Impaired hand function is a major cause of chronic disability among stroke survivors. Although a number of treatment approaches have been developed to facilitate the recovery of hand function, most target mildly impaired individuals. Efforts to rehabilitate individuals with severe impairment often treat the hand/wrist in isolation without consideration of the deleterious effects of proximal joint demands, like those experienced when lifting the arm against gravity to reach and retrieve a glass from a cabinet. Our long-term goal is to bring effective therapeutic strategies to those with moderate to severe hand impairment. To do this we have focused on the role of abnormal joint coupling in arm functioning. Following the loss of corticospinal tract fibers, movement in individuals with stroke s impaired by stereotypic multi-joint movement patterns (synergies) that result in the loss of independent joint control. For instance in the paretic arm, shoulder abduction is abnormally coupled with elbow flexion (flexor-synergy). As part of the first cycle of this R01 (years 1-5), we quantified torque-coupling patterns, and associated muscle activations, isometrically by using a 6 Degree-of-Freedom load cell. We also discovered that multi-joint isometric efforts were constrained to these abnormal coupling patterns. As part of the second cycle of this R01 (years 6-10), we progressed the work into dynamics, utilizing robotic devices to establish that reaching work area is reduced as a function of increasing abduction loading, and conducting robotic joint perturbation studies to demonstrate the integrated nature of the loss of independent joint control and vibration reflexes. Finally, recent work using the asymmetric tonic reflex and transcranial magnetic stimulation to probe brainstem excitability has provided evidence of increase reliance on the ipsilateral reticular formation, presumably through the reticulospinal tract, as the source of loss of independent joint control. The overall goal of the current renewal (years 11-15) is to further our understanding of the effects of the flexion synergy on wrist/hand function and the underlying neurophysiology. To do this we will determine the extent to which isometric shoulder abduction effort (Aim 1) and functional arm reaching (Aim 2) alter muscle activation during isometric hand muscle activations. These studies will inform our third approach to detect the intention behind actual hand movements and ultimately determine the impact of the flexion synergy on dynamic wrist/finger movement (Aim 3). Detecting wrist/hand movement intent within the context of a quantitatively controlled whole-limb movement in individuals with moderate to severe impairment is innovative and has the potential to propel the field vertically. We will use the results from Aims 1-3 to develop an effective algorithm for detecting hand opening, closing, and relaxation, a key component in restoring function to the paretic hand in individuals with moderate to severe impairment following stroke. Thus, the outcome of this study is expected to have a crucial impact on future rehabilitation approaches even for the most severely impaired stroke survivors.
The proposed research is relevant to public health because it seeks to quantify wrist and finger activity in the paretic upper limb of chronic hemiparetic stroke survivors while lifting up the arm and during functional movements. This is relevant to the NIH's mission because it will not only lead to a better understanding of how arm movements may impact the control of wrist and fingers following a stroke but it will also seek to determine hand movement intent by picking up weak signals from paretic wrist and finger muscles. This requires the use of sophisticated signal analysis techniques. The accurate determination of movement intent is expected to lead to the development of new clinical devices that facilitate the return of basic hand function (i.e., grasping and releasing objects) even in the more impaired stroke survivors.
|Sánchez, Natalia; Acosta, Ana Maria; Lopez-Rosado, Roberto et al. (2017) Lower Extremity Motor Impairments in Ambulatory Chronic Hemiparetic Stroke: Evidence for Lower Extremity Weakness and Abnormal Muscle and Joint Torque Coupling Patterns. Neurorehabil Neural Repair 31:814-826|
|Ellis, Michael D; Schut, Ingrid; Dewald, Julius P A (2017) Flexion synergy overshadows flexor spasticity during reaching in chronic moderate to severe hemiparetic stroke. Clin Neurophysiol 128:1308-1314|
|Lan, Yiyun; Yao, Jun; Dewald, Julius P A (2017) The Impact of Shoulder Abduction Loading on Volitional Hand Opening and Grasping in Chronic Hemiparetic Stroke. Neurorehabil Neural Repair 31:521-529|
|Lan, Yiyun; Yao, Jun; Dewald, Julius P A (2017) Reducing the Impact of Shoulder Abduction Loading on the Classification of Hand Opening and Grasping in Individuals with Poststroke Flexion Synergy. Front Bioeng Biotechnol 5:39|
|Gurari, Netta; Drogos, Justin M; Dewald, Julius P A (2017) Individuals with chronic hemiparetic stroke can correctly match forearm positions within a single arm. Clin Neurophysiol 128:18-30|
|Ellis, Michael D; Lan, Yiyun; Yao, Jun et al. (2016) Robotic quantification of upper extremity loss of independent joint control or flexion synergy in individuals with hemiparetic stroke: a review of paradigms addressing the effects of shoulder abduction loading. J Neuroeng Rehabil 13:95|
|Yao, Jun; Sheaff, Clay; Carmona, Carolina et al. (2016) Impact of Shoulder Abduction Loading on Brain-Machine Interface in Predicting Hand Opening and Closing in Individuals With Chronic Stroke. Neurorehabil Neural Repair 30:363-72|
|McPherson, Laura Miller; Negro, Francesco; Thompson, Chris K et al. (2016) Properties of the motor unit action potential shape in proximal and distal muscles of the upper limb in healthy and post-stroke individuals. Conf Proc IEEE Eng Med Biol Soc 2016:335-339|
|Hawe, Rachel L; Dewald, Jules P A (2015) Development of a method to quantify inter-limb coupling in individuals with hemiparetic stroke. Conf Proc IEEE Eng Med Biol Soc 2015:3476-9|
|Sánchez, Natalia; Acosta, Ana Maria; Stienen, Arno H A et al. (2015) A Multiple Degree of Freedom Lower Extremity Isometric Device to Simultaneously Quantify Hip, Knee, and Ankle Torques. IEEE Trans Neural Syst Rehabil Eng 23:765-75|
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