The Experts below are selected from a list of 306 Experts worldwide ranked by ideXlab platform
Bahman Nasseroleslami - One of the best experts on this subject based on the ideXlab platform.
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Visuomotor control of ankle joint using position vs force
European Journal of Neuroscience, 2019Co-Authors: Amir B Farjadian, Mohsen Nabian, Amber Hartman, Shengche Yen, Bahman NasseroleslamiAbstract:Ankle joint plays a critical role in daily activities involving interactions with environment using force and position control. Neuromechanical dysfunctions (e.g., due to stroke or brain injury), therefore, have a major impact on individuals' quality of life. The effective design of neuro-rehabilitation protocols for robotic rehabilitation platforms relies on understanding the control characteristics of the ankle joint in interaction with external environment using force and position, as the findings in upper limb may not be generalizable to the lower limb. This study aimed to characterize the skilled performance of ankle joint in Visuomotor position and force control. A two-degree-of-freedom (DOF) robotic footplate was used to measure individuals' force and position. Healthy individuals (n = 27) used ankle force or position for point-to-point and tracking control tasks in 1-DOF and 2-DOF virtual game environments. Subjects' performance was quantified as a function of accuracy and completion time. In contrast to comparable performance in 1-DOF control tasks, the performance in 2-DOF tasks was different and had characteristic patterns in the position and force conditions, with a significantly better performance for position. Subjective questionnaires on the perceived difficulty matched the objective experimental results, suggesting that the poor performance in force control was not due to experimental set-up or fatigue but can be attributed to the different levels of challenge needed in neural control. It is inferred that in Visuomotor Coordination, the neuromuscular specialization of ankle provides better control over position rather than force. These findings can inform the design of neuro-rehabilitation platforms, selection of effective tasks and therapeutic protocols.
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Visuomotor control of ankle joint using position vs force
bioRxiv, 2018Co-Authors: Amir B Farjadian, Mohsen Nabian, Amber Hartman, Shengche Yen, Bahman NasseroleslamiAbstract:Ankle joint plays a critical role in daily activities involving interactions with environment using force and position control. Neuromechanical dysfunctions (e.g. due to stroke or brain injury), therefore, have a major impact on individuals' quality of life. The effective design of neuro-rehabilitation protocols for robotic rehabilitation platforms, relies on understanding the control characteristics of the ankle joint in interaction with external environment using force and position. This is particularly of interest since the findings in upper-limb may not be generalizable to the lower-limb. This study aimed to characterize the skilled performance of ankle joint in Visuomotor position and force control. A 2-degree of freedom (DOF) robotic footplate was used to measure individuals force and position. Healthy individuals (n = 27) used ankle force or position for point-to-point and tracking control tasks in 1-DOF and 2-DOF virtual game environments. Subjects' performance was quantified as a function of accuracy and completion time. While the performance measures in 1-DOF control tasks were comparable, the subjects' performance in 2-DOF tasks was significantly better with position control. Subjective questionnaires on the perceived difficulty matched the objective experimental results; suggesting that the poor performance in force control was not due to experimental setup or fatigue but can be attributed to the different levels of challenge needed in neural control. It is inferred that in Visuomotor Coordination, the neuromuscular specialization of ankle provides better control over position rather than force. These findings can inform the design of neuro-rehabilitation platforms, selection of effective tasks, and therapeutic protocols.
Mohsen Nabian - One of the best experts on this subject based on the ideXlab platform.
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Visuomotor control of ankle joint using position vs force
European Journal of Neuroscience, 2019Co-Authors: Amir B Farjadian, Mohsen Nabian, Amber Hartman, Shengche Yen, Bahman NasseroleslamiAbstract:Ankle joint plays a critical role in daily activities involving interactions with environment using force and position control. Neuromechanical dysfunctions (e.g., due to stroke or brain injury), therefore, have a major impact on individuals' quality of life. The effective design of neuro-rehabilitation protocols for robotic rehabilitation platforms relies on understanding the control characteristics of the ankle joint in interaction with external environment using force and position, as the findings in upper limb may not be generalizable to the lower limb. This study aimed to characterize the skilled performance of ankle joint in Visuomotor position and force control. A two-degree-of-freedom (DOF) robotic footplate was used to measure individuals' force and position. Healthy individuals (n = 27) used ankle force or position for point-to-point and tracking control tasks in 1-DOF and 2-DOF virtual game environments. Subjects' performance was quantified as a function of accuracy and completion time. In contrast to comparable performance in 1-DOF control tasks, the performance in 2-DOF tasks was different and had characteristic patterns in the position and force conditions, with a significantly better performance for position. Subjective questionnaires on the perceived difficulty matched the objective experimental results, suggesting that the poor performance in force control was not due to experimental set-up or fatigue but can be attributed to the different levels of challenge needed in neural control. It is inferred that in Visuomotor Coordination, the neuromuscular specialization of ankle provides better control over position rather than force. These findings can inform the design of neuro-rehabilitation platforms, selection of effective tasks and therapeutic protocols.
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Visuomotor control of ankle joint using position vs force
bioRxiv, 2018Co-Authors: Amir B Farjadian, Mohsen Nabian, Amber Hartman, Shengche Yen, Bahman NasseroleslamiAbstract:Ankle joint plays a critical role in daily activities involving interactions with environment using force and position control. Neuromechanical dysfunctions (e.g. due to stroke or brain injury), therefore, have a major impact on individuals' quality of life. The effective design of neuro-rehabilitation protocols for robotic rehabilitation platforms, relies on understanding the control characteristics of the ankle joint in interaction with external environment using force and position. This is particularly of interest since the findings in upper-limb may not be generalizable to the lower-limb. This study aimed to characterize the skilled performance of ankle joint in Visuomotor position and force control. A 2-degree of freedom (DOF) robotic footplate was used to measure individuals force and position. Healthy individuals (n = 27) used ankle force or position for point-to-point and tracking control tasks in 1-DOF and 2-DOF virtual game environments. Subjects' performance was quantified as a function of accuracy and completion time. While the performance measures in 1-DOF control tasks were comparable, the subjects' performance in 2-DOF tasks was significantly better with position control. Subjective questionnaires on the perceived difficulty matched the objective experimental results; suggesting that the poor performance in force control was not due to experimental setup or fatigue but can be attributed to the different levels of challenge needed in neural control. It is inferred that in Visuomotor Coordination, the neuromuscular specialization of ankle provides better control over position rather than force. These findings can inform the design of neuro-rehabilitation platforms, selection of effective tasks, and therapeutic protocols.
Michael A Nitsche - One of the best experts on this subject based on the ideXlab platform.
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nonlinear effects of dopamine d1 receptor activation on Visuomotor Coordination task performance
Cerebral Cortex, 2020Co-Authors: Po See Chen, Michael A Nitsche, Asif Jamil, Lin Cho Liu, Shyh Yuh Wei, Huai Hsuan Tseng, Min Fang KuoAbstract:Dopamine plays an important role in the modulation of neuroplasticity, which serves as the physiological basis of cognition. The physiological effects of dopamine depend on receptor subtypes, and the D1 receptor is critically involved in learning and memory formation. Evidence from both animal and human studies shows a dose-dependent impact of D1 activity on performance. However, the direct association between physiology and behavior in humans remains unclear. In this study, four groups of healthy participants were recruited, and each group received placebo or medication inducing a low, medium, or high amount of D1 activation via the combination of levodopa and a D2 antagonist. After medication, fMRI was conducted during a Visuomotor learning task. The behavioral results revealed an inverted U-shaped effect of D1 activation on task performance, where medium-dose D1 activation led to superior learning effects, as compared to placebo as well as low- and high-dose groups. A respective dose-dependent D1 modulation was also observed for cortical activity revealed by fMRI. Further analysis demonstrated a positive correlation between task performance and cortical activation at the left primary motor cortex. Our results indicate a nonlinear curve of D1 modulation on motor learning in humans and the respective physiological correlates in corresponding brain areas.
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prior state of cortical activity influences subsequent practicing of a Visuomotor Coordination task
Neuropsychologia, 2008Co-Authors: Andrea Antal, Michael A Nitsche, Silva Begemeier, Walter PaulusAbstract:Abstract According to the Bienenstock–Cooper–Munro (BCM) rule, a low overall cortical activity level is suggested to enhance synaptic strength of active neuronal connections, while a high level of activity should diminish it. Whereas the relevance of this mechanism for neuroplasticity in humans has been ascertained on the neurophysiological level, its functional relevance remains unclear so far. The aim of this study was to explore the impact of the pre-performance cortical activity and excitability state on subsequent performance practicing a Visuomotor paradigm. Excitability of the primary motor cortex (M1) or the visual area MT/V5 was modulated by 10 min of anodal or cathodal transcranial direct current stimulation (tDCS) in healthy subjects before practice of a Visuomotor tracking task. The percentage of correct tracking movements increased significantly in the early phase of practice after both anodal and cathodal stimulations over both cortical areas compared to the no-stimulation condition showing a behavioral improvement at the beginning of the practice process. Stimulation of a control cortical area did not result in significant difference with regard to the practice between cathodal, anodal and sham stimulation. However, the steepness of improvement between the different time-points was significantly increased only at the beginning of the task, and was reduced at the 5′–10′ (V5) and 10′–15′ (M1) time-window with regard to anodal stimulation, compared to the ‘no-stimulation’ condition. With regard to cathodal stimulation, the steepness of improvement was significantly lower at the 10′–15′ time-window (M1) compared to the ‘no-stimulation’ condition. The results of our study underline the principal functional relevance of the BCM rule for the efficacy of Visuomotor practice, but imply that also other mechanisms have to be taken into account.
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direct current stimulation over v5 enhances Visuomotor Coordination by improving motion perception in humans
Journal of Cognitive Neuroscience, 2004Co-Authors: Andrea Antal, Michael A Nitsche, Wolfgang Kruse, Tamas Z Kincses, Klauspeter Hoffmann, Walter PaulusAbstract:The primary aim of this study was to determine the extent to which human MT+/V5, an extrastriate visual area known to mediate motion processing, is involved in Visuomotor Coordination. To pursue this we increased or decreased the excitability of MT+/V5, primary motor, and primary visual cortex by the application of 7 min of anodal and cathodal transcranial direct current stimulation (tDCS) in healthy human subjects while they were performing a Visuomotor tracking task involving hand movements. The percentage of correct tracking movements increased specifically during and immediately after cathodal stimulation, which decreases cortical excitability, only when V5 was stimulated. None of the other stimulation conditions affected Visuomotor performance. We propose that the improvement in performance caused by cathodal tDCS of V5 is due to a focusing effect on to the complex motion perception conditions involved in this task. This hypothesis was proven by additional experiments: Testing simple and complex motion perception in dot kinetograms, we found that a diminution in excitability induced by cathodal stimulation improved the subject's perception of the direction of the coherent motion only if this was presented among random dots (complex motion perception), and worsened it if only one motion direction was presented (simple movement perception). Our data suggest that area V5 is critically involved in complex motion perception and identification processes important for Visuomotor Coordination. The results also raise the possibility of the usefulness of tDCS in rehabilitation strategies for neurological patients with Visuomotor disorders.
Jasper Dingemanse - One of the best experts on this subject based on the ideXlab platform.
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Pharmacokinetic and pharmacodynamic interactions between almorexant, a dual orexin receptor antagonist, and desipramine
European Neuropsychopharmacology, 2014Co-Authors: Hans G. Cruz, Petra Hoever, Joop M. A. Van Gerven, Justin L. Hay, Federica Alessi, Erik T. Te Beek, Jasper DingemanseAbstract:Abstract Almorexant is a dual orexin receptor antagonist (DORA) with sleep-enabling effects in humans. Insomnia is often associated with mental health problems, including depression. Hence, potential interactions with antidepressants deserve attention. Desipramine was selected as a model drug because it is mainly metabolized by CYP2D6, which is inhibited by almorexant in vitro. A single-center, randomized, placebo-controlled, two-way crossover study in 20 healthy male subjects was conducted to evaluate the pharmacokinetic and pharmacodynamic interactions between almorexant and desipramine. Almorexant 200 mg or matching placebo (double-blind) was administered orally once daily in the morning for 10 days, and a single oral dose of 50 mg desipramine (open-label) was administered on Day 5. Almorexant increased the exposure to desipramine 3.7-fold, suggesting that almorexant is a moderate inhibitor of desipramine metabolism through inhibition of CYP2D6. Conversely, desipramine showed no relevant effects on the pharmacokinetics of almorexant. Pharmacodynamic evaluations indicated that almorexant alone reduced Visuomotor Coordination, postural stability, and alertness, and slightly increased calmness. Desipramine induced a reduction in subjective alertness and an increase in pupil/iris ratio. Despite the increase in exposure to desipramine, almorexant and desipramine in combination showed the same pharmacodynamic profile as almorexant alone, except for prolonging reduced alertness and preventing the miotic effect of almorexant. Co-administration also prolonged the mydriatic effect of desipramine. Overall, repeated administration of almorexant alone or with single-dose desipramine was well tolerated. The lack of a relevant interaction with antidepressants, if confirmed for other DORAs, would be a key feature for a safer class of hypnotics.
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orexin receptor antagonism an ascending multiple dose study with almorexant
Journal of Psychopharmacology, 2012Co-Authors: Petra Hoever, Georg Dorffner, Joop M. A. Van Gerven, Eleonora Chiossi, Sanne De Haas, Jasper DingemanseAbstract:The objectives of this study were to investigate the multiple-dose tolerability, safety, pharmacokinetics, and pharmacodynamics of the dual orexin receptor antagonist almorexant. Healthy subjects received daily doses of almorexant (100, 200, 400 or 1000 mg) or placebo in the morning for four days followed by two days with evening administration (Days 5-6). Each dose level was investigated in a new group of 10 subjects (eight active, two placebo, 1:1 sex). Dose-dependent increases in frequency and intensity were observed for somnolence and other adverse events. Pharmacokinetics at steady state showed rapid absorption, low concentrations eight hours post-dose, and minimal accumulation. Following evening, administration absorption was delayed and C(max) decreased. Almorexant at 400 and 1000 mg administered in the morning reduced vigilance, alertness, Visuomotor Coordination, and motor Coordination assessed in a psychometric test battery. Polysomnography recordings following evening administration showed a trend towards shorter latency to sleep stages 3 and 4, and shorter latency to, and longer time in, rapid-eye-movement sleep at higher doses when compared to placebo. Whether these findings in healthy subjects translate into relevant sleep-enabling effects in insomnia patients needs to be investigated in future studies.
Walter Paulus - One of the best experts on this subject based on the ideXlab platform.
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prior state of cortical activity influences subsequent practicing of a Visuomotor Coordination task
Neuropsychologia, 2008Co-Authors: Andrea Antal, Michael A Nitsche, Silva Begemeier, Walter PaulusAbstract:Abstract According to the Bienenstock–Cooper–Munro (BCM) rule, a low overall cortical activity level is suggested to enhance synaptic strength of active neuronal connections, while a high level of activity should diminish it. Whereas the relevance of this mechanism for neuroplasticity in humans has been ascertained on the neurophysiological level, its functional relevance remains unclear so far. The aim of this study was to explore the impact of the pre-performance cortical activity and excitability state on subsequent performance practicing a Visuomotor paradigm. Excitability of the primary motor cortex (M1) or the visual area MT/V5 was modulated by 10 min of anodal or cathodal transcranial direct current stimulation (tDCS) in healthy subjects before practice of a Visuomotor tracking task. The percentage of correct tracking movements increased significantly in the early phase of practice after both anodal and cathodal stimulations over both cortical areas compared to the no-stimulation condition showing a behavioral improvement at the beginning of the practice process. Stimulation of a control cortical area did not result in significant difference with regard to the practice between cathodal, anodal and sham stimulation. However, the steepness of improvement between the different time-points was significantly increased only at the beginning of the task, and was reduced at the 5′–10′ (V5) and 10′–15′ (M1) time-window with regard to anodal stimulation, compared to the ‘no-stimulation’ condition. With regard to cathodal stimulation, the steepness of improvement was significantly lower at the 10′–15′ time-window (M1) compared to the ‘no-stimulation’ condition. The results of our study underline the principal functional relevance of the BCM rule for the efficacy of Visuomotor practice, but imply that also other mechanisms have to be taken into account.
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direct current stimulation over v5 enhances Visuomotor Coordination by improving motion perception in humans
Journal of Cognitive Neuroscience, 2004Co-Authors: Andrea Antal, Michael A Nitsche, Wolfgang Kruse, Tamas Z Kincses, Klauspeter Hoffmann, Walter PaulusAbstract:The primary aim of this study was to determine the extent to which human MT+/V5, an extrastriate visual area known to mediate motion processing, is involved in Visuomotor Coordination. To pursue this we increased or decreased the excitability of MT+/V5, primary motor, and primary visual cortex by the application of 7 min of anodal and cathodal transcranial direct current stimulation (tDCS) in healthy human subjects while they were performing a Visuomotor tracking task involving hand movements. The percentage of correct tracking movements increased specifically during and immediately after cathodal stimulation, which decreases cortical excitability, only when V5 was stimulated. None of the other stimulation conditions affected Visuomotor performance. We propose that the improvement in performance caused by cathodal tDCS of V5 is due to a focusing effect on to the complex motion perception conditions involved in this task. This hypothesis was proven by additional experiments: Testing simple and complex motion perception in dot kinetograms, we found that a diminution in excitability induced by cathodal stimulation improved the subject's perception of the direction of the coherent motion only if this was presented among random dots (complex motion perception), and worsened it if only one motion direction was presented (simple movement perception). Our data suggest that area V5 is critically involved in complex motion perception and identification processes important for Visuomotor Coordination. The results also raise the possibility of the usefulness of tDCS in rehabilitation strategies for neurological patients with Visuomotor disorders.
