Thesis (M.Ph.)--Chinese University of Hong Kong. / Bibliography: leaves [292-305].

This thesis sought to: 1) examine the effect of a number of organism and task constraints on the control of two forms of physiological tremor, namely postural and finger-pinch force tremor; and 2) determine if the expected constraint-related changes in tremor output were associated with alterations in the control strategy utilised by the performer. The organism constraints were age and resistance-training (for both forms of tremor), while the task constraints were visual feedback, target size and limb preference (postural tremor) and mean force, target shape and limb preference (force tremor). The postural (index finger) tremor amplitude of young adults was significantly greater in the augmented vision (AV) than normal vision (NV) conditions and when using the non-preferred than preferred limb. Even greater differences/changes in postural tremor amplitude were observed as a function of aging and training. Older adults had significantly more index finger tremor amplitude than young adults. Regardless, the older adults who completed a six weeks program of unilateral strength- or coordination-training were able to significantly reduce their tremor amplitude. Although the training-related reductions in tremor amplitude were of a greater magnitude for the trained than untrained limb, a significant reduction in the tremor amplitude of the untrained limb was also observed for the coordination-training group. All of these significant differences/changes in tremor amplitude were associated with significant changes in a number of other dependent variables. For example, the task- and age-related increases in tremor amplitude were primarily a result of greater 8-12 Hz tremor power and were associated with increased EMG activity/co-activation of the extensor digitorum (ED) and flexor digitorum superficialis (FDS) muscles and a significant reduction in intra-limb (index finger-hand and forearm-upper arm) coupling. The significant reductions in tremor amplitude observed for the resistance-trained older adults was a result of a significant decline in 8-12 Hz power and were associated with a significant reduction in ED and FDS co-activation. However, no significant change in intra-limb coupling was observed. The overall trends observed in the results for the finger-pinch force tremor experiments were similar to those for postural tremor. Older adults had significantly more finger-pinch force tremor (i.e. force variability and targeting error) than young adults, although older adults who performed six weeks of unilateral strength-training were able to significantly reduce the force variability and targeting error of the trained limb. No significant training-related reduction in force tremor was however observed for the untrained limb. The significant age-related increase in force tremor was a result of greater low frequency (less than 2 Hz) power and was associated with a significant loss of inter-digit force sharing and coupling as well as tactile sensitivity. Interestingly, the training-related decreases in force tremor were not associated with significant changes in any of the frequency, sharing or coupling measures. Collectively, the results of the five experiments contained in this thesis add much to our understanding of postural and force tremor. Results indicated that numerous task and organism constraints can have a substantial effect on the resulting tremor output. Furthermore, the task- and age-related differences in the power spectral, muscle activity and coupling measures suggested that the changes in tremor output were the result of the use of an altered (sub-optimal) control strategy. The age-related increase in postural and force tremor amplitude may therefore reflect not only an overall decline in neuromuscular system function, but also the relative inability of older adults to effectively coordinate the output of numerous degrees of freedom (limb segments). The effect of the aging process on tremor output was somewhat reversible, with the older adults who performed resistance-training significantly improving their control of both postural and force tremor. There was some evidence that resistance-training could produce cross-education effects in older adults, although these were only statistically significant for postural tremor amplitude in the coordination-training group and for wrist flexion strength in the strength-training group. The relative brevity of the training program (6 weeks) and the observable cross-education effects suggest that the reduction in tremor amplitude and increases in strength were primarily a result of neural adaptations. Such findings further support the prescription of resistance-training for improving physical function in older individuals.

Background: Vocal tremor affects over half a million Americans. Tremor can affect structures within the respiratory, laryngeal, velopharyngeal, or oral regions (Critchley, 1949). No study has related the of tremor severity in structures in all four of these regions to the severity of vocal tremor. Purpose: The purpose of this study was (a) to describe the distribution and severity of tremor throughout the vocal tract and (b) to relate that to the severity of the voice tremor. We hypothesized that tremor would be widespread throughout the vocal tract, but most prevalent in the larynx, specifically in the true vocal folds. Additionally, we expected vocal tremor severity to be directly related to the distribution and severity of tremor in structures of the vocal tract. Method: Twenty adults with vocal tremor and two age-matched controls participated in the study. Two judges, experienced in assessment of laryngeal movement disorders, rated the tremor severity in each of 15 structures during sustained /i/, /s/, /h/, and rest breathing, and the severity of the voice tremor during sustained /i/, /s/, and /h/. Results: A novel finding of this study was the identification of distribution and severity of tremor in vocal tract structures associated with mild, moderate, and severe vocal tremor. Participants with mild voice tremor tended to show tremor limited to structures of the larynx, and in some cases, the velopharynx, and on average, had three structures affected (most commonly true vocal folds, supraglottic structures, and hypopharynx). Participants with moderate voice tremor tended to show tremor in the larynx and velopharynx, and on average, had five structures affected (most commonly true vocal folds, supraglottic structures, hypopharynx, vertical laryngeal movement, and some other velar, oral, or respiratory structure). Those with severe voice tremor showed tremor in the larynx, velopharynx, and beyond and on average, had eight structures affected (most commonly true vocal folds, supraglottic structures, hypopharynx, vertical laryngeal movement, anterior and lateral chest movement, velum, and jaw). A second novel finding, obtained through regression analyses, was that tremor severity of the supraglottic structures and vertical laryngeal movement contributed the most to the voice tremor severity during sustained phonation (r=0.77, F=16.17, p<0.0001). A strong positive correlation (r=0.72) was found between the Tremor Index, a composite value of the distribution and severity of structural tremor, and the severity of the voice tremor during sustained phonation. The correlation between the severity of tremor in the true vocal folds and the voice tremor was moderate (r=0.46). Mean voice tremor severity was greater in participants over age 75 (mean=2.25) than those between 66 and 75 years (mean=1.5) and under age 65 (mean=1.8). Mean Tremor Index, was greater in participants over age 65 (mean TI=68) than those under age 65 (mean=41). In this group of 20 participants, laryngeal/hypopharyngeal structures were most frequently (95%) and severely (rated 1.7 out of 3) affected, followed by velopharyngeal (40% occurrence, 1.3 severity), respiratory (40% occurrence, 1.1 severity), and oral (40% occurrence, 1.0 severity) regions during sustained phonation. Tremor was also identified more often and with greater severity in the larynx for sustained /s/ (70% occurrence, 1.7 severity), /h/ (40% occurrence, 1.7 severity), and rest breathing (45% occurrence, 1.6 severity) than other regions. During the voiceless and rest breathing tasks, the greatest tremor severity was noted in the true vocal folds. Conclusion: Evaluation of the distribution and severity of tremor may be useful in guiding behavioral and medical treatment of voice tremor and for providing prognostic information regarding response to laryngeal botulinum toxin injection.

No description available.

Although tremor is the most common movement disorder, there are few non-invasive treatment options. One of the obstacles to creating effective tremor suppression devices is our lack of understanding regarding where tremor originates (which muscles), how it propagates through the limb (to which degrees of freedom, DOF), and where it manifests most severely (which DOF). To investigate these questions, we created a simple, linear time-invariant model to simulate tremor, with tremorogenic muscle activity input (in the 15 major superficial muscles from the shoulder to the wrist) and joint displacement output (in the 7 major upper limb DOF). The model included excitation-contraction dynamics, musculoskeletal geometry (muscle moment arms) and the mechanical impedance (inertia, damping, and stiffness) of the limb. From our simulation results, we determined four principles of tremor propagation. First, the distribution of tremor depends strongly on musculoskeletal dynamics. Second, the spreading of tremor is due to inertial coupling (primarily) and musculoskeletal geometry (secondarily). Third, tremor spreads narrowly in the sense that most of the tremor caused by a muscle occurs in a small number of DOF. Lastly, assuming uniform distribution of tremorogenic activity among upper-limb muscles, tremor increases proximal-distally, and the contribution from muscles increases proximal-distally.

Parkinson's disease (PD) is a neuro-degenerative chronic disorder with cardinal signs of bradykinesia, resting tremor, rigidity, and postural abnormality/instability. Tremor, which is a manifestation of both normal and abnormal activities in the nervous system, can be described as an involuntary and periodic oscillation of any limb. Such an oscillation with a small amplitude, which is barely visible to the naked eye, is present in healthy people. This is called a physiological tremor and is asymptomatic. This tremor is believed to be the result of at least two distinct oscillations. A passive mechanical oscillation that is produced by the irregularities of motor unit firing, and by blood ejection during cardiac systole. The frequency and amplitude of these oscillations are dependent on the mechanical properties of the limb including joint stiffness and limb inertia. There is another component of oscillation that does not respond to elastic or inertial loading, which is called the central component, and is believed to arise from an unknown oscillating neuronal network within the central nervous system. Unlike physiological tremor, pathological tremors are symptomatic and can impair motor performance. Parkinson's disease (PD) tremor is generally manifested at rest, but also occurs during posture or motion. Classical PD rest tremor is known to be a central tremor of 4-6 Hz and peripheral origins have only a minimal role. However, whether or not the same central mechanism remains active during action tremor (including posture and movement) should yet be answered. Contrary to PD rest tremor, reported results on action tremor in the literature are diverse; and the reason for the changes in tremor characteristics in situations other than rest, or generally during muscle activation, is not fully understood. The lack of generality in the results of studies on action tremor, makes the efforts of treatment difficult, and is a barrier for mechanical/engineering approaches of suppressing this tremor. To investigate the role of mechanisms other than classic rest tremor, and possible sub-categories of tremulous PD in yielding diverse results, this study was conducted on twenty PD patients and fourteen healthy age-matched (on average) controls. To evaluate the possible contribution of (enhanced) physiological tremor, the study considered the effect of loading on postural hand tremor in a complete range of 0-100% MVC (Maximum Voluntary Contraction). The study looked at two measures of tremor amplitude and one measure of tremor frequency, and focused on two frequency bands of classic-rest (3.5-6.5 Hz) and physiological (7.5-16.5 Hz) tremors. The study revealed that PD tremor was not uniformly distributed in the three dimensional space, and then focused on the investigation of tremor in the dominant axis, which was the same as direction of loading. It also revealed that dopaminergic medication could significantly affect tremor components only in PD band, compared to the components in the physiological band. The study was an extension to previous studies and yielded similar results for the previously reported range of loading. However, with the extended range of loading, it revealed novel results particularly after separating PD patients into sub-groups. It was hypothesized that the coexistence of physiological mechanism, and considerable difference between sub-types of tremulous PD patients, are responsible for most of the diversity in the previously reported studies. This study showed that for clearer results the sub-groups are inevitable, and that automatic classification (clustering) provided the most separable sub-groups. These sub-groups had distinct trends of load effect on tremor amplitude and frequency. No matter which categorization method was used, at least one sub-group exhibited significantly higher tremor energy compared to the healthy participants not only in the PD band, but also in the physiological band. This meant that, for some sub-groups of PD, the physiological tremor is a very important mechanism and not the same as that of healthy people. The coexistence hypothesis was also affirmed by examining tremor spectrums' peak frequency and magnitude in the two separate bands. The necessity of the separation of tremulous PD patients into sub-groups, and the coexistence of physiological and classic PD tremor mechanisms for some of them are the factor that should be considered in the design of a suppressing device and also in the proposed treatment of action tremor in this population.

Parkinson's disease (PD) is a neuro-degenerative chronic disorder with cardinal signs of bradykinesia, resting tremor, rigidity, and postural abnormality/instability. Tremor, which is a manifestation of both normal and abnormal activities in the nervous system, can be described as an involuntary and periodic oscillation of any limb. Such an oscillation with a small amplitude, which is barely visible to the naked eye, is present in healthy people. This is called a physiological tremor and is asymptomatic. This tremor is believed to be the result of at least two distinct oscillations. A passive mechanical oscillation that is produced by the irregularities of motor unit firing, and by blood ejection during cardiac systole. The frequency and amplitude of these oscillations are dependent on the mechanical properties of the limb including joint stiffness and limb inertia. There is another component of oscillation that does not respond to elastic or inertial loading, which is called the central component, and is believed to arise from an unknown oscillating neuronal network within the central nervous system. Unlike physiological tremor, pathological tremors are symptomatic and can impair motor performance. Parkinson's disease (PD) tremor is generally manifested at rest, but also occurs during posture or motion. Classical PD rest tremor is known to be a central tremor of 4-6 Hz and peripheral origins have only a minimal role. However, whether or not the same central mechanism remains active during action tremor (including posture and movement) should yet be answered. Contrary to PD rest tremor, reported results on action tremor in the literature are diverse; and the reason for the changes in tremor characteristics in situations other than rest, or generally during muscle activation, is not fully understood. The lack of generality in the results of studies on action tremor, makes the efforts of treatment difficult, and is a barrier for mechanical/engineering approaches of suppressing this tremor. To investigate the role of mechanisms other than classic rest tremor, and possible sub-categories of tremulous PD in yielding diverse results, this study was conducted on twenty PD patients and fourteen healthy age-matched (on average) controls. To evaluate the possible contribution of (enhanced) physiological tremor, the study considered the effect of loading on postural hand tremor in a complete range of 0-100% MVC (Maximum Voluntary Contraction). The study looked at two measures of tremor amplitude and one measure of tremor frequency, and focused on two frequency bands of classic-rest (3.5-6.5 Hz) and physiological (7.5-16.5 Hz) tremors. The study revealed that PD tremor was not uniformly distributed in the three dimensional space, and then focused on the investigation of tremor in the dominant axis, which was the same as direction of loading. It also revealed that dopaminergic medication could significantly affect tremor components only in PD band, compared to the components in the physiological band. The study was an extension to previous studies and yielded similar results for the previously reported range of loading. However, with the extended range of loading, it revealed novel results particularly after separating PD patients into sub-groups. It was hypothesized that the coexistence of physiological mechanism, and considerable difference between sub-types of tremulous PD patients, are responsible for most of the diversity in the previously reported studies. This study showed that for clearer results the sub-groups are inevitable, and that automatic classification (clustering) provided the most separable sub-groups. These sub-groups had distinct trends of load effect on tremor amplitude and frequency. No matter which categorization method was used, at least one sub-group exhibited significantly higher tremor energy compared to the healthy participants not only in the PD band, but also in the physiological band. This meant that, for some sub-groups of PD, the physiological tremor is a very important mechanism and not the same as that of healthy people. The coexistence hypothesis was also affirmed by examining tremor spectrums' peak frequency and magnitude in the two separate bands. The necessity of the separation of tremulous PD patients into sub-groups, and the coexistence of physiological and classic PD tremor mechanisms for some of them are the factor that should be considered in the design of a suppressing device and also in the proposed treatment of action tremor in this population.

Thesis (M.S.)--University of Wisconsin--Madison, 1984. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 15-16).

Although tremor is the most common movement disorder, there exist few effective tremor-suppressing devices, in part because the characteristics of tremor throughout the upper limb are unknown. To clarify, optimally suppressing tremor requires a knowledge of the mechanical origin, propagation, and distribution of tremor throughout the upper limb. Here we present the first systematic investigation of how tremor propagates between the shoulder, elbow, forearm, and wrist. We simulated tremor propagation using a linear, time-invariant, lumped-parameter musculoskeletal model relating joint torques and the resulting joint displacements. The model focused on the seven main degrees of freedom (DOF) from the shoulder to the wrist and included coupled joint inertia, damping, and stiffness. We deliberately implemented a simple model to focus first on the most basic effects. Simulating tremorogenic joint torque as a sinusoidal input, we used the model to establish fundamental principles describing how input parameters (torque location and frequency) and joint impedance (inertia, damping, and stiffness) affect tremor propagation. We expect that the methods and principles presented here will serve as the groundwork for future refining studies to understand the origin, propagation, and distribution of tremor throughout the upper limb in order to enable the future development of optimal tremor-suppressing devices.

Accurate Detection of Parkinson`s Disease in Tremor Syndromes Using Olfactory Testing