scholarly journals Movement speed is biased by prior experience

2014 ◽  
Vol 111 (1) ◽  
pp. 128-134 ◽  
Author(s):  
Ulrike Hammerbeck ◽  
Nada Yousif ◽  
Richard Greenwood ◽  
John C. Rothwell ◽  
Jörn Diedrichsen
Keyword(s):  
Training Group ◽  
Movement Speed ◽  
Movement Direction ◽  
Task Constraints ◽  
Reaching Task ◽  
Optimal Balance ◽  
Fast Training ◽  
Human Participants ◽  
Selection Of ◽  
Dependent Mechanism

How does the motor system choose the speed for any given movement? Many current models assume a process that finds the optimal balance between the costs of moving fast and the rewards of achieving the goal. Here, we show that such models also need to take into account a prior representation of preferred movement speed, which can be changed by prolonged practice. In a time-constrained reaching task, human participants made 25-cm reaching movements within 300, 500, 700, or 900 ms. They were then trained for 3 days to execute the movement at either the slowest (900-ms) or fastest (300-ms) speed. When retested on the 4th day, movements executed under all four time constraints were biased toward the speed of the trained movement. In addition, trial-to-trial variation in speed of the trained movement was significantly reduced. These findings are indicative of a use-dependent mechanism that biases the selection of speed. Reduced speed variability was also associated with reduced errors in movement amplitude for the fast training group, which generalized nearly fully to a new movement direction. In contrast, changes in perpendicular error were specific to the trained direction. In sum, our results suggest the existence of a relatively stable but modifiable prior of preferred movement speed that influences the choice of movement speed under a range of task constraints.

scholarly journals Chronic Stroke Survivors Improve Reaching Accuracy by Reducing Movement Variability at the Trained Movement Speed

2017 ◽  
Vol 31 (6) ◽  
pp. 499-508 ◽  
Author(s):  
Ulrike Hammerbeck ◽  
Nada Yousif ◽  
Damon Hoad ◽  
Richard Greenwood ◽  
Jörn Diedrichsen ◽  
...  
Keyword(s):  
Chronic Phase ◽  
Training Group ◽  
Chronic Stroke ◽  
Movement Speed ◽  
Stroke Survivors ◽  
Movement Variability ◽  
Reaching Task ◽  
Arm Reaching ◽  
Fast Training ◽  
Elbow Movement

Background. Recovery from stroke is often said to have “plateaued” after 6 to 12 months. Yet training can still improve performance even in the chronic phase. Here we investigate the biomechanics of accuracy improvements during a reaching task and test whether they are affected by the speed at which movements are practiced. Method. We trained 36 chronic stroke survivors (57.5 years, SD ± 11.5; 10 females) over 4 consecutive days to improve endpoint accuracy in an arm-reaching task (420 repetitions/day). Half of the group trained using fast movements and the other half slow movements. The trunk was constrained allowing only shoulder and elbow movement for task performance. Results. Before training, movements were variable, tended to undershoot the target, and terminated in contralateral workspace (flexion bias). Both groups improved movement accuracy by reducing trial-to-trial variability; however, change in endpoint bias (systematic error) was not significant. Improvements were greatest at the trained movement speed and generalized to other speeds in the fast training group. Small but significant improvements were observed in clinical measures in the fast training group. Conclusions. The reduction in trial-to-trial variability without an alteration to endpoint bias suggests that improvements are achieved by better control over motor commands within the existing repertoire. Thus, 4 days’ training allows stroke survivors to improve movements that they can already make. Whether new movement patterns can be acquired in the chronic phase will need to be tested in longer term studies. We recommend that training needs to be performed at slow and fast movement speeds to enhance generalization.

scholarly journals Statistical Characteristics of Unsteady Storms in Radar Observations for the Beijing–Tianjin Region

2015 ◽  
Vol 54 (1) ◽  
pp. 106-116 ◽  
Author(s):  
Yu Wang ◽  
Hong-Qing Wang ◽  
Lei Han ◽  
Yin-Jing Lin ◽  
Yan Zhang
Keyword(s):  
Warm Season ◽  
Environmental Parameters ◽  
Statistical Characteristics ◽  
Movement Speed ◽  
Movement Direction ◽  
Upper Troposphere ◽  
Maximum Value ◽  
Dynamic Factors ◽  
The Mean ◽  
Wind Profiles

AbstractThis study was designed to provide basic information for the improvement of storm nowcasting. According to the mean direction deviation of storm movement, storms were classified into three types: 1) steady storms (S storms, extrapolated efficiently), 2) unsteady storms (U storms, extrapolated poorly), and 3) transitional storms (T storms). The U storms do not fit the linear extrapolation processes because of their unsteady movements. A 6-yr warm-season radar observation dataset was used to highlight and analyze the differences between U storms and S storms. The analysis included geometric features, dynamic factors, and environmental parameters. The results showed that storms with the following characteristics changed movement direction most easily in the Beijing–Tianjin region: 1) smaller storm area, 2) lower thickness (echo-top height minus base height), 3) lower movement speed, 4) weaker updrafts and the maximum value located in the mid- and upper troposphere, 5) storm-relative vertical wind profiles dominated by directional shear instead of speed shear, 6) lower relative humidity in the mid- and upper troposphere, and 7) higher surface evaporation and ground roughness.

scholarly journals Changes in activity of fast-spiking interneurons of the monkey striatum during reaching at a visual target

2017 ◽  
Vol 117 (1) ◽  
pp. 65-78 ◽  
Author(s):  
Kévin Marche ◽  
Paul Apicella
Keyword(s):  
Target Location ◽  
Visual Target ◽  
Movement Speed ◽  
Gabaergic Interneurons ◽  
Movement Preparation ◽  
Movement Initiation ◽  
Reaching Task ◽  
Advance Information ◽  
Fast Spiking ◽  
Task Conditions

Recent works highlight the importance of local inhibitory interneurons in regulating the function of the striatum. In particular, fast-spiking interneurons (FSIs), which likely correspond to a subgroup of GABAergic interneurons, have been involved in the control of movement by exerting strong inhibition on striatal output pathways. However, little is known about the exact contribution of these presumed interneurons in movement preparation, initiation, and execution. We recorded the activity of FSIs in the striatum of monkeys as they performed reaching movements to a visual target under two task conditions: one in which the movement target was presented at unsignaled left or right locations, and another in which advance information about target location was available, thus allowing monkeys to react faster. Modulations of FSI activity around the initiation of movement (53% of 55 neurons) consisted mostly of increases reaching maximal firing immediately before or, less frequently, after movement onset. Another subset of FSIs showed decreases in activity during movement execution. Rarely did movement-related changes in FSI firing depend on response direction and movement speed. Modulations of FSI activity occurring relatively early in relation to movement initiation were more influenced by the preparation for movement, compared with those occurring later. Conversely, FSI activity remained unaffected, as monkeys were preparing a movement toward a specific location and instead moved to the opposite direction when the trigger occurred. These results provide evidence that changes in activity of presumed GABAergic interneurons of the primate striatum could make distinct contributions to processes involved in movement generation. NEW & NOTEWORTHY We explored the functional contributions of striatal fast-spiking interneurons (FSIs), presumed GABAergic interneurons, to distinct steps of movement generation in monkeys performing a reaching task. The activity of individual FSIs was modulated before and during the movement, consisting mostly of increased in firing rates. Changes in activity also occurred during movement preparation. We interpret this variety of modulation types at different moments of task performance as reflecting differential FSI control over distinct phases of movement.

Modulation of preparatory neuronal activity in dorsal premotor cortex due to stimulus-response compatibility

1994 ◽  
Vol 71 (3) ◽  
pp. 1281-1284 ◽  
Author(s):  
D. J. Crammond ◽  
J. F. Kalaska
Keyword(s):  
Neuronal Activity ◽  
Premotor Cortex ◽  
Spatial Location ◽  
Dorsal Premotor Cortex ◽  
Reaching Task ◽  
Stimulus Response ◽  
Sustained Activity ◽  
Spatial Attributes ◽  
Direction Of Movement ◽  
Selection Of

1. Neuronal activity was recorded in the dorsal premotor cortex (PMd) of two monkeys performing a multidirectional, instructed-delay (ID) reaching task in which visuospatial cues signaled the direction of movement either congruent with the instruction cue ("direct-delay" trials, DD) or redirected 180 degrees opposite to the cue ("redirected-delay" trials, RD). Therefore, this task had two degrees of stimulus-response (S-R) compatibility because in one-half of the trials the spatial attributes of the visual cue were incongruent with those of the intended movement. 2. The majority of PMd cells discharged both at short latency to the RD or DD cues and subsequently with sustained activity during the remaining ID period (IDP). The earliest responses (< 250 ms) in both DD and RD trials covaried with cue location and so could be either a "visuospatial" response or a neuronal correlate of the selection of action with highest S-R compatibility, namely move to the stimulus. In contrast, later IDP activity usually covaried with the direction of movement signaled by the cues, independent of their spatial location, supporting the hypothesis that IDP discharge in PMd ultimately encodes attributes of intended reaching movements.

The role of intrinsic factors in control of arm movement direction: implications from directional preferences

2011 ◽  
Vol 105 (3) ◽  
pp. 999-1010 ◽  
Author(s):  
Natalia Dounskaia ◽  
Jacob A. Goble ◽  
Wanyue Wang
Keyword(s):  
Arm Movement ◽  
Movement Direction ◽  
Revealed Preferences ◽  
Intrinsic Nature ◽  
Intrinsic Factors ◽  
Intersegmental Dynamics ◽  
Drawing Task ◽  
Dominant Tendency ◽  
Selection Of

The role of extrinsic and intrinsic factors in control of arm movement direction remains under debate. We addressed this question by investigating preferences in selection of movement direction and whether factors causing these preferences have extrinsic or intrinsic nature. An unconstrained free-stroke drawing task was used during which participants produced straight strokes on a horizontal table, choosing the direction and the beginning and end of each stroke arbitrarily. The variation of the initial arm postures across strokes provided a possibility to distinguish between the extrinsic and intrinsic origins of directional biases. Although participants were encouraged to produce strokes equally in all directions, each participant demonstrated preferences for some directions over the others. However, the preferred directions were not consistent across participants, suggesting no directional preferences in extrinsic space. Consistent biases toward certain directions were revealed in intrinsic space representing initial arm postures. Factors contributing to the revealed preferences were analyzed within the optimal control framework. The major bias was explained by a tendency predicted by the leading joint hypothesis (LJH) to minimize active interference with interaction torque generated by shoulder motion at the elbow. Some minor biases may represent movements of minimal inertial resistance or maximal kinematic manipulability. These results support a crucial role of intrinsic factors in control of the movement direction of the arm. Based on the LJH interpretation of the major bias, we hypothesize that the dominant tendency was to minimize neural effort for control of arm intersegmental dynamics. Possible organization of neural processes underlying optimal selection of movement direction is discussed.

scholarly journals Motor cortical control of movement speed with implications for brain-machine interface control

2014 ◽  
Vol 112 (2) ◽  
pp. 411-429 ◽  
Author(s):  
Matthew D. Golub ◽  
Byron M. Yu ◽  
Andrew B. Schwartz ◽  
Steven M. Chase
Keyword(s):  
Kalman Filter ◽  
Motor Cortex ◽  
Movement Speed ◽  
Movement Direction ◽  
Single Trial ◽  
Population Activity ◽  
Related Information ◽  
Lower Accuracy ◽  
Motor Cortical ◽  
Speed Accuracy

Motor cortex plays a substantial role in driving movement, yet the details underlying this control remain unresolved. We analyzed the extent to which movement-related information could be extracted from single-trial motor cortical activity recorded while monkeys performed center-out reaching. Using information theoretic techniques, we found that single units carry relatively little speed-related information compared with direction-related information. This result is not mitigated at the population level: simultaneously recorded population activity predicted speed with significantly lower accuracy relative to direction predictions. Furthermore, a unit-dropping analysis revealed that speed accuracy would likely remain lower than direction accuracy, even given larger populations. These results suggest that the instantaneous details of single-trial movement speed are difficult to extract using commonly assumed coding schemes. This apparent paucity of speed information takes particular importance in the context of brain-machine interfaces (BMIs), which rely on extracting kinematic information from motor cortex. Previous studies have highlighted subjects' difficulties in holding a BMI cursor stable at targets. These studies, along with our finding of relatively little speed information in motor cortex, inspired a speed-dampening Kalman filter (SDKF) that automatically slows the cursor upon detecting changes in decoded movement direction. Effectively, SDKF enhances speed control by using prevalent directional signals, rather than requiring speed to be directly decoded from neural activity. SDKF improved success rates by a factor of 1.7 relative to a standard Kalman filter in a closed-loop BMI task requiring stable stops at targets. BMI systems enabling stable stops will be more effective and user-friendly when translated into clinical applications.

scholarly journals First person – Maayan Barnea-Zohar and Sabina E. Winograd-Katz

2021 ◽  
Vol 134 (9) ◽  
Keyword(s):  
Cell Size ◽  
Cell Fusion ◽  
Cell Biology ◽  
Early Career ◽  
First Person ◽  
Research Assistant ◽  
Weizmann Institute ◽  
Early Career Researchers ◽  
Selection Of ◽  
Dependent Mechanism

ABSTRACT First Person is a series of interviews with the first authors of a selection of papers published in Journal of Cell Science, helping early-career researchers promote themselves alongside their papers. Maayan Barnea-Zohar and Sabina E. Winograd-Katz are co-first authors on ‘ An SNX10-dependent mechanism downregulates fusion between mature osteoclasts’, published in JCS. Maayan is a research assistant in the lab of Ari Elson at the Weizmann Institute of Science, Rehovot, Israel, investigating cell–cell fusion in osteoclasts and how cell size is determined. Sabina is a research assistant and lab manager in the lab of Benjamin Geiger at the Weizmann Institute of Science, investigating cell biology and signaling.

scholarly journals Inter-personal motor interaction is facilitated by hand pairing

2022 ◽  
Vol 12 (1) ◽  
Author(s):  
Keivan Mojtahedi ◽  
Kimia Kiani ◽  
Marco Santello ◽  
Qiushi Fu
Keyword(s):  
Single Agent ◽  
Internal Force ◽  
Vertical Movement ◽  
Movement Speed ◽  
Dominant Hand ◽  
Hand Dominance ◽  
Haptic Communication ◽  
Human Participants ◽  
Movement Synchrony ◽  
First Time

AbstractThe extent to which hand dominance may influence how each agent contributes to inter-personal coordination remains unknown. In the present study, right-handed human participants performed object balancing tasks either in dyadic conditions with each agent using one hand (left or right), or in bimanual conditions where each agent performed the task individually with both hands. We found that object load was shared between two hands more asymmetrically in dyadic than single-agent conditions. However, hand dominance did not influence how two hands shared the object load. In contrast, hand dominance was a major factor in modulating hand vertical movement speed. Furthermore, the magnitude of internal force produced by two hands against each other correlated with the synchrony between the two hands’ movement in dyads. This finding supports the important role of internal force in haptic communication. Importantly, both internal force and movement synchrony were affected by hand dominance of the paired participants. Overall, these results demonstrate, for the first time, that pairing of one dominant and one non-dominant hand may promote asymmetrical roles within a dyad during joint physical interactions. This appears to enable the agent using the dominant hand to actively maintain effective haptic communication and task performance.

Sign in / Sign up

Export Citation Format

Share Document