms. This model of postural sway dynamics predicted sway angle and the trajectory of the center of mass. Knowing these relationships can advance an understanding of the ankle strategy employed in balance control.
Zenodo (CERN European Organization for Nuclear Research), Nov 23, 2020
A Sliding Linear Investigative Platform for Assessing Lower Limb Stability (SLIP-FALLS) was emplo... more A Sliding Linear Investigative Platform for Assessing Lower Limb Stability (SLIP-FALLS) was employed to study postural control biomechanical reaction to external perturbations in a short ≤16mm postural perturbation. Head acceleration were evaluated while blindfolded subjects stood on a platform that was given a short anterior perturbation presented in one of 2 sequential 4s intervals (2-Alternative-Forced-Choice) for a set of 30 trials. Anterior-Posterior head acceleration (Head Accl AP) were investigated among the movement and non-movement intervals for the healthy adults. A strong ringing signal was observed in Head Accl AP movement interval that was absent in non-movement interval. A positive power law trading relationship was found between Head Accl AP gain and move length standing blindfolded subjects. This could explain the observed negative power law relationship between translation length and peak acceleration threshold in previous psychophysical detection threshold studies.
IEEE Transactions on Neural Systems and Rehabilitation Engineering, Jun 1, 2010
A phase-locked loop (PLL) model of the response of the postural control system to periodic platfo... more A phase-locked loop (PLL) model of the response of the postural control system to periodic platform motion is proposed. The PLL model is based on the hypothesis that quiet standing (QS) postural sway can be characterized as a weak sinusoidal oscillation corrupted with noise. Because the signal to noise ratio is quite low, the characteristics of the QS oscillator are not measured directly from the QS sway, instead they are inferred from the response of the oscillator to periodic motion of the platform. When a sinusoidal stimulus is applied, the QS oscillator changes speed as needed until its frequency matches that of the platform, thus achieving phase lock in a manner consistent with a PLL control mechanism. The PLL model is highly effective in representing the frequency, amplitude, and phase shift of the sinusoidal component of the phase-locked response over a range of platform frequencies and amplitudes. Qualitative analysis of the PLL control mechanism indicates that there is a finite range of frequencies over which phase lock is possible, and that the size of this capture range decreases with decreasing platform amplitude. The PLL model was tested experimentally using nine healthy subjects and the results reveal good agreement with a mean phase shift error of 13.7° and a mean amplitude error of 0.8 mm.
Limit of Liability/Disclaimer of Warranty: While the publisher and author have used their best ef... more Limit of Liability/Disclaimer of Warranty: While the publisher and author have used their best efforts in preparing this book, they make no representations or warranties with respect to the accuracy or completeness of the contents of this book and specifically disclaim any implied warranties of merchantability or fitness for a particular purpose. No warranty may be created or extended by sales representatives or written sales materials. The advice and strategies contained herein may not be suitable for your situation. You should consult with a professional where appropriate. Neither the publisher nor author shall be liable for any loss of profit or any other commercial damages, including but not limited to special, incidental, consequential, or other damages. For general information on our other products and services or for technical support, please contact our Customer Care Department within the United States at (800) 762-2974, outside the United States at (317) 572-3993 or fax (317) 572-4002.
1st Annual International IEEE-EMBS Special Topic Conference on Microtechnologies in Medicine and Biology. Proceedings (Cat. No.00EX451), 2000
A comprehensive definition of Rehabilitative Biomicrosystems is presented from scientific, techno... more A comprehensive definition of Rehabilitative Biomicrosystems is presented from scientific, technological, clinical and end-user perspectives. Rehabilitative Biomicrosystems are those implanted or surface-mounted, biocompatible micro-or nano-devices, techniques or concepts that 1) provide enhanced functional capability to individuals with disability, or 2) enable scientists and engineers to measure how various systems of the body work in an intact situation, and how these systems miss-act (or fail to) when impaired. Design goals, achievable through rigorous in vitro, in vivo and clinical research, advance the understanding of, and produce Rehabilitative Biomicrosystems that are reliable, robust, safe, functionally transparent and cosmetically acceptable. Educational programs at Louisiana Tech University are described that integrate Rehabilitation, Neural, and Biomicrosystems Engineering to form the field of Rehabilitative Biomicrosystems.
Many studies of human postural control use data from video-captured discrete marker locations to ... more Many studies of human postural control use data from video-captured discrete marker locations to analyze via complex inverse kinematic reconstruction the postural responses to a perturbation. We propose here that Principal Component Analysis of this marker data provides a simpler way to get an overview of postural perturbation responses. Using short (1, 4, and 16 mm) anterior platform step translations that are on the order of a young adult's normal sway path length, we find that the low order eigenmodes (which we call eigenposes) of the time-series marker data correspond dominantly to a simple anterior-posterior pendular motion about the ankle, and secondarily (and with less energy) to hip flexion and extension. A third much weaker mode is occasionally seen that is represented by knee flexion.
Biomedical Engineering Online, Oct 8, 2010
Background: A fundamental unsolved problem in psychophysical detection experiments is in discrimi... more Background: A fundamental unsolved problem in psychophysical detection experiments is in discriminating guesses from the correct responses. This paper proposes a coherent solution to this problem by presenting a novel classification method that compares biomechanical and psychological responses. Methods: Subjects (13) stood on a platform that was translated anteriorly 16 mm to find psychophysical detection thresholds through a Adaptive 2-Alternative-Forced-Choice (2AFC) task repeated over 30 separate sequential trials. Anterior-posterior center-of-pressure (APCoP) changes (i.e., the biomechanical response R B) were analyzed to determine whether sufficient biomechanical information was available to support a subject's psychophysical selection (R Ψ) of interval 1 or 2 as the stimulus interval. A time-series-bitmap approach was used to identify anomalies in interval 1 (a 1) and interval 2 (a 2) that were present in the resultant APCoP signal. If a 1 > a 2 then R B = Interval 1. If a 1 < a 2 , then R B = Interval 2. If a 2-a 1 < 0.1, R B was set to 0 (no significant difference present in the anomaly scores of interval 1 and 2). Results: By considering both biomechanical (R B) and psychophysical (R Ψ) responses, each trial run could be classified as a: 1) HIT (and True Negative), if R B and R Ψ both matched the stimulus interval (SI); 2) MISS, if R B matched SI but the subject's reported response did not; 3) PSUEDO HIT, if the subject signalled the correct SI, but R B was linked to the non-SI; 4) FALSE POSITIVE, if R B = R Ψ , and both associated to non-SI; and 5) GUESS, if R B = 0, if insufficient APCoP differences existed to distinguish SI. Ensemble averaging the data for each of the above categories amplified the anomalous behavior of the APCoP response. Conclusions: The major contributions of this novel classification scheme were to define and verify by logistic models a 'GUESS' category in these psychophysical threshold detection experiments, and to add an additional descriptor, "PSEUDO HIT". This improved classification methodology potentially could be applied to psychophysical detection experiments of other sensory modalities.
This chapter contains sections titled: A New Challenge: Space-Variant Unsupervised Classification... more This chapter contains sections titled: A New Challenge: Space-Variant Unsupervised Classifications Power of Pairs: Vector versus Scalar Data Generalization of Shannon's Entropy Information Theory to Open Systems Benchmarks of Space-Variant Unsupervised Classification Multispectral Medical Imaging Multispectral Remote Sensing Biological Relevance Conclusion This chapter contains sections titled: Acknowledgments References
Journal of Neurophysiology, 1983
Thermal stimulation A sequence of heat stimuli was delivered to the arm or hand of humans during ... more Thermal stimulation A sequence of heat stimuli was delivered to the arm or hand of humans during psychophysical studies. The same sequence was used in electrophysiological experiments in monkeys. Each stimulus was a nearly rectangular temperature pulse
Changes in micturition volume thresholds in conscious dogs following spinal opiate administration
Journal of the Autonomic Nervous System, 1986
Micturition difficulties appear as an often-reported side effect of the clinical use of opiates f... more Micturition difficulties appear as an often-reported side effect of the clinical use of opiates for spinal analgesia. Only a few experimental studies have focused specifically on this problem, especially in an unanesthetized animal model where chronic pharmacological studies can be carried out. The changes in micturition volume thresholds that occurred following spinal intrathecal injections of 1 mg of morphine sulphate were measured in 11 conscious dogs and compared with threshold changes produced in these same dogs by i.v. injections of various doses of morphine sulphate and by intrathecal and i.v. injections of naloxone HCl. In all cases, intrathecal or systemic morphine at doses of 1.0 mg or greater significantly (P less than 0.05) increased the bladder volume at which micturition took place. Naloxone, injected intrathecally to reverse the effects of intrathecal morphine, significantly reduced the micturition volume threshold, in most cases to below control volumes. A 400 microgram dose of naloxone, injected intrathecally without prior injection of morphine, significantly lowered the volume threshold in 9 dogs, even though two of these dogs had elevated thresholds following naloxone injection. The reduction in volume thresholds by i.v. naloxone not preceded by morphine injection was not statistically significant over that of control. These results are interpreted in light of recent findings concerning localization of endogenous opiate receptors within the micturition reflex pathway.
Variations in Anterior-Posterior CoP Patterns in Elderly Adults Between Psychophysically Detected and Non-Detected Short Horizontal Perturbations
2005 IEEE Engineering in Medicine and Biology 27th Annual Conference, 2005
Using an ultra-low-vibration Sliding Linear Investigative Platform for Assessing Lower Limb Stabi... more Using an ultra-low-vibration Sliding Linear Investigative Platform for Assessing Lower Limb Stability (SLIP-FALLS), postural responses were evaluated while subjects stood on a platform that was given a short anterior perturbation presented in one of 2 sequential test intervals for a set of 30 trials. An adaptive 2-Alternative-Forced-Choice protocol required the subject to detect platform movement. Anterior-Posterior Centers-of-Pressure (AP CoP) were compared among the detected and non-detected trials for the Healthy Elderly Adults (HEA) and Diabetic Peripheral Neuropathy (DPN) elderly adults. Results indicate that there is a significant difference between the CoP patterns for a detected and non-detected trial. Also, the range of sway is found to be higher in the case of DPN elderly adults when compared to HEA. However, the AP CoP pattern for detected trials in both HEA and DPN were the same.
Speed-torque calibration of the MAGTURBO and wheelchair aerobic fitness trainer
Images of the Twenty-First Century. Proceedings of the Annual International Engineering in Medicine and Biology Society
Calibration experiments were performed to establish regression equations that can be used to calc... more Calibration experiments were performed to establish regression equations that can be used to calculate power outputs for a commercially available magnetic eddy breaking device (Minoura MAGTURBO) and for the wheelchair aerobic fitness trainer (WAFT) which incorporates this turbo in its design. For both the turbo and the WAFT, there is a significant quadratic relationship between power and rotational velocity for each resistance setting. Of the seven turbo settings, four strata are seen in the relationship between speed and power. The WAFT with modified MAGTURBO offers independent manipulation of speed and resistance for each wheel. This flexibility makes the WAFT appropriate for graded exercise stress testing and conditioning of persons with lower limb disabilities who have widely varied exercise capacities
Variation of human knee stiffness with angular perturbation intensity
Proceedings of 17th International Conference of the Engineering in Medicine and Biology Society, 1995
ABSTRACT
Detecting thresholds and interactions among displacement, acceleration, and velocity, for young adults on a horizontally translated platform
Annual International Conference of the IEEE Engineering in Medicine and Biology Society, 1998
We are interested in determining the lower limits of detectability of the control system for stan... more We are interested in determining the lower limits of detectability of the control system for standing posture and balance. Our Sliding Linear Investigative Platform For Analyzing Lower Limb Stability (SLIP-FALLS) allows us to study the psychophysical thresholds for movement detection in standing without the interference of vibratory cues. Three neurologically intact young adults were recruited to determine their initial detection
Introduction to Functional Electrical Stimulation, Neuroprosthetics, and Rehabilitation Engineering
IEEE Transactions on Rehabilitation Engineering, 1996
Medical & Biological Engineering & Computing, 1994
FUNCTIONAL ELECTRICAL stimulation (FES) has been proposed as a technique for restoring control of... more FUNCTIONAL ELECTRICAL stimulation (FES) has been proposed as a technique for restoring control of paralysed joints; yet, little is known about the interaction of FES with residual neural reflex loops. The peripheral neural loops are typically left intact after many types of spinal cord injury and the attendant loss of joint control. In fact, reflexes often become hyperexcitable as a result of factors such as the absence of descending supraspinal inhibition (PENN and Cogcos, 1990). Functional movement about a joint can be
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Papers by Charles Robinson