neuromechlab.catholic.edu - Research topics

Neuromechanics Laboratory

Catholic University of America/National Rehabilitation Hospital

Research topics

Biomechanics of hand musculoskeletal system

We employ in vivo and in vitro experimental techniques, in conjunction with computational simulations, to better understand the biodynamics of complex multiarticular hand musculotendons.

Fig. 1. Investigating dynamics of finger musculotendon structure: (A) In vitro experiment; (B) Numerical modeling of the extensor mechanism. During the in vitro experiment, six degrees-of-freedom load cell recorded fingertip force and moment produced by loading of individual tendons within the extensor mechanism. The computational model of the extensor hood is comprised of lateral bands (LB), central band (CB), extensor digitorum communis (EDC) tendon, and interosseous (INT) tendon. The extensor mechanism inserts into terminal slip (TS) and central slip (CS). Adapted from Lee et al., 2008 and Lee et al., 2016.

Use of novel biomimetic exoskeletons for stroke rehabilitation

We develop novel exoskeleton devices that mimic biodynamics of the hand muscles, which can provide targeted assistance to multiarticular musculotendons of the hand. This system can deliver 'subject-specific' assistance to patients, reflecting particular impairment characteristics of individual patients.

Fig. 2. Targeted assistance of extrinsic extensor tendon. Subject is performing finger extension task, assisted by a biomimetic exoskeleton device (BiomHED).

Neurophysiology of functional impairment post-stroke

We investigate different neurophysiological factors that may lead to functional impairment of upper-limb post-stroke, including involuntary coupling between distal and proximal muscles and impairment in task-specific modulation of muscle coordination patterns. Similar methodologies are employed to test the feasibility of using electromechanical devices to promote neural plasticity of patients with neurological injuries.

Fig. 3. Time-dependent coherence estimate for the EDC-FDI muscle pair during dorsal fingertip force production: (A) without assistance; (B) with targeted assistance to EDC. During force production without assistance, the coherence values in the β- and γ-bands increased during the initiation of the force production (0ms – 1000ms) and when the fingertip force reached the target force level (1000ms – 4000ms). When assisted (ETEDC), similar pattern of coherence increase during initial force production was observed, albeit to a much lesser degree.

Fig. 4. Muscle activation pattern of (A,B) severely impaired subjects: (A) Severe-impairment (CMSH 3), (B) Severe-impairment (CMSH 2); (C) Moderate-impairment (CMSH 5); and (D) No-impairment (CMSH 7) across six tasks. Activation patterns of severely impaired subjects were very similar across different tasks (except overall magnitude) (A,B); qualitative examination of the data shows the inter-task variability, or complexity in muscle activation patterns across tasks, was greater in subjects with less impairment (i.e., higher CMSH). Adapted from Lee et al., 2013.

Quantitative analysis of pathological conditions of movement disorders

We aim to characterize and differentiate abnormal behavior of patients with various movement disorders, such as essential tremor and dystonia, using rigorous analytical methods.

Fig. 5. Time-frequency analysis. for postural and kinetic tremor in (A) ET and (B) DT. Temporal fluctuation of tremor power (5-8Hz) is more synchronized with that of voluntary movements (0 - 2Hz) in dystonic tremor (DT) patients, while the tremor and movement powers are out-of-phase in essential tremor (ET) patients. Adapted from Panyakaew et al., 2020.

Altered decision-making post-stroke: virtual-reality based training

We aim to elucidate altered decision-making process of stroke survivors affecting their arm use by identifying key underlying mechanisms of learned nonuse (LNU) development, in which different motor and sensory impairments of stroke survivors contribute to ‘underestimation’ of utility of their more-impaired arms. We use novel virtual-reality (VR) technologies to increase perceived utility of more-impaired arms post-stroke, helping them reverse LNU in VR environment.

Fig. 6. Virtual-reality environment to encourage more-impaired arm use. Subjects perform various tasks in the virtual-reality environment designed to encourage their more-impaired arm use.

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