Dissertations / Theses on the topic 'Hand motor control'

Thumb and Index fingers are involved in many daily tasks, it is understandable how injuries, musculoskeletal, rheumatologic, and neurological diseases could affect hand function causing severe disability. The evaluation of motor control deficits of the thumb-index system is necessary to identify impairments and to propose specific therapeutic or surgical proposes. Pinch maximal voluntary contraction is the most investigated parameter, it is a valid estimator of general hand function. However, thumb and index are rarely involved at their maximal contraction, usually they are used in precision pinches at low submaximal forces exerted for a short-to-long time. For this reason other parameters must be investigated. In this dissertation, a multiparametric evaluation of thumb-index system was proposed. The battery of tests consisted of the maximal voluntary contraction (MVC) of pinch grip (TP, tip pinch and PP, palmar pinch) and of the opposite movement (E, extension of thumb and index), the endurance (SC, sustained contraction), the accuracy and precision of pinch force in a pinch and release task (DC, dynamic contraction) and the force coordination between hands in a bimanual simultaneous task (BSC, bimanual strength coordination). The tasks were measured with a measurement system consisted of two pinch gauges, connected to a PC, the visual feedback was displayed on a monitor through the graphical user interface of an ad-hoc developed software. To be usable in the clinical context, it is important to check the reliability of the tasks and collecting data in healthy samples permits on the one hand to analyse how values changes as function of anthropometric variables, hand dominance, dexterity, and on the other hand to define the reference values to compare pathological populations. Therefore this dissertation was conducted through test-retest reliability studies and cross-sectional studies to establish normative data of PP, TP, E MVCs, SC, DC and BSC in the Italian population. All the tasks proved reliable and consistent, MVC and SC showed high reliability, DC and BSC reliability was lower but clinically suitable. Strength, analysed through PP, TP, E MVCs, declined in line with the normal process of aging that also entails muscle fibers and the reduction of daily activities in older adults. In relative terms, E-MVC showed the highest strength loss in the over 75y. SC showed similar values in all age groups, variables of DC and BSC showed instead large effect related to age-decline. Women performed better than men only in SC, in MVC, DC and BSC men excelled. A hand dominance effect emerged only in TP and PP MVC. Correlations between tasks were very low to low, suggesting that different constructs were measured by the tasks. This Ph.D. project proposed novel tasks to evaluate pinch motor control which were showed reliable in healthy people and their normative data were obtained, representing a useful aid in the clinical field. The results become a starting point for future studies to highlight impairments of the thumb-index system in different neurological and musculoskeletal disorders and to guide the rehabilitation and the therapeutic intervention.

The dexterity of the human hand depends largely on the ability to move the fingers independently, the execution of which requires the coordination of multiple muscles. How these muscle ensembles are recruited by the central nervous system is not clear. Therefore, the objective of this dissertation was to identify some of the neural mechanisms whereby certain hand muscles are recruited into functional groups, or muscle synergies, needed for the generation of specific hand and finger movements.We characterized the organization of synaptic inputs onto the motor neurons supplying different compartments of a multi-tendoned finger flexor, the flexor digitorum superficialis (FDS). We found that the motor neurons controlling different finger compartments of the FDS do not receive entirely segregated inputs, and that the motor neurons supplying adjacent compartments receive substantially more common synaptic input than motor neurons supplying compartments further apart. The FDS and another multi-tendoned finger flexor, the flexor digitorum profundus (FDP), both insert onto each finger and function together to flex the fingers. Surprisingly, we found that the motor neurons controlling the compartments of FDS and FDP to the same finger receive completely independent inputs, despite similar mechanical functions of the two muscles. Thus, there is more neural coupling between motor neurons supplying compartments of the same muscle that move different fingers than there is between motor neurons supplying the compartments of two different muscles that move the same finger.Although the motor neurons supplying the flexors of the tips of the thumb [flexor pollicis longus (FPL)] and index finger [index compartment of the flexor digitorum profundus (FDP2)] receive substantial shared synaptic input during a precision grip task, the removal of the normal tactile feedback from the digit pads did not change the amount of common input to the two motor neuron pools, indicating these last-order divergent neurons do not require tactile afferent inputs for activation. Finally, in contrast to the substantial shared input to motor neurons supplying these two extrinsic muscles (FPL and FDP2), the motor neurons supplying two intrinsic muscles of the thumb [adductor pollicis (AdP)] and index finger [first dorsal interosseous (FDI)] were shown to receive few shared inputs during precision grip.

This PhD project was funded by EDEN2020 (Enhanced Delivery Ecosystem for Neurosurgery in 2020). Brain disease represent a cost about 800 billion euros per year in Europe and outcome of treatment is demonstrated to critically depend on the knowledge of functional anatomy and its preservation. By combining pre-operative MRI and diffusion-MRI imaging, intra-operative ultrasounds, robotic assisted catheter steering, brain diffusion modelling and a robotics assisted neurosurgical robot (the Neuromate), EDEN2020 aims at realizing an integrated technology platform for minimally invasive neurosurgery which will provide a significative step change in treatment of brain disease. To date, neurosurgical instruments for diagnostic and therapy (drugs infusion) are inserted via rigid cannulas. This represents a primary technological limitation of treatment with direct consequences in patient’s post-operative outcome, since the insertion of rigid cannulas cannot be planned along procedure-optimised trajectories which take into account tissue microstructures and respect the bundles’ topographical anatomo-functional organisation. To bridge this gap, main aim of EDEN2020 is to engineer a steerable catheter for chronic neuro-oncological disease than can be robotically guided and kept in situ for extended period, which insertion can be tailored on clinical conditions and individual anatomy. The correct trajectory and final positioning of a catheter must be planned and guided through the brain structures by the knowledge of the anatomo-functional organization of the neural circuits subserving the essential motor and cognitive functions to avoid lesions resulting in permanent deficits impacting on the quality of life of patients. In addition, since the diffusivity is enhanced when it follows the white matter pathways belongings to the network in which an individual tumour has grown, as showed by data generated by EDEN consortium, these circuits became the target of the drug. In EDEN animal trials (ovine model), the circuit targeted for delivery was the corticospinal tract, due to the anatomical restriction imposed by the sheep brain. In humans, this descending system, which is essential for everyday life activities allowing the skilled use of the hand (i.e. the ability to manipulate objects and tools), has a much higher level of complexity and its functional organisation has not yet been described in detail as in other animal models. The complexity of the neural organization underlying motor control of hand gestures in humans results in a dramatic degree of freedom, but at the same time in a poor ability to recover after lesions. When this connectivity is infiltrated by a tumour and thus became the possible target of drug delivery devices (EDEN), its complexity must be taken into consideration to avoid the onset of deficits. The great majority of brain tumours occurs in the frontal lobe and, particularly Low Grade Gliomas (LGGs), develop close or within the cortical but mostly subcortical structures involved in motor control. Therefore, to track safely the entrance and the trajectory of catheters, a reference atlas of the neural circuitry controlling hand movement is mandatory to identify which cortical and subcortical areas must not be lesioned to avoid permanent inability. Based on this premises, this PhD project investigated, with a multidisciplinary approach, the frontal networks subserving hand function to provide a frame for understanding the connectivity involved in hand skilled movements, which became a possible target for drug delivery in tumours developing in primary motor and/or pre-motor regions. The skilled use of the hand is allowed by the high level of human sensorimotor control implemented by the corticospinal system, particularly developed in primates, connecting distant and functionally different areas via subcortical bundles and finally acting on the spinal cord with a huge bundle of descending fibres. This complex network computes the sensory information related to the goal of the action to shape the appropriate motor command for motoneurons, the final common path to muscles. Non-human primate studies have demonstrated that the main motor output of the corticospinal tract is the primary motor cortex (M1), which act on the spinal motoneurons, in producing voluntary hand and finger movements. The monkey M1 has recently been demonstrated to represent an anatomo-functional non-unitary sector, subdivided in a caudal region dense with cortico-motoneuronal cells and a rostral sector with few monosynaptic connections to alpha-motoneurons and/or with slower projections to the spinal cord. To control and execute skilled hand movements, M1 is highly interconnected with other frontal and parietal cortical pre-motor regions, with subcortical structures such as the basal ganglia and with the cerebellum. A precise description of the human circuitry allowing for realization of dextrous hand movement is still missing in the human, as the electrophysiological and anatomical experimental approaches developed in animal models cannot be performed (i.e. intracortical microstimulation, neuronal tracing, lesion studies etc.). The unique setting of brain tumour resection with the brain mapping technique gives a great opportunity to use clinical data to evaluate neural networks in humans. In this setting, during surgical resection, Direct Electrical Stimulation (DES) is applied onto the exposed cortical and subcortical areas in order to identify the eloquent sites, i.e. where DES elicits motor responses, thus individuating the structures directly acting on the motor descending pathways, or induces transient impairment of the execution of a task, due to its interference with the physiological activity of the stimulated area. This approach allows for the extension of the resection of the tumour beyond its boundaries, increasing the patients’ survival while preserving their functional integrity. As has emerged by recent publications of our group, among the different stimulation paradigms available for intraoperative monitoring, the high frequency stimulation (‘the pulse technique’), which elicits motor evoked potentials (MEPs), is the most reliable paradigm for mapping the descending fibres originating form primary and non-primary motor areas, also in lesions infiltrating M1, while long and short-range fronto-parietal premotor pathways are well identified when low frequency stimulation (‘the Penfield technique’) is applied while the patient is performing a dedicated object manipulation task, clearly interfering with its performance. With a multidisciplinary approach, by combining electrophysiological data with virtual anatomical dissections by means of high angular resolution diffusion imaging (HARDI) tractography we correlated the functional properties of the stimulated sites with specific anatomical structures. In this PhD project, we focused on: the anatomo-functional properties of the human hand representation in M1 (study 1); the oncological and functional efficiency of high-frequency mapping in tumours harbouring within M1 (study 2); the frontal premotor pathways involved in controlling fine hand movements (study 3). Study 1, conducted on 17 patients who underwent an awake procedure, reported a possible subdivision, based on anatomo-functional analysis, of the human hand-knob in two sectors (a posterior one, close to the central sulcus, and an anterior one, close to the precentral sulcus) with different cortical excitability, different hand-muscle electromyographic (EMG) pattern when stimulations were delivered during the object manipulation task and, finally, with different local cortico-cortical connectivity. Overall data suggests that the two sectors may exert different roles in motor control. Study 2 consisted of a retrospective analysis of 102 patients who underwent an asleep procedure for the removal of tumours harbouring with M1 and its descending fibres. The neurophysiological protocols adopted for the intraoperative brain mapping were correlated with the clinical condition, the tumour imaging features, the extent of the resection and the post-operative functional outcome. First, results indicated that M1 tumour removal is feasible and safe and the high frequency stimulation was revealed as the most efficient and versatile paradigm in guiding resection of M1, affording 85.3% complete resection and only 2% permanent morbidity. The study confirmed the possible subdivision of M1 in a rostral less excitable region and a caudal more excitable region reported in Study1 with its clinical impact: the rostral sector can be indeed considered a safe point of entry for surgery and thus for catheters. Study 3 aimed at characterizing the effect of DES on the electrical activity (EMG) of hand movers during a dedicated object-manipulation task during subcortical stimulation of the frontal white matter anterior to M1 (precentral gyrus) and the anatomical evaluation of the stimulated sites by means of diffusion tractography, in 36 patients who underwent an awake surgery. Results indicated that stimulations of dorsal premotor connections with the spinal cord, dorsal striatum, local U-shaped connections and the superior longitudinal fasciculus I and II resulted in abrupt arrest of the hand, while more ventral stimulation, mainly targeting the third branch of the superior longitudinal fasciculus (SLF III) resulted in clumsy hand movements. Resection cavities analysis showed that transient post-operative upper-limb motor deficit occurred only disconnecting the supplementary motor area corticofugal fibres and the frontal U-shaped connections. Overall data suggests that DES on dorsal premotor white matter could interfere with areas involved in the very final stages of the motor program, while DES on ventral premotor white matter could halt the sensorimotor transformations necessary for correct hand shaping.

Robotic arms and hands come in all shapes and sizes, they can be general purpose or task-specific. They can be pre-programed by a computer or controlled by a human operator. There is a certain subsection of robotic hands which try to mimic the shape, movement and function of the human hand, these are sometimes known as biomimetic robotics. This project explores the human robot interaction by creating an anthropomorphic robotic hand with an accompanying exoskeleton. The hand, which consists of a 3D-printed body and fingers, is connected to a forearm where the servos that control the fingers are housed. The exoskeleton connects to the operator's hand allowing finger tracking through a set of potentiometers. This setup allows the operator to intuitively control a robotic hand with a certain degree of precision. We set out to answer research questions in regard to the form and function of a biomimetic hand and the exoskeleton. Along the way, a multitude of problems were encountered such as budgetary issues resulting in only half the fingers having movement. Despite this, good results were gathered from the functioning fingers and our research questions were answered.
Robotarmar och händer finns många former och storlekar, de kan vara för allmänna ändamål eller uppgiftsspecifika. De kan programmeras av en dator eller styras av en mänsklig operatör. Det finns en viss typ av robothänder som försöker efterlikna formen, rörelsen och funktionen hos den mänskliga handen, och brukar kallas biomimetisk robotik. Detta projekt utforskar interaktionen mellan människa och robot genom att skapa en antropomorf robothand med tillhörande exoskelett. Handen, som består av en 3D-printad kropp och fingrar, är ansluten till en underarm där servormotorerna som styr fingrarna sitter. Exoskelettet ansluts till operatörens hand vilket möjliggör spårning av fingrarnas rörelse genom ett antal potentiometrar. Detta tillåter operatören att intuitivt styra en robothand med en viss grad av precision. Vi valde att besvara ett antal forskningsfrågor med avseende på form och funktion av en biomimetisk hand och exoskelettet. Under projektets gång påträffades en mängd problem såsom budgetproblem som resulterade i att bara hälften av fingrarna kan kontrolleras. Trots detta fick vi bra resultat från de fungerande fingrarna och våra forskningsfrågor kunde besvaras.

This thesis describes a series of experiments in human observers using neurophysiological and behavioural approaches to investigate the effects of varying haptic stimuli, attentional demand and age on motor control and perception during haptic sensing (i.e., using the hand to seek sensory information by touch). In Experiments I-IV, transcranial magnetic stimulation (TMS) was used to explore changes in corticomotor excitability when participants were actively engaged in haptic sensing tasks. These studies showed that corticospinal excitability, as reflected in motor evoked potential (MEP) amplitude, was greatly enhanced when participants were engaged in different forms of haptic sensing. Interestingly, this extra corticomotor facilitation was absent when participants performed finger movements without haptic sensing or when attention was diverted away from haptic input by a concurrent cognitive task (Exp I). This provided strong evidence that the observed corticomotor facilitation was likely central in origin and related to haptic attention. Neuroimaging has shown activation of the parieto-frontal network likely subserves this aspect of haptic perception. Further, this haptic-specific corticomotor facilitation was finely modulated depending on whether participants focused attention on identifying material (texture) as opposed to geometric properties of scanned surfaces (Exp II). With regards to aging effects, haptic-related corticomotor facilitation was associated with higher recognition accuracy in seniors (Exp III). In line with this, seniors exhibited similar levels of haptic-related corticomotor facilitation to young adults when task demands were adjusted for age (Exp IV). Interestingly, both young and senior adults also showed substantial corticomotor facilitation in the ‘resting’ hand when the ipsilateral hand was engaged in haptic sensing (Exp IV). Simply touching the stimulus without being required to identify its properties (no attentional task demands) produced no extra corticomotor facilitation in either hand or age group, attesting again to the specificity of the effects with regards to haptic attention. In Experiments V-VI, the ability to recognise 2-D letters by touch was investigated using kinematic and psychophysical measures. In Experiment V, we characterized how age affected contact forces deployed at the fingertip. This investigation showed that older adults exhibited lower normal force and increased letter-to-letter variability in normal force when compared to young adults. This difference in contact force likely contributed to longer contact times and lower recognition accuracy in older adults, suggesting a central contribution to age-related declines in haptic perception. Consistent with this interpretation, Experiment VI showed that haptic letter recognition in older adults was characterized not only by lower recognition accuracy but also by substantial increases in response times and specific patterns of confusion between letters. All in all, these investigations highlight the critical interaction of central factors such as attentional demand with aging effects on motor and perceptual aspects of haptic sensing. Of particular significance is the clear demonstration that corticomotor excitability is greatly enhanced when a haptic sensing component (i.e., attending to specific haptic features) is added to simple finger movements performed at minimal voluntary effort levels (typically <15 % of the maximal effort). These observations underline the therapeutic potential of active sensory training strategies based on haptic sensing tasks for the re-education of motor and perceptual deficits in hand function (e.g., subsequent to a stroke). The importance of adjusting attentional demands and stimuli is highlighted, particularly with regards to special considerations in the aging population.

The reactive control of fingertip forces maintaining grasp stability was examined in man during a prehensile task. Blindfolded subjects used the precision grip between the tips of index finger and thumb to restrain an object that was subjected to unpredictable load forces. These were delivered tangential to the parallel grip surfaces of the object. Load forces, grip forces (perpendicular to the grip surfaces) and position of the object were recorded.Subjects automatically adjusted the grip forces to loads of various amplitudes and rates. Thereby they maintained a reliable safety margin against frictional slips without using excessive grip forces. A rapid rise in grip force lasting about 0.2 s was triggered after a short delay following the onset of a sustained ramp load increase. This 'catch-up' response caused a quick restoration of an adequate grip:load force ratio that prevented frictional slips. If the ramp load continued to increase after the catchup response, the grip force also increased in parallel with the load change in a 'tracking' manner. Consequently, during the hold phases of 'ramp-and-hold' loads, the employed grip forces were approximately proportional to the load amplitude. Sensory information about the rate of change of the load force parametrically scaled the 'catchup' and 'tracking' responses.Following anesthetic block of sensory input from the digits, the grip responses were both delayed and attenuated or even abolished. To compensate for these impairments, subjects had to voluntarily maintain exceedingly high grip forces to prevent the object from slipping. The grip control improved slightly during hand and forearm support conditions that allowed marked wrist movements to occur in response to the loading. This indicates that signals from receptors in muscles, joints or skin areas proximal to the digits can to some extent be used to adjust grip forces during impaired digital sensibility. In contrast, these signals had only minor influence on the control during normal digital sensibility.Grip responses to loads delivered in various directions revealed that the load direction, in relation to gravity and to the hand's geometry, represents intrinsic task variables in the automatic processes that maintain a stable grasp. The load direction influenced both the response latencies and the magnitudes of the grip responses. The response latencies were shortest for loads in directions that were the most critical with regard to the consequences of frictional slippage, i.e., loads directed away from the palm or in the direction of gravity. Recordings of signals in cutaneous afferents innervating the finger tips demonstrated that these effects on the response latencies depended on differences in the time needed by the central nervous system to implement the motor responses. The short latencies in the most ‘criticar load directions may reflect the preparation of a default response, while additional central processing would be needed to execute the response to loads in other directions. Adjustments to local frictional anisotropies at the digit-object interface largely explained the magnitude effects.In conclusion, grip responses are automatically adjusted to the current loading condition during unpredictable loading of a hand held object. Subjects call up a previously acquired sensorimotor transform that supports grasp stability by preventing both object slippage and excessive grip forces. Cutaneous sensory information about tangential forces and frictional conditions at the digit-object interface is used to initiate and scale the grip responses to the current loading conditions, largely in a predictive manner.

Diss. (sammanfattning) Umeå : Umeå universitet, 1995, Härtill 5 uppsatser

digitalisering@umu

The goal of this study is to determine the intentional movement direction based on the neural signals recorded from the motor cortex using optical brain imaging techniques. Towards this goal, we developed a cross-correlation analysis technique to determine the movement direction from the hemodynamic signals recorded from the motor cortex. Healthy human subjects were asked to perform a two-dimensional hand movement in two orthogonal directions while the hemodynamic signals were recorded from the motor cortex simultaneously with the movements. The movement directions were correlated with the hemodynamic signals to establish the cross-correlation patterns of firings among these neurons. Based on the specific cross-correlation patterns with respect to the different movement directions, we can distinguish the different intentional movement directions between front-back and right-left movements. This is based on the hypothesis that different movement directions can be determined by different cooperative firings among various groups of neurons. By identifying the different correlation patterns of brain activities with each group of neurons for each movement, we can decode the specific movement direction based on the hemodynamic signals. By developing such a computational method to decode movement direction, it can be used to control the direction of a wheelchair for paralyzed patients based on the changes in hemodynamic signals recorded using non-invasive optical imaging techniques.

Body ownership can be studied via the rubber hand illusion (RHI), in which an artificial limb can be perceived as belonging to oneself. In the so-called moving RHI paradigm, both body ownership and sense of agency, induced by self-produced movements, can be investigated. The key question of this approach is whether movements generated by oneself increase the illusion of body ownership. Thus far, the results from moving RHI studies are inconsistent.This has led to uncertainty regarding the influences of the motor control mechanism on body ownership. Therefore, this study will present the first meta-analysis on moving RHI to estimate the illusory effectiveness induced by self-produced movements. A total of 23 experimental comparisons with 821 subjects were included in the meta-analysis. The results showed that the overall illusory effect induced by self-produced movements was superior toits control (e.g., asynchronous active movements) (Hedge’s g = 1.38, p < 0.001). However, due to dissimilarity in results between the studies, the sample size in the meta-analysis may not represent the general population. The subgroup analysis showed that studies using physical hands, such as wooden hands, yielded the largest effect compared to studies using a virtual projected hand or a video recorded image of the participant’s own hands. It can be speculated whether a three-dimensional hand with “realness” has an illusory advantage compared to hands presented in virtual or video image settings. Future studies need to apply aunified framework, particularly in experimental setups and measurements. This would obtain consistent results of the strength of the illusion within the moving RHI paradigm.

Although upper limb motor impairments are common, the primary tools for assessing and tracking these impairments in a clinical setting are subjective, qualitative rating scales that lack resolution and repeatability. Markerless motion capture technology has the potential to greatly improve clinical assessment by providing quick, low-cost, and accurate tools to objectively quantify motor deficits. Here we lay some of the groundwork necessary to enable markerless motion capture systems to be used in clinical settings. First, we adapted five motor tests common in clinical assessments so they can be administered via markerless motion capture. We implemented these modified tests using a particular motion capture sensor (Leap MotionTM Controller, hereafter referred to as the Leap Motion sensor) and administered the tests to 100 healthy subjects to evaluate the feasibility of administrating these tests via markerless motion capture. Second, to determine the ability of the Leap Motion sensor to accurately measure tremor, we characterized the frequency response of the Leap Motion sensor. During the administration of the five modified motor tests on 100 healthy subjects, the subjects had little trouble interfacing with the Leap Motion sensor and graphical user interface, performing the tasks with ease. The Leap Motion sensor maintained an average sampling rate above 106 Hz across all subjects during each of the five tests. The rate of adverse events caused by the Leap Motion sensor (mainly jumps in time or space) was generally below 1%. In characterizing the frequency response of the Leap Motion sensor, we found its bandwidth to vary between 1.7 and 5.5 Hz for actual tremor amplitudes above 1.5 mm, with larger bandwidth for larger amplitudes. To improve the accuracy of tremor measurements, we provide the magnitude ratios that can be used to estimate the actual amplitude of the oscillations from the measurements by the Leap Motion sensor. These results suggest that markerless motion capture systems are on the verge of becoming suitable for routine clinical use, but more work is necessary to further improve the motor tests before they can be administered via markerless motion capture with sufficient robustness for clinical settings.

Muscle spindles are complex sensory organs that have been strongly implicated in the control and perception of movements. Human muscle spindles in relaxed muscles behave as stretch receptors, responding to the length and velocity of their parent muscles. However, it has been unclear how they discharge during active movements since their discharges are also affected by fusimotor activity and extrafusal contractions. The vast majority of neurophysiological recordings of muscle afferents have been obtained under passive conditions, or active but behaviourally restricted conditions. These restrictions prevent predictions of human muscle afferent activity during purposeful multi-joint movements, naturally occurring during tasks such as hand shaping, grasping or key-pressing. An experimental protocol was therefore developed which allowed recordings of muscle receptor afferent activity using microneurography during unrestrained wrist and digit movements. Along with single afferent discharges, recordings were obtained of electromyographic activity of major forearm muscles and the kinematics of the wrist and digits. This approach allowed investigations of the factors shaping afferent discharge during everyday manual tasks, i.e., block-grasping and pressing sequences of keys, and during active sinusoidal joint movements. The afferents’ ability to encode information concerning the state of the muscle and joint kinematics during these tasks was also assessed. The responses of spindle afferents from load-bearing muscles were approximatelly 90 degrees more phase-advanced than expected on the length of their parent muscles. That is, the discharges of primary muscle spindle afferents were significantly affected by both velocity and acceleration, the discharges of secondary afferents by velocity, and neither afferent type was particularly affected by static muscle length. Accordingly, these afferents failed to encode length, encoded velocity well and acceleration poorly. The representation of muscle length and velocity was, however, significantly improved when the discharge activity of Golgi tendon afferents was taken into consideration along with muscle spindle activity. The discharge of primary afferents during both key-pressing and block-grasping was best correlated to the muscle velocities observed ~100-160 ms in the future. This predictive ability went beyond what could be expected from the spindles’ simultaneous sensitivity to velocity and acceleration, and could thus only be explained by implicating the fusimotor drive. In addition, evidence is presented that the fusimotor control of spindles was contingent on entire movement sequences during the key-pressing task. It is proposed that the phase relationship between the discharge rate of spindle afferents and the length of their parent muscles is load dependent. Moreover, muscle spindles seem to act as forward sensory models of their parent muscle, which makes sensorial feedback control possible despite neural delays.

La capacité de coordonner efficacement nos yeux avec nos mains est déterminante pour le succès de nos actions quotidiennes. En outre la capacité de prédire les conséquences sensorielles de nos propres actions est cruciale pour nos habilités motrices. Dans ce travail, à l’aide d’une tâche dans laquelle les participants doivent suivre avec leurs yeux une cible visuelle bougée par leur main, nous nous intéressons aux mécanismes prédictifs sous-tendant la coordination œil-main. Dans une première étude utilisant un protocole d’adaptation à une rotation visuomotrice, nous montrons que ces mécanismes prédictifs peuvent être mis à jour indépendamment de notre capacité à effectuer des mouvements précis de la main. Dans l’étude suivante nous cherchons à déterminer l’effet de la préférence manuelle, et montrons que malgré des différences évidentes en termes de précision concernant le contrôle manuel, la capacité d’anticiper les conséquences visuelles de nos actions reste identique que la cible soit bougée par la main droite ou gauche. Enfin, grâce à la stimulation magnétique transcranienne, nous testons l'hypothèse selon laquelle ces mécanismes prédictifs utilisent des signaux efférents de la main issus du cortex moteur primaire (M1). Nos résultats montrent que si cette contribution existe, elle doit se faire nécessairement en amont de M1. Au bout du compte nous proposons que la coordination œil-main soit sous-tendue par des mécanismes prédictifs similaires pour nos deux mains, situés vraisemblablement en amont de M1, et pouvant être mis à jour indépendamment du contrôle de la main
The ability to coordinate efficiently eye and hand actions is central for humans in everyday activities. Furthermore it is argued that the ability to predict the sensory consequences of self-initiated movements is crucial for skilled motor behavior. Here by means of a task in which participants were asked to track with the eyes a visual target that was moved by their hand, we investigated the predictive mechanisms underlying eye-hand coordination. In a first study, using a protocol in which participants had to adapt to rotated hand visual feedback, we show that these predictive mechanisms can be updated independently of the ability to perform accurate hand movements. In a follow up study we tested the effect of hand dominance, and showed that, despite obvious differences in the accuracy of hand movement control, the ability to predict visual consequences of right and left hand actions was similar. Finally, by means of transcranial magnetic stimulation, we tested the hypothesis that those predictive mechanisms rely on hand efferent signals from the primary motor cortex (M1). However our results failed to support this view, and instead suggest that if such a contribution exists, it must be upstream of M1. Overall, we propose that eye-hand coordination relies on similar predictive mechanisms for both hands, possibly located upstream of M1, which can be updated independently of hand movement control

Direct cortico-motoneuronal (CM) connections of corticospinal tract neurons are a distinctive feature of the primate motor system which are known to be important for the capacity to perform independent finger movements. However, it is still unclear how the appropriate combinations of CM cells are recruited to produce the selective (fractionated) control over muscles of the upper limb that is necessary for independent finger movements. I have investigated whether GABAergic intracortical inhibitory (ICI) circuits in human motor cortex contribute to the selection of the appropriate CM cells during a motor task requiring selective activation of one of several intrinsic hand muscles. Behaviour of ICI circuits during voluntary contraction was compared for the dominant and non-dominant hemisphere of right-handed subjects, as hemispheric differences in ICI may contribute to preferential use of the right hand for fine motor tasks. Finally, I investigated the range of forces over which ICI contributes to selective activation of a hand muscle. Neurologically normal adult human subjects were recruited for all experiments. Surface electrodes recorded electromyographic activity of abductor pollicis brevis (APB), first dorsal interosseous and abductor digiti minimi muscles during controlled isometric contractions of APB at different force levels while subjects attempted to keep the other two muscles relaxed using visual feedback of EMG. Paired-pulse transcranial magnetic stimulation (TMS) was used to assess ICI at rest and during selective activation of a hand muscle. TMS intensity and interstimulus interval were varied in different trials. Data were compared for two different directions of induced current in the brain; posteriorly directed current (PA stimulation) and anteriorly directed current (AP stimulation). ICI is suppressed for corticospinal neurons controlling the muscle targeted for selective activation; no change in ICI was seen for corticospinal neurons controlling the muscles required to be relaxed. This indicates that differential modulation of ICI in human motor cortex contributes to selective activation of a hand muscle. The direction of current flow induced in the brain proved to be critical for demonstrating this effect. It was observed with AP stimulation but not PA stimulation. I argue that this is due to preferential activation by PA stimulation of interneurons producing I1 waves in corticospinal neurons. These interneurons are not acted upon by ICI circuits. This problem makes the conventional PA paired-pulse TMS technique unreliable for the assessment of ICI during voluntary contraction. With AP stimulation it was demonstrated that ICI is not modulated during weak selective activation of a hand muscle (<5percent of maximal voluntary contraction), but ICI effects on CM cells controlling the target muscle are progressively suppressed at higher levels of activation. The present study is the first to examine hemispheric differences in ICI during selective isometric contraction of an intrinsic hand muscle. No hemispheric differences were observed. These studies have demonstrated a functional role for ICI in fractionation of hand muscle activity in normal subjects. It also provides an improved basis for investigating the changes in ICI with TMS in various neurological conditions in which it has been reported that GABAergic inhibition is abnormal.
Thesis (Ph.D.)--School of Molecular and Biochemical Science, 2004.

Coordinated gaze and hand movements predominate a number of our interactions in reachable space and yet few studies examine the potential contribution of tactile feedback in planning these actions. This thesis was designed to investigate eye and hand coordination during movement sequences when reaching out to interact with objects. We developed a virtual reality paradigm that allowed us to control visual, tactile, and in some cases, auditory feedback provided to participants. Participants reached and touched five objects in succession. We measured behaviour that resulted from removing one or more of the aforementioned sources of feedback – focusing on task accuracy, and the timing and dynamics of eye and hand movements. Our principle manipulations were to remove visual feedback of the hand, and/or to change the object response to contact. We also unexpectedly removed tactile feedback signaling contact. In Experiment 1, we examined gaze and hand movement timing relative to contact events. Gaze remained long enough to capture contact in central vision, but also followed a time course indicating that contact timing was predicted. In Experiment 2 we examined the influence of dynamic object consequences (i.e., motion). Gaze remained to monitor consequences that follow initial contact especially when the hand was invisible; with longer delays it became difficult to differentiate between predictive or reactive movements. In Experiment 3 we directly tested whether gaze would hold upon a site of action during prolonged manipulation. Here, gaze remained past contact time and instead its departure was associated with the completion of action. Our findings are congruent with the notion that visually guided reaches are controlled to facilitate directing the hand to viewed locations of action – without visual feedback of the hand accuracy diminished and hand approach changed across all experiments. However, we provide consistent evidence that gaze is also controlled to capture planned sensory consequences related to action at its viewed location. Monitoring these sites would facilitate comparing predicted sensory events with those that are actively measured and improve control throughout the movement sequence. Such a process also indicates the importance of considering tactile feedback when examining coordinated eye and hand movements.
Thesis (Ph.D, Neuroscience Studies) -- Queen's University, 2009-11-13 16:12:30.086

abstract: Dexterous manipulation is a representative task that involves sensorimotor integration underlying a fine control of movements. Over the past 30 years, research has provided significant insight, including the control mechanisms of force coordination during manipulation tasks. Successful dexterous manipulation is thought to rely on the ability to integrate the sense of digit position with motor commands responsible for generating digit forces and placement. However, the mechanisms underlying the phenomenon of digit position-force coordination are not well understood. This dissertation addresses this question through three experiments that are based on psychophysics and object lifting tasks. It was found in psychophysics tasks that sensed relative digit position was accurately reproduced when sensorimotor transformations occurred with larger vertical fingertip separations, within the same hand, and at the same hand posture. The results from a follow-up experiment conducted in the same digit position-matching task while generating forces in different directions reveal a biased relative digit position toward the direction of force production. Specifically, subjects reproduced the thumb CoP higher than the index finger CoP when vertical digit forces were directed upward and downward, respectively, and vice versa. It was also found in lifting tasks that the ability to discriminate the relative digit position prior to lifting an object and modulate digit forces to minimize object roll as a function of digit position are robust regardless of whether motor commands for positioning the digits on the object are involved. These results indicate that the erroneous sensorimotor transformations of relative digit position reported here must be compensated during dexterous manipulation by other mechanisms, e.g., visual feedback of fingertip position. Furthermore, predicted sensory consequences derived from the efference copy of voluntary motor commands to generate vertical digit forces may override haptic sensory feedback for the estimation of relative digit position. Lastly, the sensorimotor transformations from haptic feedback to digit force modulation to position appear to be facilitated by motor commands for active digit placement in manipulation.
Dissertation/Thesis
Doctoral Dissertation Kinesiology 2014

Recent evidence suggests that when performing reach-and-grasp actions on day-to-day objects, lift-actions are faster to execute relative to use-actions, and that a “use-on-lift” interference occurs and produces switch costs when changing actions from using to then lifting (Jax & Buxbaum, 2010; Osiurak & Badets, 2016). Such findings result from paradigms that include the sudden appearance of objects, requiring participants to react quickly to the features of the object, independent of the functionality of the objects. Because of the importance this topic has to day-to-day interactions with objects, the following four experiments were executed with objects continuously visible to participants. When imitating images of hand actions on objects, participants showed no differences in the initiation time of use- and lift-actions, suggesting that no systematic differences exist between these two actions. Using this as a baseline, we compared a more generative approach, as when actions are instructed by auditory sentences. In this case, we see that switching actions is difficult, switching objects is even more difficult, and that use-actions are modestly faster than lift-actions; the reverse of what previous research shows. In a third experiment modelled after the paradigm used in studies producing rapid lift- and slowed use-actions, we showed that use-actions are actually facilitating lift-actions. Further, we demonstrate that having a use-action goal in mind provides the knowledge required to perform a lift-action, and that use-actions are again faster than lift-actions. These results are a critical addition to the task-switching literature on the cognitive control of motor processes associated with hand actions as distinctions are made between non-naturalistic and realistic settings relevant to day-to-day interactions with objects. We show that use-actions facilitate lift-actions and that, in realistic settings, both use- and lift-actions require access to stored knowledge.
Graduate
0633
hvanmook@uvic.ca

碩士
長庚大學
機械工程研究所
88
Impairment of volitional motor activity is common after stroke, head injury, spinal cord injury and other conditions of upper motor neuron dysfunction. This finding is particularly relevant in stroke patients who have achieved substantial recovery of speech and gait, but volitional motor activity of the hand remained incomplete or absent. Therefore, the evaluation and training of the hand motor control functions become an important part of the rehabilitation therapy for these patients. In view of the above, this study is made aimed at the clinical needs of the upper motor neuropathy patients by combining the efforts of doctors, rehabilitation therapists and engineers and by integrating the sensors, computerized images, feedback controls and computer technologies for developing and pioneering a human hand motor control assessment and training system as well as a hand continuous passive motion rehabilitation training system for the patients. This study will be proceeded by dividing it into three parts, the first part was using the 5DT gloves available in the market and combining which with the hardware units of hand/palm pressure measurement module, digit hand-writing pad module and biofeedback hand dexterity assessment, training module, etc. to design and develop a hand motor control assessment and training system, whose functions include: articulation activity real time measurement and display, hand/palm pressure measurement, virtual 3D palm interaction display, hand-writing performance evaluation, etc.; the second part was to design a hand continuous passive motion (CPM) mechanical glove, which has 5 tendon driven fingers, each has a 2 degree of freedom. With the aid of interacting windows and post-treatment database, the goal of continuous passive motion and functional movement training can then be achieved. While the third part was using the hand motor control assessment and training system developed in to use to carry out clinical evaluations and experiments on hand motor control functions for 13 normal individuals and 26 patients with focal dystonia (such as patients with writer''s cramp). Tests were conducted in 2 modes of: writing without wearing the glove, writing by wearing the glove with hand/palm pressure sensors. The main evaluation items included as follows : the hesitation time during writing, the number of letters written, the delay time for starting writing, the contact pressure of hand against paper during writing, the contact pressure of hand against pen during writing. The experimental were analyzed. The results showed apparent differences between normal subject and patients with writing contraction disease, for example, the average hesitation time per letter of the patient group was 3.5 times longer than that of the normal subject group, the delay time for starting writing of the former group was 2.25 times as longer as that of the latter, moreover, the pen/paper contact pressures of the former were 1.43 times higher than those of the latter. With the accomplishment of this study, the developed hand motor control assessment and continuous passive motion rehabilitation training system not only can be immediately provided for evaluation and rehabilitation training by the clinical physicians for patients with hand motor control function disorders, but also can be synchronously used to collect physical signals (such as articulation activity degrees, finger/palm pressures, etc.) of the patients during the course of rehabilitation training. Quantitative index introduces in this study may be used for evaluating the therapeutic effects of the palm motor control functions of the patients. Besides, the prototype of the pioneered system should have the potential of applying for patent, and the design conception, software/hardware of the developed system can be transferred to the relevant medical industries in order to inspire the interest of people in researching, developing and manufacturing high-tech rehabilitation treatment apparatus, thus promote the upgrading of domestic medical care industry.

abstract: The human hand is a complex biological system. Humans have evolved a unique ability to use the hand for a wide range of tasks, including activities of daily living such as successfully grasping and manipulating objects, i.e., lifting a cup of coffee without spilling. Despite the ubiquitous nature of hand use in everyday activities involving object manipulations, there is currently an incomplete understanding of the cortical sensorimotor mechanisms underlying this important behavior. One critical aspect of natural object grasping is the coordination of where the fingers make contact with an object and how much force is applied following contact. Such force-to-position modulation is critical for successful manipulation. However, the neural mechanisms underlying these motor processes remain less understood, as previous experiments have utilized protocols with fixed contact points which likely rely on different neural mechanisms from those involved in grasping at unconstrained contacts. To address this gap in the motor neuroscience field, transcranial magnetic stimulation (TMS) and electroencephalography (EEG) were used to investigate the role of primary motor cortex (M1), as well as other important cortical regions in the grasping network, during the planning and execution of object grasping and manipulation. The results of virtual lesions induced by TMS and EEG revealed grasp context-specific cortical mechanisms underlying digit force-to-position coordination, as well as the spatial and temporal dynamics of cortical activity during planning and execution. Together, the present findings provide the foundation for a novel framework accounting for how the central nervous system controls dexterous manipulation. This new knowledge can potentially benefit research in neuroprosthetics and improve the efficacy of neurorehabilitation techniques for patients affected by sensorimotor impairments.
Dissertation/Thesis
Doctoral Dissertation Neuroscience 2017

碩士
長庚大學
機械工程研究所
90
Patients with writer’s cramp or upper motorneuron disease (ex. Parkinson’s disease, stroke, and other brain injuries) often have difficulty in processing upper arm movement because of involuntary muscle contraction or neuron regression. This often results in trembling of the involved extremity. Most patients , still experience palm/arm movement obstacles even after treatment/surgery. Therefore, clinical evaluation and rehabilitation training for writing with a pen and arm movement are important parts of the postoperative management.. In this research , clinical testing and quantitative evaluation of the writing function of the patients was done. A series of robotic manipulators for arm movement assessment and rehabilitation was designed and its applications were tested quantitatively and diagrammatically. In the first part of this research , an evaluation system was developed which aimed to quantitatively measure the patients’ arm function using four parameters : the contact pressure between paper and pen, the time delay before start of writing, the hesitation time spent between words, and the total written words in a given time. An evaluation standard for quantitative writing was set-up, clinical testing and subsequent statistical analysis of the results was done. A total of 26 patients and 13 control subjects were studied. The results were analyzed using the SPSS statistical software and showed that t test values of the four estimation parameters were all less than 0.05. This means that there was a significant difference between the evaluation parameters of the patients and normal control subjects. These results can provide a reference for clinicians when diagnosing patients. The second part of the research was aimed to decrease the time and energy spent by therapists who usually have to repeatedly say or demonstrate the correct motions for arm rehabilitation. A mechanical device was designed to manipulate the arm movement and provide the patient with a continuous passive rehabilitation. The machine used was a SCARA type robotic manipulator with four degrees of freedom. This was connected to a computer with a software based on Windows 2000 and Visual Basic 6.0. Also designed for this project to adjust the rehabilitation parameters (i.e. velocity, circle/ellipse movement locus size, etc.). This set up enables the doctor or therapist to choose the proper rehabilitation parameters and patterns for patients who will undergo a continuous upper arm continuous passive rehabilitation. The third part of the research was aimed to consolidate the mechanical 3-D Digitizer already existing in the market and the interface software we developed into a manipulator for the evaluation of upper arm movement function in order to improve the defects noted during initial rehabilitation. This would also provide diagrammatic (arm movement locus radial error, distribution diagram) and quantitative (radial error of normal value, radial error of absolute value, average drawing circle rate, etc.) evaluation indicators and clinical test standards. This consolidated robotic manipulator was further tested on 11 stroke paralysis patients, 5 normal elders, and 6 normal youths. The results showed that there was a significant difference between the three test groups. From the quantitative evaluation indicators, it is shown that the radial error of absolute value was 2 to 3 times more among the stroke patients compared to that of the normal elders, and 3 to 4 times more compared to that of the normal youths. From the diagrammatic evaluation indicators, we found that in the arm movement locus radial error distribution diagram, stroke paralysis patient had the widest area of radial error of absolute value compared to the rest. The error value was about 4 to 9 times more than the normal elder group and 9 to 16 times more than the normal youth group. This objectively result shows that the stroke patients had more serious functional defects. These results can provide a reference for clinicians in the diagnosis of functional defects of patients. The hand writing function evaluation system for using a pen and the manipulator for the assessment of arm function will be able to provide assistance to the clinician as new tools to evaluate patients’ palm/arm motor function. The robotic manipulator can be used for the postoperative rehabilitation the training of the patient. The standards and quantitative evaluation indicators developed in this research can be used as new tool and methods of the treatment for upper motorneuron or palm/arm movement dysfunction patients.

The study of movement has always fascinated artists, photographers and researchers. Across the years, several attempts to capture, freeze, study and reproduce motion were made. Nowadays, motion capture plays an important role within many fields, from graphical animation, filmmaking, virtual reality, till medicine. In fact, movement analysis allows to measure kinematic and kinetic performance of the human body. The quantitative data obtained from measurements may support the diagnosis and treatment of many pathologies, allowing to take clinical decisions and supporting the follow-up of treatments or rehabilitation. This approach is nowadays named evidence based medicine. In this work, motion capture techniques and advanced signal processing techniques were exploited in order to: (i) develop a protocol for the validation and quality assurance of the clinical strength measurements, (ii) develop an algorithm for clinical gait analysis data interpretation and identification of pathological patterns, and (iii) design user-friendly software tools to help clinicians using the novel data processing algorithms and reporting the results of measurements. This work was divided into three sections: Part 1 contains a survey about the history of motion analysis and a review of the earliest experiments in biomechanics. The review covered the first historical attempts, that were mainly based on photography, till the state-of-the-art technology used today, i.e. the optoelectronic system. The working principle of optoelectronic system was reviewed as well as its applications and modern setups in the clinical practice. Some modern functional evaluation protocols, aimed to the quantitative evaluation of physical performance and clinical diagnosis of motor disorders, were also reviewed. Special attention was paid to the most common motion analysis exam that is nowadays worldwide standardized, i.e. the Gait Analysis. Examples of Gait Analysis studies on subjects with pathology and follow-up were reviewed. Part 2 concerns the design of an experimental setup, involving motion analysis, for the quality assurance of clinical strength measurements. Measurements of force are popular in the clinical practice as they allow to evaluate the muscle weakness, health status of patients and the effects of therapies. A variety of protocols was proposed to conduct such measurements, implying the acquisition of forces, angles and angular velocities when the maximum voluntary force is exerted. Hand held dynamometry (HHD), based on single component load cell, was extensively used in clinical practice; however, several shortcomings were identified. The most relevant were related to the operator’s ability. This work was aimed to investigate the inherent inaccuracy sources in knee strength measurements when are conducted by a single component load cell. The analysis was conducted by gathering the outputs of a compact six-component load cell, comparable in dimension and mass to clinical HHDs, and an optoelectronic system. Quality of measurements was investigated in terms of quantifying, by an ad-hoc metrics, the effects induced in the overall inaccuracy by: (i) the operator’s ability to place and to hold still the HHD and (ii) ignoring the transversal components of the force exchanged between the patient and the experimenter. The main finding was that the use of a single component HHD induced an overall inaccuracy of 5% in the strength measurements, when operated by a trained clinician and angular misplacements are kept within the values found in this work (≤15°) and with a knee ROM ≤ 22°. Even if the measurement outputs were reliable and accurate enough for both knee flexion and extension, extension trials were the most critical due to the higher force exerted, i.e. 249.4±27.3 N vs. 146.4±23.9 N of knee flexion. The most relevant source of inaccuracy was identified in the angular displacement of HHD on the horizontal plane. A dedicated software, with graphical user interface, was designed and implemented. The purposes of this software were to: (i) speed up data processing, (ii) allow user to select the proper processing workflow, and (iii) provide clinicians with a tool for quick data processing and reporting. Part 3 concerns the research study about gait analysis on subjects with pathology. Gait analysis is often used for the assessment of the gait abilities in children with cerebral palsy and to quantify improvements/variations after a treatment. To simplify GA interpretation and to quantify deviation from normality, some synthetic descriptors were developed in literature, such as the Movement Analysis Profile (MAP) and the Linear Fit Method (LFM). The aims of this work were: (i) to use synthetic descriptors in order to quantify gait variations in subjects with Cerebral Palsy that underwent surgery involving bone repositioning and muscle/tendon lengthening at the level of the femur and hamstring group (SEMLS); (ii) test the effectiveness of a recently proposed index, i.e. the LFM, on such patients; (iii) design and implement a novel index that may overcome the limitations of the previous methods. Gait Analysis exams of 10 children with Cerebral Palsy, pre and post treatment, were collected. Data were analysed by means of MAP and LFM indices. To overcome the limitations observed for the methods, another index was designed as a modified version of the MAP, namely the OC-MAP. It took into account the effect on deviation due to offset and allowed to compute the deviation from normality on tracks purified by the offset. An overall improvement of the gait pattern was observed for most of the subjects after surgery. The highest effect was observed for the knee flexion/extension angle. Patients who had initial high deviations also had the largest improvements. Worsening in the kinematics of the pelvis could be explained as a consequence of SEML involving a lengthening of hamstring group. Pre-post differences were higher than the Minimally Clinical Important Difference for all parameters, except hip flexion. An improvement towards normality was observed for all the parameters, with exception of pelvic tilt for which a worsening was observed. LFM provided results similar to OC-MAP offset analysis but could not be considered reliable due to intrinsic limitations. As offset in gait features played an important role in gait deviation, OC-MAP synthetic analysis is recommended to study gait pattern of subjects with Cerebral Palsy. A dedicated software, with graphical user interface, was designed and implemented. The purpose of this software was to compute the synthetic descriptors on a large amount of data, to speedup data processing and to provide clinicians with a quick access to the results