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Dynamic Functional Connectivity Between Cortex and Muscles

Perel, Sagi (2012) Dynamic Functional Connectivity Between Cortex and Muscles. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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The motor-cortex is recognized as the origin of the major direct path from cortex to muscles. Although it has been studied for over a century, relatively little is known about how the motor cortex facilitates reach-to-grasp movements. We collected a rich dataset from monkeys trained to reach and grasp objects of different shapes, presented at various orientations and spatial locations. We simultaneously recorded single-unit activity from motor cortical areas (mainly the caudal bank of the pre-central gyrus), EMG activity from selected muscles (in the arm, wrist and hand) and high-resolution kinematic data from the wrist and hand. We show that motor-cortical neurons modulate their activity in an object specific manner, resulting in object specific co-activation of muscles and joint movements. We studied the multivariate relationships between the firing rates of individual neurons, EMG, joint angles and joint angle velocities and found that both EMG and kinematic features were encoded in the neural firing rates. Kinematic features were much better predictors of neural firing rates than EMG. We found that the best predictors of neural firing rates were neither individual muscles or joints, nor kinematic or EMG synergies extracted using PCA/ICA, but neuron-specific combinations of EMG and kinematic features. We show better predictions of both muscle activations and JA values by combining the activity of a few tens of sequentially recorded neurons; suggesting that neural activity contains synergistic information related to EMG, not independently present in individual neurons. By using functional connectivity, defined as the probability of observing changes in EMG following spikes from a trigger neuron, we further elucidated motor cortical activity to muscle activation. By studying both the short-time scale functional connectivity, on the order of milliseconds; and long-time scale functional connectivity, on the order of hundreds of milliseconds, we found that flexible long-time scale functional connections between individual neurons and muscles were modulated by kinematic features that could account for the relatively weaker neural firing rate relation to EMG. To support our findings, we show examples of simultaneous short-time scale functional connectivity and conclude that neuronal-muscular functional connectivity is flexible and task-dependent.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Thesis AdvisorSchwartz, Andrewabs21@pitt.eduABS21
Committee MemberKass ,
Committee MemberWeber, Douglasdjw50@pitt.eduDJW50
Committee MemberZhang, Xudongxuz9@pitt.eduXUZ9
Date: 26 September 2012
Date Type: Publication
Defense Date: 30 April 2012
Approval Date: 26 September 2012
Submission Date: 9 May 2012
Access Restriction: No restriction; Release the ETD for access worldwide immediately.
Number of Pages: 317
Institution: University of Pittsburgh
Schools and Programs: Swanson School of Engineering > Bioengineering
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: Motor Cortex, M1, Functional Connectivity, Reach to Grasp, Post Spike Effects, EMG, Spike Triggered Averaging, Single Snippet Analysis, Scan Test
Date Deposited: 26 Sep 2012 14:56
Last Modified: 15 Nov 2016 13:58


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