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1.
Annu Int Conf IEEE Eng Med Biol Soc ; 2022: 732-735, 2022 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-36086467

RESUMO

In this paper, a novel prototype of a cable-driven prosthetic hand with biorealisitic muscle property was developed. A pair of antagonistic muscles controlled the flexion and extension of the prosthetic index finger. Biorealistic properties of muscle were emulated using a neuromorphic model of muscle reflex in real time. The model output was coupled to a servo motor that tracked the computed muscle force. The servo motor was able to track model output within a frequency range from 0 to 8.29 (Hz) with a phase shift from 2 to 205 (deg). Surface electromyography signals collected from the amputee's forearm were used as α commands to drive the muscle model. With this prototype system, we evaluated its characteristics for force and stiffness control. Results of the force variability test showed that the standard deviation of fingertip force was linear to the mean fingertip force, indicating that force variability was proportional to the background force. At different levels of antagonistic co-contraction, the index finger and muscles displayed different levels of stiffness corresponding to the degree of co-activation. This prototype system showed the similar compliant behaviors of human limbs actuated with biological muscles. In further studies, this prototype system would be thoroughly evaluated for its biorealistic properties, and integrated with sensors to investigate feedback strategies of various sensory information for individuals with amputation. Clinical Relevance- This article established an antagonistic control of a cable-driven prosthetic hand with biorealistic properties of muscle reflex for application to individuals with amputation.


Assuntos
Mãos , Reflexo de Estiramento , Eletromiografia , Dedos/fisiologia , Humanos , Músculos
2.
Annu Int Conf IEEE Eng Med Biol Soc ; 2022: 4196-4199, 2022 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-36086470

RESUMO

Electronic skin (E-skin) is an emerging wearable device typically used to mimic the function of the human skin, mainly by replicating the role of tactile sensory receptors in the skin. This study showed an interesting modification of the E-skin, called an electro-prosthetic E-skin, which adds the functionality of distance sensing and stimulation of the palmar digital nerve. The electro-prosthetic E-skin operates as a closed loop to deliver the finger aperture distance information to the nervous system. This E-skin was implemented as an additional layer mounted to the original human skin, to be worn on the fingertip with a thin silicone substrate. The E-skin was designed to be mounted onto the index fingertip, to deliver the distance information between the fingertips and to enhance the finger aperture distance control. In this study, we demonstrated that electro-prosthetic proprioception (EPP), implemented with the electro-prosthetic E-skin, successfully delivered the distance information between the fingertips and enhanced the finger aperture distance control accuracy. Clinical Relevance- Presented electro-prosthetic E-skin delivering finger aperture distance via electro-prosthetic proprioception (EPP) will enhance accuracy of the finger aperture distance control. This technology can be applied to the neurosurgery to minimize unforced errors caused by the limited human control accuracy over the fingertip.


Assuntos
Dedos , Dispositivos Eletrônicos Vestíveis , Dedos/fisiologia , Humanos , Propriocepção , Pele , Tato/fisiologia
3.
Annu Int Conf IEEE Eng Med Biol Soc ; 2022: 702-706, 2022 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-36086496

RESUMO

Natural control of assistive devices requires continuous positional encoding and decoding of the user's volition. Human movement is encoded by recruitment and rate coding of spinal motor units. Surface electromyography provides some information on the neural code of movement and is usually decoded into finger joint angles. However, the current approaches to mapping the electrical signal into joint angles are unsatisfactory. There are no methods that allow precise estimation of joint angles during natural hand movements within the large numbers of degrees of freedom of the hand. We propose a framework to train a neural network from digital cameras and high-density surface electromyography from the extrinsic (forearm and wrist) hand muscles. Furthermore, we show that our 3D convolutional neural network optimally predicted 14 functional flexion/extension joints of the hand. We found in our experiments (4 subjects; mean age of 26±2.12 years) that our model can predict individual sinusoidal finger movement at different speeds (0.5 and 1.5 Hz), as well as two and three finger pinching, and hand opening and closing, covering 14 degrees of freedom of the hand. Our deep learning method shows a mean absolute error of 2.78±0.28 degrees with a mean correlation coefficient between predicted and expected joint angles of 0.94, 95% confidence interval (CI) [0.81, 0.98] with simulated real-time inference times lower than 30 milliseconds. These results demonstrate that our approach is capable of predicting the user's volition similar to digital cameras through a non-invasive wearable neural interface. Clinical relevance- This method establishes a viable interface that can be used for both immersive virtual reality medical simulations environments and assistive devices such as exoskeleton and prosthetics.


Assuntos
Aprendizado Profundo , Adulto , Eletromiografia/métodos , Dedos/fisiologia , Mãos/fisiologia , Humanos , Movimento/fisiologia , Adulto Jovem
4.
Annu Int Conf IEEE Eng Med Biol Soc ; 2022: 3615-3618, 2022 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-36086613

RESUMO

Crosstalk is the result of the propagation of muscle electrical signals on surface electromyogram channels simultaneously. The objective of this paper is to study the behavior of three blind source separation (BSS) methods for crosstalk reduction during finger extensor muscle contractions: FastICA, joint diagonalization of covariance matrices and optimal filtering. These methods have been tested on artificial mixtures defined by a temporal sum of the real signals from isolated contraction of two independent biomechanical muscles for the extension of the index and little finger. Artificial mixtures display a ground truth for comparison between the methods. The separation was better using the optimal filtering compared to the other two methods. The optimal filtering have then be tested on real mixtures recorded during a simultaneous contraction of the two muscles. The results are less satisfactory but open doors to new perspectives.


Assuntos
Algoritmos , Músculo Esquelético , Eletromiografia/métodos , Dedos/fisiologia , Músculo Esquelético/fisiologia , Extremidade Superior
5.
IEEE Int Conf Rehabil Robot ; 2022: 1-6, 2022 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-36176169

RESUMO

Applying an external force to a person's hyperextended fingertip produces electrical activity in the extensor digitorum communis, even if the person does not try to open their hand. Based on this, a finger extensor facilitation technique conducted by therapists was developed. In this study, we developed a finger extensor facilitation training device named iPARKO that imitates this technique. We examined the relationship between the metacarpophalangeal (MP) joint angle of the four fingers and the activities in the extensor digitorum communis resulting from active training using iPARKO. At the same time, the relationship between the MP joint angle and the reduced activities in the flexor digitorum superficialis was also examined. The experiments were conducted on five healthy subjects. It was found that as the MP joint approached its own maximum hyperextension position, the amount of activity of the extensor digitorum communis increased, and the amount of activity of the flexor digitorum superficialis decreased.


Assuntos
Dedos , Articulação Metacarpofalângica , Articulações dos Dedos/fisiologia , Dedos/fisiologia , Mãos , Humanos , Articulação Metacarpofalângica/fisiologia , Músculo Esquelético/fisiologia
6.
Sensors (Basel) ; 22(18)2022 Sep 08.
Artigo em Inglês | MEDLINE | ID: mdl-36146164

RESUMO

The sense of touch is fundamental for a one-to-one mapping between the environment and a robot that physically interacts with the environment. Herein, we describe a tactile fingertip design that can robustly detect interaction forces given data collected from a camera. This design is based on the photoelastic effect observed in silicone matter. Under the force applied to the silicone rubber, owing to the stress-induced birefringence, the light propagating within the silicone rubber is subjected to the angular phase shift, where the latter is proportional to the increase in the image brightness in the camera frames. We present the calibration and test results of the photoelastic sensor design on a bench using a robot arm and with a certified industrial force torque sensor. We also discuss the applications of this sensor design and its potential relationship with human mechano-transduction receptors. We achieved a force sensing range of up to 8 N with a force resolution of around 0.5 N. The photoelastic tactile fingertip is suitable for robot grasping and might lead to further progress in robust tactile sensing.


Assuntos
Robótica , Percepção do Tato , Dedos/fisiologia , Humanos , Elastômeros de Silicone , Tato/fisiologia
7.
PLoS One ; 17(8): e0272033, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35947592

RESUMO

The effects of mental fatigue have been studied in relation to specific percentages of maximal aerobic or anaerobic efforts, maximal voluntary contractions or the performance of sport specific skills. However, its effects on tremor, dexterity and force steadiness have been only marginally explored. The present work aimed at filling this gap. In twenty-nine young individuals, measurement of postural, kinetic and isometric tremor, pinch force steadiness and finger and hand dexterity were performed before and after either 100 min of mental fatigue or control tasks. During the interventions blood pressure, oxygen saturation and heart rate and perceived effort in continuing the task were recorded every 10 minutes. Tremor was analysed in both time (standard deviation) and frequency domain (position, amplitude and area of the dominant peak) of the acceleration signal. Finger dexterity was assessed by Purdue pegboard test and hand dexterity in terms of contact time in a buzz wire exercise. Force steadiness was quantified as coefficient of variation of the force signal. Postural, kinetic and isometric tremors, force steadiness and dexterity were not affected. Higher oxygen saturation values and higher variability of heart rate and blood pressure were found in the intervention group during the mental fatigue protocol (p < .001). The results provide no evidence that mental fatigue affects the neuromuscular parameters that influence postural, kinetic or isometric tremor, force steadiness and dexterity when measured in single-task conditions. Increased variability in heart rate may suggest that the volunteers in the intervention group altered their alert/stress state. Therefore, it is possible that the alterations that are commonly observed during mental fatigue, and that could have affected tremor, steadiness and dexterity only last for the duration of the cognitive task and are not detectable anymore soon after the mental task is terminated.


Assuntos
Dedos , Tremor , Dedos/fisiologia , Humanos , Contração Isométrica/fisiologia , Fadiga Mental , Destreza Motora/fisiologia , Músculo Esquelético/fisiologia
8.
Sensors (Basel) ; 22(16)2022 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-36016055

RESUMO

In order to assist patients with finger rehabilitation training and grasping objects, we propose a new type of soft rehabilitation gloves (SRGs), which has both flexion/extension and abduction/adduction movement function for every finger. This paper describes the structure design of the bending actuator and rotating actuator, the fabrication process of the soft actuator, and the implementation of the soft wearable gloves based on a fabric glove. FEM simulation analysis and experiments were conducted to characterize the mechanical behavior and performance of the soft glove in terms of the angle output and force output upon pressurization. To operate this soft wearable glove, we designed the hardware system for SRGs with a flexible strain sensor and force sensor in the loop and introduced a force/position hybrid PID control algorithm to regulate the pressure inputted. Experiment evaluation focused on rehabilitation training gestures; motions and the precise grasping assistance function were executed. The rotating actuator between each finger can supply abduction/adduction motion manner for patients, which will improve rehabilitation effect. The experimental results demonstrated that the developed SRGs have the potential to improve hand movement freedom and the range of grasping successfully.


Assuntos
Robótica , Dispositivos Eletrônicos Vestíveis , Dedos/fisiologia , Mãos/fisiologia , Força da Mão/fisiologia , Humanos
9.
Curr Opin Neurobiol ; 76: 102621, 2022 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-36027737

RESUMO

Running our fingers across a textured surface gives rise to two types of skin deformations, each transduced by different tactile nerve fibers. Coarse features produce large-scale skin deformations whose spatial configuration is reflected in the spatial pattern of activation of some tactile fibers. Scanning a finely textured surface elicits vibrations in the skin, which in turn evoked temporally patterned responses in other fibers. These two neural codes-spatial and temporal-drive a spectrum of neural response properties in somatosensory cortex: At one extreme, neurons are sensitive to spatial patterns and encode coarse features; at the other extreme, neurons are sensitive to vibrations and encode fine features. While the texture responses of nerve fibers are dependent on scanning speed, those of cortical neurons are less so, giving rise to a speed invariant texture percept. Neurons in high-level somatosensory cortices combine information about texture with information about task variables.


Assuntos
Percepção do Tato , Dedos/inervação , Dedos/fisiologia , Córtex Somatossensorial/fisiologia , Tato/fisiologia , Percepção do Tato/fisiologia , Percepção Visual
10.
Conscious Cogn ; 104: 103382, 2022 09.
Artigo em Inglês | MEDLINE | ID: mdl-35914430

RESUMO

In psychology and neuroscience, opposition to free will has asserted that any degree of perceived self-control or choice is a mere epiphenomenon which provides no meaningful influence on action. The present research tested the validity of this conclusion by designing a paradigm in which the potential effect of self-monitoring on motor output could be investigated. Using a repetitive finger tapping task that evokes automatic patterns in participants tapping responses, we have obtained evidence that (1) participants may voluntarily reduce the predictability of their tapping patterns (2) by exercising cognitive control that (3) modulates response-locked steady-state movement-related potentials over primary and supplementary motor areas. These findings challenge the most radical accounts of the nonexistence of free will and instead provide support for a more balanced model of human behaviour in which cognitive control may constrain automatic response tendencies in response preparation and action execution.


Assuntos
Córtex Motor , Autonomia Pessoal , Cognição , Eletroencefalografia , Potenciais Evocados/fisiologia , Dedos/fisiologia , Humanos , Córtex Motor/fisiologia , Movimento/fisiologia
11.
Artigo em Inglês | MEDLINE | ID: mdl-35834448

RESUMO

Electromyography (EMG) is one of the most common methods to detect muscle activities and intentions. However, it has been difficult to estimate accurate hand motions represented by the finger joint angles using EMG signals. We propose an encoder-decoder network with an attention mechanism, an explainable deep learning model that estimates 14 finger joint angles from forearm EMG signals. This study demonstrates that the model trained by the single-finger motion data can be generalized to estimate complex motions of random fingers. The color map result of the after-training attention matrix shows that the proposed attention algorithm enables the model to learn the nonlinear relationship between the EMG signals and the finger joint angles, which is explainable. The highly activated entries in the color map of the attention matrix derived from model training are consistent with the experimental observations in which certain EMG sensors are highly activated when a particular finger moves. In summary, this study proposes an explainable deep learning model that estimates finger joint angles based on EMG signals of the forearm using the attention mechanism.


Assuntos
Aprendizado Profundo , Eletromiografia/métodos , Dedos/fisiologia , Humanos , Movimento/fisiologia , Músculo Esquelético/fisiologia
12.
Comput Math Methods Med ; 2022: 1020504, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35898486

RESUMO

Background: The muscles related to piano practice are mainly concentrated in the fingers and upper limbs, and the muscles related to other parts of the body are weak. Compared with other sports injuries, the injuries caused by piano practice are mainly chronic injuries caused by long-term strain of the upper limbs, and acute injuries rarely occur. The purpose of this study was to analyze the therapeutic effect of hand muscle injury caused by piano practice. Method: A total of 60 patients with hand muscle injury caused by piano practice admitted to our hospital from January 2019 to June 2020 were selected. According to the number random grouping method, they were randomly divided into two groups. There were 30 patients in the observation group, including 20 males and 10 females, aged 24-53 (39.51 ± 7.01) years old, and the course of disease was 1-5 (3.24 ± 1.62) months. In the control group, there were 30 patients, including 18 males and 12 females, aged 24-56 (39.62 ± 7.17) years old, and the course of disease was 1.5-5 (3.14 ± 1.71) months. If the observation group experienced excessive pain, the group took ibuprofen sustained-release capsules. On weekdays, exercise your fingers 2-3 times per day. After the intervention, the wrist joint function score of the observation group was higher than that before the intervention. Results: Before treatment, there was no significant difference in pain level scores between the two groups (P > 0.05). After treatment, the limb pain score in the observation group was lower than that in the control group. The effective rate of hand tendon rehabilitation in the observation group was 93.33%. The effective rate of hand tendon rehabilitation in the control group was 70.00%. The comparison results showed that there was statistical significance (P < 0.05). The score of the observation group was significantly higher than that of the control group, with statistically significant differences (P < 0.05). Conclusion: Piano workouts can cause hand muscle difficulties, which can be alleviated by daily finger gymnastics. Daily finger exercises are simple and not limited by time and place. Piano practitioners can use the spare time of daily training and performance to exercise for a long time, so as to prevent or recover finger muscle damage caused by piano practice. It has the potential to help pianists avoid hand muscle injuries when practicing while also allowing music to reach its full potential.


Assuntos
Mãos , Música , Adulto , Feminino , Dedos/fisiologia , Mãos/fisiologia , Humanos , Masculino , Pessoa de Meia-Idade , Músculo Esquelético/fisiologia , Dor
13.
J Neurosci Methods ; 380: 109675, 2022 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-35872154

RESUMO

BACKGROUND: The conventional focus on discrete finger movements (i.e., index finger flexion or button-box key presses) has been an effective method to study neuromotor control using magnetoencephalography (MEG). However, this approach is challenging for young children and not possible for some people with physical disability. NEW METHOD: We have developed a novel, interactive MEG compatible reach-to-target task to investigate neuromotor function, specifically for use with young children. We used an infrared touch-screen frame to detect responses to targets presented using custom software. The game can be played using a conventional computer monitor or during MEG recordings via projector. We termed this game the Target-Touch Motor Task (TTMT). RESULTS: We demonstrate that the TTMT is a feasible motor task for use with young children including children with physical impairments. TTMT response-to-target trial counts are also comparable to conventional methods. Artifacts from the touch screen, while present > 100 Hz, did not affect MEG source analysis in the beta band (14-30 Hz). MEG responses during TTMT game play reveal robust cortical activity from expected areas of motor cortex as typically observed following movements of the upper limb. COMPARISON WITH EXISTING METHOD(S): The TTMT paradigm allows participation by individuals with a broad range of motor abilities on a reach-to-target' functional task rather than conventional tasks focusing on discrete finger movements. CONCLUSIONS: The TTMT is well suited for young children and successfully activates expected motor cortical areas. The TTMT opens-up new opportunities for the assessment of motor function across the lifespan, including for children with physical limitations.


Assuntos
Magnetoencefalografia , Córtex Motor , Criança , Pré-Escolar , Dedos/fisiologia , Humanos , Magnetoencefalografia/métodos , Córtex Motor/fisiologia , Movimento/fisiologia
14.
J Neurosci ; 42(29): 5771-5781, 2022 Jul 20.
Artigo em Inglês | MEDLINE | ID: mdl-35701160

RESUMO

Sensory perception and memory are enhanced during restricted phases of ongoing brain rhythms, but whether voluntary movement is constrained by brain rhythm phase is not known. Voluntary movement requires motor commands to be released from motor cortex (M1) and transmitted to spinal motoneurons and effector muscles. Here, we tested the hypothesis that motor commands are preferentially released from M1 during circumscribed phases of ongoing sensorimotor rhythms. Healthy humans of both sexes performed a self-paced finger movement task during electroencephalography (EEG) and electromyography (EMG) recordings. We first estimated the time of motor command release preceding each finger movement by subtracting individually measured corticomuscular transmission latencies from EMG-determined movement onset times. Then, we determined the phase of ipsilateral and contralateral sensorimotor mu (8-12 Hz) and beta (13-35 Hz) rhythms during release of each motor command. We report that motor commands were most often released between 120 and 140° along the contralateral beta cycle but were released uniformly along the contralateral mu cycle. Motor commands were also released uniformly along ipsilateral mu and beta cycles. Results demonstrate that motor command release coincides with restricted phases of the contralateral sensorimotor beta rhythm, suggesting that sensorimotor beta rhythm phase may sculpt the timing of voluntary human movement.SIGNIFICANCE STATEMENT Perceptual and cognitive function is optimal during specific brain rhythm phases. Although brain rhythm phase influences motor cortical neuronal activity and communication between the motor cortex and spinal cord, its role in voluntary movement is poorly understood. Here, we show that the motor commands needed to produce voluntary movements are preferentially released from the motor cortex during contralateral sensorimotor beta rhythm phases. Our findings are consistent with the notion that sensorimotor rhythm phase influences the timing of voluntary human movement.


Assuntos
Ritmo beta , Córtex Motor , Desempenho Psicomotor , Ritmo beta/fisiologia , Eletroencefalografia , Eletromiografia , Feminino , Dedos/fisiologia , Humanos , Masculino , Atividade Motora/fisiologia , Córtex Motor/fisiologia , Desempenho Psicomotor/fisiologia
15.
Sci Data ; 9(1): 373, 2022 06 29.
Artigo em Inglês | MEDLINE | ID: mdl-35768439

RESUMO

Surface electromyography (sEMG) is commonly used to observe the motor neuronal activity within muscle fibers. However, decoding dexterous body movements from sEMG signals is still quite challenging. In this paper, we present a high-density sEMG (HD-sEMG) signal database that comprises simultaneously recorded sEMG signals of intrinsic and extrinsic hand muscles. Specifically, twenty able-bodied participants performed 12 finger movements under two paces and three arm postures. HD-sEMG signals were recorded with a 64-channel high-density grid placed on the back of hand and an 8-channel armband around the forearm. Also, a data-glove was used to record the finger joint angles. Synchronisation and reproducibility of the data collection from the HD-sEMG and glove sensors were ensured. The collected data samples were further employed for automated recognition of dexterous finger movements. The introduced dataset offers a new perspective to study the synergy between the intrinsic and extrinsic hand muscles during dynamic finger movements. As this dataset was collected from multiple participants, it also provides a resource for exploring generalized models for finger movement decoding.


Assuntos
Dedos , Mãos , Eletromiografia , Dedos/fisiologia , Mãos/fisiologia , Humanos , Movimento/fisiologia , Músculo Esquelético/fisiologia , Reprodutibilidade dos Testes
16.
Neuroimage ; 258: 119365, 2022 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-35690256

RESUMO

BACKGROUND: Transcranial magnetic stimulation (TMS) is widely used to probe corticospinal excitability and fast sensorimotor integration in the primary motor hand area (M1-HAND). A conditioning electrical stimulus, applied to the contralateral hand, can suppress the motor evoked potential (MEP) elicited by TMS of M1-HAND when the afferent stimulus arrives in M1-HAND at the time of TMS. The magnitude of this short-latency afferent inhibition (SAI) is expressed as the ratio between the conditioned and unconditioned MEP amplitude. OBJECTIVE/HYPOTHESIS: We hypothesized that corticospinal excitability and SAI are influenced by the recent history of peripheral electrical stimulation. METHODS: In twenty healthy participants, we recorded MEPs from the right first dorsal interosseus muscle. MEPs were evoked by single-pulse TMS of the left M1-HAND alone (unconditioned TMS) or by TMS preceded by electrical stimulation of the right index finger ("homotopic" conditioning) or little finger ("heterotopic" conditioning). The three conditions were either pseudo-randomly intermixed or delivered in blocks in which a single condition was repeated five or ten times. MEP amplitudes and SAI magnitudes were compared using linear mixed-effect models and one-way ANOVAs. RESULTS: All stimulation protocols consistently produced SAI, which was stronger after homotopic stimulation. Randomly intermingling the three stimulation conditions reduced the relative magnitude of homotopic and heterotopic SAI as opposed to blocked stimulation. The apparent attenuation of SAI was caused by a suppression of the unconditioned but not the conditioned MEP amplitude during the randomly intermixed pattern. CONCLUSION(S): The recent history of afferent stimulation modulates corticospinal excitability. This "history effect" impacts on the relative magnitude of SAI depending on how conditioned and unconditioned responses are intermixed and needs to be taken into consideration when probing afferent inhibition and corticospinal excitability.


Assuntos
Potencial Evocado Motor , Estimulação Magnética Transcraniana , Análise de Variância , Estimulação Elétrica/métodos , Eletromiografia , Potencial Evocado Motor/fisiologia , Dedos/fisiologia , Humanos , Inibição Neural/fisiologia , Estimulação Magnética Transcraniana/métodos
17.
Artigo em Inglês | MEDLINE | ID: mdl-35586946

RESUMO

OBJECTIVES: The multifinger force deficit (MFFD) is the decline in force generated by an individual finger as the number of fingers contributing to the action is increased. It has been proposed that as a measure of neural sufficiency rather than muscle status, it provides a means of detecting individuals at risk of cognitive decline. Age-related deficits in central neural drive exert a disproportionate impact on the rate at which force can be generated. We examined whether a MFFD derived from the maximum rate at which force is generated, is more sensitive to individual differences in cognitive status, than one calculated using the maximum level of force. METHODS: Monotonic associations between each of two variants of the MFFD, and cognition (measured with the Montreal Cognitive Assessment), were estimated cross sectionally using generalized partial rank correlations, in which age, level of education and degree of handedness were included as covariates. The participants (n=26) were community dwelling adults aged 66-87. RESULTS: The MFFD derived using the maximum rate of force development was negatively associated with cognitive status. The association for the MFFD based on the maximum level of force, was not statistically reliable. The associations with cognitive status obtained for both variants of the MFFD were of greater magnitude than those reported previously for standard grip strength dynamometry. CONCLUSION: The sensitivity with which the MFFD detects risk of cognitive decline may be enhanced by using the maximum rate of force developed by each finger, rather than the maximum force generated by each finger.


Assuntos
Dedos , Força da Mão , Cognição , Dedos/fisiologia , Força da Mão/fisiologia , Humanos , Vida Independente
18.
PLoS One ; 17(5): e0268137, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35544543

RESUMO

Fine hand movements require the synergistic contraction of intrinsic and extrinsic muscles to achieve them. In this paper, a Finite Element Digital Human Hand Model (FE-DHHM) containing solid tendons and ligaments and driven by the Muscle-Tendon Junction (MTJ) displacements of FDS, FDP and ED measured by ultrasound imaging was developed. The synergistic contraction of these muscles during the finger flexion movements was analyzed by simulating five sets of finger flexion movements. The results showed that the FDS and FDP contracted together to provide power during the flexion movements, while the ED acted as an antagonist. The peak stresses of the FDS, FDP and ED were all at the joints. In the flexion without resistance, the FDS provided the main driving force, and the FDS and FDP alternated in a "plateau" of muscle force. In the flexion with resistance, the muscle forces of FDS, FDP, and ED were all positively correlated with fingertip forces. The FDS still provided the main driving force, but the stress maxima occurred in the FDP at the DIP joint.


Assuntos
Dedos , Tendões , Fenômenos Biomecânicos , Articulações dos Dedos/fisiologia , Dedos/fisiologia , Análise de Elementos Finitos , Humanos , Movimento , Músculo Esquelético/fisiologia , Amplitude de Movimento Articular , Tendões/fisiologia
19.
Med Eng Phys ; 104: 103797, 2022 06.
Artigo em Inglês | MEDLINE | ID: mdl-35641068

RESUMO

Recent development of surface electromyogram (sEMG) decomposition technique provides a good basis of decoding movements from individual motor unit (MU) activities that directly representing microscopic neural drives. How to interpret the function and contribution of each decomposed MU to macroscopic movements remains unclear. The objective of this study is to decode finger movement patterns by establishing a relationship between individual MU activities and movements. In this study, high-density sEMG (HD-sEMG) data were recorded by a 16 × 8 electrode array from finger extensor muscles of 10 subjects performing 10 finger movement patterns. The progressive FastICA peel-off algorithm was first applied to decompose the HD-sEMG data to obtain microscopic neural drives in terms of MU firing sequences and their corresponding action potential waveforms. Then, convolutional neural network was used for classification of the decomposed MUs by characterizing their spatial waveforms spanned over all channels of the array. On this basis, a fuzzy weighted decision strategy was designed to give a final decision of movement pattern recognition, where function of an individual MU was measured in the form of contributing into all movement patterns with different weights to solve the issue of MUs shared among multiple patterns due to muscle co-activation. The proposed method yielded an average accuracy approximating to 100%, and it outperformed other common MU-based methods or conventional myoelectric classification methods using macroscopic sEMG features (p <  0.05). The proposed method has a wide application prospect in the field of human-machine interaction and precise motor control.


Assuntos
Aprendizado Profundo , Algoritmos , Eletromiografia , Dedos/fisiologia , Humanos , Movimento
20.
Sci Rep ; 12(1): 8215, 2022 05 17.
Artigo em Inglês | MEDLINE | ID: mdl-35581308

RESUMO

Humans need to accurately process the contact forces that arise as they perform everyday haptic interactions such as sliding the fingers along a surface to feel for bumps, sticky regions, or other irregularities. Several different mechanisms are possible for how the forces on the skin could be represented and integrated in such interactions. In this study, we used a force-controlled robotic platform and simultaneous ultrasonic modulation of the finger-surface friction to independently manipulate the normal and tangential forces during passive haptic stimulation by a flat surface. To assess whether the contact pressure on their finger had briefly increased or decreased during individual trials in this broad stimulus set, participants did not rely solely on either the normal force or the tangential force. Instead, they integrated tactile cues induced by both components. Support-vector-machine analysis classified physical trial data with up to 75% accuracy and suggested a linear perceptual mechanism. In addition, the change in the amplitude of the force vector predicted participants' responses better than the change of the coefficient of dynamic friction, suggesting that intensive tactile cues are meaningful in this task. These results provide novel insights about how normal and tangential forces shape the perception of tactile contact.


Assuntos
Percepção do Tato , Tato , Dedos/fisiologia , Fricção , Humanos , Pele , Tato/fisiologia
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