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1.
Neurosci Lett ; 751: 135812, 2021 04 23.
Artigo em Inglês | MEDLINE | ID: mdl-33705933

RESUMO

An experiment was designed to determine whether accuracy constraints can influence how unimanual and bimanual motor sequences are produced and learned. The accuracy requirements of the task were manipulated using principles derived from Fitts' Law to create relatively low (ID = 3) and high (ID = 5) accuracy demands. Right-limb dominant participants (N = 28, age = 21.9 yrs; 15 females and 13 males) were required to produce unimanual left, unimanual right or bimanual movement sequences using elbow extension and flexion movements to hit a series of illuminated targets. The targets were illuminated in a repeating sequence of 16 elements. Participants performed 20 practice trials. Thirty minutes following the practice trials participants performed a retention test. Element duration (time interval between target hits) and segment harmonicity (hesitations/adjustments in movement pattern) were calculated. The results indicate longer element duration and lower harmonicity values (more adjustments) when the task required higher accuracy demands (ID = 5) compared to low accuracy demands (ID = 3). Element duration was shorter and harmonicity was higher at ID = 5 for both unimanual groups than the bimanual group. However, element duration was shorter and harmonicity was higher at ID = 3 for the bimanual group than for both unimanual groups. These results indicate that the accuracy demands of the task can influence both performance and learning of motor sequences and suggest differences between unimanual and bimanual motor sequence learning. It appears there is a bimanual advantage for tasks with lower accuracy demands whereas performance is more accurate with unimanual performance, regardless of limb, with higher accuracy demands. These results are consistent with recent research indicating that accuracy requirements change the control processes for bimanual performance differently than for unimanual tasks.


Assuntos
Lateralidade Funcional , Aprendizagem , Destreza Motora , Feminino , Mãos/fisiologia , Humanos , Masculino , Adulto Jovem
2.
Sci Data ; 8(1): 63, 2021 02 18.
Artigo em Inglês | MEDLINE | ID: mdl-33602931

RESUMO

Control of contemporary, multi-joint prosthetic hands is commonly realized by using electromyographic signals from the muscles remaining after amputation at the forearm level. Although this principle is trying to imitate the natural control structure where muscles control the joints of the hand, in practice, myoelectric control provides only basic hand functions to an amputee using a dexterous prosthesis. This study aims to provide an annotated database of high-density surface electromyographic signals to aid the efforts of designing robust and versatile electromyographic control interfaces for prosthetic hands. The electromyographic signals were recorded using 128 channels within two electrode grids positioned on the forearms of 20 able-bodied volunteers. The participants performed 65 different hand gestures in an isometric manner. The hand movements were strictly timed using an automated recording protocol which also synchronously recorded the electromyographic signals and hand joint forces. To assess the quality of the recorded signals several quantitative assessments were performed, such as frequency content analysis, channel crosstalk, and the detection of poor skin-electrode contacts.


Assuntos
Eletromiografia , Gestos , Mãos/fisiologia , Adulto , Membros Artificiais , Eletrodos , Feminino , Antebraço/fisiologia , Humanos , Contração Isométrica , Masculino , Pessoa de Meia-Idade , Movimento/fisiologia , Músculo Esquelético/fisiologia , Desenho de Prótese
3.
J Electromyogr Kinesiol ; 57: 102534, 2021 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-33618325

RESUMO

BACKGROUND: Recovery of hand function after stroke represents the hardest target for clinicians. Robot-assisted therapy has been proved to be effective for hand recovery. Nevertheless, studies aimed to refer patients to the best therapy are missing. METHODS: With the aim to identify which clinical features are predictive for referring to robot-assisted hand therapy, 174 stroke patients were assessed with: Fugl-Meyer Assessment (FMA), Functional Independence Measure (FIM), Reaching Performance Scale (RPS), Box and Block Test (BBT), Modified Ashworth Scale (MAS), Nine Hole Pegboard Test (NHPT). Moreover, patients ability to control the robot with residual force and surface EMG (sEMG) independently, was checked. ROC curves were calculated to determine which of the measures were the predictors of the event. RESULTS: sEMG control (AUC = 0.925) was significantly determined by FMA upper extremity (FMUE) (>24/66) and sensation (>23/24) sections, MAS at Flexor Carpi (<3/4) and total MAS (>4/20). Force control (AUC = 0.928) was correlated only with FMUE (>24/66). CONCLUSIONS: FMUE and MAS were the best predictors of preserved ability to control the device by two different modalities. This finding opens the possibility to plan specific therapies aimed at maximizing the highest functional outcome achievable after stroke.


Assuntos
Eletromiografia/métodos , Mãos/fisiologia , Recuperação de Função Fisiológica/fisiologia , Robótica/métodos , Reabilitação do Acidente Vascular Cerebral/métodos , Acidente Vascular Cerebral/terapia , Idoso , Estudos Transversais , Terapia por Exercício/instrumentação , Terapia por Exercício/métodos , Feminino , Previsões , Humanos , Estudos Longitudinais , Masculino , Pessoa de Meia-Idade , Músculo Esquelético/fisiologia , Projetos Piloto , Robótica/instrumentação , Acidente Vascular Cerebral/fisiopatologia , Reabilitação do Acidente Vascular Cerebral/instrumentação , Resultado do Tratamento
4.
Neural Netw ; 136: 1-10, 2021 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-33401114

RESUMO

In recent years, deep learning has emerged as a powerful tool for developing Brain-Computer Interface (BCI) systems. However, for deep learning models trained entirely on the data from a specific individual, the performance increase has only been marginal owing to the limited availability of subject-specific data. To overcome this, many transfer-based approaches have been proposed, in which deep networks are trained using pre-existing data from other subjects and evaluated on new target subjects. This mode of transfer learning however faces the challenge of substantial inter-subject variability in brain data. Addressing this, in this paper, we propose 5 schemes for adaptation of a deep convolutional neural network (CNN) based electroencephalography (EEG)-BCI system for decoding hand motor imagery (MI). Each scheme fine-tunes an extensively trained, pre-trained model and adapt it to enhance the evaluation performance on a target subject. We report the highest subject-independent performance with an average (N=54) accuracy of 84.19% (±9.98%) for two-class motor imagery, while the best accuracy on this dataset is 74.15% (±15.83%) in the literature. Further, we obtain a statistically significant improvement (p=0.005) in classification using the proposed adaptation schemes compared to the baseline subject-independent model.


Assuntos
Interfaces Cérebro-Computador/classificação , Encéfalo/fisiologia , Eletroencefalografia/classificação , Imaginação/fisiologia , Redes Neurais de Computação , Transferência de Experiência/fisiologia , Adulto , Algoritmos , Eletroencefalografia/métodos , Feminino , Mãos/fisiologia , Humanos , Aprendizado de Máquina/classificação , Masculino , Desempenho Psicomotor/fisiologia , Adulto Jovem
5.
PLoS One ; 16(1): e0243381, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33406125

RESUMO

Human perception is based on expectations. We expect visual upright and gravity upright, sensed through vision, vestibular and other sensory systems, to agree. Equally, we expect that visual and vestibular information about self-motion will correspond. What happens when these assumptions are violated? Tilting a person from upright so that gravity is not where it should be impacts both visually induced self-motion (vection) and the perception of upright. How might the two be connected? Using virtual reality, we varied the strength of visual orientation cues, and hence the probability of participants experiencing a visual reorientation illusion (VRI) in which visual cues to orientation dominate gravity, using an oriented corridor and a starfield while also varying head-on-trunk orientation and body posture. The effectiveness of the optic flow in simulating self-motion was assessed by how much visual motion was required to evoke the perception that the participant had reached the position of a previously presented target. VRI was assessed by questionnaire When participants reported higher levels of VRI they also required less visual motion to evoke the sense of traveling through a given distance, regardless of head or body posture, or the type of visual environment. We conclude that experiencing a VRI, in which visual-vestibular conflict is resolved and the direction of upright is reinterpreted, affects the effectiveness of optic flow at simulating motion through the environment. Therefore, any apparent effect of head or body posture or type of environment are largely indirect effects related instead, to the level of VRI experienced by the observer. We discuss potential mechanisms for this such as reinterpreting gravity information or altering the weighting of orientation cues.


Assuntos
Ego , Gravitação , Percepção de Movimento/fisiologia , Orientação Espacial , Percepção Visual/fisiologia , Adulto , Feminino , Mãos/fisiologia , Humanos , Masculino , Postura/fisiologia
6.
PLoS One ; 16(1): e0245191, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33411838

RESUMO

Brain-machine interfaces (BMI) allows individuals to control an external device by controlling their own brain activity, without requiring bodily or muscle movements. Performing voluntary movements is associated with the experience of agency ("sense of agency") over those movements and their outcomes. When people voluntarily control a BMI, they should likewise experience a sense of agency. However, using a BMI to act presents several differences compared to normal movements. In particular, BMIs lack sensorimotor feedback, afford lower controllability and are associated with increased cognitive fatigue. Here, we explored how these different factors influence the sense of agency across two studies in which participants learned to control a robotic hand through motor imagery decoded online through electroencephalography. We observed that the lack of sensorimotor information when using a BMI did not appear to influence the sense of agency. We further observed that experiencing lower control over the BMI reduced the sense of agency. Finally, we observed that the better participants controlled the BMI, the greater was the appropriation of the robotic hand, as measured by body-ownership and agency scores. Results are discussed based on existing theories on the sense of agency in light of the importance of BMI technology for patients using prosthetic limbs.


Assuntos
Interfaces Cérebro-Computador , Encéfalo/fisiologia , Retroalimentação Sensorial/fisiologia , Mãos/fisiologia , Movimento/fisiologia , Eletroencefalografia , Feminino , Humanos , Masculino
7.
Nat Commun ; 12(1): 221, 2021 01 11.
Artigo em Inglês | MEDLINE | ID: mdl-33431883

RESUMO

Dedicated maps for cognitive quantities such as timing, size and numerosity support the view that topography is a general principle of brain organization. To date, however, all of these maps were driven by the visual system. Here, we ask whether there are supramodal topographic maps representing cognitive dimensions irrespective of the stimulated sensory modality. We measured haptically and visually driven numerosity-selective neural responses using model-based analyses and ultra-high field (7T) fMRI. We found topographically organized neural populations tuned to haptic numerosity. The responses to visual or haptic numerosity shared a similar cortical network. However, the maps of the two modalities only partially overlap. Thus, although both visual and haptic numerosities are processed in a similar supramodal functional network, the underlying neural populations may be related, but distinct. Therefore, we hypothesize that overlap between modality-specific maps facilitates cross-modal interactions and supramodal representation of cognitive quantities.


Assuntos
Rede Nervosa/fisiologia , Tato/fisiologia , Adulto , Feminino , Dedos/fisiologia , Mãos/fisiologia , Humanos , Masculino , Pessoa de Meia-Idade , Movimento (Física) , Atividade Motora/fisiologia , Estimulação Luminosa , Percepção Visual/fisiologia
8.
Neurosci Lett ; 740: 135424, 2021 01 01.
Artigo em Inglês | MEDLINE | ID: mdl-33075419

RESUMO

Repetitive transcranial magnetic stimulation (rTMS) is used to modulate neuronal excitability of the human brain. Distant effects on contralateral corticomotor excitability can be exerted by interhemispheric modulation by low-frequency rTMS on ipsilateral hemisphere. To modulate corticospinal excitability, accurate determination of the stimulation site is important to maximize the effects of rTMS. In the present study, we investigated the difference in the distant effect of 1 Hz rTMS with respect to inducing functional improvement in the non-dominant hand by inhibiting the dominant hemisphere depending on cortical target areas. Ten healthy right-handed volunteers without any neurological disorders were enrolled. The anatomical hand knob (HK) identified from individual magnetic resonance imaging and the transcranial magnetic stimulation (TMS) induced hand motor hotspot (hMHS) by recording motor evoked potentials (MEPs) in the contralateral first dorsal interosseous muscle were determined. All participants underwent three conditions of 1 Hz rTMS on left hemisphere intervention; rTMS application over the HK, rTMS application over the hMHS, and sham-rTMS. Before and after each intervention, all participants undergone motor function assessments with their left hand. The cortical mapping showed that the hMHS was located anteriorly and laterally compared to the HK. Motor function tests showed the most significant improvements after the hMHS stimulation. When we compared the distant effects of target site on corticospinal excitability and motor behavior, delivering 1 Hz rTMS to the hMHS was more effective than delivering it to the HK for improving corticomotor excitability, motor skill, and dexterity. These results suggest that TMS-induced hMHS is an optimal target area to induce distant effect of low-frequency rTMS in motor function.


Assuntos
Córtex Cerebral/fisiologia , Mãos/fisiologia , Destreza Motora/fisiologia , Estimulação Magnética Transcraniana/métodos , Adulto , Mapeamento Encefálico , Estudos Cross-Over , Potencial Evocado Motor/fisiologia , Feminino , Lateralidade Funcional/fisiologia , Humanos , Imagem por Ressonância Magnética , Masculino , Córtex Motor/fisiologia , Músculo Esquelético/fisiologia , Desempenho Psicomotor/fisiologia , Tempo de Reação/fisiologia , Método Simples-Cego
9.
Apunts, Med. esport (Internet) ; 55(208): 137-142, oct.-dic. 2020. tab, ilus
Artigo em Inglês | IBECS | ID: ibc-197957

RESUMO

INTRODUCTION: Two of the main modifiable risk factors for suffering an injury in the anterior cruciate ligament are known to be the Hamstring-to-Quadriceps (H/Q) Ratio and neuromuscular fatigue. The main purpose of this research was to study the effect of neuromuscular fatigue on the H/Q Ratio and the maximum isometric strength of the quadriceps and hamstrings in teenage female basketball and handball players. MATERIAL AND METHODS: This is an experimental, pre-post intervention study with a sample of 19 female basketball players and 11 female handball players (17.02±1.19 yo, 177.8±7.2cm and 68.6±9.3kg). To assess muscle strength, a maximum isometric strength test was performed in a 90° hip and 60° knee position. The H/Q Ratio was then calculated. The 30-15 Intermittent Fatigue Test (30-15 IFT) was used to induce fatigue, measured using the Rating of Perceived Exertion (RPE) scale. A descriptive analysis and a Student's t-test were performed to study the differences in the H/Q Ratio, muscle strength and pre-post intervention fatigue. RESULTS: Although the H/Q Ratio decreased after the 30-15 IFT, the differences were not statistically significant. Regarding strength values, the right and left quadriceps presented strength reductions of 4.52% and 5.55%, respectively. The reduction in strength was statistically significant (p≤0.05), especially in the right hamstring (7.3%) and in the left hamstring (7.5%). The study conclusions suggest that leg muscular strength decreases after a fatigue test and that there is a tendency for the H/Q Ratio to decrease also


No disponible


Assuntos
Humanos , Feminino , Adolescente , Adulto Jovem , Músculos Isquiossurais/fisiologia , Fadiga Muscular/fisiologia , Força Muscular , Músculo Quadríceps/fisiologia , Basquetebol/fisiologia , Exercício Físico/fisiologia , Futebol/fisiologia , Estudos Prospectivos , Antropometria/métodos , Atletas/estatística & dados numéricos , Fadiga/fisiopatologia , Mãos/fisiologia , Músculo Esquelético/fisiologia
10.
Sci Rep ; 10(1): 22381, 2020 12 24.
Artigo em Inglês | MEDLINE | ID: mdl-33361768

RESUMO

From a motor control perspective, human-to-human object handovers can be described as coordinated joint-actions transferring the power over an object from a passer to a receiver. Although, human-to-human handovers are very reliable in terms of success, it is unclear how both actors plan and execute their actions independently while taking into account the partners behaviour. Here, we measured grip-forces of passer and receiver while handing over an object. In order to study mutual interaction in human-to-human handovers, we measured how changes in relevant features (sensory information available to the passer and receiver's reaching velocity) in one partner affect grip-force profiles not only at the manipulated side but also at the partner's side. The data reveals strong effects of sensory manipulations on time-related (duration and release delay) and dynamometric measures (force rates). Variation of reaching velocities had the largest impact on the receiver's force rates. Furthermore, there are first indications that the vertical object movement is used as an implicit cue to signal the start of the handover in situations where vision is restricted.


Assuntos
Força da Mão/fisiologia , Mãos/fisiologia , Movimento/fisiologia , Adulto , Fenômenos Biomecânicos , Humanos , Masculino
11.
Sci Rep ; 10(1): 22307, 2020 12 18.
Artigo em Inglês | MEDLINE | ID: mdl-33339859

RESUMO

When we use virtual and augmented reality (VR/AR) environments to investigate behaviour or train motor skills, we expect that the insights or skills acquired in VR/AR transfer to real-world settings. Motor behaviour is strongly influenced by perceptual uncertainty and the expected consequences of actions. VR/AR differ in both of these aspects from natural environments. Perceptual information in VR/AR is less reliable than in natural environments, and the knowledge of acting in a virtual environment might modulate our expectations of action consequences. Using mirror reflections to create a virtual environment free of perceptual artefacts, we show that hand movements in an obstacle avoidance task systematically differed between real and virtual obstacles and that these behavioural differences occurred independent of the quality of the available perceptual information. This suggests that even when perceptual correspondence between natural and virtual environments is achieved, action correspondence does not necessarily follow due to the disparity in the expected consequences of actions in the two environments.


Assuntos
Mãos/fisiologia , Destreza Motora/fisiologia , Movimento/fisiologia , Realidade Virtual , Artefatos , Meio Ambiente , Humanos
12.
J Comp Eff Res ; 9(18): 1293-1300, 2020 12.
Artigo em Inglês | MEDLINE | ID: mdl-33325276

RESUMO

Aim: This study aims to investigate reliability of quantitative ultrasound measurement of the flexor digitorum superficialis (FDS) and flexor digitorum profundus (FDP) muscles in stroke. Materials & methods: Patients with a history of stroke were recruited. FDP and FDS muscles on both upper extremities were investigated with ultrasound. Two independent assessors acquired images and analyzed them using a program and Heckmatt scale. Results: Forty-eight patients were included. The inter-rater intraclass correlation coefficient for echo intensities was calculated as 0.91 while intrarater intraclass correlation coefficient as 0.80. For Heckmatt scale, the inter-rater reliability for FDS was Kw = 0.74 (p < 0.0005) and for FDP it was Kw = 0.73 (p < 0.0005). Mean echo intensity values showed significant strong correlations with Heckmatt scores (r = 0.663 and r = 0.633 with both p values <0.001). Conclusion: Quantitative ultrasound imaging of FDS and FDP is a reliable method to demonstrate echo intensity changes of muscles in stroke.


Assuntos
Articulação da Mão/diagnóstico por imagem , Mãos/diagnóstico por imagem , Espasticidade Muscular/etiologia , Espasticidade Muscular/reabilitação , Acidente Vascular Cerebral/complicações , Ultrassonografia/métodos , Adolescente , Adulto , Idoso , Mãos/fisiologia , Articulação da Mão/fisiologia , Humanos , Estudos Longitudinais , Pessoa de Meia-Idade , Músculo Esquelético/diagnóstico por imagem , Músculo Esquelético/fisiologia , Estudos Prospectivos , Reprodutibilidade dos Testes , Acidente Vascular Cerebral/diagnóstico por imagem , Reabilitação do Acidente Vascular Cerebral , Resultado do Tratamento , Dedo em Gatilho , Ultrassonografia/normas , Adulto Jovem
13.
Prax Kinderpsychol Kinderpsychiatr ; 69(7): 614-624, 2020 Oct.
Artigo em Alemão | MEDLINE | ID: mdl-33146085

RESUMO

Effectiveness of a Manual Dexterity Training in German Kindergarten The present study examines effects of a manual dexterity training with cup stacking/speed stacking exercises for children in the last year of German kindergarten. Between pre- and posttest, nine trainings sessions were conducted within two weeks. The training group consisted of N = 20 children, the waiting control group of N = 17 children. Pre- and posttest consisted of the manual dexterity scale of the Movement ABC-2 (Petermann, 2011). Compared to the control group, the training group showed significantly lower pretest scores but higher posttest scores. Results were discussed in the light of need for replications. The importance of early prevention and intervention of motor coordination problems is highlighted.


Assuntos
Exercício Físico , Mãos/fisiologia , Instituições Acadêmicas , Criança , Alemanha , Humanos
15.
PLoS One ; 15(9): e0239032, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32925937

RESUMO

Knowing where our limbs are in space is essential for moving and for adapting movements to various changes in our environments and bodies. The ability to adapt movements declines with age, and age-related cognitive decline can explain a decreased ability to adopt and deploy explicit, cognitive strategies in motor learning. Age-related sensory decline could also lead to a reduced fidelity of sensory position signals and error signals, each of which can affect implicit motor adaptation. Here we investigate two estimates of limb position; one based on proprioception, the other on predicted sensory consequences of movements. Each is considered a measure of an implicit adaptation process and may be affected by both age and cognitive strategies. Both older (n = 38) and younger (n = 42) adults adapted to a 30° visuomotor rotation in a centre-out reaching task. We make an explicit, cognitive strategy available to half of participants in each age group with a detailed instruction. After training, we first quantify the explicit learning elicited by instruction. Instructed older adults initially use the provided strategy slightly less than younger adults but show a similar ability to evoke it after training. This indicates that cognitive explanations for age-related decline in motor learning are limited. In contrast, training induced much larger shifts of state estimates of hand location in older adults compared to younger adults. This is not modulated by strategy instructions, and appears driven by recalibrated proprioception, which is almost twice as large in older adults, while predictions might not be updated in older adults. This means that in healthy aging, some implicit processes may be compensating for other changes to maintain motor capabilities, while others also show age-related decline (data: https://osf.io/qzhmy).


Assuntos
Fatores Etários , Atividade Motora/fisiologia , Desempenho Psicomotor/fisiologia , Adaptação Fisiológica/fisiologia , Adaptação Psicológica/fisiologia , Idoso , Feminino , Mãos/fisiologia , Humanos , Aprendizagem/fisiologia , Masculino , Movimento , Propriocepção , Rotação , Adulto Jovem
16.
PLoS One ; 15(7): e0236824, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32735569

RESUMO

In our daily life, we often interact with objects using both hands raising the question the question to what extent information between the hands is shared. It has, for instance, been shown that curvature adaptation aftereffects can transfer from the adapted hand to the non-adapted hand. However, this transfer only occurred for dynamic exploration, e.g. by moving a single finger over a surface, but not for static exploration when keeping static contact with the surface and combining the information from different parts of the hand. This raises the question to what extent adaptation to object shape is shared between the hands when both hands are used in static fashion simultaneously and the object shape estimates require information from both hands. Here we addressed this question in three experiments using a slant adaptation paradigm. In Experiment 1 we investigated whether an aftereffect of static bimanual adaptation occurs at all and whether it transfers to conditions in which one hand was moving. In Experiment 2 participants adapted either to a felt slanted surface or simply be holding their hands in mid-air at similar positions, to investigate to what extent the effects of static bimanual adaptation are posture-based rather than object based. Experiment 3 further explored the idea that bimanual adaptation is largely posture based. We found that bimanual adaptation using static touch did lead to aftereffects when using the same static exploration mode for testing. However, the aftereffect did not transfer to any exploration mode that included a dynamic component. Moreover, we found similar aftereffects both with and without a haptic surface. Thus, we conclude that static bimanual adaptation is of proprioceptive nature and does not occur at the level at which the object is represented.


Assuntos
Mãos/fisiologia , Desempenho Psicomotor , Percepção do Tato/fisiologia , Adaptação Fisiológica , Adulto , Feminino , Humanos , Masculino , Equilíbrio Postural/fisiologia , Tato , Adulto Jovem
17.
PLoS One ; 15(7): e0236416, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32735572

RESUMO

Proprioception acquires a crucial role in estimating the configuration of our body segments in space when visual information is not available. Proprioceptive accuracy is assessed by asking participants to match the perceived position of an unseen body landmark through reaching movements. This task was also adopted to study the perceived hand structure by computing the relative distances between averaged proprioceptive judgments (hand Localization Task). However, the pattern of proprioceptive errors leading to the misperceived hand structure is unexplored. Here, we aimed to characterize this pattern across different hand landmarks, having different anatomo-physiological properties and cortical representations. Furthermore, we sought to describe the error consistency and its stability over time. To this purpose, we analyzed the proprioceptive errors of 43 healthy participants during the hand Localization Task. We found larger but more consistent errors for the fingertips compared to the knuckles, possibly due to poorer proprioceptive signal, compensated by other sources of spatial information. Furthermore, we found a shift (overlap effect) and a temporal drift of the hand perceived position towards the shoulder of origin, which was consistent within and between subjects. The overlap effect had a greater influence on lateral compared to medial landmarks, leading to the hand width overestimation. Our results are compatible with domain-general and body-specific spatial biases affecting the proprioceptive localization of the hand landmarks, thus the apparent hand structure misperception.


Assuntos
Mãos/fisiologia , Movimento/fisiologia , Propriocepção/fisiologia , Desempenho Psicomotor/fisiologia , Adulto , Feminino , Dedos/fisiologia , Corpo Humano , Humanos , Julgamento , Aprendizagem/fisiologia , Masculino , Polegar/fisiologia , Percepção Visual/fisiologia , Adulto Jovem
18.
PLoS One ; 15(8): e0236497, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32785230

RESUMO

When human movement is assisted or controlled with a muscle actuator, such as electrical muscle stimulation, a critical issue is the integration of such induced movement with the person's motion intention and how this movement then affects their motor control. Towards achieving optimal integration and reducing feelings of artificiality and enforcement, we explored perceptual simultaneity through electrical muscle stimulation, which involved changing the interval between intentional and induced movements. We report on two experiments in which we evaluated the ranges between detection and stimulus for perceptual simultaneity achievable with an electromyography-triggered electrical muscle stimulation system. We found that the peak range was approximately 80-160 ms, with the timing of perceptual simultaneity shifting according to different adaptation states. Our results indicate that perceptual simultaneity is controllable using this adaptation strategy.


Assuntos
Eletromiografia , Córtex Motor/fisiologia , Movimento/fisiologia , Músculo Esquelético/fisiologia , Adulto , Estimulação Elétrica , Mãos/fisiologia , Humanos , Masculino , Córtex Motor/diagnóstico por imagem , Músculo Esquelético/diagnóstico por imagem , Visão Ocular/fisiologia , Adulto Jovem
19.
PLoS One ; 15(8): e0237768, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32813742

RESUMO

INTRODUCTION: In cycling, the utilization of the drops position (i.e. the lowest handlebar position relative to the ground) allows for reduced frontal area, likely improved aerodynamics and thus performance compared to the tops (i.e. the position producing the most upright trunk). The reduced trunk angle during seated submaximal cycling has been shown to influence cardiorespiratory factors but the effects on pedalling forces and joint specific power are unclear. The purpose of this study was to investigate the effect of changing handgrip position on joint specific power and cycling kinematics at different external work rates in recreational and professional cyclists. METHOD: Nine professional and nine recreational cyclists performed cycling bouts using three different handgrip positions and three external work rates (i.e. 100W, 200W and external work rate corresponding to the lactate threshold (WRlt)). Joint specific power was calculated from kinematic measurements and pedal forces using 2D inverse dynamics. RESULTS: We found increased hip joint power, decreased knee joint power and increased peak crank torque for the professional cyclist compared to the recreational cyclists, but only at WRlt where the professional cyclists were working at a higher external work rate. There was no main effect of changing handgrip position on any joint, but there was a small interaction effect of external work rate and handgrip position on hip joint power contribution (Generalized eta squared (ηg2) = 0.012). At 100W, changing handgrip position from the tops to the drops decreased the hip joint contribution (-2.0 ± 3.9 percentage points (pct)) and at the WRlt, changing handgrip position increased the hip joint power (1.6 ± 3.1 pct). There was a small effect of handgrip position with the drops leading to increased peak crank torque (ηg2 = 0.02), increased mean dorsiflexion (ηg2 = 0.05) and increased hip flexion (ηg2 = 0.31) compared to the tops. DISCUSSION: The present study demonstrates that there is no main effect of changing handgrip position on joint power. Although there seems to be a small effect on hip joint power when comparing across large ranges in external work rate, any potential negative performance effect would be outweighed by the aerodynamic benefit of the drops position.


Assuntos
Atletas , Desempenho Atlético/fisiologia , Ciclismo/fisiologia , Postura/fisiologia , Articulação do Tornozelo/fisiologia , Fenômenos Biomecânicos , Mãos/fisiologia , Articulação do Quadril/fisiologia , Humanos , Articulação do Joelho/fisiologia , Masculino , Torque , Adulto Jovem
20.
PLoS Comput Biol ; 16(8): e1008081, 2020 08.
Artigo em Inglês | MEDLINE | ID: mdl-32750070

RESUMO

We rarely experience difficulty picking up objects, yet of all potential contact points on the surface, only a small proportion yield effective grasps. Here, we present extensive behavioral data alongside a normative model that correctly predicts human precision grasping of unfamiliar 3D objects. We tracked participants' forefinger and thumb as they picked up objects of 10 wood and brass cubes configured to tease apart effects of shape, weight, orientation, and mass distribution. Grasps were highly systematic and consistent across repetitions and participants. We employed these data to construct a model which combines five cost functions related to force closure, torque, natural grasp axis, grasp aperture, and visibility. Even without free parameters, the model predicts individual grasps almost as well as different individuals predict one another's, but fitting weights reveals the relative importance of the different constraints. The model also accurately predicts human grasps on novel 3D-printed objects with more naturalistic geometries and is robust to perturbations in its key parameters. Together, the findings provide a unified account of how we successfully grasp objects of different 3D shape, orientation, mass, and mass distribution.


Assuntos
Força da Mão/fisiologia , Modelos Biológicos , Desempenho Psicomotor/fisiologia , Adulto , Biologia Computacional , Feminino , Mãos/fisiologia , Humanos , Masculino , Torque , Adulto Jovem
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