Role of motor cortex in coordinating multi-joint movements: Is it time for a new paradigm?

2000 ◽  
Vol 78 (11) ◽  
pp. 923-933 ◽  
Author(s):  
Stephen H Scott
Keyword(s):  
Motor Cortex ◽  
Neural Activity ◽  
Cortical Activity ◽  
Reaching Movements ◽  
Cortical Region ◽  
Joint Movement ◽  
Global Features ◽  
Motor Patterns ◽  
New Device ◽  
Motor Cortical

Reaching movements to spatial targets require motor patterns at the shoulder to be coordinated carefully with those at the elbow to smoothly move the hand through space. While the motor cortex is involved in this volitional task, considerable debate remains about how this cortical region participates in planning and controlling movement. This article reviews two opposing interpretations of motor cortical function during multi-joint movements. On the one hand, studies performed predominantly on single-joint movement generally support the notion that motor cortical activity is intimately involved in generating motor patterns at a given joint. In contrast, studies on reaching demonstrate correlations between motor cortical activity and features of movement related to the hand, suggesting that the motor cortex may be involved in more global features of the task. Although this latter paradigm involves a multi-joint motor task in which neural activity is correlated with features of movement related to the hand, this neural activity is also correlated to other movement variables. Therefore it is difficult to assess if and how the motor cortex contributes to the coordination of motor patterns at different joints. In particular, present paradigms cannot assess whether motor cortical activity contributes to the control of one joint or multiple joints during whole-arm tasks. The final point discussed in this article is the development of a new experimental device (KINARM) that can both monitor and manipulate the mechanics of the shoulder and elbow independently during multi-joint motor tasks. It is hoped that this new device will provide a new approach for examining how the motor cortex is involved in motor coordination.Key words: reaching movements, biomechanics, motor coordination, proximal arm.

scholarly journals Disruption of cortical dopaminergic modulation impairs preparatory activity and delays licking initiation

2018 ◽  
Author(s):  
Ke Chen ◽  
Roberto Vincis ◽  
Alfredo Fontanini
Keyword(s):  
Parkinson’S Disease ◽  
Parkinson's Disease ◽  
Motor Cortex ◽  
Neural Activity ◽  
Cortical Activity ◽  
Motor Deficits ◽  
Receptor Modulation ◽  
Dopaminergic Modulation ◽  
Preparatory Activity ◽  
Motor Cortical

ABSTRACTDysfunction of motor cortices is thought to contribute to motor disorders such as Parkinson’s disease (PD). However, little is known on the link between cortical dopaminergic loss, abnormalities in motor cortex neural activity and motor deficits. We address the role of dopamine in modulating motor cortical activity by focusing on the anterior lateral motor cortex (ALM) of mice performing a cued-licking task. We first demonstrate licking deficits and concurrent alterations of spiking activity in ALM of mice with unilateral depletion of dopaminergic neurons (i.e., mice injected with 6-OHDA into the medial forebrain bundle). Hemi-lesioned mice displayed delayed licking initiation, shorter duration of licking bouts, and lateral deviation of tongue protrusions. In parallel with these motor deficits, we observed a reduction in the prevalence of cue responsive neurons and altered preparatory activity. Acute and local blockade of D1 receptors in ALM recapitulated some of the key behavioral and neural deficits observed in hemi-lesioned mice. Altogether, our data show a direct relationship between cortical D1 receptor modulation, cue-evoked and preparatory activity in ALM, and licking initiation.SIGNIFICANCE STATEMENTThe link between dopaminergic signaling, motor cortical activity and motor deficits is not fully understood. This manuscript describes alterations in neural activity of the anterior lateral motor cortex (ALM) that correlate with licking deficits in mice with unilateral dopamine depletion or with intra-ALM infusion of dopamine antagonist. The findings emphasize the importance of cortical dopaminergic modulation in motor initiation. These results will appeal not only to researchers interested in cortical control of licking, but also to a broader audience interested in motor control and dopaminergic modulation in physiological and pathological conditions. Specifically, our data suggest that dopamine deficiency in motor cortex could play a role in the pathogenesis of the motor symptoms of Parkinson’s disease.

Comparison of Onset Time and Magnitude of Activity for Proximal Arm Muscles and Motor Cortical Cells Before Reaching Movements

1997 ◽  
Vol 77 (2) ◽  
pp. 1016-1022 ◽  
Author(s):  
Stephen H. Scott
Keyword(s):  
Primary Motor Cortex ◽  
Onset Time ◽  
Relative Magnitude ◽  
Reaching Movements ◽  
Electromyographic Activity ◽  
Cortical Cells ◽  
Motor Patterns ◽  
Direction Of Movement ◽  
Arm Muscles ◽  
Motor Cortical

Scott, Stephen H. Comparison of onset time and magnitude of activity for proximal arm muscles and motor cortical cells before reaching movements. J. Neurophysiol. 77: 1016–1022, 1997. The activity of motor cortical cells and proximal arm muscles during the initiation of planar reaching movements were analyzed to identify whether features of coordinated motor patterns of muscles spanning the elbow and shoulder were evident in the discharge patterns of motor cortical cells. Shoulder and elbow muscles were divided into four groups, flexors and extensors at each joint. Features of the initial agonist activity, onset time and magnitude, at the shoulder and elbow were compared for movements in different spatial directions. As observed for human movements, differences in the onset time and the relative magnitude of electromyographic activity (EMG) of muscles acting about the shoulder and elbow were dependent on the direction of movement. Motor cortical cells were categorized as elbow or shoulder related on the basis of their response to passive movement of the joints. Differences in the onset time and the relative magnitude of activity of cells related to the shoulder and elbow were both dependent on the direction of movement and were similar to those observed for muscles spanning these joints. There was a modest, but significant correlation between the onset time and magnitude of EMG for individual muscles. A similar magnitude-time coupling was observed for individual motor cortical cells. Variations in the discharge pattern of motor cortical cells before movement that mirror those observed for muscles spanning the shoulder and elbow support the potential role of primary motor cortex in the selection, timing, and magnitude of agonist motor patterns at the shoulder and elbow to initiate reaching movements.

scholarly journals Motor cortical plasticity in response to skill acquisition in adult monkeys

2020 ◽  
Author(s):  
Ankur Gupta ◽  
Abdulraheem Nashef ◽  
Sharon Israely ◽  
Michal Segal ◽  
Ran Harel ◽  
...  
Keyword(s):  
Motor Cortex ◽  
Skill Acquisition ◽  
Cortical Neurons ◽  
Cortical Plasticity ◽  
Task Demands ◽  
Cortical Region ◽  
Cortical Maps ◽  
Specific Outcome ◽  
Motor Cortical

SummaryCortical maps often undergo plastic changes during learning or in response to injury. In sensory areas, these changes are thought to be triggered by alterations in the pattern of converging inputs and a functional reassignment of the deprived cortical region. In the motor cortex, training on a task that engages distal effectors was shown to increase their cortical representation (as measured by response to intracortical microstimulation). However, this expansion could be a specific outcome of using a demanding dexterous task. We addressed this question by measuring the long-term changes in cortical maps of monkeys that were sequentially trained on two different tasks involving either proximal or distal joints. We found that motor cortical remodeling in adult monkeys was symmetric such that both distal and proximal movements can comparably alter motor maps in a fully reversible manner according to task demands. Further, we found that the change in mapping often included a switch between remote joints (e.g., a finger site switched to a shoulder site) and reflected a usage-consistent reorganization of the map rather than the local expansion of one representation into nearby sites. Finally, although cortical maps were considerably affected by the performed task, motor cortical neurons throughout the motor cortex were equally likely to fire in a task-related manner independent of the task and/or the recording site. These results may imply that in the motor system, enhanced motor efficiency is achieved through a dynamical allocation of larger cortical areas and not by specific recruitment of task-relevant cells.

scholarly journals Chronic Stability of Single-Channel Neurophysiological Correlates of Gross and Fine Reaching Movements in the Rat

2019 ◽  
Author(s):  
David T. Bundy ◽  
David J Guggenmos ◽  
Maxwell D Murphy ◽  
Randolph J. Nudo
Keyword(s):  
Motor Cortex ◽  
Local Field ◽  
Neural Activity ◽  
Local Field Potential ◽  
Primary Motor Cortex ◽  
Spectral Power ◽  
Premotor Cortex ◽  
Field Potential ◽  
Motor Recovery ◽  
Reaching Movements

AbstractFollowing injury to motor cortex, reorganization occurs throughout spared brain regions and is thought to underlie motor recovery. Unfortunately, the standard neurophysiological and neuroanatomical measures of post-lesion plasticity are only indirectly related to observed changes in motor execution. While substantial task-related neural activity has been observed during motor tasks in rodent primary motor cortex and premotor cortex, the long-term stability of these responses in healthy rats is uncertain, limiting the interpretability of longitudinal changes in the specific patterns of neural activity during motor recovery following injury. This study examined the stability of task-related neural activity associated with execution of reaching movements in healthy rodents. Rats were trained to perform a novel reaching task combining a ‘gross’ lever press and a ‘fine’ pellet retrieval. In each animal, two chronic microelectrode arrays were implanted in motor cortex spanning the caudal forelimb area (rodent primary motor cortex) and the rostral forelimb area (rodent premotor cortex). We recorded multiunit spiking and local field potential activity from 10 days to 7-10 weeks post-implantation to characterize the patterns of neural activity observed during each task component and analyzed the consistency of channel-specific task-related neural activity. Task-related changes in neural activity were observed on the majority of channels. While the task-related changes in multi-unit spiking and local field potential spectral power were consistent over several weeks, spectral power changes were more stable, despite the trade-off of decreased spatial and temporal resolution. These results show that rodent primary and premotor cortex are both involved in reaching movements with stable patterns of task-related activity across time, establishing the relevance of the rodent for future studies designed to examine changes in task-related neural activity during recovery from focal cortical lesions.

Neural Activity in Primary Motor Cortex Related to Mechanical Loads Applied to the Shoulder and Elbow During a Postural Task

2001 ◽  
Vol 86 (4) ◽  
pp. 2102-2108 ◽  
Author(s):  
D. William Cabel ◽  
Paul Cisek ◽  
Stephen H. Scott
Keyword(s):  
Motor Cortex ◽  
Neural Activity ◽  
Primary Motor Cortex ◽  
Cell Activity ◽  
Motor Patterns ◽  
Mechanical Loads ◽  
Central Target ◽  
Extensor Torque ◽  
Vector Sum ◽  
Joint Loads

Whole-arm motor tasks performed by nonhuman primates have become a popular paradigm to examine neural activity during motor action, but such studies have traditionally related cell discharge to hand-based variables. We have developed a new robotic device that allows the mechanics of the shoulder and elbow joints to be manipulated independently. This device was used in the present study to examine neural activity in primary motor cortex (MI) in monkeys ( macaca mulatta) actively maintaining their hand at a central target as they compensated for loads applied to the shoulder and/or elbow. Roughly equal numbers of neurons were sensitive to mechanical loads only at the shoulder, only at the elbow, or loads at both joints. Neurons possessed two important properties. First, cell activity during multi-joint loads could be predicted from its activity during single-joint loads as a vector sum in a space defined by orthogonal axes for the shoulder and elbow. Second, most neurons were related to flexor torque at one joint coupled with extensor torque at the other, a distribution that paralleled the observed activity of forelimb muscles. These results illustrate that while MI activity may be described by independent axes representing each mechanical degree-of-freedom, neural activity is also strongly influenced by the specific motor patterns used to perform a given task.

scholarly journals Plastic Changes in Primate Motor Cortex Following Paired Peripheral Nerve Stimulation

2020 ◽  
Author(s):  
Bonne Habekost ◽  
Maria Germann ◽  
Stuart N Baker
Keyword(s):  
Motor Cortex ◽  
Task Performance ◽  
Nerve Stimulation ◽  
Neural Activity ◽  
Primary Motor Cortex ◽  
Index Finger ◽  
Paired Stimulation ◽  
Motor Cortical ◽  
Decoding Accuracy ◽  
Stimulation Of

Repeated paired stimulation of two peripheral nerves can produce lasting changes in motor cortical excitability, but little is known of the underlying neuronal basis. Here we trained two macaque monkeys to perform selective thumb and index finger abduction movements. Neural activity was recorded from the contralateral primary motor cortex during task performance, and following stimulation of the ulnar and median nerves, and the nerve supplying the extensor digitorum communis (EDC) muscle. Responses were compared before and after one hour of synchronous or asynchronous paired ulnar/median nerve stimulation. Task performance was significantly enhanced after asynchronous, and impaired after synchronous stimulation. The amplitude of short latency neural responses to median and ulnar nerve stimulation was increased after asynchronous stimulation; later components were reduced after synchronous stimulation. Synchronous stimulation increased neural activity during thumb movement and decreased it during index finger movement; asynchronous stimulation decreased activity during both movements. To assess how well neural activity could separate behavioral or sensory conditions, linear discriminant analysis was used to decode which nerve was stimulated, or which digit moved. Decoding accuracy for nerve stimulation was decreased after synchronous, and increased after asynchronous paired stimulation. Decoding accuracy for task performance was decreased after synchronous, but unchanged after asynchronous paired stimulation. Paired stimulation produces changes in motor cortical circuits which outlast the stimulation. Some of these changes depend on precise stimulus timing.

scholarly journals Motor Cortical Representation of Position and Velocity During Reaching

2007 ◽  
Vol 97 (6) ◽  
pp. 4258-4270 ◽  
Author(s):  
Wei Wang ◽  
Sherwin S. Chan ◽  
Dustin A. Heldman ◽  
Daniel W. Moran
Keyword(s):  
Neural Activity ◽  
Cortical Neurons ◽  
Three Dimensional ◽  
Reaching Movements ◽  
Hand Position ◽  
Cortical Representation ◽  
Reaching Task ◽  
Position Signal ◽  
Motor Cortical ◽  
Highly Correlated

This study examines motor cortical representation of hand position and its relationship to the representation of hand velocity during reaching movements. In all, 978 motor cortical neurons were recorded from the proximal arm area of rostral motor cortex. The results demonstrate that position and velocity are simultaneously encoded by single motor cortical neurons in an additive fashion and that the relative weights of the position and velocity signals change dynamically during reaching. The two variables—hand position and hand velocity—are highly correlated in the standard center-out reaching task. A new reaching task (standard reaching) is introduced to minimize these correlations. Likewise, a new decoding method (indirect OLE) was developed to analyze the data by simultaneously decoding both three-dimensional (3D) hand position and 3D hand velocity from correlated neural activity. This method shows that, on average, the reconstructed velocity led the actual hand velocity by 122 ms, whereas the reconstructed position signal led the actual hand position by 81 ms.

scholarly journals Spontaneous emergence of behaviorally relevant motifs in human motor cortex

2020 ◽  
Author(s):  
Tomer Livne ◽  
DoHyun Kim ◽  
Nicholas V. Metcalf ◽  
Gordon L. Shulman ◽  
Maurizio Corbetta
Keyword(s):  
Motor Cortex ◽  
Spontaneous Activity ◽  
Neural Activity ◽  
Daily Life ◽  
Hand Movement ◽  
Cortical Activity ◽  
Hand Movements ◽  
Human Motor Cortex ◽  
Spontaneous Neural Activity ◽  
Human Motor

AbstractSpontaneous neural activity has been shown to preserve the inter-regional structure of cortical activity evoked by a task. It is unclear, however, whether patterns of spontaneous activity within a cortical region comprise representations associated with specific behaviors or mental states. The current study investigated the hypothesis that spontaneous neural activity in human motor cortex represents motor responses that commonly occur in daily life. To test this hypothesis 15 healthy participants were scanned in a 3T fMRI scanner while performing four simple hand movements differing by their daily life relevance, and while not performing any specific task (resting-state scans). Using the task data, we identified cortical patterns in a motor ROI corresponding to the different hand movements. These task-defined patterns were compared to spontaneous cortical activity patterns in the same motor ROI. The results indicated a higher similarity of the spontaneous patterns to the most common hand movement than to the least common hand movement. This finding provides the first evidence that spontaneous activity in human cortex forms fine-scale, patterned representations associated with behaviors that frequently occur in daily life.

scholarly journals Cyclic, condition-independent activity in primary motor cortex predicts corrective movement behavior

2018 ◽  
Author(s):  
Adam G. Rouse ◽  
Marc H. Schieber ◽  
Sridevi V. Sarma
Keyword(s):  
Motor Cortex ◽  
Neural Activity ◽  
Time Course ◽  
Primary Motor Cortex ◽  
Reaching Movements ◽  
Movement Behavior ◽  
Cyclic Activity ◽  
Cyclic Condition ◽  
Neuron Populations ◽  
Optimizing Control

AbstractReaching movements have previously been observed to have large condition-independent neural activity and cyclic neural dynamics. A new precision center-out task was used to test whether cyclic neural activity in the primary motor cortex (M1) occurred not only during initial reaching movements but also during subsequent corrective movements. Corrective movements were observed to be discrete with a time course and bell-shaped speed profile similar to the initial movements. Cyclic trajectories identified in the condition-independent neural activity were similar for initial and corrective submovements. The phase of the cyclic condition-independent neural activity predicted when peak movement speeds occurred, even when the subject made multiple corrective movements. Rather than being controlled as continuations of the initial reach, a discrete cycle of motor cortex activity encodes each corrective submovement.Significance StatementDuring a precision center-out task, initial and subsequent corrective movements occur as discrete submovements with bell-shaped speed profiles. A cycle of condition-independent activity in primary motor cortex neuron populations corresponds to each submovement whether initial or corrective, such that the phase of this cyclic activity predicts the time of peak speed. These submovements accompanied by cyclic neural activity offer important clues into how the we successfully execute precise, corrective reaching movements and may have implications for optimizing control of brain-computer interfaces.

scholarly journals Reaching Movements With Similar Hand Paths But Different Arm Orientations. I. Activity of Individual Cells in Motor Cortex

1997 ◽  
Vol 77 (2) ◽  
pp. 826-852 ◽  
Author(s):  
Stephen H. Scott ◽  
John F. Kalaska
Keyword(s):  
Motor Cortex ◽  
Dynamic Range ◽  
Reaching Movements ◽  
Movement Direction ◽  
Electromyographic Activity ◽  
Cortical Cells ◽  
Directional Tuning ◽  
Level Of Activity ◽  
Motor Cortical ◽  
Significant Change

Scott, Stephen H. and John F. Kalaska. Reaching movements with similar hand paths but different arm orientations. I. Activity of individual cells in motor cortex. J. Neurophysiol. 77: 826–852, 1997. This study shows that the discharge of many motor cortical cells is strongly influenced by attributes of movement related to the geometry and mechanics of the arm and not only by spatial attributes of the hand trajectory. The activity of 619 directionally tuned cells was recorded from the motor cortex of two monkeys during reaching movements with the use of similar hand paths but two different arm orientations, in the natural parasagittal plane and abducted into the horizontal plane. Nearly all cells (588 of 619, 95%) showed statistically significant changes in activity between the two arm orientations [analysis of variance (ANOVA), P < 0.01]. A majority of cells showed a significant change in their overall level of activity (ANOVA, main effect of task, P < 0.01) between arm orientations before, during, and after movement. Many cells (433 of 619, 70%) also showed a significant change in the relation of their discharge with movement direction(ANOVA, task × direction interaction term, P < 0.01) during movement, including changes in the dynamic range of discharge with movement and changes in the directional preference of cells that were directionally tuned in both arm orientations. Similar effects were seen for the discharge of cells while the monkey maintained constant arm postures over the different peripheral targets with the use of different arm orientations. Repeated data files from the same cell with the use of the same arm orientation showed only small changes in the level of discharge or in directional tuning, suggesting that changes in cell discharge between arm orientations cannot be explained by random temporal variations in cell activity. The distribution of movement-related preferred directions of the whole sample differed between arm orientations, and also differed strongly between cells receiving passive input predominantly from the shoulder or elbow. The electromyographic activity of most prime mover muscles at the shoulder and elbow was also strongly affected by arm orientation, resulting in changes in overall level of activity and/or directional tuning that often resembled those of the proximal arm-related motor cortical cells. A mathematical model that represented movements in terms of movement direction centered on the hand could not account for any of the arm-orientation-related response changes seen in this task, whereas models in intrinsic parameter spaces of joint kinematics and joint torques predicted many of the effects.

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