scholarly journals Refinement of learned skilled movement representation in motor cortex deep output layer

2017 ◽  
Vol 8 (1) ◽  
Author(s):  
Qian Li ◽  
Ho Ko ◽  
Zhong-Ming Qian ◽  
Leo Y. C. Yan ◽  
Danny C. W. Chan ◽  
...  
Keyword(s):  
Motor Cortex ◽  
Skilled Movement ◽  
Output Layer ◽  
Movement Representation

scholarly journals Dense Movement with Embedded Sparse Action-Type Representations in the Output Layer of Motor Cortex

2020 ◽  
Author(s):  
Stephen P. Currie ◽  
Julian Ammer ◽  
Brian Premchand ◽  
Constantinos Eleftheriou ◽  
Aldo AA Faisal ◽  
...  
Keyword(s):  
Motor Cortex ◽  
Output Layer ◽  
Action Type

A Model of Reaching Dynamics in Primary Motor Cortex

1998 ◽  
Vol 10 (1) ◽  
pp. 35-45 ◽  
Author(s):  
Sohie Lee Moody ◽  
David Zipser
Keyword(s):  
Neural Network ◽  
Motor Cortex ◽  
Recurrent Neural Network ◽  
Cortical Neurons ◽  
Primary Motor Cortex ◽  
Voluntary Movements ◽  
Reaching Movement ◽  
Time Constants ◽  
Movement Representation ◽  
The Individual

Features of virtually all voluntary movements are represented in the primary motor cortex. The movements can be ongoing, imminent, delayed, or imagined. Our goal was to investigate the dynamics of movement representation in the motor cortex. To do this we trained a fully recurrent neural network to continually output the direction and magnitude of movements required to reach randomly changing targets. Model neurons developed preferred directions and other properties similar to real motor cortical neurons. The key finding is that when the target for a reaching movement changes location, the ensemble representation of the movement changes nearly monotonically, and the individual neurons comprising the representation exhibit strong, nonmonotonic transients. These transients serve as internal recurrent signals that force the ensemble representation to change more rapidly than if it were limited by the time constants of individual neurons. These transients, if they exist, could be observed in experiments that require only slight modifications of the standard paradigm used to investigate movement representation in the motor cortex.

scholarly journals Differentiation of cerebral representation of occlusion and swallowing with fMRI

2013 ◽  
Vol 304 (10) ◽  
pp. G847-G854 ◽  
Author(s):  
Paul G. Mihai ◽  
Oliver von Bohlen und Halbach ◽  
Martin Lotze
Keyword(s):  
Motor Cortex ◽  
Primary Motor Cortex ◽  
Neural Representation ◽  
Motor Representation ◽  
Functional Representation ◽  
Fmri Study ◽  
Sensory Nucleus ◽  
Supplementary Motor Cortex ◽  
Movement Representation ◽  
First Time

Early work on representational specificity and recent findings on temporomandibular joint (TMJ) movement representation raise doubts that a specific swallow representation does exist. Additionally, during cortical stimulation TMJ movements and swallowing show a high overlap of representational areas in the primary motor cortex. It has thus been hypothesized that they overall might share the same neural structures. To differentiate these two movements, we performed a functional MRI (fMRI) study that enabled a direct comparison of functional representation of both actions in the same subject group. Effort during these tasks was controlled by skin conductance response. When balancing effort, we found a comparable neural representation pattern for both tasks but increased resources necessary to perform swallowing in direct comparison between tasks. For the first time, with the usage of fMRI, we demonstrated a representation in the brainstem for swallowing and occlusion. Increased activation for swallowing was observed in bilateral sensorimotor cortex, bilateral premotor and supplementary motor cortex, motor cingulate, thalamus, cerebellar hemispheres, left pallidum, bilateral pons, and midbrain. Peaks of activation in primary motor cortex between both conditions were about 5 mm adjacent. Brainstem activation was found corresponding to the sensory nucleus of the trigeminal nerve, the solitary nucleus for swallowing, and the trigeminal nucleus for occlusion. Our data suggest that cerebral representation of occlusion and swallowing are spatially widely overlapping, differing predominantly with respect to the quantity of neural resources involved. Both brainstem and primary motor representation differ in location with respect to somatotopy and contribution of cranial nerve nuclei.

scholarly journals Movement representation in the primary motor cortex and its contribution to generalizable EMG predictions

2013 ◽  
Vol 109 (3) ◽  
pp. 666-678 ◽  
Author(s):  
Emily R. Oby ◽  
Christian Ethier ◽  
Lee E. Miller
Keyword(s):  
Motor Cortex ◽  
Single Neuron ◽  
Primary Motor Cortex ◽  
Point Force ◽  
Tuning Curves ◽  
Central Target ◽  
Hold Period ◽  
End Point ◽  
Movement Representation ◽  
Limb Posture

It is well known that discharge of neurons in the primary motor cortex (M1) depends on end-point force and limb posture. However, the details of these relations remain unresolved. With the development of brain-machine interfaces (BMIs), these issues have taken on practical as well as theoretical importance. We examined how the M1 encodes movement by comparing single-neuron and electromyographic (EMG) preferred directions (PDs) and by predicting force and EMGs from multiple neurons recorded during an isometric wrist task. Monkeys moved a cursor from a central target to one of eight peripheral targets by exerting force about the wrist while the forearm was held in one of two postures. We fit tuning curves to both EMG and M1 activity measured during the hold period, from which we computed both PDs and the change in PD between forearm postures (ΔPD). We found a unimodal distribution of these ΔPDs, the majority of which were intermediate between the typical muscle response and an unchanging, extrinsic coordinate system. We also discovered that while most neuron-to-EMG predictions generalized well across forearm postures, end-point force measured in extrinsic coordinates did not. The lack of force generalization was due to musculoskeletal changes with posture. Our results show that the dynamics of most of the recorded M1 signals are similar to those of muscle activity and imply that a BMI designed to drive an actuator with dynamics like those of muscles might be more robust and easier to learn than a BMI that commands forces or movements in external coordinates.

Development and plasticity of complex movement representations

2021 ◽  
Vol 125 (2) ◽  
pp. 628-637
Author(s):  
Anna C. Singleton ◽  
Andrew R. Brown ◽  
G. Campbell Teskey
Keyword(s):  
Motor Cortex ◽  
Body Parts ◽  
Movement Representation ◽  
Complex Movement

The motor cortex is topographically organized into maps of different body parts. We used to think that the function of motor cortex was to drive individual muscles, but more recently we have learned that it is also organized to make complex movements. However, the development and plasticity of those complex movements is completely unknown. In this paper, the emergence and topography of complex movement representation, as well as their plasticity during development, is detailed.

Rapid Plasticity of Human Cortical Movement Representation Induced by Practice

1998 ◽  
Vol 79 (2) ◽  
pp. 1117-1123 ◽  
Author(s):  
Joseph Classen ◽  
Joachim Liepert ◽  
Steven P. Wise ◽  
Mark Hallett ◽  
Leonardo G. Cohen
Keyword(s):  
Motor Cortex ◽  
Skill Acquisition ◽  
Neural Plasticity ◽  
Short Term Memory ◽  
Movement Direction ◽  
Transcranial Electrical Stimulation ◽  
Continuous Training ◽  
Direct Stimulation ◽  
Short Period ◽  
Movement Representation

Classen, Joseph, Joachim Liepert, Steven P. Wise, Mark Hallett, and Leonardo G. Cohen. Rapid plasticity of human cortical movement representation induced by practice. J. Neurophysiol. 79: 1117–1123, 1998. The process of acquiring motor skills through the sustained performance of complex movements is associated with neural plasticity. However, it is unknown whether even simple movements, repeated over a short period of time, are effective in inducing cortical representational changes. Whether the motor cortex can retain specific kinematic aspects of a recently practiced movement is also unknown. We used focal transcranial magnetic stimulation (TMS) of the motor cortex to evoke isolated and directionally consistent thumb movements. Thumb movements then were practiced in a different direction. Subsequently, TMS came to evoke movements in or near the recently practiced direction for several minutes before returning to the original direction. To initiate a change of the TMS-evoked movement direction, 15 or 30 min of continuous training were required in most of the subjects and, on two occasions, as little as 5 or 10 min. Substantially smaller effects followed more direct stimulation of corticofugal axons with transcranial electrical stimulation, pointing to cortex as the site of plasticity. These findings suggest that the training rapidly, and transiently, established a change in the cortical network representing the thumb, which encoded kinematic details of the practiced movement. This phenomenon may be regarded as a short-term memory for movement and be the first step of skill acquisition.

scholarly journals Is the Movement Representation in the Motor Cortex a Moving Target?

Neuron ◽  
2007 ◽  
Vol 54 (4) ◽  
pp. 500-502 ◽  
Author(s):  
John F. Kalaska ◽  
Andrea Green
Keyword(s):  
Motor Cortex ◽  
Moving Target ◽  
Movement Representation
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