Westendorff, Stephanie

[["dc.bibliographiccitation.firstpage","287"],["dc.bibliographiccitation.issue","2"],["dc.bibliographiccitation.journal","Experimental Brain Research"],["dc.bibliographiccitation.lastpage","296"],["dc.bibliographiccitation.volume","208"],["dc.contributor.author","Westendorff, Stephanie"],["dc.contributor.author","Gail, Alexander"],["dc.date.accessioned","2017-09-07T11:47:48Z"],["dc.date.available","2017-09-07T11:47:48Z"],["dc.date.issued","2010"],["dc.description.abstract","Reach movement planning involves the representation of spatial target information in different reference frames. Neurons at parietal and premotor stages of the cortical sensorimotor system represent target information in eye- or hand-centered reference frames, respectively. How the different neuronal representations affect behavioral parameters of motor planning and control, i.e. which stage of neural representation is relevant for which aspect of behavior, is not obvious from the physiology. Here, we test with a behavioral experiment if different kinematic movement parameters are affected to a different degree by either an eye- or hand-reference frame. We used a generalized anti-reach task to test the influence of stimulus-response compatibility (SRC) in eye- and hand-reference frames on reach reaction times, movement times, and endpoint variability. While in a standard anti-reach task, the SRC is identical in the eye- and hand-reference frames, we could separate SRC for the two reference frames. We found that reaction times were influenced by the SRC in eye- and hand-reference frame. In contrast, movement times were only influenced by the SRC in hand-reference frame, and endpoint variability was only influenced by the SRC in eye-reference frame. Since movement time and endpoint variability are the result of planning and control processes, while reaction times are consequences of only the planning process, we suggest that SRC effects on reaction times are highly suited to investigate reference frames of movement planning, and that eye- and hand-reference frames have distinct effects on different phases of motor action and different kinematic movement parameters."],["dc.identifier.doi","10.1007/s00221-010-2481-2"],["dc.identifier.gro","3150734"],["dc.identifier.pmid","21076817"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/7523"],["dc.language.iso","en"],["dc.notes.status","zu prüfen"],["dc.relation.issn","0014-4819"],["dc.title","What is ‘anti’ about anti-reaches? Reference frames selectively affect reaction times and endpoint variability"],["dc.type","journal_article"],["dc.type.internalPublication","unknown"],["dc.type.peerReviewed","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","2360"],["dc.bibliographiccitation.issue","7"],["dc.bibliographiccitation.journal","Journal of Neurophysiology"],["dc.bibliographiccitation.lastpage","2375"],["dc.bibliographiccitation.volume","113"],["dc.contributor.author","Westendorff, Stephanie"],["dc.contributor.author","Kuang, Shenbing"],["dc.contributor.author","Taghizadeh, Bahareh"],["dc.contributor.author","Donchin, Opher"],["dc.contributor.author","Gail, Alexander"],["dc.date.accessioned","2017-09-07T11:47:49Z"],["dc.date.available","2017-09-07T11:47:49Z"],["dc.date.issued","2015"],["dc.description.abstract","Different error signals can induce sensorimotor adaptation during visually guided reaching, possibly evoking different neural adaptation mechanisms. Here we investigate reach adaptation induced by visual target errors without perturbing the actual or sensed hand position. We analyzed the spatial generalization of adaptation to target error to compare it with other known generalization patterns and simulated our results with a neural network model trained to minimize target error independent of prediction errors. Subjects reached to different peripheral visual targets and had to adapt to a sudden fixed-amplitude displacement (“jump”) consistently occurring for only one of the reach targets. Subjects simultaneously had to perform contralateral unperturbed saccades, which rendered the reach target jump unnoticeable. As a result, subjects adapted by gradually decreasing reach errors and showed negative aftereffects for the perturbed reach target. Reach errors generalized to unperturbed targets according to a translational rather than rotational generalization pattern, but locally, not globally. More importantly, reach errors generalized asymmetrically with a skewed generalization function in the direction of the target jump. Our neural network model reproduced the skewed generalization after adaptation to target jump without having been explicitly trained to produce a specific generalization pattern. Our combined psychophysical and simulation results suggest that target jump adaptation in reaching can be explained by gradual updating of spatial motor goal representations in sensorimotor association networks, independent of learning induced by a prediction-error about the hand position. The simulations make testable predictions about the underlying changes in the tuning of sensorimotor neurons during target jump adaptation."],["dc.identifier.doi","10.1152/jn.00483.2014"],["dc.identifier.gro","3150727"],["dc.identifier.pmid","25609106"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/7515"],["dc.language.iso","en"],["dc.notes.status","final"],["dc.relation.issn","0022-3077"],["dc.title","Asymmetric generalization in adaptation to target displacement errors in humans and in a neural network model"],["dc.type","journal_article"],["dc.type.internalPublication","unknown"],["dc.type.peerReviewed","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","9490"],["dc.bibliographiccitation.issue","30"],["dc.bibliographiccitation.journal","The Journal of neuroscience"],["dc.bibliographiccitation.lastpage","9499"],["dc.bibliographiccitation.volume","29"],["dc.contributor.author","Gail, Alexander"],["dc.contributor.author","Klaes, Christian"],["dc.contributor.author","Westendorff, Stephanie"],["dc.date.accessioned","2017-09-07T11:47:44Z"],["dc.date.available","2017-09-07T11:47:44Z"],["dc.date.issued","2009"],["dc.description.abstract","Planning goal-directed movements requires the combination of visuospatial with abstract contextual information. Our sensory environment constrains possible movements to a certain extent. However, contextual information guides proper choice of action in a given situation and allows flexible mapping of sensory instruction cues onto different motor actions. We used anti-reach tasks to test the hypothesis that spatial motor-goal representations in cortical sensorimotor areas are gain modulated by the behavioral context to achieve flexible remapping of spatial cue information onto arbitrary motor goals. We found that gain modulation of neuronal reach goal representations is commonly induced by the behavioral context in individual neurons of both, the parietal reach region (PRR) and the dorsal premotor cortex (PMd). In addition, PRR showed stronger directional selectivity during the planning of a reach toward a directly cued goal (pro-reach) compared with an inferred target (anti-reach). PMd, however, showed stronger overall activity during reaches toward inferred targets compared with directly cued targets. Based on our experimental evidence, we suggest that gain modulation is the computational mechanism underlying the integration of spatial and contextual information for flexible, rule-driven stimulus–response mapping, and thereby forms an important basis of goal-directed behavior. Complementary contextual effects in PRR versus PMd are consistent with the idea that posterior parietal cortex preferentially represents sensory-driven, “automatic” motor goals, whereas frontal sensorimotor areas are stronger engaged in the representation of rule-based, “inferred” motor goals."],["dc.identifier.doi","10.1523/jneurosci.1095-09.2009"],["dc.identifier.gro","3150713"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/7500"],["dc.language.iso","en"],["dc.notes.status","zu prüfen"],["dc.relation.issn","0270-6474"],["dc.title","Implementation of Spatial Transformation Rules for Goal-Directed Reaching via Gain Modulation in Monkey Parietal and Premotor Cortex"],["dc.type","journal_article"],["dc.type.internalPublication","unknown"],["dc.type.peerReviewed","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","421"],["dc.bibliographiccitation.issue","9"],["dc.bibliographiccitation.journal","Journal of Vision"],["dc.bibliographiccitation.lastpage","421"],["dc.bibliographiccitation.volume","12"],["dc.contributor.author","Anton-Erxleben, Katharina"],["dc.contributor.author","Westendorff, Stephanie"],["dc.contributor.author","Treue, Stefan"],["dc.contributor.author","Gail, Alexander"],["dc.date.accessioned","2018-02-26T14:23:21Z"],["dc.date.available","2018-02-26T14:23:21Z"],["dc.date.issued","2012"],["dc.description.abstract","Background: Attention improves the visual system’s spatial resolution and distorts the perception of visual space: Perceived locations are repulsed away from the attentional focus (Suzuki & Cavanagh, 1997). However, little is known about whether and how attention affects visual space in action. Methods: Here, we tested the effects of exogenous attention on visually guided reach movements. Attention was drawn involuntarily to a transient, uninformative cue (white square, 72ms) at one of two locations at 11.4º eccentricity and ±45º polar angle in either the upper left or upper right quadrant, respectively. After a brief delay (56ms), a reach target (green circle, 29ms) appeared at a randomly chosen position along an imaginary half-circle within the upper visual field with the same eccentricity as the cue positions. In the ‘attended’ condition, cue and target appeared within the same quadrant, whereas in the ‘unattended’ condition they appeared in opposite hemifields. For each target location, we calculated the distance between reach endpoint and target for the attended and the unattended condition. Results & Conclusions: In the attended condition, reach endpoints toward targets in the vicinity of the attentional cue were repulsed away from the cue by up to ~0.9º, relative to the unattended condition. The spatial profile of the magnitude of this effect follows an ‘M’-shape centered on the focus of attention; i.e., the cue did not affect reaches toward targets at the cued location or far away from it. Reaction times (target onset to movement start) tended to be slower for targets near the cue, whereas movement times (movement start to landing time) at all locations tended to be faster in the attended than in the unattended condition. These results are consistent with an attentional distortion of visual space and suggest a parallelism between the perception and action systems for the representation of location."],["dc.identifier.doi","10.1167/12.9.421"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/12628"],["dc.language.iso","en"],["dc.notes.status","final"],["dc.title","Attention distorts reach space"],["dc.type","journal_article"],["dc.type.internalPublication","unknown"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","85"],["dc.bibliographiccitation.lastpage","88"],["dc.contributor.author","Hoffmann, Klaus-Peter"],["dc.contributor.author","Abu-Saleh, L."],["dc.contributor.author","Audí, Josep Marcel Cardona"],["dc.contributor.author","Dietl, H."],["dc.contributor.author","Frank, H."],["dc.contributor.author","Gail, Alexander"],["dc.contributor.author","Kaniusas, Eugenijus"],["dc.contributor.author","Krautschneider, Wolfgang"],["dc.contributor.author","Lewis, S."],["dc.contributor.author","Meiners, Thomas"],["dc.contributor.author","Ruff, Roman"],["dc.contributor.author","Russold, Michael"],["dc.contributor.author","Schroeder, D."],["dc.contributor.author","Westendorff, Stephanie"],["dc.date.accessioned","2018-02-26T13:58:22Z"],["dc.date.available","2018-02-26T13:58:22Z"],["dc.date.issued","2005"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/12625"],["dc.language.iso","en"],["dc.notes.status","zu prüfen"],["dc.publisher","Institute of Biomedical Engineering, UNB"],["dc.relation.conference","Proceedings of the 2005 MyoElectric Controls/Powered Prosthetics Symposium"],["dc.relation.eventend","2005-08-19"],["dc.relation.eventlocation","Fredericton, New Brunswick"],["dc.relation.eventstart","2005-08-17"],["dc.relation.isbn","1-55131-100-3"],["dc.relation.ispartof","MEC '05 Integrating Prosthetics and Medicine"],["dc.title","Implantable myoelectric assistance system for the intuitive control of a bionic hand prostheses"],["dc.type","conference_paper"],["dc.type.internalPublication","unknown"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","536"],["dc.bibliographiccitation.issue","3"],["dc.bibliographiccitation.journal","Neuron"],["dc.bibliographiccitation.lastpage","548"],["dc.bibliographiccitation.volume","70"],["dc.contributor.author","Klaes, Christian"],["dc.contributor.author","Westendorff, Stephanie"],["dc.contributor.author","Chakrabarti, Shubhodeep"],["dc.contributor.author","Gail, Alexander"],["dc.date.accessioned","2017-09-07T11:47:46Z"],["dc.date.available","2017-09-07T11:47:46Z"],["dc.date.issued","2011"],["dc.description.abstract","In natural situations, movements are often directed toward locations different from that of the evoking sensory stimulus. Movement goals must then be inferred from the sensory cue based on rules. When there is uncertainty about the rule that applies for a given cue, planning a movement involves both choosing the relevant rule and computing the movement goal based on that rule. Under these conditions, it is not clear whether primates compute multiple movement goals based on all possible rules before choosing an action, or whether they first choose a rule and then only represent the movement goal associated with that rule. Supporting the former hypothesis, we show that neurons in the frontoparietal reach areas of monkeys simultaneously represent two different rule-based movement goals, which are biased by the monkeys' choice preferences. Apparently, primates choose between multiple behavioral options by weighing against each other the movement goals associated with each option."],["dc.identifier.doi","10.1016/j.neuron.2011.02.053"],["dc.identifier.gro","3150723"],["dc.identifier.pmid","21555078"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/7511"],["dc.language.iso","en"],["dc.notes.status","zu prüfen"],["dc.relation.issn","0896-6273"],["dc.title","Choosing Goals, Not Rules: Deciding among Rule-Based Action Plans"],["dc.type","journal_article"],["dc.type.internalPublication","unknown"],["dc.type.peerReviewed","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","1972"],["dc.bibliographiccitation.issue","7"],["dc.bibliographiccitation.journal","IEEE Transactions on Instrumentation and Measurement"],["dc.bibliographiccitation.lastpage","1981"],["dc.bibliographiccitation.volume","62"],["dc.contributor.author","Lewis, Sören"],["dc.contributor.author","Russold, Michael"],["dc.contributor.author","Dietl, Hans"],["dc.contributor.author","Ruff, Roman"],["dc.contributor.author","Audí, Josep Marcel Cardona"],["dc.contributor.author","Hoffmann, Klaus-Peter"],["dc.contributor.author","Abu-Saleh, Lait"],["dc.contributor.author","Schroeder, Dietmar"],["dc.contributor.author","Krautschneider, Wolfgang H."],["dc.contributor.author","Westendorff, Stephanie"],["dc.contributor.author","Gail, Alexander"],["dc.contributor.author","Meiners, Thomas"],["dc.contributor.author","Kaniusas, Eugenijus"],["dc.date.accessioned","2017-09-07T11:47:44Z"],["dc.date.available","2017-09-07T11:47:44Z"],["dc.date.issued","2013"],["dc.description.abstract","This paper presents intramuscular electromyogram (EMG) signals obtained with a fully implantable measurement system that were recorded during goal directed arm movements. In a first implantation thin film electrodes were epimysially implanted on the deltoideus of a rhesus macaque and the encapsulation process was monitored by impedance measurements. Increase of impedance reached a constant level after four weeks indicating a complete encapsulation of electrodes. EMG recorded with these electrodes yielded a signal-to-noise ratio of about 80 dB at 200 Hz. The EMG recorded during goal-directed arm movements showed a high similarity to movements in the same direction and at the same time presented clear differences between different movement directions in time domain. Six classifiers and seven time and frequency domain features were investigated with the aim of discriminating the direction of arm movement from EMG signals. Reliable recognition of arm movements was achieved for a subset of the movements under investigation only. A second implantation of the whole measurement system for nine weeks demonstrated simple handling during surgery and good biotolerance in the animals."],["dc.identifier.doi","10.1109/tim.2013.2253992"],["dc.identifier.gro","3150712"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/7499"],["dc.language.iso","en"],["dc.notes.status","final"],["dc.relation.issn","0018-9456"],["dc.title","Fully Implantable Multi-Channel Measurement System for Acquisition of Muscle Activity"],["dc.type","journal_article"],["dc.type.internalPublication","unknown"],["dc.type.peerReviewed","no"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","5426"],["dc.bibliographiccitation.issue","15"],["dc.bibliographiccitation.journal","The Journal of neuroscience"],["dc.bibliographiccitation.lastpage","5436"],["dc.bibliographiccitation.volume","30"],["dc.contributor.author","Westendorff, Stephanie"],["dc.contributor.author","Klaes, Christian"],["dc.contributor.author","Gail, Alexander"],["dc.date.accessioned","2017-09-07T11:47:48Z"],["dc.date.available","2017-09-07T11:47:48Z"],["dc.date.issued","2010"],["dc.description.abstract","Flexible sensorimotor planning is the basis for goal-directed behavior. We investigated the integration of visuospatial information with context-specific transformation rules during reach planning. We were especially interested in the relative timing of motor-goal decisions in monkey dorsal premotor cortex (PMd) and parietal reach region (PRR). We used a rule-based mapping task with different cueing conditions to compare task-dependent motor-goal latencies. The task allowed us a separation of cue-related from motor-related activity, and a separation of activity related to motor planning from activity related to motor initiation or execution. The results show that selectivity for the visuospatial goal of a pending movement occurred earlier in PMd than PRR whenever the task required spatial remapping. Such remapping was needed if the spatial representation of a cue or of a default motor plan had to be transformed into a spatially incongruent representation of the motor goal. In contrast, we did not find frontoparietal latency differences if the spatial representation of the cue or the default plan was spatially congruent with the motor goal. The fact that frontoparietal latency differences occurred only in conditions with spatial remapping was independent of the subjects' partial a priori knowledge about the pending goal. Importantly, frontoparietal latency differences existed for motor-goal representations during movement planning, without immediate motor execution. We interpret our findings as being in support of the hypothesis that latency differences reflect a dynamic reorganization of network activity in PRR, and suggest that the reorganization is contingent on frontoparietal projections from PMd."],["dc.identifier.doi","10.1523/jneurosci.4628-09.2010"],["dc.identifier.gro","3150731"],["dc.identifier.pmid","20392964"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/7520"],["dc.language.iso","en"],["dc.notes.status","public"],["dc.relation.issn","0270-6474"],["dc.title","The Cortical Timeline for Deciding on Reach Motor Goals"],["dc.type","journal_article"],["dc.type.internalPublication","unknown"],["dc.type.peerReviewed","no"],["dspace.entity.type","Publication"]]