Predictive Pointing Movements and Saccades Toward a Moving Target

The authors investigated whether and, if so, how velocity information is used to control predictive manual pointing movements and saccades. Participants (N = 6) intercepted an occluded moving target as if it were still visible. They kept their eyes fixated while the target moved. The target traveled over a fixed distance and changed its velocity on the way. The presentation time of the final velocity was varied. Both the eye and the hand overshot the slow target and undershot the fast target, particularly when the duration of the final velocity was short. Thus, responses were biased in the direction of the target's initial velocity. The error seemed to arise because participants did not take their latency into account when aiming at the target. Instead, they strategically aimed farther ahead when the target was fast. Amplitude was also more related to the position of velocity change than to final velocity duration. Both findings suggest that target velocity is not extrapolated but that individuals add an increment to the position of velocity change.     

The Coding of Location

One prediction of the recent target hypothesis for movement control (MacNeilage, 1970; Russell, 1976) holds that location reproduction is not solely dependent upon stored kinesthetic information. Three experiments were performed to test this prediction by requiring the subject to reproduce the location with the limb opposite to the one used for criterion production. This switched-limb procedure was assumed to force the subject to rely upon more abstract information rather than the kinesthetic cues of the criterion movement. With movement direction invariant, switched-limb reproduction was equal to same-limb reproduction. The alteration of movement direction hampered switched-limb reproduction but same-limb reproduction was not greatly affected. These findings gave some support to the target hypothesis but suggested that the context of the movement may affect the potency of the location code. Implications of the switched-limb technique for future research were briefly discussed.     

Haptic and Visual Influences on Grasp Point Selection

When using precision grip to pick up objects, there are many possible pairs of grasp points that permit the thumb and index finger to exert opposed forces for secure grip. Previously, it was shown that individuals select grasp points so that the line between them (grasp axis) passes through or near the center of mass (CoM), thus minimizing the torque around the grasp axis during lifting. The accuracy of grasp axis selection depended on object spatial symmetry, indicating the importance of vision. The authors investigated how grasp point selection is influenced by haptic as well as visual information. Ten participants lifted cuboids whose CoM was located either symmetrically in the geometric center or asymmetrically toward one end. Results for the asymmetric cuboid revealed that grasp points migrated toward the asymmetric CoM from the geometric center. This was more pronounced in the presence of visual cues that reliably indicated the location of CoM. The results suggest that grasp point selection is influenced by a multimodal representation of CoM.     

Planning Maximally Smooth Hand Movements Constrained to Nonplanar Workspaces

The article characterizes hand paths and speed profiles for movements performed in a nonplanar, 2-dimensional workspace (a hemisphere of constant curvature). The authors assessed endpoint kinematics (i.e., paths and speeds) under the minimum-jerk model assumptions and calculated minimal amplitude paths (geodesics) and the corresponding speed profiles. The authors also calculated hand speeds using the 2/3 power law. They then compared modeled results with the empirical observations. In all, 10 participants moved their hands forward and backward from a common starting position toward 3 targets located within a hemispheric workspace of small or large curvature. Comparisons of modeled observed differences using 2-way RM-ANOVAs showed that movement direction had no clear influence on hand kinetics (p < .05). Workspace curvature affected the hand paths, which seldom followed geodesic lines. Constraining the paths to different curvatures did not affect the hand speed profiles. Minimum-jerk speed profiles closely matched the observations and were superior to those predicted by 2/3 power law (p < .001). The authors conclude that speed and path cannot be unambiguously linked under the minimum-jerk assumption when individuals move the hand in a nonplanar 2-dimensional workspace. In such a case, the hands do not follow geodesic paths, but they preserve the speed profile, regardless of the geometric features of the workspace.     

Patients’ intention to speak up for health care providers’ hand hygiene in inpatient diabetic foot wound treatment: a cross-sectional survey in diabetes outpatient centres in Lower Saxony,Germany*

Hand hygiene in wound care by health care providers (HCPs) is a key principle in treating hospitalized patients with diabetic foot infections. This study aimed to estimate the extent to which patients with type-2-diabetes (T2D) intend to speak up for HCPs’ hand hygiene during inpatient foot treatment, test whether this motivation increases given the hospital would invite patients to speak up, and identify associations with socio-demographics, knowledge of hand hygiene requirements, and diabetes-related factors. A questionnaire-survey was conducted in eight diabetes outpatient centres in Lower Saxony/Germany. Intentions to speak up (without and with institutional encouragement) and knowledge about hand hygiene during foot-care were assessed. Analyses of variance were conducted, partly as repeated measures-models with intention-items as within-subject factor. N = 473 patients participated (response = 77.4%). N = 177 (41%) strongly intended to speak up. Institutional encouragement was associated with an increased rate of strong (54% vs. 41%; p < .001) and higher mean intention (M = 3.9 vs. 3.4 with vs. without encouragement [5-point-scales]; F(1, 434)?=?41.5, p < .001). In patients without diabetic foot syndrome, this effect was limited to those with at least medium school education (F(2, 292)?=?4.4, p = .013) and knowledge on HCPs’ hand hygiene (F(2, 294)?=?3.1, p = .047). In conclusion, a majority of T2D-patients in diabetes outpatient centres intend to speak for HCPs’ hand hygiene in inpatient foot treatment, and are receptive to institutional encouragement. However, this presupposes at least medium education and knowledge about hand hygiene, emphasizing that patient empowerment begins with knowledge.     

Effects of Sensory Deficit on Phalanx Force Deviation During Power Grip Post Stroke

The effect of sensory deficits on power grip force from individual phalanges was examined. The authors found that stroke survivors with sensory deficits (determined by the Semmes-Weinstein monofilament test) gripped with phalanx force directed more tangential to the object surface, than those without, although both groups had similar motor deficits (Chedoke-McMaster and Fugl-Meyer), grip strength, and skin friction. Altered grip force direction elevates risk of finger slippage against the object thus grip loss/object dropping, hindering activities of daily living. Altered grip force direction was associated with altered muscle activation patterns. In summary, the motor impairment level alone may not describe hand motor control in detail. Information about sensory deficits helps elucidate patients' hand motor control with functional relevance.     

Hearing visuo‐tactile synchrony – Sound‐induced proprioceptive drift in the invisible hand illusion

The rubber hand illusion (RHI) and its variant the invisible hand illusion (IHI) are useful for investigating multisensory aspects of bodily self‐consciousness. Here, we explored whether auditory conditioning during an RHI could enhance the trisensory visuo‐tactile‐proprioceptive interaction underlying the IHI. Our paradigm comprised of an IHI session that was followed by an RHI session and another IHI session. The IHI sessions had two parts presented in counterbalanced order. One part was conducted in silence, whereas the other part was conducted on the backdrop of metronome beats that occurred in synchrony with the brush movements used for the induction of the illusion. In a first experiment, the RHI session also involved metronome beats and was aimed at creating an associative memory between the brush stroking of a rubber hand and the sounds. An analysis of IHI sessions showed that the participants’ perceived hand position drifted more towards the body‐midline in the metronome relative to the silent condition without any sound‐related session differences. Thus, the sounds, but not the auditory RHI conditioning, influenced the IHI. In a second experiment, the RHI session was conducted without metronome beats. This confirmed the conditioning‐independent presence of sound‐induced proprioceptive drift in the IHI. Together, these findings show that the influence of visuo‐tactile integration on proprioceptive updating is modifiable by irrelevant auditory cues merely through the temporal correspondence between the visuo‐tactile and auditory events.     

异体手移植几个问题的讨论

异体手移植的临床开展是自体断肢再植技术和免疫学研究发展的结晶,是异体器官移植领域内新的突破,为手缺失患者带来了重新获得新手的希望.但目前异体手移植技术尚不成熟,能否在免疫抑制剂作用下获得长期存活尚不确定.在远期疗效尚未肯定的情况下,建议加强医生自身修养和伦理道德教育,规定由少数具备条件的单位大力开展异体手移植的基础及临床研究,达到既保护患者利益,又能保证异体手移植技术顺利走向成熟,最终广泛应用于临床,造福于人类.     

Fake hand in movement: Visual motion cues from the rubber hand are processed for kinesthesia

The feeling that a fake (e.g. rubber) hand belongs to a person's own body can be elicited by synchronously stroking the fake hand and the real hand, with the latter hidden from view. Here, we sought to determine whether visual motion signals from that incorporated rubber hand would provide relevant cues for sensing movement (i.e. kinesthesia). After 180 s of visuo-tactile synchronous or asynchronous stroking, the fake hand was moved along the lateral or the sagittal axis. After synchronous stroking, movement of the rubber hand induced illusory movement of the static (real) hand in the same direction; the illusion was slightly more frequent and more intense when the fake hand was moved along the sagittal axis. We therefore conclude that visual signals of motion originating from the rubber hand are integrated for kinesthesia by the central nervous system just as visual signals from the real hand are.     

橡胶手错觉:拥有感研究的实验范式及其应用

橡胶手错觉是一种健康个体将非肉体的假手视为自己真实身体的一部分的体验, 这种错觉可以通过同时轻刷被试面前可见的橡胶手及其不可见的真手而产生.橡胶手错觉已成为一种研究身体拥有感的重要范式, 其产生机制可以分为“自下而上的认知匹配”与“自上而下的认知匹配”两种加工方式.前者涉及视觉与触觉刺激的同步性; 而后者涉及被试心中预存的身体意象与身体图式(包括真假手之间模态特征,位置空间的相似性).综合上述证据, 身体模型假说与个人边缘空间理论进一步为拥有感产生的复杂机制提供了整合两种加工方式的解释.橡胶手错觉范式已经被用于探索精神分裂症患者等特殊被试病理分析,错觉产生和心理特质之间的关系, 以及神经外科和术后恢复上.未来的研究应该更加重视范式本身的拓展, 应用虚拟现实技术来提高身体模态的仿真效果, 利用橡胶手拥有感的易感性作为筛选与预测身体意象障碍疾病的指标.