scholarly journals Assessing the usage of indirect motor pathways following a hemiparetic stroke

2020 ◽  
Author(s):  
Runfeng Tian ◽  
Julius P.A. Dewald ◽  
Yuan Yang
Keyword(s):  
Model Simulation ◽  
Brain Activity ◽  
Shoulder Abduction ◽  
Joint Control ◽  
Motor Pathways ◽  
Co Activation ◽  
Shoulder Abductor ◽  
Hemiparetic Stroke ◽  
Muscle Connectivity ◽  
Flexion Synergy

AbstractA hallmark impairment in a hemiparetic stroke is a loss of independent joint control resulting in abnormal co-activation of shoulder abductor and elbow flexor muscles in their paretic arm, clinically known as the flexion synergy. The flexion synergy appears while generating shoulder abduction (SABD) torques as lifting the paretic arm. This likely be caused by an increased reliance on contralesional indirect motor pathways following damage to direct corticospinal projections. The assessment of functional connectivity between brain and muscle signals, i.e., brain-muscle connectivity (BMC), may provide insight into such changes to the usage of motor pathways. Our previous model simulation shows that multi-synaptic connections along the indirect motor pathway can generate nonlinear connectivity. We hypothesize that increased usage of indirect motor pathways (as increasing SABD load) will lead to an increase of nonlinear BMC. To test this hypothesis, we measured brain activity, muscle activity from shoulder abductors when stroke participants generate 20% and 40% of maximum SABD torque with their paretic arm. We computed both linear and nonlinear BMC between EEG and EMG. We found dominant nonlinear BMC at contralesional/ipsilateral hemisphere for stroke, whose magnitude increased with the SABD load. These results supported our hypothesis and indicated that nonlinear BMC could provide a quantitative indicator for determining the usage of indirect motor pathways following a hemiparetic stroke.

scholarly journals Neck rotation modulates flexion synergy torques, indicating an ipsilateral reticulospinal source for impairment in stroke

2012 ◽  
Vol 108 (11) ◽  
pp. 3096-3104 ◽  
Author(s):  
Michael D. Ellis ◽  
Justin Drogos ◽  
Carolina Carmona ◽  
Thierry Keller ◽  
Julius P. A. Dewald
Keyword(s):  
Reticular Formation ◽  
Muscle Activation ◽  
External Rotation ◽  
Statistical Design ◽  
Head Rotation ◽  
Elbow Flexion ◽  
Shoulder Abduction ◽  
Joint Control ◽  
Age Range ◽  
Flexion Synergy

The effect of reticular formation excitability on maximum voluntary torque (MVT) generation and associated muscle activation at the shoulder and elbow was investigated through natural elicitation (active head rotation) of the asymmetric tonic neck reflex (ATNR) in 26 individuals with stroke and 9 age-range-matched controls. Isometric MVT generation at the shoulder and elbow was quantified with the head rotated (face pointing) contralateral and ipsilateral to the paretic (stroke) and dominant (control) arm. Given the dominance of abnormal torque coupling of elbow flexion with shoulder abduction (flexion synergy) in stroke and well-developed animal models demonstrating a linkage between reticular formation and ipsilateral elbow flexors and shoulder abductors, we hypothesized that constituent torques of flexion synergy, specifically elbow flexion and shoulder abduction, would increase with contralateral head rotation. The findings of this investigation support this hypothesis. Increases in MVT for three of four flexion synergy constituents (elbow flexion, shoulder abduction, and shoulder external rotation) were observed during contralateral head rotation only in individuals with stroke. Electromyographic data of the associated muscle coactivations were nonsignificant but are presented for consideration in light of a likely underpowered statistical design for this specific variable. This study not only provides evidence for the reemergence of ATNR following stroke but also indicates a common neuroanatomical link, namely, an increased reliance on ipsilateral reticulospinal pathways, as the likely mechanism underlying the expression of both ATNR and flexion synergy that results in the loss of independent joint control.

Abstract TP147: Quantitative Measures of Strength and Synergy Differentiate Individuals With Chronic Stroke With and Without Clinically Detectable Elbow Contracture

Stroke ◽  
2020 ◽  
Vol 51 (Suppl_1) ◽  
Author(s):  
Grace C Bellinger ◽  
Michael D Ellis
Keyword(s):  
Quantitative Measure ◽  
Chronic Stroke ◽  
Future Research ◽  
Emg Activity ◽  
Shoulder Abduction ◽  
Joint Control ◽  
Elbow Extension ◽  
Unaffected Side ◽  
Elbow Contracture ◽  
Flexion Synergy

Many individuals with chronic stroke demonstrate contracture of the elbow flexors. The development of contracture may be attributable to underlying impairments such as weakness, flexion synergy, and hyperactive reflexes. This study explored differences in motor impairment and function between 17 individuals with clinically detectable elbow flexor contracture and 17 individuals with full passive range of motion. The groups did not differ in age (61.61 ± 7.99, 55.06 ± 12.48, p = 0.078), years post-stroke (12.92 ± 9.34, 10.60 ± 7.16, p = 0.423), or Fugl-Meyer Motor Assessment score (FMA, 26.35 ± 5.86, 26.47 ± 8.70, p = 0.963). The passive range limitation in the contracture group was 3 to 36° (11.65 ± 8.30°). Kinetics, kinematics, and EMG were used to quantify four motor impairments and reaching function. Shoulder abduction and elbow extension strength were measured isometrically and normalized to the unaffected side. Flexion synergy was quantified as a force-based measure assessing independent joint control. Flexor spasticity was quantified while reaching at 50% of maximum shoulder abduction as the change in biceps EMG from reach onset to peak angular velocity, normalized by maximal EMG activity. Reaching function was defined as maximum reaching distance against gravity and normalized by target distance (-10° of full extension). The groups differed in elbow extension strength (Contracture, 0.315 ± 0.129; No contracture, 0.559 ± 0.153; p < 0.001) and flexion synergy (0.146 ± 0.186, 0.397 ± 0.229, p = 0.009). The groups did not differ in shoulder abduction strength (0.500 ± 0.174, 0.615 ± 0.199, p = 0.080), flexor spasticity (0.079 ± 0.090, 0.056 ± 0.115, p = 0.523), or reaching function (0.501 ± 0.391, 0.714 ± 0.296, p = 0.082). The findings of this study suggest a relationship between elbow contracture and the concurrent presence of elbow extension weakness and flexion synergy. The quantitative measure of reaching function will likely differentiate individuals with and without contracture if the assessment is modified so that the standardized reaching target is located at 0° of elbow extension (normal range). Future research should use quantitative metrics to further explore the temporal recovery of impairments in order to prevent the development of contracture.

scholarly journals The Impact of Shoulder Abduction Loading on Volitional Hand Opening and Grasping in Chronic Hemiparetic Stroke

2017 ◽  
Vol 31 (6) ◽  
pp. 521-529 ◽  
Author(s):  
Yiyun Lan ◽  
Jun Yao ◽  
Julius P. A. Dewald
Keyword(s):  
Shoulder Abduction ◽  
Grasping Forces ◽  
Finger Flexion ◽  
Enhanced Expression ◽  
Hemiparetic Stroke ◽  
Chronic Hemiparetic Stroke ◽  
And Control ◽  
The Impact ◽  
Hand Opening ◽  
Flexion Synergy

Background. Up to 60% of individuals with moderate to severe chronic hemiparetic stroke experience excessive involuntary wrist/finger flexion that constrains functional hand movements including hand opening. It’s not known how stroke-induced brain injury impacts volitional hand opening and grasping forces as a result of the expression of abnormal coupling between shoulder abduction and wrist/finger flexion or the flexion synergy. Objective. The goal of this study is to understand how shoulder abduction loading affects volitional hand opening and grasping forces in individuals with moderate to severe chronic hemiparetic stroke. Methods. Thirty-six individuals (stroke, 26; control, 10) were recruited for this study. Each participant was instructed to perform maximal hand opening and grasping forces while the arm was either fully supported or lifted with a weight equal to 25% or 50% of the participant’s maximal shoulder abduction torque. Hand pentagon area, defined as the area formed by the tips of thumb and fingers, was calculated during hand opening. Forces were recorded during grasping. Results. In individuals with moderate stroke, increasing shoulder abduction loading reduced the ability to maximally open the hand. In individuals with severe stroke, who were not able to open the hand, grasping forces were generated and increased with shoulder abduction loading. Stroke individuals also showed a reduced ability to control volitional grasping forces due to the enhanced expression of flexion synergy. Conclusions. Shoulder abduction loading reduced the ability to volitionally open the hand and control grasping forces after stroke. Neural mechanisms and clinical implications of these findings are discussed.

scholarly journals Anterior and posterior subareas of the dorsolateral frontal cortex in socially relevant decisions based on masked affect expressions

F1000Research ◽  
2015 ◽  
Vol 3 ◽  
pp. 212
Author(s):  
Denise Prochnow ◽  
Sascha Brunheim ◽  
Hannes Kossack ◽  
Simon B. Eickhoff ◽  
Hans J. Markowitsch ◽  
...  
Keyword(s):  
Frontal Cortex ◽  
Brain Activity ◽  
Posterior Portion ◽  
Affective Stimuli ◽  
Subjective Awareness ◽  
Co Activation ◽  
Dorsal Portion ◽  
Choice Criterion ◽  
Socially Relevant

Socially-relevant decisions are based on clearly recognizable but also not consciously accessible affective stimuli. We studied the role of the dorsolateral frontal cortex (DLFC) in decision-making on masked affect expressions using functional magnetic resonance imaging. Our paradigm permitted us to capture brain activity during a pre-decision phase when the subjects viewed emotional expressions below the threshold of subjective awareness, and during the decision phase, which was based on verbal descriptions as the choice criterion. Using meta-analytic connectivity modeling, we found that the preparatory phase of the decision was associated with activity in a right-posterior portion of the DLFC featuring co-activations in the left-inferior frontal cortex. During the subsequent decision a right-anterior and more dorsal portion of the DLFC became activated, exhibiting a different co-activation pattern. These results provide evidence for partially independent sub-regions within the DLFC, supporting the notion of dual associative processes in intuitive judgments.

scholarly journals Connectome-harmonic decomposition of human brain activity reveals dynamical repertoire re-organization under LSD

2017 ◽  
Author(s):  
Selen Atasoy ◽  
Leor Roseman ◽  
Mendel Kaelen ◽  
Morten L. Kringelbach ◽  
Gustavo Deco ◽  
...  
Keyword(s):  
Human Brain ◽  
Brain Activity ◽  
Power Laws ◽  
Lysergic Acid ◽  
Brain Dynamics ◽  
Co Activation ◽  
Harmonic Decomposition ◽  
Health And Disease ◽  
Novel Method ◽  
Brain States

ABSTRACTRecent studies have started to elucidate the effects of lysergic acid diethylamide (LSD) on the human brain but the underlying dynamics are not yet fully understood. Here we used ‘connectome-harmonic decomposition’, a novel method to investigate the dynamical changes in brain states. We found that LSD alters the energy and the power of individual harmonic brain states in a frequency-selective manner. Remarkably, this leads to an expansion of the repertoire of active brain states, suggestive of a general re-organization of brain dynamics given the non-random increase in co-activation across frequencies. Interestingly, the frequency distribution of the active repertoire of brain states under LSD closely follows power-laws indicating a re-organization of the dynamics at the edge of criticality. Beyond the present findings, these methods open up for a better understanding of the complex brain dynamics in health and disease.

scholarly journals Anterior and posterior subareas of the dorsolateral frontal cortex in socially relevant decisions based on masked affect expressions

F1000Research ◽  
2014 ◽  
Vol 3 ◽  
pp. 212 ◽  
Author(s):  
Denise Prochnow ◽  
Sascha Brunheim ◽  
Hannes Kossack ◽  
Simon B. Eickhoff ◽  
Hans J. Markowitsch ◽  
...  
Keyword(s):  
Frontal Cortex ◽  
Brain Activity ◽  
Posterior Portion ◽  
Affective Stimuli ◽  
Subjective Awareness ◽  
Co Activation ◽  
Dorsal Portion ◽  
Choice Criterion ◽  
Socially Relevant

Socially-relevant decisions are based on clearly recognizable but also not consciously accessible affective stimuli. We studied the role of the dorsolateral frontal cortex (DLFC) in decision-making on masked affect expressions using functional magnetic resonance imaging. Our paradigm permitted us to capture brain activity during a pre-decision phase when the subjects viewed emotional expressions below the threshold of subjective awareness, and during the decision phase, which was based on verbal descriptions as the choice criterion. Using meta-analytic connectivity modeling, we found that the preparatory phase of the decision was associated with activity in a right-posterior portion of the DLFC featuring co-activations in the left-inferior frontal cortex. During the subsequent decision a right-anterior and more dorsal portion of the DLFC became activated, exhibiting a different co-activation pattern. These results provide evidence for partially independent sub-regions within the DLFC, supporting the notion of dual associative processes in intuitive judgments.

scholarly journals On co-activation pattern analysis and non-stationarity of resting brain activity

2021 ◽  
Author(s):  
Teppei Matsui ◽  
Trung Quang Pham ◽  
Koji Jimura ◽  
Junichi Chikazoe
Keyword(s):  
Pattern Analysis ◽  
Brain Activity ◽  
Simulated Data ◽  
Real Data ◽  
Functional Magnetic Resonance ◽  
Care Needs ◽  
Sliding Windows ◽  
The Real ◽  
Co Activation ◽  
Cap Analysis

AbstractThe non-stationarity of resting-state brain activity has received increasing attention in recent years. Functional connectivity (FC) analysis with short sliding windows and coactivation pattern (CAP) analysis are two widely used methods for assessing the non-stationary characteristics of brain activity observed with functional magnetic resonance imaging (fMRI). However, whether these techniques adequately capture non-stationarity needs to be verified. In this study, we found that the results of CAP analysis were similar for real fMRI data and simulated stationary data with matching covariance structures and spectral contents. We also found that, for both the real and simulated data, CAPs were clustered into spatially heterogeneous modules. Moreover, for each of the modules in the real data, a spatially similar module was found in the simulated data. The present results suggest that care needs to be taken when interpreting observations drawn from CAP analysis as it does not necessarily reflect non-stationarity or a mixture of states in resting brain activity.

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