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Digby Elliott - One of the best experts on this subject based on the ideXlab platform.
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Effector mass and trajectory optimization in the online regulation of goal-directed Movement
Experimental brain research, 2015Co-Authors: James J. Burkitt, Digby Elliott, Victoria Staite, Afrisa Yeung, James L. LyonsAbstract:Goal-directed Aiming Movements are planned and executed so that they optimize speed, accuracy and energy expenditure. In particular, the primary subMovements involved in manual Aiming attempts typically undershoot targets in order to avoid costly time and energy overshoot errors. Furthermore, in Aiming Movements performed over a series of trials, the Movement planning process considers the sensory information associated with the most recent Aiming attempt. The goal of the current study was to gain further insight into how the sensory consequences associated with the recent and forthcoming Aiming attempts impact performance. We first examined whether performers are more conservative in their Aiming Movements with a heavy, as opposed to a light, stylus by determining whether primary subMovements undershot the target to a greater extent in the former due to an anticipated increase in spatial variability. Our results show that Movements with the heavy stylus demonstrated greater undershoot biases in the primary subMovements, as well as greater trial-to-trial spatial variability at specific trajectory kinematic landmarks. In addition, we also sought to determine whether the sensory information experienced on a previous Aiming Movement affected Movement planning and/or online control on the subsequent Aiming attempt. To vary the type sensory consequences experienced on a trial-to-trial basis, participants performed Aiming Movements with light and heavy styli in either blocked or random orderings of trials. In the random-order conditions, some participants were provided advance information about stylus mass for the upcoming trial, while others were not. The blocked and random trial orders had minimal impacts on end point Aiming performance. Furthermore, similarities in the times to key kinematic landmarks in the trajectories of the random-order groups suggest that recent trial experience had a greater effect on the upcoming Aiming Movement compared with advance task knowledge.
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Common vs. independent limb control in sequential vertical Aiming: Extending or reversing target-Aiming Movements
Journal of Exercise Movement and Sport, 2014Co-Authors: Ross W Roberts, Simon J. Bennett, James Lyons, Digby ElliottAbstract:In discrete Aiming, adult performers optimize their Movement to maximize speed and accuracy, and to minimize energy expenditure. This research was designed to examine trajectory regulation in sequential vertical Aiming. In Experiment 1, participants performed single up and down Aiming Movements, as well as sequential Aiming Movements that involved extending the initial Movement to a second target. Of interest was how the first Aiming Movement was organized to accommodate the second Aiming Movement. Overall, participants exhibited shorter Movement times and times to peak acceleration and velocity when moving up. Peak acceleration was also greater for upward aims, but only for the single target trials. Downward Movements were spatially more variable. Analyses examining the relationship between kinematic events in the first and second Aiming Movements revealed positive r-values when moving up but little relationship when moving down. These results suggest that sequential upward Movements are planned together, while downward Aiming involves more concurrent control and the independent regulation of the two Movement components. In Experiment 2, the experimental design was similar except that in the sequential Aiming condition participants reversed the direction of their first Movement, thus returning to the home position. Consistent with previous research, participants exhibited shorter Movement times and higher peak accelerations and velocities under two-target than one-target conditions. Correlational analyses revealed positive relationships between Movement one and two for both up and down initial Movements. For up Movements, there was a stronger relationship between the peak acceleration in Movement one and kinematic events in Movement two, while for down Movements, late markers co-varied with Movement two. These findings are consistent with the notion that, in a reversal Movement, the two components are organized together to optimize time and energy by using the same muscular forces to decelerate Movement one and accelerate Movement two. Acknowledgments: This research was supported by the Natural Sciences and Engineering Research Council of Canada (NSERC).
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Dissociable contributions of motor-execution and action-observation to intramanual transfer
Experimental Brain Research, 2012Co-Authors: Spencer J. Hayes, James W. Roberts, Digby Elliott, Matthew Andrew, Simon J. BennettAbstract:We examined the hypothesis that different processes and representations are associated with the learning of a Movement sequence through motor-execution and action-observation. Following a pre-test in which participants attempted to achieve an absolute, and relative, time goal in a sequential goal-directed Aiming Movement, participants received either physical or observational practice with feedback. Post-test performance indicated that motor-execution and action-observation participants learned equally well. Participants then transferred to conditions where the gain between the limb Movements and their visual consequences were manipulated. Under both bigger and smaller transfer conditions, motor-execution and action-observation participants exhibited similar intramanual transfer of absolute timing. However, participants in the action-observation group exhibited superior transfer of relative timing than the motor-execution group. These findings suggest that learning via action-observation is underpinned by a visual–spatial representation, while learning via motor-execution depends more on specific force–time planning (feed forward) and afferent processing associated with sensorimotor feedback. These behavioural effects are discussed with reference to neural processes associated with striatum, cerebellum and motor cortical regions (pre-motor cortex; SMA; pre-SMA).
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Between-person effects on attention and action: Joe and Fred revisited
Psychological research, 2009Co-Authors: Spencer J. Hayes, Steve Hansen, Digby ElliottAbstract:Previous study indicates that target-target inhibition of return (IOR) is not restricted to a single nervous system. Specifically, watching another person perform a goal-directed Aiming Movement engages similar inhibitory processes on a subsequent Aiming attempt as if having performed the preceding Movement oneself. This between-person effect has been attributed to the mirror neuron system. In the study reported here, we replicated this finding and examined the relative importance of automatic stimulus alerting events and action-observation by dissociating these two influences. This was done by having two people alternately perform sets of two Aiming trials to the same equally probable targets. Under some experimental conditions, one or both of the performers moved to a non-illuminated target. In this way, we dissociated the stimulus and observed event under some between-person conditions. Although IOR was greatest when the stimulus and observed events were compatible, both contributed to the between-person inhibitory processes slowing the responses (Experiment 1). The impact of observing another person perform an Aiming Movement appears to have more to do with realizing a particular spatial goal than seeing the biological motion associated with achieving that goal (Experiment 2). Findings that both the illumination of a visual target signal and the observation of another person's action engage similar attention-action processes are consistent with action-based accounts of visual selective attention.
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The effect of response uncertainty on illusory biases of perception and action.
Neuroscience letters, 2006Co-Authors: Katherine M Keetch, James Lyons, Cheryl M Glazebrook, Melanie Y Lam, Daniel J Weeks, Digby ElliottAbstract:When task requirements were known in advance, Glazebrook et al. [C.M. Glazebrook, V.P. Dhillon, K.M. Keetch, J. Lyons, E. Amazeen, D.J. Weeks, D. Elliott, Perception-action and the Müller-Lyer illusion: amplitude or endpoint bias?, Exp. Brain Res. 160 (2005) 71-78.] demonstrated that perceptual biases associated with the Müller-Lyer illusion resulted from a misperception of figure extent, while manual Aiming biases resulted from a misperception of vertex position. In this study, we examined the degree to which prior knowledge of task requirements influenced how participants coded visual-spatial information associated with Müller-Lyer configurations. Specifically, we investigated how illusory biases are affected when uncertainty exists as to whether participants will be required to make a perceptual-cognitive decision about the length of a figure or complete a rapid Aiming Movement to a figure vertex. Although Aiming Movements were completed in a similar manner regardless of the prior knowledge condition, perceptual biases were associated with a misperception of extent when the task was known and a misperception of both extent and position when the task was unknown. These findings indicate that people are flexible in the manner in which they code visual-spatial information.
Luc Proteau - One of the best experts on this subject based on the ideXlab platform.
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Modulation of the primary impulse of spatially-constrained video-Aiming Movements
Human movement science, 2009Co-Authors: David Tinjust, Luc ProteauAbstract:It has been suggested that temporally-constrained goal directed Movements are based on a single subMovement control strategy that could be modulated online. On the contrary, spatially-constrained Movements might encourage participants to produce very fast, open-loop, but somewhat inaccurate/variable primary Movement impulses and, if necessary, to perform a discrete correction. We wanted to determine whether the primary impulse of a spatially-constrained manual Aiming Movement was modulated online. On Movement extent, results revealed that a first modulation mechanism acted soon after Movement initiation. This modulation was largely independent of target size and apparently stabilized the output of the Movement planning processes. A second modulation mechanism further reduced the variability of the Movement's primary impulse so that Movements ended on target. Movement direction appeared to be under continuous control.
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Visual control of manual Aiming Movements in 6- to 10-year-old children and adults.
Journal of motor behavior, 2004Co-Authors: Léna Lhuisset, Luc ProteauAbstract:Recent results indicate that adults modulate their initial Movement impulse toward a stationary visual target by processing visual afferent information. The authors investigated whether the mechanisms responsible for those modulations are already in place in young children or develop as the children grow older. Adults (n = 10) and 6-, 8- and 10-year-old children (ns = 6, 7, and 7, respectively) performed a video-Aiming task while vision of the cursor they were moving was (acquisition) or was not (transfer) visible. The results indicated that within-participant variability of the initial impulse trajectory of the children's Aiming Movement leveled-off in acquisition between peak extent deceleration and the end of the initial impulse, whereas it increased linearly as Movement unfolded in transfer. The results also indicated that children modulate their initial Movement impulse when visual afferent information is available, although to a lesser extent than adults do, and strongly imply that contrary to past suggestions, the initial impulse of an Aiming Movement is not ballistic.
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On the role of static and dynamic visual afferent information in goal-directed Aiming Movements.
Experimental brain research, 2001Co-Authors: Patrick Bédard, Luc ProteauAbstract:Movement planning has been shown to be optimized when the participant is permitted to see his or her hand resting on the starting base prior to Movement initiation. However, this proposition is opposed by contradictory results. In the present study, we wanted to determine whether these conflicting results were caused by procedural differences. The results showed that seeing one's hand on the starting base did not result in more accurate Aiming Movement than when this information was not available. However, lower Aiming errors were found when one was asked to foveate the starting base and then the target prior to Movement initiation, but only when no dynamic visual information was available during Movement. When an Aiming Movement was performed while one's hand was visible in visual periphery, foveating the starting base or not prior to Movement initiation did not modify Aiming accuracy. These results suggest that gazing at the starting base and then at the target provides an eye-based representation of the Movement to be performed that can be used by the CNS to plan a manual Aiming Movement. Information for better planning of the direction – but not the extent – dimension of an upcoming Movement can also be derived from dynamic visual information available in peripheral vision.
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What Causes Specificity of Practice in a Manual Aiming Movement: Vision Dominance or Transformation Errors?
Journal of motor behavior, 2001Co-Authors: Luc Proteau, Heather CarnahanAbstract:Abstract The withdrawal of vision of the arm during a manual Aiming task has been found to result in a large increase in Aiming error, regardless of the amount of practice in normal vision before its withdrawal. In the present study, the authors investigated whether the increase in error reflects the domination of visual afferent information over the Movement representation developed during practice to the detriment of other sources of afferent information or whether it reflects only transformation errors of the location of the target from an allocentric to an egocentric frame of reference. Participants (N = 40) performed Aiming Movements with their dominant or nondominant arm in a full-vision or target-only condition. The results of the present experiment supported both of those hypotheses. The data indicated that practice does not eliminate the need for visual information for optimizing Movement accuracy and that learning is specific to the source or sources of afferent information more likely to ensure...
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Exploring the limits of peripheral vision for the control of Movement.
Journal of motor behavior, 2000Co-Authors: Luc Proteau, K. Boivin, Stéphane Linossier, Khemais AbahniniAbstract:The role played by peripheral visual information in the control of Aiming Movements is not fully understood, as is indicated by the conflicting results reported in the literature. In the present study, the authors tested and confirmed the hypothesis that the source of the conflict lies in the portion of the visual peripheral field that has been under scrutiny in the different studies. Participants (N = 60) moved a computer mouse from a fixed starting position to 1 of 3 targets under varied vision conditions. The portion of the peripheral visual field that best ensured directional accuracy of a sweeping Movement was found to be located between 20° and 10° of visual angle, whereas the area found to favor directional accuracy of an Aiming Movement comprised 30° through 10° of visual angle.
Romeo Chua - One of the best experts on this subject based on the ideXlab platform.
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Movement duration does not affect automatic online control
Human movement science, 2010Co-Authors: Erin K. Cressman, Brendan D. Cameron, Ian M. Franks, Melanie Y Lam, Romeo ChuaAbstract:Pisella et al. (2000) have shown that fast Aiming Movements are automatically modified on-line in response to a change in target position. Specifically, when a Movement is less than 300ms in duration the reach is completed to a target's new location even when one never intended to respond to the target jump. In contrast, when Movements are slower, the reach is completed according to instructions. At present, it is unclear if it is possible for one's intentions to guide the initial stages of these slow Movements. To determine if the intentional control mechanism can guide the initial stages of a slow Aiming Movement, participants aimed to targets that could jump at Movement onset, with a slow and very slow Movement time goal. In particular, participants were to point towards ("pro-point") or away from ("anti-point") the target jump, with a Movement time goal of 500 or 1200ms. Results showed that in the anti-point condition, Movement trajectories first deviated in the same direction as the target jump, followed by a response in the intended (opposite) direction. This suggests that while Movement outcome is controlled by the intentional system, even in these slow Aiming Movements the automatic system is engaged at Movement onset.
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Response preparation changes following practice of an asymmetrical bimanual Movement
Experimental Brain Research, 2008Co-Authors: Dana Maslovat, Romeo Chua, Anthony N. Carlsen, Ryu Ishimoto, Ian M. FranksAbstract:The purpose of the current study was to examine the effects of practice on the advance preparation of an asymmetrical bimanual Movement. Participants performed 170 trials of a discrete bimanual Aiming Movement where the right arm moved twice the amplitude of the left, in response to an auditory “go” signal. During three of the first and last ten trials, the “go” signal was replaced with a startle (124 dB) stimulus, which is thought to trigger a prepared Movement. Startle and non-startle (control) trials from early and late practice were compared on various kinematic and EMG measures. Results indicated that it is possible to pre-program a bimanual asymmetrical Movement, and that advance preparation of Movement amplitude changes with practice. Evidence was also provided that the different amplitude Movements were performed using similar EMG timing between limbs, while adjusting the relative ratio of EMG amplitude. Furthermore, learning of the task appeared to be related to the ability to prepare the correct asymmetrical EMG amplitudes rather than changing the timing of the EMG pattern.
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Response preparation changes following practice of an asymmetrical bimanual Movement
Experimental Brain Research, 2008Co-Authors: Dana Maslovat, Romeo Chua, Anthony N. Carlsen, Ryu Ishimoto, Ian M. FranksAbstract:The purpose of the current study was to examine the effects of practice on the advance preparation of an asymmetrical bimanual Movement. Participants performed 170 trials of a discrete bimanual Aiming Movement where the right arm moved twice the amplitude of the left, in response to an auditory “go” signal. During three of the first and last ten trials, the “go” signal was replaced with a startle (124 dB) stimulus, which is thought to trigger a prepared Movement. Startle and non-startle (control) trials from early and late practice were compared on various kinematic and EMG measures. Results indicated that it is possible to pre-program a bimanual asymmetrical Movement, and that advance preparation of Movement amplitude changes with practice. Evidence was also provided that the different amplitude Movements were performed using similar EMG timing between limbs, while adjusting the relative ratio of EMG amplitude. Furthermore, learning of the task appeared to be related to the ability to prepare the correct asymmetrical EMG amplitudes rather than changing the timing of the EMG pattern.
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Dual-target interference for the 'automatic pilot' in the dorsal stream.
Experimental brain research, 2007Co-Authors: Brendan D. Cameron, Ian M. Franks, James T. Enns, Romeo ChuaAbstract:When a target moves to a new location during a rapid Aiming Movement, the hand follows it, even when the participant intends not to. Pisella et al. (Nat Neurosci 3:729–736, 2000) claim that the posterior parietal cortex, in the dorsal visual stream, is responsible for this ‘automatic pilot’. Here we study the limits of automaticity in the dorsal stream through analysis of Aiming Movements to two targets in sequence. Participants were given a goal of moving rapidly to two targets, with the first Movement being completed within approximately 200 ms. On 30% of trials, the first or the second target jumped unpredictably to a new location at Movement onset, allowing us to measure the automatic capture of the hand. The results showed that hand Movements were less responsive to target jumps in a 2-target condition than in a 1-target control condition. This indicates that the ‘automatic pilot’ is susceptible to interference from multiple visual inputs, implying that the dorsal stream is less effective at guiding actions online when multiple targets are attended.
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eye hand coordination in goal directed Aiming
Human Movement Science, 2001Co-Authors: Gordon Binsted, Werner Helsen, Romeo Chua, Digby ElliottAbstract:In a number of studies, we have demonstrated that the spatial-temporal coupling of eye and hand Movements is optimal for the pickup of visual information about the position of the hand and the target late in the hand's trajectory. Several experiments designed to examine temporal coupling have shown that the eyes arrive at the target area concurrently with the hand achieving peak acceleration. Between the time the hand reached peak velocity and the end of the Movement, increased variability in the position of the shoulder and the elbow was accompanied by a decreased spatial variability in the hand. Presumably, this reduction in variability was due to the use of retinal and extra-retinal information about the relative positions of the eye, hand and target. However, the hand does not appear to be a slave to the eye. For example, we have been able to decouple eye Movements and hand Movements using Muller-Lyer configurations as targets. Predictable bias, found in primary and corrective saccadic eye Movements, was not found for hand Movements, if on-line visual information about the target was available during Aiming. That is, the hand remained accurate even when the eye had a tendency to undershoot or overshoot the target position. However, biases of the hand were evident, at least in the initial portion of an Aiming Movement, when vision of the target was removed and vision of the hand remained. These findings accent the versatility of human motor control and have implications for current models of visual processing and limb control.
Karl M. Newell - One of the best experts on this subject based on the ideXlab platform.
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SubMovement control processes in discrete Aiming as a function of space-time constraints
PloS one, 2017Co-Authors: Tsung-yu Hsieh, Yeou Teh Liu, Karl M. NewellAbstract:There is preliminary evidence that there are several types of subMovements in Movement Aiming that reflect different processes of control and can result from particular task constraints. The purpose of the study was to investigate the effect of Movement space and time task criteria on the prevalence of different subMovement control characteristics in discrete Aiming. Twelve participants completed 3 distance x 5 time conditions each with 100 trials in a target-Aiming Movement task. The kinematic structure of the trajectory determined the prevalence of 5 subMovement types (none; pre-peak, post-peak Movement velocity; undershoot, overshoot). The findings showed that the overall number of subMovements increased in the slower space-time conditions and was predominantly characterized by post-peak trajectory subMovements rather than discrete overshoot subMovements. Overshoot subMovements were more frequent in the high average Movement velocity and short time duration conditions. We concluded that there are qualitatively different distributional patterns of subMovement types in discrete Aiming tasks that are organized by the quantitative scaling of the average Movement velocity arising from multiple control processes to meet the specific space-time task constraints.
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Matching and Minimizing Movement Time in Speed-Accuracy Tasks.
Motor control, 2016Co-Authors: Tsung-yu Hsieh, Matheus M. Pacheco, Karl M. NewellAbstract:The goal of present experiment was to test whether different speed-accuracy paradigms outcomes (time minimization and time matching) were due to different temporal and spatial task constraints. Fifteen participants twice performed 100 trials of time minimization and time matching tasks with the yoked temporal and spatial requirements (criterion time and target width). The results showed that performing an Aiming Movement under the same spatial and temporal constraints resulted in similar outcomes with distributional properties (skewness and kurtosis) being slightly affected by practice effects. There was a trade-off in the information entropy for space and time (temporal information entropy decreased as spatial information entropy increased) with practice. Nevertheless, the joint space-time entropy of outcome did not change across tasks and conditions—revealing a common level of space-time entropy between these two categories of Aiming tasks. These findings support the hypothesis that under the same spati...
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Information entropy and the variability of space-time Movement error
Journal of motor behavior, 2006Co-Authors: Shih-chiung Lai, Gottfried Mayer-kress, Karl M. NewellAbstract:The authors investigated the effects of Movement time and Movement distance on the information entropy and variability of spatial and temporal error in a discrete Aiming Movement. In Experiment 1, the authors held Movement distance (100 mm) constant and manipulated 11 Movement times (300-800 ms) of 8 participants. In Experiment 2, the authors tested 6 Movement distances at 2 given Movement times (15-60 mm at 300 ms; 40-240 mm at 800 ms) in 8 participants. The variability and entropy for spatial error increased with average Movement velocity, whereas the variability and entropy for temporal error decreased as a function of average Movement velocity. The common variance between variable error and entropy averaged about 84% and 72% for spatial and temporal errors, respectively, suggesting that the probabilistic approach of entropy reveals features that are not present in the standard deviation index of variability. The findings provide further evidence that information entropy may be a useful single-index representation of variability in the Movement speed-accuracy relation.
Ian M. Franks - One of the best experts on this subject based on the ideXlab platform.
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Movement duration does not affect automatic online control
Human movement science, 2010Co-Authors: Erin K. Cressman, Brendan D. Cameron, Ian M. Franks, Melanie Y Lam, Romeo ChuaAbstract:Pisella et al. (2000) have shown that fast Aiming Movements are automatically modified on-line in response to a change in target position. Specifically, when a Movement is less than 300ms in duration the reach is completed to a target's new location even when one never intended to respond to the target jump. In contrast, when Movements are slower, the reach is completed according to instructions. At present, it is unclear if it is possible for one's intentions to guide the initial stages of these slow Movements. To determine if the intentional control mechanism can guide the initial stages of a slow Aiming Movement, participants aimed to targets that could jump at Movement onset, with a slow and very slow Movement time goal. In particular, participants were to point towards ("pro-point") or away from ("anti-point") the target jump, with a Movement time goal of 500 or 1200ms. Results showed that in the anti-point condition, Movement trajectories first deviated in the same direction as the target jump, followed by a response in the intended (opposite) direction. This suggests that while Movement outcome is controlled by the intentional system, even in these slow Aiming Movements the automatic system is engaged at Movement onset.
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Response preparation changes following practice of an asymmetrical bimanual Movement
Experimental Brain Research, 2008Co-Authors: Dana Maslovat, Romeo Chua, Anthony N. Carlsen, Ryu Ishimoto, Ian M. FranksAbstract:The purpose of the current study was to examine the effects of practice on the advance preparation of an asymmetrical bimanual Movement. Participants performed 170 trials of a discrete bimanual Aiming Movement where the right arm moved twice the amplitude of the left, in response to an auditory “go” signal. During three of the first and last ten trials, the “go” signal was replaced with a startle (124 dB) stimulus, which is thought to trigger a prepared Movement. Startle and non-startle (control) trials from early and late practice were compared on various kinematic and EMG measures. Results indicated that it is possible to pre-program a bimanual asymmetrical Movement, and that advance preparation of Movement amplitude changes with practice. Evidence was also provided that the different amplitude Movements were performed using similar EMG timing between limbs, while adjusting the relative ratio of EMG amplitude. Furthermore, learning of the task appeared to be related to the ability to prepare the correct asymmetrical EMG amplitudes rather than changing the timing of the EMG pattern.
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Response preparation changes following practice of an asymmetrical bimanual Movement
Experimental Brain Research, 2008Co-Authors: Dana Maslovat, Romeo Chua, Anthony N. Carlsen, Ryu Ishimoto, Ian M. FranksAbstract:The purpose of the current study was to examine the effects of practice on the advance preparation of an asymmetrical bimanual Movement. Participants performed 170 trials of a discrete bimanual Aiming Movement where the right arm moved twice the amplitude of the left, in response to an auditory “go” signal. During three of the first and last ten trials, the “go” signal was replaced with a startle (124 dB) stimulus, which is thought to trigger a prepared Movement. Startle and non-startle (control) trials from early and late practice were compared on various kinematic and EMG measures. Results indicated that it is possible to pre-program a bimanual asymmetrical Movement, and that advance preparation of Movement amplitude changes with practice. Evidence was also provided that the different amplitude Movements were performed using similar EMG timing between limbs, while adjusting the relative ratio of EMG amplitude. Furthermore, learning of the task appeared to be related to the ability to prepare the correct asymmetrical EMG amplitudes rather than changing the timing of the EMG pattern.
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Dual-target interference for the 'automatic pilot' in the dorsal stream.
Experimental brain research, 2007Co-Authors: Brendan D. Cameron, Ian M. Franks, James T. Enns, Romeo ChuaAbstract:When a target moves to a new location during a rapid Aiming Movement, the hand follows it, even when the participant intends not to. Pisella et al. (Nat Neurosci 3:729–736, 2000) claim that the posterior parietal cortex, in the dorsal visual stream, is responsible for this ‘automatic pilot’. Here we study the limits of automaticity in the dorsal stream through analysis of Aiming Movements to two targets in sequence. Participants were given a goal of moving rapidly to two targets, with the first Movement being completed within approximately 200 ms. On 30% of trials, the first or the second target jumped unpredictably to a new location at Movement onset, allowing us to measure the automatic capture of the hand. The results showed that hand Movements were less responsive to target jumps in a 2-target condition than in a 1-target control condition. This indicates that the ‘automatic pilot’ is susceptible to interference from multiple visual inputs, implying that the dorsal stream is less effective at guiding actions online when multiple targets are attended.