Phantom Hand Research Articles

MIMO multiband antenna system with nonresonant elements

ABSTRACTMulti‐input multi‐output (MIMO) technology will enable high‐data rates in wireless devices to allow speech and video calls to streaming media and web browsing all over a common platform. MIMO technology needs M antennas both in transmission and reception. As the space in a wireless device is limited, including M antennas is a challenge. To face such challenge, a MIMO antenna system is proposed which comprises two small nonresonant elements operating in the frequency region 824–960 MHz and two identical elements operating at 1710–2170 MHz. The size of each of the nonresonant elements is only 5 × 5 × 5 mm3. The proposed MIMO system is analyzed in terms of bandwidth, efficiency, correlation, and multiplexing efficiency. MIMO capacity is measured in a reverberation chamber considering a free‐space Rayleigh scenario and also including the effect of a phantom head and hand. The results reveal that the proposed MIMO system provides capacity close to the ideal bound while having a small size and able to operate at several 2G, 3G, and 4G long term evolution standards. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:183–190, 2015

Perceptual Changes of Interaction Between Hand and Object in an Experimental Phantom Hand

ABSTRACTThe authors examined whether the wrist and elbow were perceived as flexed when a stick was fixed to the hand while the joints were extended during anesthesia. Ten healthy participants lay on their back on a bed with their eyes closed, and a stick was fixed to their right hand. Surprisingly, while the perceived position of the wrist and elbow moved toward flexion from 10 to 40 min after the ischemic block, the stick fixed to the hand was also perceived as having moved toward flexion from 10 to 20 min after the block. Such coupling the change in the perceived stick position with the change in body image suggests a new type of hand–object illusion.

Can transcranial direct current stimulation enhance performance of myoelectric control for multifunctional prosthesis?

Pattern recognition based myoelectric control has been studied by many researchers. However, the classification accuracy was pretty low for amputees towards multifunctional prosthesis control in practice. In this work, a novel method of transcranial direct current stimulation (tDCS) which can modulate brain activity was used to enhance performance for myoelectric prosthesis control. The pilot study was conducted on three able-bodied subjects and one transradial amputee. Surface electromyography (EMG) signals were acquired from both arms when performing eleven hand and wrist motions in pre-tDCS and post-tDCS sessions. Time domain (TD) features and linear discriminant analysis (LDA) classifier were adopted to process EMG. For the non-dominant hand of the healthy subjects, active anodal tDCS of the contralateral primary motor cortex was able to significantly improve average classification accuracy by 3.82% (p <; 0.05), while sham tDCS could not have such effect (p > 0.05). For amputated (phantom) hand of the amputee, active anodal tDCS was able to significantly improve average classification accuracy by 12.56%, while sham tDCS could not have such effect. For the dominant hand and intact hand, the average classification accuracies were stable and not significantly improved using either active tDCS or sham tDCS. The results show that tDCS is a powerful noninvasive method to modulate brain function and enhance EMG classification performance especially for the amputated hand towards multifunctional prosthesis control. The method proposed has a huge potential to promote EMG pattern recognition based control scheme to clinical application.

Using multiple high-count electrode arrays in human median and ulnar nerves to restore sensorimotor function after previous transradial amputation of the hand.

Peripheral nerve interfaces that can record from and stimulate large numbers of different nerve fibers selectively and independently may help restore intuitive and effective motor and sensory function after hand amputation. To this end, and extending previous work in two subjects, two 100-electrode Utah Slanted Electrode Arrays (USEAs) were implanted for four weeks in the residual ulnar and median nerves of a 50-year-old male whose left, dominant hand had been amputated 21 years previously. Subsequent experiments involved 1) recording from USEAs for real-time control of a virtual prosthetic hand; 2) stimulation to evoke somatosensory percepts; and 3) closed-loop sensorimotor control. Overall, partial motor control and sensation were achieved using USEAs. 1) Isolated action potentials recorded from nerve motor fibers, although sparse at these distal implant sites, were activated during fictive movements of the phantom hand. Unlike in our previous two subjects, electromyographic (EMG) activity contributed to most online recordings and decodes, but was reduced in offline analyses using common average referencing. Online and offline Kalman-filter decodes of thresholded neural or EMG spikes independently controlled different digits of the virtual hand with one or two degrees of freedom. 2) Microstimulation through individual electrodes of the two USEAs evoked up to 106 different percepts, covering much of the phantom hand. The subject discriminated among five perceived stimulus locations, and between two somatosensory submodalities at a single location. 3) USEA-evoked percepts, mimicking contact with either a near or distal virtual target, were used to terminate movements of the virtual hand controlled with USEA recordings comprised wholly or mostly of EMG. These results further indicate that USEAs can help restore sensory and motor function after hand loss.

Epidural electrocorticography of phantom hand movement following long-term upper-limb amputation.

Introduction: Prostheses for upper-limb amputees are currently controlled by either myoelectric or peripheral neural signals. Performance and dexterity of these devices is still limited, particularly when it comes to controlling hand function. Movement-related brain activity might serve as a complementary bio-signal for motor control of hand prosthesis.Methods: We introduced a methodology to implant a cortical interface without direct exposure of the brain surface in an upper-limb amputee. This bi-directional interface enabled us to explore the cortical physiology following long-term transhumeral amputation. In addition, we investigated neurofeedback of electrocorticographic brain activity related to the patient’s motor imagery to open his missing hand, i.e., phantom hand movement, for real-time control of a virtual hand prosthesis.Results: Both event-related brain activity and cortical stimulation revealed mutually overlapping cortical representations of the phantom hand. Phantom hand movements could be robustly classified and the patient required only three training sessions to gain reliable control of the virtual hand prosthesis in an online closed-loop paradigm that discriminated between hand opening and rest.Conclusion: Epidural implants may constitute a powerful and safe alternative communication pathway between the brain and external devices for upper-limb amputees, thereby facilitating the integrated use of different signal sources for more intuitive and specific control of multi-functional devices in clinical use.

Primary somatosensory cortex hand representation dynamically modulated by motor output

The brain’s primary motor and primary somatosensory cortices are generally viewed as functionally distinct entities. Here we show by means of magnetoencephalography with a phantom-limb patient, that movement of the phantom hand leads to a change in the response of the primary somatosensory cortex to tactile stimulation. This change correlates with the described conscious perception and suggests a greater degree of functional unification between the primary motor and somatosensory cortices than is currently realized. We suggest that this may reflect the evolution of this part of the human brain, which is thought to have occurred from an undifferentiated sensorimotor cortex.

Treatment of phantom limb pain (PLP) based on augmented reality and gaming controlled by myoelectric pattern recognition: a case study of a chronic PLP patient

A variety of treatments have been historically used to alleviate phantom limb pain (PLP) with varying efficacy. Recently, virtual reality (VR) has been employed as a more sophisticated mirror therapy. Despite the advantages of VR over a conventional mirror, this approach has retained the use of the contralateral limb and is therefore restricted to unilateral amputees. Moreover, this strategy disregards the actual effort made by the patient to produce phantom motions. In this work, we investigate a treatment in which the virtual limb responds directly to myoelectric activity at the stump, while the illusion of a restored limb is enhanced through augmented reality (AR). Further, phantom motions are facilitated and encouraged through gaming. The proposed set of technologies was administered to a chronic PLP patient who has shown resistance to a variety of treatments (including mirror therapy) for 48 years. Individual and simultaneous phantom movements were predicted using myoelectric pattern recognition and were then used as input for VR and AR environments, as well as for a racing game. The sustained level of pain reported by the patient was gradually reduced to complete pain-free periods. The phantom posture initially reported as a strongly closed fist was gradually relaxed, interestingly resembling the neutral posture displayed by the virtual limb. The patient acquired the ability to freely move his phantom limb, and a telescopic effect was observed where the position of the phantom hand was restored to the anatomically correct distance. More importantly, the effect of the interventions was positively and noticeably perceived by the patient and his relatives. Despite the limitation of a single case study, the successful results of the proposed system in a patient for whom other medical and non-medical treatments have been ineffective justifies and motivates further investigation in a wider study.

Revealing the invisible: the paradox of picturing a phantom limb

Illustrations of phantom limbs are intriguing as they depict an invisible perception. But such illustrations are also important: they provide a form of objectivity to phenomena, which particularly in the past, have often stretched credulity. Acknowledging the paradox of using images to reveal an absent though sensate body part, depictions of phantom limbs are discussed from the neurological perspective, starting with medieval pictures that showed the miraculous restoration of limbs, and which possibly represented pictorial metaphors for a phantom limb. Centuries later, phantom limbs-whether resulting from amputation or deafferentation-became illustrated, and some reasons for their illustration are considered. Although often depicted by others, the most precise and perhaps revealing illustrations of these phantoms have been those made when patients guide the artist, or draw the phantom themselves. In the case of phantom pains, the painful component too is sometimes illustrated, again, as with the miraculous, in metaphorical terms. More recently, depictions of phantoms have also been revealing in studies of some underlying mechanisms of phantom phenomena, notably in demonstrating novel patterns of referred sensations after amputation and attributable to cortical plasticity. Mention is made of photographs of phantom hands visualized using a mirror box, such visualization recalling full circle the miraculous restoration of limbs pictured in the past. The nature of the outline of the phantom is included in a discussion of demarcation of an invisible body part, before concluding that images of phantom limbs provide an invaluable background to understanding and studying these remarkable sensory phenomena.

Distributed Systems Robust to Hand Loading Based on Nonresonant Elements

ABSTRACTMiniature and multiband internal antenna systems are strongly required in emergent multifunction wireless devices. Recent techniques are focused on properly exciting ground plane radiation modes through nonresonant elements. These solutions remove the need of including quarter‐wavelength resonant antennas featured by a considerable size. Nevertheless, in this new scenario, the complexity moves toward not only the reduction of the size of the elements used to excite the ground plane mode but also to the simplification of the radiofrequency system used to attain impedance matching. This article proposes the use of distributed systems based on nonresonant elements for solving the bandwidth and efficiency limitations of previous solutions while adding robustness to hand loading effects. Two different feeding schemes, an in‐phase and an out‐of‐phase feeding scheme are simulated, measured, and compared in free‐space as well as regarding the presence of a phantom hand. The proposal provides octo‐band operation and attains a radiating system robust to hand loading effects capable of properly operating in nine communication standards, LTE700, GSM850, GSM900, DCS, PCS, UMTS, LTE2100, LTE2300, and LTE2500. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2307–2317, 2013

Effects of visual information on perceived posture of an experimental phantom foot

Our previous studies showed that a fully extended finger, wrist, and elbow became a flexed phantom hand and arm with ischemic anesthesia, and vice versa (Inui et al. in J Physiol 589:5775-5784, 2011, Exp Brain Res 221:369-375, 2012a, Exp Brain Res 218:487-494, 2012b). It was anticipated that if the ankle and knee were fixed in full extension or flexion before and during ischemic anesthesia, the perceived positions would move in the opposite direction. The present study examined what happened when participants looked at their fixed foot and leg at the end of the anesthesia. Using the left ankle and knee, ten healthy participants demonstrated the perceived postures of the right joints during an ischemic block of the right thigh (40 min) and after they looked at the right joints at the end of the block. When the right ankle and knee were fully extended before and during the block, the final joints were perceived as flexed by all participants, and vice versa. Although there was no significant difference between joints for the magnitude of the perceived changes in flexion, the magnitude in the knee was larger than that in the ankle in extension. At the end of the experiment, when participants were allowed to see their foot, its perceived position reverted to that indicated by them earlier, during the first 25 min of cuff inflation. This new finding suggests that the position of limbs is coded by visual input more dominantly than by proprioceptive input in the brain.

Adaptive Haptic Control for Telerobotics Transitioning Between Free, Soft, and Hard Environments

This paper presents an adaptive haptic control for a one degree-of-freedom master-slave teleoperated device. The aim is to reduce excessive collision forces that occur when there are significant time delays in master-slave communication. The control design also allows the operator to move the slave in free space and in a soft medium. Previous approaches to haptic teleoperation typically design for either movement in a medium or constrained contact with a solid surface; then, it is up to the operator to avoid collisions or precisely anticipate collisions. The proposed control runs on the slave side inner loop, with no time delay, and tracks commanded forces from the outer loop. A Lyapunov-stable backstepping-with-tuning-functions design provides a way to ensure smooth forces are applied that guarantee stability in the presence of unmodeled environmental stiffness and viscosity. Experiments using a Phantom hand controller interacting with simulated environment show that collision forces are substantially reduced compared to two other control methods. In collision-free operation, the performance is comparable to other methods.

Systematic changes in the perceived posture of the wrist and elbow during formation of a phantom hand and arm

Our previous study showed that a fully flexed or extended hand became perceived as an extended or flexed 'phantom' hand as ischemic anesthesia progressed (Inui et al. in J Physiol 589:5775-5784, 2011). Here, we examined what happened if the hand was held in the midposition before and during the anesthesia. Twenty healthy participants reported the perceived postures of their right wrist and elbow during an ischemic block of the right upper arm using the left hand and arm. If the actual arm and hand were fully extended, then the perceived position of the elbow and wrist moved toward flexion. Conversely, if they were fully flexed, then the perceived position of the joints moved toward extension. However, when the hand was held in the midposition before and during the anesthesia, the position of the wrist was perceived to be in the same position. Hence, the fully flexed or extended position of a limb was essential for systematic changes in the perceived posture of the limb during the anesthesia. Because the start of these changes occurred as somatosensory inputs were declining, the changes depended on the fading inputs from strongly stretched muscle and skin during the anesthesia.

Disentangling motor execution from motor imagery with the phantom limb

Amputees can move their phantom limb at will. These 'movements without movements' have generally been considered as motor imagery rather than motor execution, but amputees can in fact perform both executed and imagined movements with their phantom and they report distinct perceptions during each task. Behavioural evidence for this dual ability comes from the fact that executed movements are associated with stump muscle contractions whereas imagined movements are not, and that phantom executed movements are slower than intact hand executed movements whereas the speed of imagined movements is identical for both hands. Since neither execution nor imagination produces any visible movement, we hypothesized that the perceptual difference between these two motor tasks relies on the activation of distinct cerebral networks. Using functional magnetic resonance imaging and changes in functional connectivity (dynamic causal modelling), we examined the activity associated with imagined and executed movements of the intact and phantom hands of 14 upper-limb amputees. Distinct but partially overlapping cerebral networks were active during both executed and imagined phantom limb movements (both performed at the same speed). A region of interest analysis revealed a 'switch' between execution and imagination; during execution there was more activity in the primary somatosensory cortex, the primary motor cortex and the anterior lobe of the cerebellum, while during imagination there was more activity in the parietal and occipital lobes, and the posterior lobe of the cerebellum. In overlapping areas, task-related differences were detected in the location of activation peaks. The dynamic causal modelling analysis further confirmed the presence of a clear neurophysiological distinction between imagination and execution, as motor imagery and motor execution had opposite effects on the supplementary motor area-primary motor cortex network. This is the first imaging evidence that the neurophysiological network activated during phantom limb movements is similar to that of executed movements of intact limbs and differs from the phantom limb imagination network. The dual ability of amputees to execute and imagine movements of their phantom limb and the fact that these two tasks activate distinct cortical networks are important factors to consider when designing rehabilitation programmes for the treatment of phantom limb pain.

Can maladaptive cortical plasticity form new sensory experiences? Revisiting phantom pain

Phantom pain has become an influential example of maladaptive cortical plasticity. According to this model, sensory deprivation following limb amputation allows for intra-regional invasion of neighbouring cortical representations into the former hand area of the primary sensorimotor cortex, which gives rise to pain sensations. Over the years, this model was extended to explain other disorders of pain, motor control and tinnitus, and has inspired rehabilitation strategies. Yet, other research, demonstrating that phantom hand representation is maintained in the sensorimotor system, and that phantom pain can be triggered by bottom-up aberrant inputs, may call this model to question. Using fMRI, we identified the cortical area representing the missing hand in a group of 18 arm amputees. This allowed us to directly study changes in the ‘phantom’ cortex associated with chronic phantom pain, using functional connectivity and voxel-based morphometry. We show that, while loss of sensory input is generally characterized by structural degeneration of the deprived sensorimotor cortex, the experience of persistent pain was associated with preserved intra-regional structure and functional organization. Furthermore, consistent with the dissociative nature of phantom sensations from other sensory experiences, phantom pain is also associated with reduced long-range inter-regional functional connectivity. We propose that this disrupted inter-regional connectivity may be consequential, rather than causal, of the retained yet isolated local representation of phantom pain. We therefore propose that, contrary to the maladaptive model, cortical plasticity occurs when powerful and long-lasting subjective sensory experience, most likely due to peripheral inputs, is decoupled from the external sensory environment.

Dynamic changes in the perceived posture of the hand during ischaemic anaesthesia of the arm

Contorted 'phantom' limbs often form when sensory inputs are removed, but the neural mechanisms underlying their formation are poorly understood. We tracked the evolution of an experimental phantom hand during ischaemic anaesthesia of the arm. In the first study subjects showed the perceived posture of their hand and fingers using a model hand. Surprisingly, if the wrist and fingers were held straight before and during anaesthesia, the final phantom hand was bent at the wrist and fingers, but if the wrist and fingers were flexed before and during anaesthesia, the final phantom was extended at wrist and fingers. Hence, no 'default' posture existed for the phantom hand. The final perceived posture may depend on the initial and evolving sensory input during the block rather than the final sensory input (which should not differ for the two postures). In the second study subjects selected templates to indicate the perceived size of their hand. Perceived hand size increased by 34 ± 4% (mean ± 95% CI) during the block. Sensory changes were monitored. In all subjects, impairment of large-fibre cutaneous sensation began distally with von Frey thresholds increasing before cold detection thresholds (Aδ fibres) increased. Some C fibres subserving heat pain still conducted at the end of cuff inflation. These data suggest that changes in both perceived hand size and perceived position of the finger joints develop early when large-fibre cutaneous sensation is beginning to degrade. Hence it is unlikely that block of small-fibre afferents is critical for phantom formation in an ischaemic block.

Brachial Plexus Block in Phantom Limb Pain: A Case Report

The purpose of this case report is twofold: first, to present evidence of long-lasting relief in a patient suffering from phantom limb pain after pharmacologically blocking his plexus brachialis and, second, to replicate results from a previous study focusing on cortical reorganization and phantom limb pain. Before regional anesthesia, the patient suffered from a phantom hand that cramped and was immovable. We performed a diagnostic axillary blockade of the brachial plexus to differentiate peripheral from more central contributions to phantom limb pain. During blockade of the brachial plexus, the patient reported a reduction of phantom limb pain for the first time following years of suffering and a complete loss of cramping together with muscle relaxation of the phantom hand. Additionally, we found cortical reorganization in the primary somatosensory cortex (re-reorganization). Strikingly, the relaxed phantom limb together with the reduction of phantom limb pain remained preserved even 6 months after blockade of the brachial plexus. A single temporary blockade of the brachial plexus may relieve phantom limb pain and unpleasant phantom feelings (cramping) for an extended period.

Object Discrimination With an Artificial Hand Using Electrical Stimulation of Peripheral Tactile and Proprioceptive Pathways With Intrafascicular Electrodes

Trans-radial amputee subjects were implanted with intrafascicular electrodes in the stumps of the median and ulnar nerves. Electrical stimulation through these electrodes was used to provide sensations of touch and finger position referred to the amputated hand. Two subjects were asked to identify different objects as to size and stiffness by manipulating them with a myo-electric hand without visual or auditory cues. Both subjects were provided with information about contact force with the objects via tactile sensations referred to their phantom hands. One subject, who was provided with information about finger position in the prosthetic hand via a different tactile sensation referred to his phantom hand, was unable to correctly identify the objects. The other subject, who received information about finger position via a proprioceptive sensation referred to his phantom hand, correctly identified the objects at a level statistically significantly above chance performance.

The appearance of new phantom fingers post-amputation in a phocomelus

We report the unusual case of a woman with right upper limb phocomelia who, post-amputation of her right hand following trauma, sprouted a phantom hand that contained five digits, including a phantom thumb and index finger that had been absent since her birth. These two phantom digits were initially half normal size, however, more than three decades later, with mirror visual feedback treatment, she was able to elongate them to normal length. This suggests that a hardwired representation of a complete hand had always been present in her brain, but inhibited by the presence of afferents from the phocomelic hand. Amputation of the phocomelic hand then led to disinhibition of this dormant representation, and the emergence of a phantom hand with five fingers, which was then further enhanced by false visual feedback from a mirror. The case powerfully demonstrates the interaction of nature and nurture in creating and sustaining body image.

Phantom hands: a window into how we perceive limb position and movement

Phantom hands: a window into how we perceive limb position and movement

“Pulling telescoped phantoms out of the stump”: Manipulating the perceived position of phantom limbs using a full-body illusion

Most amputees experience phantom limbs, or the sensation that their amputated limb is still attached to the body. Phantom limbs can be perceived in the location previously occupied by the intact limb, or they can gradually retract inside the stump, a phenomenon referred to as “telescoping”. Telescoping is relevant from a clinical point of view, as it tends to be related to increased levels of phantom pain. In the current study we demonstrate how a full-body illusion can be used to temporarily revoke telescoping sensations in upper limb amputees. During this illusion participants view the body of a mannequin from a first person perspective while being subjected to synchronized visuo-tactile stimulation through stroking, which makes them experience the mannequin’s body as their own. In Experiment 1 we used an intact mannequin, and showed that amputees can experience ownership of an intact body as well as referral of touch from both hands of the mannequin. In Experiment 2 and 3 we used an amputated mannequin, and demonstrated that depending on the spatial location of the strokes applied to the mannequin, participants experienced their phantom hand to either remain telescoped, or to actually be located below the stump. The effects were supported by subjective data from questionnaires, as well as verbal reports of the perceived location of the phantom hand in a visual judgment task. These findings are of particular interest, as they show that the temporary revoking of telescoping sensations does not necessarily have to involve the visualization of an intact hand or illusory movement of the phantom (as in the rubber hand illusion or mirror visual feedback therapy), but that it can also be obtained through mere referral of touch from the stump to the spatial location corresponding to that previously occupied by the intact hand. Moreover, our study also provides preliminary evidence for the fact that these manipulations can have an effect on phantom pain sensations.