Dissociating effector and movement direction selection during the preparation of manual reaching movements: Evidence from lateralized ERP components

1. Neuronal activity was recorded in the motor cortex of a monkey that performed reaching movements with the use of two different arm postures. In the first posture (control), the monkey used its natural arm orientation, approximately in the sagittal plane. In the second posture (abducted), the monkey had to adduct its elbow nearly to shoulder level to grasp the handle. The path of the hand between targets was similar in both arm postures, but the joint kinematics and kinetics were different. 2. In both postures, the activity of single cells was often broadly tuned with movement direction and static arm posture over the targets. In a large proportion of cells, either the level of tonic activity, the directional tuning, or both, varied between the two postures during the movement and target hold periods. 3. For most directions of movement, there was a statistically significant difference in the direction of the population vector for the two arm postures. Furthermore, whereas the population vector tended to point in the direction of movement for the control posture, there was a poorer correspondence between the direction of movement and the population vector for the abducted posture. These observed changes are inconsistent with the notion that the motor cortex encodes purely hand trajectory in space.

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Proximal-distal differences in movement smoothness reflect differences in biomechanics

Journal of Neurophysiology ◽

10.1152/jn.00712.2015 ◽

2017 ◽

Vol 117 (3) ◽

pp. 1239-1257 ◽

Cited By ~ 9

Author(s):

Layne H. Salmond ◽

Andrew D. Davidson ◽

Steven K. Charles

Keyword(s):

Neural Control ◽

Sudden Change ◽

Mechanical Impedance ◽

Past Research ◽

Reaching Movements ◽

Movement Direction ◽

Movement Duration ◽

Neural Noise ◽

Movement Smoothness ◽

Flexion Extension

Smoothness is a hallmark of healthy movement. Past research indicates that smoothness may be a side product of a control strategy that minimizes error. However, this is not the only reason for smooth movements. Our musculoskeletal system itself contributes to movement smoothness: the mechanical impedance (inertia, damping, and stiffness) of our limbs and joints resists sudden change, resulting in a natural smoothing effect. How the biomechanics and neural control interact to result in an observed level of smoothness is not clear. The purpose of this study is to 1) characterize the smoothness of wrist rotations, 2) compare it with the smoothness of planar shoulder-elbow (reaching) movements, and 3) determine the cause of observed differences in smoothness. Ten healthy subjects performed wrist and reaching movements involving different targets, directions, and speeds. We found wrist movements to be significantly less smooth than reaching movements and to vary in smoothness with movement direction. To identify the causes underlying these observations, we tested a number of hypotheses involving differences in bandwidth, signal-dependent noise, speed, impedance anisotropy, and movement duration. Our simulations revealed that proximal-distal differences in smoothness reflect proximal-distal differences in biomechanics: the greater impedance of the shoulder-elbow filters neural noise more than the wrist. In contrast, differences in signal-dependent noise and speed were not sufficiently large to recreate the observed differences in smoothness. We also found that the variation in wrist movement smoothness with direction appear to be caused by, or at least correlated with, differences in movement duration, not impedance anisotropy. NEW & NOTEWORTHY This article presents the first thorough characterization of the smoothness of wrist rotations (flexion-extension and radial-ulnar deviation) and comparison with the smoothness of reaching (shoulder-elbow) movements. We found wrist rotations to be significantly less smooth than reaching movements and determined that this difference reflects proximal-distal differences in biomechanics: the greater impedance (inertia, damping, stiffness) of the shoulder-elbow filters noise in the command signal more than the impedance of the wrist.

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Proprioceptive activity in primate primary somatosensory cortex during active arm reaching movements

Journal of Neurophysiology ◽

10.1152/jn.1994.72.5.2280 ◽

1994 ◽

Vol 72 (5) ◽

pp. 2280-2301 ◽

Cited By ~ 107

Author(s):

M. J. Prud'homme ◽

J. F. Kalaska

Keyword(s):

Motor Cortex ◽

Somatosensory Cortex ◽

Parietal Cortex ◽

Arm Movements ◽

Reaching Movements ◽

Movement Direction ◽

Tonic Activity ◽

Directional Tuning ◽

Central Target ◽

Tonic Response

1. We studied the activity of 254 cells in the primary somatosensory cortex (SI) responding to inputs from peripheral proprioceptors in a variety of tasks requiring active reaching movements of the contralateral arm. 2. The majority of cells with receptive fields on the proximal arm (shoulder and elbow) were broadly and unimodally tuned for movement direction, often with approximately sinusoidal tuning curves similar to those seen in motor and parietal cortex. 3. The predominant temporal response profiles were directionally tuned phasic bursts during movement and tonic activity that varied with different arm postures. 4. Most cells showed both phasic and tonic response components to differing degrees, and the population formed a continuum from purely phasic to purely tonic cells with no evidence of separate distinct phasic and tonic populations. This indicates that the initial cortical neuronal correlates of the introspectively distinguishable sensations of movement and position are represented in an overlapping or distributed manner in SI. 5. The directional tuning of the phasic and tonic response components of most cells was generally similar, although rarely identical. 6. We tested 62 cells during similar active and passive arm movements. Many cells showed large differences in their responses in the two conditions, presumably due to changes in peripheral receptor discharge during active muscle contractions. 7. We tested 86 cells in a convergent movement task in which monkeys made reaching movements to a single central target from eight peripheral starting positions. A majority of the cells (46 of 86, 53.5%) showed a movement direction-related hysteresis in which their tonic activity after movement to the central target varied with the direction by which the arm moved to the target. The directionality of this hysteresis was coupled with the movement-related directional tuning of the cells. 8. We recorded the discharge of 93 cells as the monkeys performed the task while compensating for loads in different directions. The large majority of cells showed a statistically significant modulation of activity as a function of load direction, which was qualitatively similar to that seen in motor cortex under similar task conditions. Quantitatively, however, the sensitivity of SI proprioceptive cells to loads was less than that seen in motor cortex but greater than in parietal cortex. 9. We interpret these results in terms of their implications for the central representation of the spatiotemporal form (“kinematics”) of arm movements and postures. Most importantly, the results emphasize the important influence of muscle contractile activity on the central proprioceptive representation of active movements.

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Interacting Noise Sources Shape Patterns of Arm Movement Variability in Three-Dimensional Space

Journal of Neurophysiology ◽

10.1152/jn.00590.2010 ◽

2010 ◽

Vol 104 (5) ◽

pp. 2654-2666 ◽

Cited By ~ 15

Author(s):

Gregory A. Apker ◽

Timothy K. Darling ◽

Christopher A. Buneo

Keyword(s):

Dimensional Space ◽

Three Dimensional ◽

Vertical Plane ◽

Reaching Movements ◽

Movement Direction ◽

Dependent Manner ◽

Movement Variability ◽

Noise Sources ◽

Principal Axes ◽

Three Dimensional Space

Reaching movements are subject to noise in both the planning and execution phases of movement production. The interaction of these noise sources during natural movements is not well understood, despite its importance for understanding movement variability in neurologically intact and impaired individuals. Here we examined the interaction of planning and execution related noise during the production of unconstrained reaching movements. Subjects performed sequences of two movements to targets arranged in three vertical planes separated in depth. The starting position for each sequence was also varied in depth with the target plane; thus required movement sequences were largely contained within the vertical plane of the targets. Each final target in a sequence was approached from two different directions, and these movements were made with or without visual feedback of the moving hand. These combined aspects of the design allowed us to probe the interaction of execution and planning related noise with respect to reach endpoint variability. In agreement with previous studies, we found that reach endpoint distributions were highly anisotropic. The principal axes of movement variability were largely aligned with the depth axis, i.e., the axis along which visual planning related noise would be expected to dominate, and were not generally well aligned with the direction of the movement vector. Our results suggest that visual planning–related noise plays a dominant role in determining anisotropic patterns of endpoint variability in three-dimensional space, with execution noise adding to this variability in a movement direction-dependent manner.

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Effects of Direction and Curvature on Variable Error Pattern of Reaching Movements

Motor Control ◽

10.1123/mcj.3.4.414 ◽

1999 ◽

Vol 3 (4) ◽

pp. 414-423 ◽

Cited By ~ 3

Author(s):

Slobodan Jaric ◽

Charli Tortoza ◽

Ismael F.C. Fatarelli ◽

Gil L. Almeida

Keyword(s):

Principal Component ◽

Reaching Movements ◽

Movement Direction ◽

Final Position ◽

Movement Kinematics ◽

Starting Position ◽

Movement Curvature ◽

Variable Errors ◽

Different Levels ◽

Insight Into

A number of studies have analyzed various indices of the final position variability in order to provide insight into different levels of neuromotor processing during reaching movements. Yet the possible effects of movement kinematics on variability have often been neglected. The present study was designed to test the effects of movement direction and curvature on the pattern of movement variable errors. Subjects performed series of reaching movements over the same distance and into the same target. However, due either to changes in starting position or to applied obstacles, the movements were performed in different directions or along the trajectories of different curvatures. The pattern of movement variable errors was assessed by means of the principal component analysis applied on the 2-D scatter of movement final positions. The orientation of these ellipses demonstrated changes associated with changes in both movement direction and curvature. However, neither movement direction nor movement curvature affected movement variable errors assessed by area of the ellipses. Therefore it was concluded that the end-point variability depends partly, but not exclusively, on movement kinematics.

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Proximal Versus Distal Control of Two-Joint Planar Reaching Movements in the Presence of Neuromuscular Noise

Journal of Biomechanical Engineering ◽

10.1115/1.4006811 ◽

2012 ◽

Vol 134 (6) ◽

Cited By ~ 8

Author(s):

Hung P. Nguyen ◽

Jonathan B. Dingwell

Keyword(s):

System Performance ◽

Reaching Movements ◽

Energetic Cost ◽

Movement Direction ◽

Joint Control ◽

Total Work ◽

Upper Arm ◽

Reaching Accuracy ◽

Distal Joint ◽

Human Nervous System

Determining how the human nervous system contends with neuro-motor noise is vital to understanding how humans achieve accurate goal-directed movements. Experimentally, people learning skilled tasks tend to reduce variability in distal joint movements more than in proximal joint movements. This suggests that they might be imposing greater control over distal joints than proximal joints. However, the reasons for this remain unclear, largely because it is not experimentally possible to directly manipulate either the noise or the control at each joint independently. Therefore, this study used a 2 degree-of-freedom torque driven arm model to determine how different combinations of noise and/or control independently applied at each joint affected the reaching accuracy and the total work required to make the movement. Signal-dependent noise was simultaneously and independently added to the shoulder and elbow torques to induce endpoint errors during planar reaching. Feedback control was then applied, independently and jointly, at each joint to reduce endpoint error due to the added neuromuscular noise. Movement direction and the inertia distribution along the arm were varied to quantify how these biomechanical variations affected the system performance. Endpoint error and total net work were computed as dependent measures. When each joint was independently subjected to noise in the absence of control, endpoint errors were more sensitive to distal (elbow) noise than to proximal (shoulder) noise for nearly all combinations of reaching direction and inertia ratio. The effects of distal noise on endpoint errors were more pronounced when inertia was distributed more toward the forearm. In contrast, the total net work decreased as mass was shifted to the upper arm for reaching movements in all directions. When noise was present at both joints and joint control was implemented, controlling the distal joint alone reduced endpoint errors more than controlling the proximal joint alone for nearly all combinations of reaching direction and inertia ratio. Applying control only at the distal joint was more effective at reducing endpoint errors when more of the mass was more proximally distributed. Likewise, controlling the distal joint alone required less total net work than controlling the proximal joint alone for nearly all combinations of reaching distance and inertia ratio. It is more efficient to reduce endpoint error and energetic cost by selectively applying control to reduce variability in the distal joint than the proximal joint. The reasons for this arise from the biomechanical configuration of the arm itself.

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Interaction of Visual and Proprioceptive Feedback During Adaptation of Human Reaching Movements

Journal of Neurophysiology ◽

10.1152/jn.00947.2004 ◽

2005 ◽

Vol 93 (6) ◽

pp. 3200-3213 ◽

Cited By ~ 152

Author(s):

Robert A. Scheidt ◽

Michael A. Conditt ◽

Emanuele L. Secco ◽

Ferdinando A. Mussa-Ivaldi

Keyword(s):

Visual Feedback ◽

Visual Information ◽

Internal Representation ◽

Proprioceptive Feedback ◽

Reaching Movements ◽

Movement Direction ◽

Visual Channel ◽

Hand Path ◽

Motor Commands ◽

Position Regulation

People tend to make straight and smooth hand movements when reaching for an object. These trajectory features are resistant to perturbation, and both proprioceptive as well as visual feedback may guide the adaptive updating of motor commands enforcing this regularity. How is information from the two senses combined to generate a coherent internal representation of how the arm moves? Here we show that eliminating visual feedback of hand-path deviations from the straight-line reach (constraining visual feedback of motion within a virtual, “visual channel”) prevents compensation of initial direction errors induced by perturbations. Because adaptive reduction in direction errors occurred with proprioception alone, proprioceptive and visual information are not combined in this reaching task using a fixed, linear weighting scheme as reported for static tasks not requiring arm motion. A computer model can explain these findings, assuming that proprioceptive estimates of initial limb posture are used to select motor commands for a desired reach and visual feedback of hand-path errors brings proprioceptive estimates into registration with a visuocentric representation of limb position relative to its target. Simulations demonstrate that initial configuration estimation errors lead to movement direction errors as observed experimentally. Registration improves movement accuracy when veridical visual feedback is provided but is not invoked when hand-path errors are eliminated. However, the visual channel did not exclude adjustment of terminal movement features maximizing hand-path smoothness. Thus visual and proprioceptive feedback may be combined in fundamentally different ways during trajectory control and final position regulation of reaching movements.

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ENCODING OF LIMB STATE BY SINGLE NEURONS IN THE CUNEATE NUCLEUS OF AWAKE MONKEYS

10.1101/2021.03.17.435880 ◽

2021 ◽

Author(s):

Christopher Versteeg ◽

Joshua M Rosenow ◽

Sliman J Bensmaia ◽

Lee E Miller

Keyword(s):

Sensory Information ◽

Muscle Spindles ◽

Limb Movement ◽

Reaching Movements ◽

Movement Direction ◽

Single Muscle ◽

Single Neurons ◽

Cuneate Nucleus

The cuneate nucleus (CN) is among the first sites along the neuraxis where proprioceptive signals can be integrated, transformed, and modulated. The objective of the study was to characterize the proprioceptive representations in CN. To this end, we recorded from single CN neurons in three monkeys during active reaching and passive limb perturbation. We found that many neurons exhibited responses that were tuned approximately sinusoidally to limb movement direction, as has been found for other sensorimotor neurons. The distribution of their preferred directions (PDs) was highly non-uniform and resembled that of muscle spindles within individual muscles, suggesting that CN neurons typically receive inputs from only a single muscle. We also found that the responses of proprioceptive CN neurons tended to be modestly amplified during active reaching movements compared to passive limb perturbations, in contrast to cutaneous CN neurons whose responses were not systematically different in the active and passive conditions. Somatosensory signals thus seem to be subject to a 'spotlighting' of relevant sensory information rather than uniform suppression as has been suggested previously.

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Task Effects on Three-Dimensional Dynamic Postures during Seated Reaching Movements: An Analysis Method and Illustration

Proceedings of the Human Factors and Ergonomics Society Annual Meeting ◽

10.1177/154193129604001303 ◽

1996 ◽

Vol 40 (13) ◽

pp. 594-598 ◽

Cited By ~ 18

Author(s):

Xudong Zhang ◽

Don B. Chaffin

Keyword(s):

Hand Movement ◽

Three Dimensional ◽

Reaching Movements ◽

Movement Direction ◽

Motion Direction ◽

Hand Motion ◽

Movement Data ◽

Task Effects ◽

Posture Prediction ◽

The Relationship

This paper presents a new method to empirically investigate the effects of task factors on three-dimensional (3D) dynamic postures during seated reaching movements. The method relies on a statistical model in which the effects of hand location and those of various task factors on dynamic postures are distinguished. Two statistical procedures are incorporated: a regression description of the relationship between the time-varying hand location and postural profiles to compress the movement data, and a series of analyses of variance to test the hypothesized task effects using instantaneous postures with prescribed hand locations as dependent measures. The use of this method is illustrated by an experiment which examines two generic task factors: 1) hand movement direction, and 2) motion completion time. The results suggest that the hand motion direction is a significant task factor and should be included as an important attribute when describing or modeling instantaneous postures. It was also found that the time to complete a motion under a self-paced mode was significantly different from a motivated mode, but the time difference did not significantly affect instantaneous postures. The concept of an instantaneous posture and its usage in dynamic studies of movements are discussed. Some understanding of human postural control as well as the implications for developing a general dynamic posture prediction model also are presented.

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Influence of switching rule on motor learning

10.1101/243386 ◽

2018 ◽

Author(s):

Ken Takiyama ◽

Koutaro Ishii ◽

Takuji Hayshi

Keyword(s):

Motor Learning ◽

Sensory Stimulus ◽

Reaching Movements ◽

Movement Direction ◽

Learning Effects ◽

Visuomotor Rotation ◽

Switching Rule ◽

Arm Reaching ◽

Partial Transfer ◽

The Difference

AbstractHumans and animals can flexibly switch rules to generate appropriate motor commands; for example, actions can be flexibly produced toward a sensory stimulus (e.g., pro-saccade or pro-reaching) or away from a sensory stimulus (e.g., anti-saccade or anti-reaching). Distinct neural activities are related to pro- and anti-movement actions; however, the effects of switching rules on motor learning are unclear. Here, we study the effect of switching rules on motor learning using pro- and anti-arm-reaching movements and a visuomotor rotation task. Although previous results support the perfect availability of learning effects under the same required movements, we show that the learning effects trained in pro-reaching movements are partially rather than perfectly available in anti-reaching movements even under the same required movement direction between those two conditions. The partial transfer is independent of the difference in the visual cue, the cognitive demand, and the actual movement direction between the pro- and anti-reaching movements. We further demonstrate that the availability of learning effects trained with pro-reaching movements is partial not only in anti-reaching movements but in reaching movements with other rules and the availability of learning effects trained with anti-reaching movements is also partial in pro-reaching movements. We thus conclude that the switching rule causes the availability of learning effects to be partial rather than perfect even under same planned movements.New & NoteworthyMost motor learning experiments supported the involvement of planned movement directions in motor learning; the learning effects trained in a movement direction can be available at movement directions close to the trained one. Here, we show that the availability of motor learning effects is partial rather than perfect even under the same planned movements when rule is switched, which indicates that sports training and rehabilitation should include various situations under the same required motions.

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