To quantify rapid alternating movements (RAMs) we used a simple prototype developed in our labora... more To quantify rapid alternating movements (RAMs) we used a simple prototype developed in our laboratory that requires the subject to rotate two handheld foam spheres connected to optical encoders via flexible rods. Ninety-six participants, including 30 control subjects, 36 Cree subjects exposed to methylmercury, 21 subjects with Parkinson's disease, 6 subjects with cerebellar deficits, and 3 subjects with essential tremor, were involved in the study (though data for 5 were later removed). Twelve characteristics were developed and calculated from the raw data. Conditions examined included two hands at natural cadence (NC2), right and left hands separately at fast cadence (FCl), and both hands at fast cadence (FC2). Two ratios (FC2/NC2) and (FC2/FC1) combining these conditions were also examined. Test-retest reliability was > 0.80 for most characteristics but was < 0.70 for some characteristics, especially in the conditions executed at normal cadence. Correlations between characteristics and numbers of outliers with respect to the control group distribution were used to reduce the set of characteristics from 12 to 7 (i.e., duration, range, maximum slope, similarity in shape, smoothness, sharpness, and coherence). ANOVAs on the three largest groups generated significant results for most characteristics in the three conditions and the two ratios for Cree subjects and subjects with Parkinson's disease. ANOVAs on 3 age-matched groups (n ؍ 6) suggest that methylmercury affects the performance of the Cree subjects with the higher exposure, especially in terms of smoothness, sharpness, and coherence. These preliminary results suggest that this test is sufficiently specific and sensitive to characterize the 1 The study received approval from the ethics committee of the University of Que´bec at Montre´al and was conducted in agreement with the procedures proposed. Accordingly, all subjects gave informed consent. performance of different groups of subjects. Ratios tend to improve discrimination for Cree subjects in a few characteristics but not for patients with Parkinson's disease.
Quantification of movement pathologies is an important challenge of the clinical and research lab... more Quantification of movement pathologies is an important challenge of the clinical and research laboratories today. Basically, two problems must be addressed. The first one is to find the appropriate technology; the second is to develop adequate measures from the raw data which will best discriminate between health and pathology. In this paper, we propose a simple method to record and analyse tremor and other microdisplacements of the upper extremities based on the recording of position by laser analog sensors. Any microcomputer equipped to perform analog-digital conversion is compatible for use with this system. The performance of the laser system is examined and compared with the performance of accelerometers. Finally, data recorded with a laser analog sensor from a patient with Parkinson&amp;amp;#39;s disease and a control subject are presented. This new laser-based quantitative method may prove to be an important tool in early and differential diagnosis of neurodegenerative diseases of the central nervous system.
ABSTRACT Parkinson’s disease is a complex disorder for which there is no known cure. Nor do we un... more ABSTRACT Parkinson’s disease is a complex disorder for which there is no known cure. Nor do we understand fully the origin of one of the disease’s cardinal symptoms: tremor. A non-traditional approach to research in Parkinson’s disease and in Parkinsonian tremor involves the application of mathematical models. The purpose of this article is to review briefly the contributions of mathematical models to the study of Parkinsonian tremor. There is little evidence that modelling attempts have built on previous ones but there has been a trend to move the focus of modelling from the periphery to the brain, and from abstracted to more physiologically detailed views. We hope that this review will encourage more mathematical modelling in the study of Parkinson’s disease and Parkinsonian tremor.
International Archives of Occupational and Environmental Health, Feb 1, 2004
Objectives: To examine the effect of chronic exposure to methylmercury on eye movements (pursuit,... more Objectives: To examine the effect of chronic exposure to methylmercury on eye movements (pursuit, fixation and dynamic saccades) in Cree subjects from Northern Quebec. Methods: Eye movements were recorded in a group of Cree subjects (n=36) exposed chronically to methylmercury, a group of patients with ParkinsonÕs disease (PD) (n=21), and a group of control subjects (n=30) by use of an infrared eye-movement recording system. Pursuit, fixation, and prompted and remembered saccades were recorded twice for both eyes in the horizontal and vertical axes. Blinks were removed, and data were calibrated. Results: Analyses of variance revealed significant differences for all characteristics examined for fixation and pursuit, and for some characteristics in dynamic saccades. These differences arose sometimes from the Cree group, sometimes from the PD group and sometimes from both groups. Conclusions: The results suggest that eye movements of Cree subjects exposed to methylmercury are qualitatively different from those of both control subjects and patients with PD. Comparisons between more-exposed and less-exposed Cree subjects matched for age with control subjects also showed significant differences for fixation, pursuit and dynamic saccades. The average scores of the more-exposed group were clearly separated from those of the less-exposed and control groups for characteristics of fixation and pursuit, and for accuracy and sharpness of prompted saccades. This trend was less clear in other results where a possible effect of mercury exposure could not be distinguished from a possible cultural effect. Further studies should focus on the most discriminating characteristics for the Cree group, such as measures of accuracy and coherence in all tests and sharpness of saccades.
This exploratory study investigates possible relationships between fluctuations in tremor at rest... more This exploratory study investigates possible relationships between fluctuations in tremor at rest (TR) and fluctuations in eye movement amplitude during ocular fixation. TR of the hand and eye movements were analyzed in five subjects with Parkinson&#39;s disease (PD) and five age-matched controls. TR was recorded using a position laser system and eye movements were recorded using an infrared reflectometry technique (Ober2). TR amplitudes were significantly larger in the group of subjects with PD than in the control group (p&lt;/=0.01). In addition, subjects with PD showed more fluctuations in their TR (p&lt;/=0.01). Eye movements did not present more fluctuations in amplitude during ocular fixation (p&gt;/=0.05). Changes in TR amplitude were not systematically correlated with modifications of eye movement amplitude in either group. However, occasional but distinct monocular oscillations were found in subjects with PD. Coherence values between frequencies of TR from the tested hand (3.5-7Hz) and frequencies of oscillatory eye movements (within the same frequency band) were clearly higher for the eye ipsilateral to the side of the body most affected by the disease in three subjects with PD. It is believed that these monocular oscillations may be a consequence of PD. Results from two previously published exploratory studies are integrated with the present results and new avenues of research are proposed.
The discrimination between normal and pathological tremor is difficult when amplitude is relative... more The discrimination between normal and pathological tremor is difficult when amplitude is relatively small. The WFLC algorithm, a time domain adaptive Fourier transform, is designed to control physiological tremor and to improve precision during microsurgery. We added two iterative optimization processes to initialize the following parameters: initial frequency weight (omega0), amplitude adaptation rate (mu) and frequency adaptation rate (mu0). Then, we applied the methods on data sets recorded on patients with different tremors (control, parkinsonian, cerebellar, and essential) sampled at 200 Hz. After filtering the data, the WFLC algorithm tracked the time-varying dominant frequencies and amplitudes of the transformed data sets. Our results illustrate the potential of using this algorithm as an approach to discriminate between normal and pathological signals even when amplitude is not a significant discriminating factor.
Kinetic tremor recorded with a laser system during a compensatory tracking task of the index fing... more Kinetic tremor recorded with a laser system during a compensatory tracking task of the index finger was analyzed in 21 patients with PD whose tremor amplitude was between low and moderate, and 30 control subjects. Nine characteristics quantifying the tracking task and tremor including mean tracking error, reaction time, peakedness, harmonicity, median frequency, proportional power in the 3-4 Hz, 4-6 Hz and 7-12 Hz ranges, and power at 0.25 Hz, were applied to the processed signal. The discriminating power of each characteristic was evaluated using differences between group means (p values), maximum percentage discrimination, and number of outliers in the patient group using z-score and 96.7(th) percentile of the control group. All nine characteristics showed significant differences between means of the two groups using Welch-modified t-tests for unequal variances. The most discriminating characteristics reflected differences in the frequency distribution of the movement and did not correlate highly with postural tremor amplitude nor with clinical ratings of tremor. Discrimination methods classified correctly up to 66.7 p.cent of the patients. Combining representative information about proportional power during posture and tracking gave a much higher discrimination (90 p.cent) with respect to the 96.7th percentile of the control group. These results suggest that by combining information coming from postural and kinetic tremors it is possible to isolate a specific aspect of PD symptomatology which could be used to reevaluate the classic distinction made between the akineto-rigid and tremulous forms of PD independently of tremor amplitude.
In this study we examine the bifurcation of the transition between walking and running. Beuter an... more In this study we examine the bifurcation of the transition between walking and running. Beuter and Lalonde (1986) have conjectured that the pertinent parameters separating walking and running can be described by a cusp singularity (Thom, 1972). In this model, the unidimensional state space is characterized by support duration and the bidimensional parameter space is characterized by the subject's weight and speed. To test this model eight males walked and ran on a motor driven treadmill at an increasing or decreasing speed with or without additional loads corresponding to 0%, 7% and 14% of their body weight. Velocities corresponding to transitions between the two modes of locomotion indicate that on the average the walk-run transition occurs at higher speed than the run-walk transition illustrating an hysteresis effect. In addition, the average difference between the transitions decreases as the load increases [mean 0 = 0.235 m/s, +/- 0.09 m/s, mean 7 = 0.104 m/s, +/- 0.07 m/s and mean 14 = 0.041 m/s, +/- 0.06 m/s] corresponding to an F ratio of F = 2.72, 0.05 less than p less than 0.1. A comparison of the differences in transition velocity at 0% and 14% is statistically different (t = 2.8, p less than 0.025). These results tend to support the existence of an elementary cusp singularity separating the two locomotion modes and suggest that the mechanisms controlling these transitions can be described by a hysterisis cycle and a small number of parameters.
Canadian Journal of Neurological Sciences, May 1, 1995
Background: Here we assess the ability of patients with cerebellar disease to execute a simple vi... more Background: Here we assess the ability of patients with cerebellar disease to execute a simple visually-guided movement task involving tracking of a target with the index finger. Methods: Spontaneous microdisplacements in index finger position are compared in patients with cerebellar deficits (ischemia [n = 3], multiple sclerosis [n = 3], degenerative cerebellar disease [n = 3]) and agematched healthy subjects. Subjects were required to maintain a constant finger position relative to a stationary baseline displayed on an oscilloscope. Results: Unusual transient abrupt movements (saccadic or myoclonic-like) directed with or against gravity were seen in patients whose neurological deficits were the most severe (7/9 patients). These abrupt myoclonic-like movements occurred independently of visual input, were not associated with clinically observable myoclonus, and were not detected previously in patients with Parkinson's disease. These abrupt myoclonic-like movements were not associated with abnormalities in either physiological tremor, or oscillations in finger microdisplacements induced by insertion of a delay (300-1400 ms) into the visual feedback of this finger "holding" experiment. An unexpected finding is that the results obtained for patients with cerebellar deficits by insertion of an experimental delay are not significantly different from those obtained with their agematched controls. Conclusions: These observations suggest that abrupt myoclonic-like movements are a characteristic abnormality of patients with a variety of cerebellar deficits and emphasize the value of this simple motor tracking task for characterizing movement disorders.
Canadian Journal of Neurological Sciences, Feb 1, 1992
The purpose of this experiment was to quantify and analyse multijoint coordination of patients wi... more The purpose of this experiment was to quantify and analyse multijoint coordination of patients with Parkinson's disease (N=5) and control subjects (N=5) during forward and backward stepping motions executed at different cadences. Coordinates of reflective markers placed on the shoulder, hip, knee, ankle and metatarsal joints were recorded in the sagittal plane using a video motion analysis system. Kinematic and kinetic analyses provided angular displacements and velocities as well as joint moments of force and powers. Results suggest the presence of two types of discoordination: one type is velocity-dependent, hence related to bradykinesia, whereas the other type appears to reflect qualitatively different coordination patterns. RESUME: L'organisation du mouvement pour executer des pas chez les parkinsoniens: bradykinesie ou incoordination. L'objectif de cette etude etait de quantifier et d'analyser la coordination multiarticulaire de patients atteints de la maladie de Parkinson (N = 5) et de sujets controles (N = 5) pendant des mouvements d'enjambement effectues vers l'avant et Farriere a differentes cadences. Les coordonnees de marqueurs reflechissants places sur Fepaule, la hanche, le genou, la cheville et le metatarse ont ete enregistrees dans le plan sagittal a l'aide d'un systeme video informatise d'analyse du mouvement. Les analyses cinematiques et cinetiques ont permis de quantifier les deplacements et vitesses angulaires ainsi que les moments de force et la puissance au niveau des differentes articulations. Les resultats suggerent la presence de deux types d'incoordination chez ces patients: Fun depend de la vitesse d'execution du mouvement et est relie a la bradykinesie, alors que Fautre semble correspondre a des patrons de coordination qualitativement differents.
The aim of this study was: (1) To determine the minimum number of characteristics necessary to di... more The aim of this study was: (1) To determine the minimum number of characteristics necessary to discriminate between postural tremor recorded in control subjects (CO), in subjects exposed to manganese (MN), and in patients with Parkinson&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s disease (PD), and (2) to examine the continuum of changes between the three groups examined. Workers previously exposed to Mn (n = 10), patients with PD (n = 10), and control subjects (CO) (n = 11) underwent a clinical examination. Blood Mn was measured at the end of exposure time for the MN group and 12 months later at the beginning of the experiment for all groups. Postural tremor with visual feedback was recorded in the index finger with a laser system. Statistical criteria were used to reduce computed tremor characteristics to a minimal set of reliable discriminating variables. Two variables were retained namely corrected wobble (CW), describing the morphology of the tremor oscillations, and variability ratio (VR), describing proportional power of tremor. Both variables had an overall correct classification rate of 77.4%. Blood Mn levels at the time of the experiment were similar for all groups and had insignificant correlation with tremor variables. However, blood Mn levels in workers which were also measured at the end of exposure time (i.e., 12 months before) showed significant correlation (Spearman&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s rank coefficient) with both harmonic index (rho = 0.70, P = 0.03) and first maximum of the autocorrelation function (rho = 0.89, P = 0.001). We conclude that (1) the tremor of workers exposed to Mn could be adequately described with only two variables; (2) a continuum of changes between tremor recorded in control subjects, in subjects exposed to Mn and in patients with PD was observed, with the MN group always found in between the control (CO) and the PD groups; (3) while blood Mn levels in workers were back at control levels at the time of the experiment, the effect of Mn on postural tremor was still detected. Thus our method has the potential to detect the effect of Mn on tremor with only two variables even after Mn level in the blood is back to normal values.
The purposes of this study were: (1) to determine the pattern of variability and relationships in... more The purposes of this study were: (1) to determine the pattern of variability and relationships in joint kinematics characterizing the development of walking and (2) to determine whether controlling for postural stability in new walkers results in less variability. The variability and relationships among hip, knee, and ankle motions were measured during 10 gait cycles of new walkers, supported new walkers, two-year-olds and seven-year-olds. Fourier series were generated for each joint motion and standard deviations were compared across groups. An age-related decline in variability was evident in select portions of the cycle. Stance and swing phase duration correlated with cycle duration for all ages. Postural support did not lessen variability in joint rotations for new walkers. Cross-correlations for hip-knee, knee-ankle, and hip-knee rotations were strong across all groups. These results suggest that a coordinative structure for walking produces strong intralimb coupling early in development, despite variability in select portions of joint motions. A current theoretical concern ini motor development research is how the nervous system acquires the ability to generate coordinated motor behaviors when the musculoskeletal system possesses numerous degrees of freedom.
Rest, postural, and kinetic tremors were recorded in Cree subjects (n ϭ 36) exposed to low levels... more Rest, postural, and kinetic tremors were recorded in Cree subjects (n ϭ 36) exposed to low levels of methylmercury (MeHg) and control subjects (n ϭ 30) using lasers designed to measure displacement. Displacement and derived velocity and acceleration time series were analyzed using quantitative characteristics in time and frequency domains. We found: 1) relatively low agreement between our results and those of a clinical examination done at the time of testing (r ϭ 0.31 for postural tremor); 2) best discrimination with velocity of static (postural with visual feedback) and kinetic tremors for which significant differences between the two groups are found in many of the characteristics examined; 3) myoclonic-like finger microdisplacements in tremor of Cree subjects; 4) significant changes in static tremor of Cree subjects following a kinetic task; 5) significant differences among three age-matched subgroups of six subjects each (Cree with higher and lower MeHg level, and a control group) in characteristics that reflect difficulty with tracking, myoclonic-like microdisplacements and change in frequency composition of tremor after the tracking task. The subtle differences detected in this preliminary study suggest that further work is warranted to determine whether they can be unambiguously associated with exposure to MeHg.
bioRxiv (Cold Spring Harbor Laboratory), Jul 5, 2023
This study explores differences in spatiotemporal cortical dynamics between five people with chro... more This study explores differences in spatiotemporal cortical dynamics between five people with chronic post-stroke aphasia and five healthy subjects. Electroencephalography was recorded during picture naming in both groups. Frequency-specific Global Field Power (GFP) results showed that the delta band has higher power to discriminate between healthy subjects and people with aphasia (PWA) than theta and alpha bands. EEG topologies computed at the time of GFP peaks in the delta band revealed strong activation oscillating between posterior and anterior areas in PWA. On the other hand, EEG topologies from healthy subjects were variable. Then, Spatial ERP (S-ERP) were developed to add spatial resolution to classical ERP analysis. S-ERP and associated analyses confirmed the previously observed oscillatory pattern in the delta frequency band among PWA during picture naming. This oscillating pattern was alternating between occipital and prefrontal areas with almost opposite phases, a characteristic not observed in healthy subjects. In addition, all PWA performed well on the picture naming task, suggesting that this oscillating pattern may be a cortical adaptation mechanism enabling them to succeed. The observation of large-scale oscillating delta activity across the scalp in all post-stroke subjects who have substantially recovered from aphasia holds the potential to inspire innovative rehabilitation methods employing non-invasive brain stimulation techniques such as transcranial alternating current stimulation (tACS).
The basal ganglia form one of the main reentrant subcortical loops which modulate the output of t... more The basal ganglia form one of the main reentrant subcortical loops which modulate the output of the cerebral cortex via thalam-ocortical projections. These neural structures play a major role in sensorimotor integration which is evident to anyone who has observed the disturbances of movement, posture, and muscle tone that result when these nuclei are damaged through injury or disease (DeLong and Georgopoulos, 1979). The role of sensorimotor integration is also evident in some dystonic patients whose movements can be improved by cutaneous stimulation of the affected body part (Albin et al., 1989). However, little is known about the nature of the sensorimotor integration that takes place in these subcortical structures (Mitchell et al, 1991) and the complex relationships existing between basal ganglia lesions and behavioral functions remains largely to be understood.
Conflict of Interest Statement: Andre Menache receives remuneration from Antidote Europe. Anne Be... more Conflict of Interest Statement: Andre Menache receives remuneration from Antidote Europe. Anne Beuter has no conflict of interest to declare.
In this study, phase plane analysis was used to describe the mechanisms involved in human intrali... more In this study, phase plane analysis was used to describe the mechanisms involved in human intralimb dynamics during a multijoint coordinated task. Nonhandicapped, spastic, and athetoid cerebral palsied individuals were videotaped as they performed a stepping task. Kinematic data for the hip and knee joint angles were digitized, smoothed, differentiated, and plotted. Phase plane analysis of movement data reveals striking differences between nonhandicapped and cerebral palsied individuals. Whereas nonhandicapped individuals have trajectories in the phase plane that suggest a self-contained second-order dynamical system, cerebral palsied individuals have self-interesting loops in their phase planes. Based upon these patterns some dynamical distinctions are offered, and suggestions are made toward a possible model.
To quantify rapid alternating movements (RAMs) we used a simple prototype developed in our labora... more To quantify rapid alternating movements (RAMs) we used a simple prototype developed in our laboratory that requires the subject to rotate two handheld foam spheres connected to optical encoders via flexible rods. Ninety-six participants, including 30 control subjects, 36 Cree subjects exposed to methylmercury, 21 subjects with Parkinson's disease, 6 subjects with cerebellar deficits, and 3 subjects with essential tremor, were involved in the study (though data for 5 were later removed). Twelve characteristics were developed and calculated from the raw data. Conditions examined included two hands at natural cadence (NC2), right and left hands separately at fast cadence (FCl), and both hands at fast cadence (FC2). Two ratios (FC2/NC2) and (FC2/FC1) combining these conditions were also examined. Test-retest reliability was > 0.80 for most characteristics but was < 0.70 for some characteristics, especially in the conditions executed at normal cadence. Correlations between characteristics and numbers of outliers with respect to the control group distribution were used to reduce the set of characteristics from 12 to 7 (i.e., duration, range, maximum slope, similarity in shape, smoothness, sharpness, and coherence). ANOVAs on the three largest groups generated significant results for most characteristics in the three conditions and the two ratios for Cree subjects and subjects with Parkinson's disease. ANOVAs on 3 age-matched groups (n ؍ 6) suggest that methylmercury affects the performance of the Cree subjects with the higher exposure, especially in terms of smoothness, sharpness, and coherence. These preliminary results suggest that this test is sufficiently specific and sensitive to characterize the 1 The study received approval from the ethics committee of the University of Que´bec at Montre´al and was conducted in agreement with the procedures proposed. Accordingly, all subjects gave informed consent. performance of different groups of subjects. Ratios tend to improve discrimination for Cree subjects in a few characteristics but not for patients with Parkinson's disease.
Quantification of movement pathologies is an important challenge of the clinical and research lab... more Quantification of movement pathologies is an important challenge of the clinical and research laboratories today. Basically, two problems must be addressed. The first one is to find the appropriate technology; the second is to develop adequate measures from the raw data which will best discriminate between health and pathology. In this paper, we propose a simple method to record and analyse tremor and other microdisplacements of the upper extremities based on the recording of position by laser analog sensors. Any microcomputer equipped to perform analog-digital conversion is compatible for use with this system. The performance of the laser system is examined and compared with the performance of accelerometers. Finally, data recorded with a laser analog sensor from a patient with Parkinson&amp;amp;#39;s disease and a control subject are presented. This new laser-based quantitative method may prove to be an important tool in early and differential diagnosis of neurodegenerative diseases of the central nervous system.
ABSTRACT Parkinson’s disease is a complex disorder for which there is no known cure. Nor do we un... more ABSTRACT Parkinson’s disease is a complex disorder for which there is no known cure. Nor do we understand fully the origin of one of the disease’s cardinal symptoms: tremor. A non-traditional approach to research in Parkinson’s disease and in Parkinsonian tremor involves the application of mathematical models. The purpose of this article is to review briefly the contributions of mathematical models to the study of Parkinsonian tremor. There is little evidence that modelling attempts have built on previous ones but there has been a trend to move the focus of modelling from the periphery to the brain, and from abstracted to more physiologically detailed views. We hope that this review will encourage more mathematical modelling in the study of Parkinson’s disease and Parkinsonian tremor.
International Archives of Occupational and Environmental Health, Feb 1, 2004
Objectives: To examine the effect of chronic exposure to methylmercury on eye movements (pursuit,... more Objectives: To examine the effect of chronic exposure to methylmercury on eye movements (pursuit, fixation and dynamic saccades) in Cree subjects from Northern Quebec. Methods: Eye movements were recorded in a group of Cree subjects (n=36) exposed chronically to methylmercury, a group of patients with ParkinsonÕs disease (PD) (n=21), and a group of control subjects (n=30) by use of an infrared eye-movement recording system. Pursuit, fixation, and prompted and remembered saccades were recorded twice for both eyes in the horizontal and vertical axes. Blinks were removed, and data were calibrated. Results: Analyses of variance revealed significant differences for all characteristics examined for fixation and pursuit, and for some characteristics in dynamic saccades. These differences arose sometimes from the Cree group, sometimes from the PD group and sometimes from both groups. Conclusions: The results suggest that eye movements of Cree subjects exposed to methylmercury are qualitatively different from those of both control subjects and patients with PD. Comparisons between more-exposed and less-exposed Cree subjects matched for age with control subjects also showed significant differences for fixation, pursuit and dynamic saccades. The average scores of the more-exposed group were clearly separated from those of the less-exposed and control groups for characteristics of fixation and pursuit, and for accuracy and sharpness of prompted saccades. This trend was less clear in other results where a possible effect of mercury exposure could not be distinguished from a possible cultural effect. Further studies should focus on the most discriminating characteristics for the Cree group, such as measures of accuracy and coherence in all tests and sharpness of saccades.
This exploratory study investigates possible relationships between fluctuations in tremor at rest... more This exploratory study investigates possible relationships between fluctuations in tremor at rest (TR) and fluctuations in eye movement amplitude during ocular fixation. TR of the hand and eye movements were analyzed in five subjects with Parkinson&#39;s disease (PD) and five age-matched controls. TR was recorded using a position laser system and eye movements were recorded using an infrared reflectometry technique (Ober2). TR amplitudes were significantly larger in the group of subjects with PD than in the control group (p&lt;/=0.01). In addition, subjects with PD showed more fluctuations in their TR (p&lt;/=0.01). Eye movements did not present more fluctuations in amplitude during ocular fixation (p&gt;/=0.05). Changes in TR amplitude were not systematically correlated with modifications of eye movement amplitude in either group. However, occasional but distinct monocular oscillations were found in subjects with PD. Coherence values between frequencies of TR from the tested hand (3.5-7Hz) and frequencies of oscillatory eye movements (within the same frequency band) were clearly higher for the eye ipsilateral to the side of the body most affected by the disease in three subjects with PD. It is believed that these monocular oscillations may be a consequence of PD. Results from two previously published exploratory studies are integrated with the present results and new avenues of research are proposed.
The discrimination between normal and pathological tremor is difficult when amplitude is relative... more The discrimination between normal and pathological tremor is difficult when amplitude is relatively small. The WFLC algorithm, a time domain adaptive Fourier transform, is designed to control physiological tremor and to improve precision during microsurgery. We added two iterative optimization processes to initialize the following parameters: initial frequency weight (omega0), amplitude adaptation rate (mu) and frequency adaptation rate (mu0). Then, we applied the methods on data sets recorded on patients with different tremors (control, parkinsonian, cerebellar, and essential) sampled at 200 Hz. After filtering the data, the WFLC algorithm tracked the time-varying dominant frequencies and amplitudes of the transformed data sets. Our results illustrate the potential of using this algorithm as an approach to discriminate between normal and pathological signals even when amplitude is not a significant discriminating factor.
Kinetic tremor recorded with a laser system during a compensatory tracking task of the index fing... more Kinetic tremor recorded with a laser system during a compensatory tracking task of the index finger was analyzed in 21 patients with PD whose tremor amplitude was between low and moderate, and 30 control subjects. Nine characteristics quantifying the tracking task and tremor including mean tracking error, reaction time, peakedness, harmonicity, median frequency, proportional power in the 3-4 Hz, 4-6 Hz and 7-12 Hz ranges, and power at 0.25 Hz, were applied to the processed signal. The discriminating power of each characteristic was evaluated using differences between group means (p values), maximum percentage discrimination, and number of outliers in the patient group using z-score and 96.7(th) percentile of the control group. All nine characteristics showed significant differences between means of the two groups using Welch-modified t-tests for unequal variances. The most discriminating characteristics reflected differences in the frequency distribution of the movement and did not correlate highly with postural tremor amplitude nor with clinical ratings of tremor. Discrimination methods classified correctly up to 66.7 p.cent of the patients. Combining representative information about proportional power during posture and tracking gave a much higher discrimination (90 p.cent) with respect to the 96.7th percentile of the control group. These results suggest that by combining information coming from postural and kinetic tremors it is possible to isolate a specific aspect of PD symptomatology which could be used to reevaluate the classic distinction made between the akineto-rigid and tremulous forms of PD independently of tremor amplitude.
In this study we examine the bifurcation of the transition between walking and running. Beuter an... more In this study we examine the bifurcation of the transition between walking and running. Beuter and Lalonde (1986) have conjectured that the pertinent parameters separating walking and running can be described by a cusp singularity (Thom, 1972). In this model, the unidimensional state space is characterized by support duration and the bidimensional parameter space is characterized by the subject's weight and speed. To test this model eight males walked and ran on a motor driven treadmill at an increasing or decreasing speed with or without additional loads corresponding to 0%, 7% and 14% of their body weight. Velocities corresponding to transitions between the two modes of locomotion indicate that on the average the walk-run transition occurs at higher speed than the run-walk transition illustrating an hysteresis effect. In addition, the average difference between the transitions decreases as the load increases [mean 0 = 0.235 m/s, +/- 0.09 m/s, mean 7 = 0.104 m/s, +/- 0.07 m/s and mean 14 = 0.041 m/s, +/- 0.06 m/s] corresponding to an F ratio of F = 2.72, 0.05 less than p less than 0.1. A comparison of the differences in transition velocity at 0% and 14% is statistically different (t = 2.8, p less than 0.025). These results tend to support the existence of an elementary cusp singularity separating the two locomotion modes and suggest that the mechanisms controlling these transitions can be described by a hysterisis cycle and a small number of parameters.
Canadian Journal of Neurological Sciences, May 1, 1995
Background: Here we assess the ability of patients with cerebellar disease to execute a simple vi... more Background: Here we assess the ability of patients with cerebellar disease to execute a simple visually-guided movement task involving tracking of a target with the index finger. Methods: Spontaneous microdisplacements in index finger position are compared in patients with cerebellar deficits (ischemia [n = 3], multiple sclerosis [n = 3], degenerative cerebellar disease [n = 3]) and agematched healthy subjects. Subjects were required to maintain a constant finger position relative to a stationary baseline displayed on an oscilloscope. Results: Unusual transient abrupt movements (saccadic or myoclonic-like) directed with or against gravity were seen in patients whose neurological deficits were the most severe (7/9 patients). These abrupt myoclonic-like movements occurred independently of visual input, were not associated with clinically observable myoclonus, and were not detected previously in patients with Parkinson's disease. These abrupt myoclonic-like movements were not associated with abnormalities in either physiological tremor, or oscillations in finger microdisplacements induced by insertion of a delay (300-1400 ms) into the visual feedback of this finger "holding" experiment. An unexpected finding is that the results obtained for patients with cerebellar deficits by insertion of an experimental delay are not significantly different from those obtained with their agematched controls. Conclusions: These observations suggest that abrupt myoclonic-like movements are a characteristic abnormality of patients with a variety of cerebellar deficits and emphasize the value of this simple motor tracking task for characterizing movement disorders.
Canadian Journal of Neurological Sciences, Feb 1, 1992
The purpose of this experiment was to quantify and analyse multijoint coordination of patients wi... more The purpose of this experiment was to quantify and analyse multijoint coordination of patients with Parkinson's disease (N=5) and control subjects (N=5) during forward and backward stepping motions executed at different cadences. Coordinates of reflective markers placed on the shoulder, hip, knee, ankle and metatarsal joints were recorded in the sagittal plane using a video motion analysis system. Kinematic and kinetic analyses provided angular displacements and velocities as well as joint moments of force and powers. Results suggest the presence of two types of discoordination: one type is velocity-dependent, hence related to bradykinesia, whereas the other type appears to reflect qualitatively different coordination patterns. RESUME: L'organisation du mouvement pour executer des pas chez les parkinsoniens: bradykinesie ou incoordination. L'objectif de cette etude etait de quantifier et d'analyser la coordination multiarticulaire de patients atteints de la maladie de Parkinson (N = 5) et de sujets controles (N = 5) pendant des mouvements d'enjambement effectues vers l'avant et Farriere a differentes cadences. Les coordonnees de marqueurs reflechissants places sur Fepaule, la hanche, le genou, la cheville et le metatarse ont ete enregistrees dans le plan sagittal a l'aide d'un systeme video informatise d'analyse du mouvement. Les analyses cinematiques et cinetiques ont permis de quantifier les deplacements et vitesses angulaires ainsi que les moments de force et la puissance au niveau des differentes articulations. Les resultats suggerent la presence de deux types d'incoordination chez ces patients: Fun depend de la vitesse d'execution du mouvement et est relie a la bradykinesie, alors que Fautre semble correspondre a des patrons de coordination qualitativement differents.
The aim of this study was: (1) To determine the minimum number of characteristics necessary to di... more The aim of this study was: (1) To determine the minimum number of characteristics necessary to discriminate between postural tremor recorded in control subjects (CO), in subjects exposed to manganese (MN), and in patients with Parkinson&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s disease (PD), and (2) to examine the continuum of changes between the three groups examined. Workers previously exposed to Mn (n = 10), patients with PD (n = 10), and control subjects (CO) (n = 11) underwent a clinical examination. Blood Mn was measured at the end of exposure time for the MN group and 12 months later at the beginning of the experiment for all groups. Postural tremor with visual feedback was recorded in the index finger with a laser system. Statistical criteria were used to reduce computed tremor characteristics to a minimal set of reliable discriminating variables. Two variables were retained namely corrected wobble (CW), describing the morphology of the tremor oscillations, and variability ratio (VR), describing proportional power of tremor. Both variables had an overall correct classification rate of 77.4%. Blood Mn levels at the time of the experiment were similar for all groups and had insignificant correlation with tremor variables. However, blood Mn levels in workers which were also measured at the end of exposure time (i.e., 12 months before) showed significant correlation (Spearman&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s rank coefficient) with both harmonic index (rho = 0.70, P = 0.03) and first maximum of the autocorrelation function (rho = 0.89, P = 0.001). We conclude that (1) the tremor of workers exposed to Mn could be adequately described with only two variables; (2) a continuum of changes between tremor recorded in control subjects, in subjects exposed to Mn and in patients with PD was observed, with the MN group always found in between the control (CO) and the PD groups; (3) while blood Mn levels in workers were back at control levels at the time of the experiment, the effect of Mn on postural tremor was still detected. Thus our method has the potential to detect the effect of Mn on tremor with only two variables even after Mn level in the blood is back to normal values.
The purposes of this study were: (1) to determine the pattern of variability and relationships in... more The purposes of this study were: (1) to determine the pattern of variability and relationships in joint kinematics characterizing the development of walking and (2) to determine whether controlling for postural stability in new walkers results in less variability. The variability and relationships among hip, knee, and ankle motions were measured during 10 gait cycles of new walkers, supported new walkers, two-year-olds and seven-year-olds. Fourier series were generated for each joint motion and standard deviations were compared across groups. An age-related decline in variability was evident in select portions of the cycle. Stance and swing phase duration correlated with cycle duration for all ages. Postural support did not lessen variability in joint rotations for new walkers. Cross-correlations for hip-knee, knee-ankle, and hip-knee rotations were strong across all groups. These results suggest that a coordinative structure for walking produces strong intralimb coupling early in development, despite variability in select portions of joint motions. A current theoretical concern ini motor development research is how the nervous system acquires the ability to generate coordinated motor behaviors when the musculoskeletal system possesses numerous degrees of freedom.
Rest, postural, and kinetic tremors were recorded in Cree subjects (n ϭ 36) exposed to low levels... more Rest, postural, and kinetic tremors were recorded in Cree subjects (n ϭ 36) exposed to low levels of methylmercury (MeHg) and control subjects (n ϭ 30) using lasers designed to measure displacement. Displacement and derived velocity and acceleration time series were analyzed using quantitative characteristics in time and frequency domains. We found: 1) relatively low agreement between our results and those of a clinical examination done at the time of testing (r ϭ 0.31 for postural tremor); 2) best discrimination with velocity of static (postural with visual feedback) and kinetic tremors for which significant differences between the two groups are found in many of the characteristics examined; 3) myoclonic-like finger microdisplacements in tremor of Cree subjects; 4) significant changes in static tremor of Cree subjects following a kinetic task; 5) significant differences among three age-matched subgroups of six subjects each (Cree with higher and lower MeHg level, and a control group) in characteristics that reflect difficulty with tracking, myoclonic-like microdisplacements and change in frequency composition of tremor after the tracking task. The subtle differences detected in this preliminary study suggest that further work is warranted to determine whether they can be unambiguously associated with exposure to MeHg.
bioRxiv (Cold Spring Harbor Laboratory), Jul 5, 2023
This study explores differences in spatiotemporal cortical dynamics between five people with chro... more This study explores differences in spatiotemporal cortical dynamics between five people with chronic post-stroke aphasia and five healthy subjects. Electroencephalography was recorded during picture naming in both groups. Frequency-specific Global Field Power (GFP) results showed that the delta band has higher power to discriminate between healthy subjects and people with aphasia (PWA) than theta and alpha bands. EEG topologies computed at the time of GFP peaks in the delta band revealed strong activation oscillating between posterior and anterior areas in PWA. On the other hand, EEG topologies from healthy subjects were variable. Then, Spatial ERP (S-ERP) were developed to add spatial resolution to classical ERP analysis. S-ERP and associated analyses confirmed the previously observed oscillatory pattern in the delta frequency band among PWA during picture naming. This oscillating pattern was alternating between occipital and prefrontal areas with almost opposite phases, a characteristic not observed in healthy subjects. In addition, all PWA performed well on the picture naming task, suggesting that this oscillating pattern may be a cortical adaptation mechanism enabling them to succeed. The observation of large-scale oscillating delta activity across the scalp in all post-stroke subjects who have substantially recovered from aphasia holds the potential to inspire innovative rehabilitation methods employing non-invasive brain stimulation techniques such as transcranial alternating current stimulation (tACS).
The basal ganglia form one of the main reentrant subcortical loops which modulate the output of t... more The basal ganglia form one of the main reentrant subcortical loops which modulate the output of the cerebral cortex via thalam-ocortical projections. These neural structures play a major role in sensorimotor integration which is evident to anyone who has observed the disturbances of movement, posture, and muscle tone that result when these nuclei are damaged through injury or disease (DeLong and Georgopoulos, 1979). The role of sensorimotor integration is also evident in some dystonic patients whose movements can be improved by cutaneous stimulation of the affected body part (Albin et al., 1989). However, little is known about the nature of the sensorimotor integration that takes place in these subcortical structures (Mitchell et al, 1991) and the complex relationships existing between basal ganglia lesions and behavioral functions remains largely to be understood.
Conflict of Interest Statement: Andre Menache receives remuneration from Antidote Europe. Anne Be... more Conflict of Interest Statement: Andre Menache receives remuneration from Antidote Europe. Anne Beuter has no conflict of interest to declare.
In this study, phase plane analysis was used to describe the mechanisms involved in human intrali... more In this study, phase plane analysis was used to describe the mechanisms involved in human intralimb dynamics during a multijoint coordinated task. Nonhandicapped, spastic, and athetoid cerebral palsied individuals were videotaped as they performed a stepping task. Kinematic data for the hip and knee joint angles were digitized, smoothed, differentiated, and plotted. Phase plane analysis of movement data reveals striking differences between nonhandicapped and cerebral palsied individuals. Whereas nonhandicapped individuals have trajectories in the phase plane that suggest a self-contained second-order dynamical system, cerebral palsied individuals have self-interesting loops in their phase planes. Based upon these patterns some dynamical distinctions are offered, and suggestions are made toward a possible model.
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