Cortical Areas Involved in Virtual Movement of Phantom Limbs: Comparison with Normal Subjects

Case report: A combination of mirror therapy and magnetic stimulation to the sacral plexus relieved phantom limb pain in a patient

Phantom limb pain (PLP) is a common sequela of amputation, experienced by 50-80% of amputees. Oral analgesics as the first-line therapy have limited effects. Since PLP usually affects activities of daily living and the psychological conditions of patients, effective treatments are imperatively needed. In this case study, a 49-year-old man was admitted to our hospital because of uncontrollable paroxysmal pain in his missing and residual leg. Due to severe injuries in a truck accident, the right lower limb of the patient was surgically amputated ~5 years ago. Around 1 month after amputation, he felt pain in his lost leg and PLP was diagnosed. Then, he started taking oral analgesics, but the pain still occurred. After admission on July 9, 2022, the patient received treatments of mirror therapy and magnetic stimulation to the sacral plexus. 1-month treatments reduced the frequency and intensity of pain in the phantom limb and the stump, without any adverse events. Analysis of high-resolution three-dimensional T1-weighted brain volume images at the end of 2-month treatments showed alterations in the thickness of cortex regions related to pain processing, compared to that before treatment. This case study gives us hints that one or both interventions of mirror therapy and sacral plexus magnetic stimulation effectively relieved PLP and stump limb pain. These non-invasive, low-cost and easily conducted treatments could be good options for PLP. But randomized controlled trials with a large number of cases are required to confirm their efficacy and safety.

Spontaneous activity patterns in human motor cortex replay evoked activity patterns for hand movements

Spontaneous brain activity, measured with resting state fMRI (R-fMRI), is correlated among regions that are co-activated by behavioral tasks. It is unclear, however, whether spatial patterns of spontaneous activity within a cortical region correspond to spatial patterns of activity evoked by specific stimuli, actions, or mental states. The current study investigated the hypothesis that spontaneous activity in motor cortex represents motor patterns commonly occurring in daily life. To test this hypothesis 15 healthy participants were scanned while performing four different hand movements. Three movements (Grip, Extend, Pinch) were ecological involving grip and grasp hand movements; one control movement involving the rotation of the wrist was not ecological and infrequent (Shake). They were also scanned at rest before and after the execution of the motor tasks (resting-state scans). Using the task data, we identified movement-specific patterns in the primary motor cortex. These task-defined patterns were compared to resting-state patterns in the same motor region. We also performed a control analysis within the primary visual cortex. We found that spontaneous activity patterns in the primary motor cortex were more like task patterns for ecological than control movements. In contrast, there was no difference between ecological and control hand movements in the primary visual area. These findings provide evidence that spontaneous activity in human motor cortex forms fine-scale, patterned representations associated with behaviors that frequently occur in daily life.

Sensorimotor Integration and Pain Perception: Mechanisms Integrating Nociceptive Processing. A Systematic Review and ALE-Meta Analysis

Pain treatment services and clinical indicators of pain chronicity focus on afferent nociceptive projections and psychological markers of pain perception with little focus on motor processes. Research supports a strong role for the motor system both in terms of pain related disability and in descending pain modulation. However, there is little understanding of the neurological regions implicated in pain-motor interactions and how the motor and sensory systems interact under conditions of pain. We performed an ALE meta-analysis on two clinical cohorts with atypical sensory and motor processes under conditions of pain and no pain. Persons with sensory altered processing (SAP) and no pain presented with greater activity in the precentral and supplementary motor area relative to persons with self-reported pain. In persons with motor altered processing (MAP), there appeared to be a suppression of activity in key pain regions such as the insula, thalamus, and postcentral gyrus. As such, activation within the motor system may play a critical role in dampening pain symptoms in persons with SAP, and in suppressing activity in key pain regions of the brain in persons with MAP. Future research endeavors should focus on understanding how sensory and motor processes interact both to understand disability and discover new treatment avenues.

Typical somatomotor physiology of the hand is preserved in a patient with an amputated arm: An ECoG case study

Electrophysiological signals in the human motor system may change in different ways after deafferentation, with some studies emphasizing reorganization while others propose retained physiology. Understanding whether motor electrophysiology is retained over longer periods of time can be invaluable for patients with paralysis (e.g. ALS or brainstem stroke) when signals from sensorimotor areas may be used for communication or control over neural prosthetic devices. In addition, a maintained electrophysiology can potentially benefit the treatment of phantom limb pains through prolonged use of these signals in a brain-machine interface (BCI). Here, we were presented with the unique opportunity to investigate the physiology of the sensorimotor cortex in a patient with an amputated arm using electrocorticographic (ECoG) measurements. While implanted with an ECoG grid for clinical evaluation of electrical stimulation for phantom limb pain, the patient performed attempted finger movements with the contralateral (lost) hand and executed finger movements with the ipsilateral (healthy) hand. The electrophysiology of the sensorimotor cortex contralateral to the amputated hand remained very similar to that of hand movement in healthy people, with a spatially focused increase of high-frequency band (65-175 Hz; HFB) power over the hand region and a distributed decrease in low-frequency band (15-28 Hz; LFB) power. The representation of the three different fingers (thumb, index and little) remained intact and HFB patterns could be decoded using support vector learning at single-trial classification accuracies of >90%, based on the first 1-3 s of the HFB response. These results indicate that hand representations are largely retained in the motor cortex. The intact physiological response of the amputated hand, the high distinguishability of the fingers and fast temporal peak are encouraging for neural prosthetic devices that target the sensorimotor cortex.

Aberrant activity in an intact residual muscle is associated with phantom limb pain in above-knee amputees

Many individuals who undergo limb amputation experience persistent phantom limb pain (PLP), but the underlying mechanisms of PLP are unknown. The traditional hypothesis was that PLP resulted from maladaptive plasticity in sensorimotor cortex that degrades the neural representation of the missing limb. However, a recent study of individuals with upper limb amputations has shown that PLP is correlated with aberrant electromyographic (EMG) activity in residual muscles, posited to reflect a retargeting of efferent projections from a preserved representation of a missing limb. Here, we assessed EMG activity in a residual thigh muscle (vastus lateralis, VL) in patients with transfemoral amputations during cyclical movements of a phantom foot. VL activity on the amputated side was compared to that recorded on patients' intact side while they moved both the phantom and intact feet synchronously. VL activity in the patient group was also compared to a sample of control participants with no amputation. We show that phantom foot movement is associated with greater VL activity in the amputated leg than that seen in the intact leg as well as that exhibited by controls. The magnitude of residual VL activity was also positively related to ratings of PLP. These results show that phantom limb movement is associated with aberrant activity in a residual muscle after lower-limb amputation and provide evidence of a positive relationship between this activity and phantom limb pain.NEW & NOTEWORTHY This study is the first to assess residual muscle activity during movement of a phantom limb in individuals with lower limb amputations. We find that phantom foot movement is associated with aberrant recruitment of a residual thigh muscle and that this aberrant activity is related to phantom limb pain.

Changes in Temporal and Spatial Patterns of Intrinsic Brain Activity and Functional Connectivity in Upper-Limb Amputees: An fMRI Study

Background

Amputation in adults is a serious procedure or traumatic outcome, one that leads to a possible “remapping” of limb representations (somatotopy) in the motor and sensory cortex. The temporal and spatial extent underlying reorganization of somatotopy is unclear. The aim of this study was to better understand how local and global structural plasticity in sensory-motor cortical networks changes temporally and spatially after upper-limb amputation.

Methods

We studied 8 healthy nonamputee control subjects and 16 complete upper-limb amputees. Resting-state MRI (rs-fMRI) was used to measure local and large-scale relative differences (compared to controls) in both the amplitude of low-frequency fluctuations (ALFF) and degree of centrality (DC) at 2 months, 6 months, and 12 months after traumatic amputation.

Results

In amputees, rs-fMRI scans revealed differences in spatial patterns of ALFF and DC among brain regions over time. Significant relative increases in ALFF and DC were detected not only in the sensory and motor cortex but also in related cortical regions believed to be involved in cognition and motor planning. We observed changes in the magnitude of ALFFs in the pre- and postcentral gyrus and primary sensory cortex, as well as in the anterior cingulate, parahippocampal gyrus, and hippocampus, 2 months after the amputation. The regional distribution of increases/decreases in ALFFs and DC documented at 2-month postamputation was very different from those at 6 and 12-month postamputation.

Conclusion

Local and wide-spread changes in ALFFs in the sensorimotor cortex and cognitive-related brain regions after upper-limb amputation may imply dysfunction not only in sensory and motor function but also in areas responsible for sensorimotor integration and motor planning. These results suggest that cortical reorganization after upper extremity deafferentation is temporally and spatially more complicated than previously appreciated, affecting DC in widespread regions.

Neuroimaging the pain network - Implications for treatment

In this chapter, we provide an overview of neuroimaging studies in chronic pain. We start with an introduction about the phenomenology of pain. In the following section, the application of functional and structural imaging techniques is shown in selected chronic pain syndromes (chronic back pain, fibromyalgia syndrome (FMS), phantom limb pain, and complex regional pain syndrome (CRPS)), and commonalities and peculiarities of imaging correlates across different types of chronic pain are discussed. We conclude this chapter with implications for treatments, with focus on behavioral interventions, sensory and motor trainings, and mirror and motor imagery trainings.

Phantom motor execution as a treatment for phantom limb pain: protocol of an international, double-blind, randomised controlled clinical trial

INTRODUCTION

Phantom limb pain (PLP) is a chronic condition that can greatly diminish quality of life. Control over the phantom limb and exercise of such control have been hypothesised to reverse maladaptive brain changes correlated to PLP. Preliminary investigations have shown that decoding motor volition using myoelectric pattern recognition, while providing real-time feedback via virtual and augmented reality (VR-AR), facilitates phantom motor execution (PME) and reduces PLP. Here we present the study protocol for an international (seven countries), multicentre (nine clinics), double-blind, randomised controlled clinical trial to assess the effectiveness of PME in alleviating PLP.

METHODS AND ANALYSIS

Sixty-seven subjects suffering from PLP in upper or lower limbs are randomly assigned to PME or phantom motor imagery (PMI) interventions. Subjects allocated to either treatment receive 15 interventions and are exposed to the same VR-AR environments using the same device. The only difference between interventions is whether phantom movements are actually performed (PME) or just imagined (PMI). Complete evaluations are conducted at baseline and at intervention completion, as well as 1, 3 and 6 months later using an intention-to-treat (ITT) approach. Changes in PLP measured using the Pain Rating Index between the first and last session are the primary measure of efficacy. Secondary outcomes include: frequency, duration, quality of pain, intrusion of pain in activities of daily living and sleep, disability associated to pain, pain self-efficacy, frequency of depressed mood, presence of catastrophising thinking, health-related quality of life and clinically significant change as patient's own impression. Follow-up interviews are conducted up to 6 months after the treatment.

ETHICS AND DISSEMINATION

The study is performed in agreement with the Declaration of Helsinki and under approval by the governing ethical committees of each participating clinic. The results will be published according to the Consolidated Standards of Reporting Trials guidelines in a peer-reviewed journal.

TRIAL REGISTRATION NUMBER

NCT03112928; Pre-results.

Preservation of hand movement representation in the sensorimotor areas of amputees

Denervation due to amputation is known to induce cortical reorganization in the sensorimotor cortex. Although there is evidence that reorganization does not lead to a complete loss of the representation of the phantom limb, it is unclear to what extent detailed, finger-specific activation patterns are preserved in motor cortex, an issue that is also relevant for development of brain-computer interface solutions for paralysed people. We applied machine learning to obtain a quantitative measure for the functional organization within the motor and adjacent cortices in amputees, using high resolution functional MRI and attempted hand gestures. Subjects with above-elbow arm amputation (n = 8) and non-amputated controls (n = 9) made several gestures with either their right or left hand. Amputees attempted to make gestures with their amputated hand. Images were acquired using 7 T functional MRI. The sensorimotor cortex was divided into four regions, and activity patterns were classified in individual subjects using a support vector machine. Classification scores were significantly above chance for all subjects and all hands, and were highly similar between amputees and controls in most regions. Decodability of phantom movements from primary motor cortex reached the levels of right hand movements in controls. Attempted movements were successfully decoded from primary sensory cortex in amputees, albeit lower than in controls but well above chance level despite absence of somatosensory feedback. There was no significant correlation between decodability and years since amputation, or age. The ability to decode attempted gestures demonstrates that the detailed hand representation is preserved in motor cortex and adjacent regions after denervation. This encourages targeting sensorimotor activity patterns for development of brain-computer interfaces.

Decoding spoken phonemes from sensorimotor cortex with high-density ECoG grids

For people who cannot communicate due to severe paralysis or involuntary movements, technology that decodes intended speech from the brain may offer an alternative means of communication. If decoding proves to be feasible, intracranial Brain-Computer Interface systems can be developed which are designed to translate decoded speech into computer generated speech or to instructions for controlling assistive devices. Recent advances suggest that such decoding may be feasible from sensorimotor cortex, but it is not clear how this challenge can be approached best. One approach is to identify and discriminate elements of spoken language, such as phonemes. We investigated feasibility of decoding four spoken phonemes from the sensorimotor face area, using electrocorticographic signals obtained with high-density electrode grids. Several decoding algorithms including spatiotemporal matched filters, spatial matched filters and support vector machines were compared. Phonemes could be classified correctly at a level of over 75% with spatiotemporal matched filters. Support Vector machine analysis reached a similar level, but spatial matched filters yielded significantly lower scores. The most informative electrodes were clustered along the central sulcus. Highest scores were achieved from time windows centered around voice onset time, but a 500 ms window before onset time could also be classified significantly. The results suggest that phoneme production involves a sequence of robust and reproducible activity patterns on the cortical surface. Importantly, decoding requires inclusion of temporal information to capture the rapid shifts of robust patterns associated with articulator muscle group contraction during production of a phoneme. The high classification scores are likely to be enabled by the use of high density grids, and by the use of discrete phonemes. Implications for use in Brain-Computer Interfaces are discussed.

Neural correlates of evoked phantom limb sensations

•

We present a neural network related to evoked phantom sensations in amputees.

•

Such networks were not related to the stimulation from the residual limb.

•

Difference in intra- and inter-hemispheric interactions between amputees and yoked controls.

•

This finding yields novel insights into the neural basis of phantom sensation.

Previous work showed the existence of changes in the topographic organization within the somatosensory cortex (SI) in amputees with phantom limb pain, however, the link between nonpainful phantom sensations such as cramping or tingling or the percept of the limb and cortical changes is less clear.

We used functional magnetic resonance imaging (fMRI) in a highly selective group of limb amputees who experienced inducible and reproducible nonpainful phantom sensations. A standardized procedure was used to locate body sites eliciting phantom sensations in each amputee. Selected body sites that could systematically evoke phantom sensations were stimulated using electrical pulses in order to induce phasic phantom sensations. Homologous body parts were also stimulated in a group of matched controls.

Activations related to evoked phantom sensations were found bilaterally in SI and the intraparietal sulci (IPS), which significantly correlated with the intensity of evoked phantom sensations. In addition, we found differences in intra- and interhemispheric interaction between amputees and controls during evoked phantom sensations. We assume that phantom sensations might be associated with a functional decoupling between bilateral SI and IPS, possibly resulting from transcallosal reorganization mechanisms following amputation.

Imagery As a Core Process in the Creativity of Successful and Awarded Artists and Scientists and Its Neurobiological Correlates

This perspective paper presents an integration of neuroimaging and phenomenological data obtained in a sample that included highly creative, internationally awarded scientists and/or artists. The cerebral blood flow was evaluated during the performance of standardized creativity tasks from the Torrance Tests of Creative Thinking Verbal Form. The phenomenological data comprised both, their experiences and processes related to their creative careers and their experiences during the performance of the creative thinking tasks during the acquisition of the brain imaging data. Highly creative individuals presented a significantly higher activation of areas involved in motor imagery and described that their creative process is frequently triggered by the spontaneous and often surprising emergence of what is being named here as primordial imagery: a sudden, multimodal, multiintegrative, highly condensed representation that is germinative, unleashing insight and multiple associations and possibilities for meaning. As evidenced in creativity, imagery is a process through which we perceive our own minds, allowing us further symbolization and access to our thoughts, possibly facilitating neural pathways.

Observation of limb movements reduces phantom limb pain in bilateral amputees

Background

Mirror therapy has been demonstrated to reduce phantom limb pain (PLP) experienced by unilateral limb amputees. Research suggests that the visual feedback of observing a limb moving in the mirror is critical for therapeutic efficacy.

Objective

Since mirror therapy is not an option for bilateral lower limb amputees, the purpose of this study was to determine if direct observation of another person’s limbs could be used to relieve PLP.

Methods

We randomly assigned 20 bilateral lower limb amputees with PLP to visual observation (n = 11) or mental visualization (n = 9) treatment. Treatment consisted of seven discrete movements which were mimicked by the amputee’s phantom limbs moving while visually observing the experimenter’s limbs moving, or closing the eyes while visualizing and attempting the movements with their phantom limbs, respectively. Participants performed movements for 20 min daily for 1 month. Response to therapy was measured using a 100-mm visual analog scale (VAS) and the McGill Short-Form Pain Questionnaire (SF-MPQ).

Results

Direct visual observation significantly reduced PLP in both legs (P < 0.05). Amputees assigned to the mental visualization condition did not show a significant reduction in PLP.

Interpretation

Direct visual observation therapy is an inexpensive and effective treatment for PLP that is accessible to bilateral lower limb amputees.

Intra-operative transdural electric stimulation in awake patient: target refining for motor cortex stimulation

INTRODUCTION

Most authors perform the implantation of epidural electrodes for motor cortex stimulation (MCS) under general anesthesia, using navigation merely based on anatomic landmarks or in combination with intra-operative sensory evoked potentials (SEP) for functional localization. However, intra-operative SEP can only provide the localization of central sulcus in patients who present sensory pathways which are at least partially preserved. Conversely, there are massive deafferentation pain syndromes (e.g., brachial plexus avulsion or amputation) in which the peripheral sensory pathways are severely or totally injured, precluding the use of intra-operative SEP. Objective. The authors present a simple technique for functional localization and intra-operative mapping of motor cortex by the implementation of transdural electrical stimulation of cerebral cortex for target refining of motor cortex during cortical electrode implantation procedures.

METHODS

Thirteen patients with complete brachial plexus root avulsion suffering from severe neuropathic pain in the affected limb were included in this report. First, the anatomical location of the motor cortex of the hand was stereotactically determined by the hand knob within the central sulcus. Functional mapping of cortex was performed by transdural bipolar electrical stimulation under local anesthesia, so patients were fully awake during the whole time of cortical mapping. The cortical mapping oriented the placement of epidural electrodes for chronic cortical stimulation for treatment of neuropathic pain.

RESULTS

Stereotactic MR images of the hand knob were considered a satisfactory landmark for the motor area of the hand in all patients. On top of the anatomical landmark, transdural electrical stimulation (4.0-6.0 mA, 30-60 Hz and pulse width of 1 ms) gave vivid sensations of movement in the deafferented hand, forearm, and arm. The phantom sensation was elicited with lower current than usual motor mapping in patients with intact limbs. It was possible to delineate the spatial map of the phantom hand on the cortical surface with acceptable resolution. The sensation of wrist flexion was elicited in all; most of the patients had clear distinction of the thumb and index. The remaining fingers were not perceived individually. The cortical area responsive to the thumb tended to occupy a lateral position related to the areas of the other fingers, following the maps of the normal homunculus. The evoked sensation was restricted to the period of stimulation, and it stopped as soon as that was discontinued. The stimulation also evoked emotional responses related to sensation of limb movement.

CONCLUSION

The proposed technique was useful for target refining in implantation of epidural electrode for motor cortex stimulation. Further studies are required to investigate if target refining by intra-operative mapping will significantly improve the results in the treatment of refractory pain.

Enhanced activation of motor execution networks using action observation combined with imagination of lower limb movements

The combination of first-person observation and motor imagery, i.e. first-person observation of limbs with online motor imagination, is commonly used in interactive 3D computer gaming and in some movie scenes. These scenarios are designed to induce a cognitive process in which a subject imagines himself/herself acting as the agent in the displayed movement situation. Despite the ubiquity of this type of interaction and its therapeutic potential, its relationship to passive observation and imitation during observation has not been directly studied using an interactive paradigm. In the present study we show activation resulting from observation, coupled with online imagination and with online imitation of a goal-directed lower limb movement using functional MRI (fMRI) in a mixed block/event-related design. Healthy volunteers viewed a video (first-person perspective) of a foot kicking a ball. They were instructed to observe-only the action (O), observe and simultaneously imagine performing the action (O-MI), or imitate the action (O-IMIT). We found that when O-MI was compared to O, activation was enhanced in the ventralpremotor cortex bilaterally, left inferior parietal lobule and left insula. The O-MI and O-IMIT conditions shared many activation foci in motor relevant areas as confirmed by conjunction analysis. These results show that (i) combining observation with motor imagery (O-MI) enhances activation compared to observation-only (O) in the relevant foot motor network and in regions responsible for attention, for control of goal-directed movements and for the awareness of causing an action, and (ii) it is possible to extensively activate the motor execution network using O-MI, even in the absence of overt movement. Our results may have implications for the development of novel virtual reality interactions for neurorehabilitation interventions and other applications involving training of motor tasks.

Imagining is Not Doing but Involves Specific Motor Commands: A Review of Experimental Data Related to Motor Inhibition

There is now compelling evidence that motor imagery (MI) and actual movement share common neural substrate. However, the question of how MI inhibits the transmission of motor commands into the efferent pathways in order to prevent any movement is largely unresolved. Similarly, little is known about the nature of the electromyographic activity that is apparent during MI. In addressing these gaps in the literature, the present paper argues that MI includes motor execution commands for muscle contractions which are blocked at some level of the motor system by inhibitory mechanisms. We first assemble data from neuroimaging studies that demonstrate that the neural networks mediating MI and motor performance are not totally overlapping, thereby highlighting potential differences between MI and actual motor execution. We then review MI data indicating the presence of subliminal muscular activity reflecting the intrinsic characteristics of the motor command as well as increased corticomotor excitability. The third section not only considers the inhibitory mechanisms involved during MI but also examines how the brain resolves the problem of issuing the motor command for action while supervising motor inhibition when people engage in voluntary movement during MI. The last part of the paper draws on imagery research in clinical contexts to suggest that some patients move while imagining an action, although they are not aware of such movements. In particular, experimental data from amputees as well as from patients with Parkinson’s disease are discussed. We also review recent studies based on comparing brain activity in tetraplegic patients with that from healthy matched controls that provide insights into inhibitory processes during MI. We conclude by arguing that based on available evidence, a multifactorial explanation of motor inhibition during MI is warranted.

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.

Using graded motor imagery for complex regional pain syndrome in clinical practice: failure to improve pain

BACKGROUND

There is good evidence from studies conducted in a single-centre research setting for the efficacy of graded motor imagery (GMI) treatment, a complex physiotherapy intervention, to reduce pain in long-standing complex regional pain syndrome (CRPS). However, whether GMI is effective in clinical practice is not established.

AIM

To establish whether GMI is effective in clinical practice.

METHODS

We undertook a prospective audit of GMI treatment at two UK centres with a special interest in the management of patients with CRPS. All patients received GMI, in conjunction with a range of other 'best practice' physical and psychological interventions.

RESULTS

The patients' average pain intensities did not improve with treatment [centre 1: n = 20, pre-post numeric rating scale (NRS) difference 0.6 [confidence interval (CI) -0.3 to 1.5]; centre 2: n = 12, pre-post NRS difference 0.2 (CI: -0.9 to 1.2)]. Patients at centre 1 reported significant functional improvement. Improved performance on left/right judgement replicated in both centres seen in the clinical trials.

CONCLUSIONS

The failure of our real-world implementation of GMI suggests that better understanding of both the GMI methodology and its interaction with other treatment methods is required to ensure that GMI research results can be translated into clinical practice. Our results highlight challenges with the translation of complex interventions for chronic pain conditions into clinical practice.

Time Course of Cortical Plasticity After Facial Nerve Palsy

Background. Functional connectivity is defined as the temporal correlation between spatially remote neurophysiological events. This method has become particularly useful for studying neuroplasticity to detect changes in the collaboration of brain areas during cortical reorganization. Methods. In this article, the authors longitudinally studied voxel-based morphometry and resting state functional magnetic resonance imaging 10 times in 1 patient during the course of Bell palsy (idiopathic facial nerve palsy) up to complete clinical recovery. Results. Morphometric analysis revealed a significant alteration in the face area of the primary motor cortex (M1) contralateral to the paretic face, with an initial increase in gray matter concentration. Functional connectivity analysis between the M1 and other parts of the facial motor network revealed acutely disrupted intrahemispheric connectivity but unaltered interhemispheric connectivity. The disrupted functional connectivity was most pronounced on the day of the onset of symptoms, with a subsequent return toward normal during the course of recovery. This time course was found to differ between the selected parts of the facial motor network. However, the increase in functional connectivity strength preceded clinical recovery in all areas and reached a stable level before the patient fully recovered. Conclusion. These results demonstrate that recovery from facial nerve palsy is complemented by cortical reorganization, with pronounced changes of functional connectivity that precede clinical recovery.

The moving phantom: motor execution or motor imagery?

Amputees who have a phantom limb often report the ability to move this phantom voluntarily. In the literature, phantom limb movements are generally considered to reflect motor imagery rather than motor execution. The aim of this study was to investigate whether amputees distinguish between executing a movement of the phantom limb and imagining moving the missing limb. We examined the capacity of 19 upper-limb amputees to execute and imagine movements of both their phantom and intact limbs. Their behaviour was compared with that of 18 age-matched normal controls. A global questionnaire-based assessment of imagery ability and timed tests showed that amputees can indeed distinguish between motor execution and motor imagery with the phantom limb, and that the former is associated with activity in stump muscles while the latter is not. Amputation reduced the speed of voluntary movements with the phantom limb but did not change the speed of imagined movements, suggesting that the absence of the limb specifically affects the ability to voluntarily move the phantom but does not change the ability to imagine moving the missing limb. These results suggest that under some conditions, for example amputation, the predicted sensory consequences of a motor command are sufficient to evoke the sensation of voluntary movement. They also suggest that the distinction between imagined and executed movements should be taken into consideration when designing research protocols to investigate the analgesic effects of sensorimotor feedback.

Decreasing phantom limb pain through observation of action and imagery: a case series

BACKGROUND

Phantom limb pain is often resistant to treatment. Techniques based on visual-kinesthetic feedback could help reduce it.

OBJECTIVE

The objective of the current study was to test if a novel intervention combining observation and imagination of movements can reduce phantom limb pain.

METHODS

This single-case multiple baseline study included six persons with upper or lower limb phantom pain. Participants' pain and imagery abilities were assessed by questionnaires. After a 3-5-week baseline, participants received a two-step intervention of 8 weeks. Intervention 1 was conducted at the laboratory with a therapist (two sessions/week) and at home (three sessions/week); and Intervention 2 was conducted at home only (five times/week). Interventions combined observation and imagination of missing limb movements. Participants rated their pain level and their ease to imagine daily throughout the study.

RESULTS

Time series analyses showed that three participants rated their pain gradually and significantly lower during Intervention 1. During Intervention 2, additional changes in pain slopes were not significant. Four participants reported a reduction of pain greater than 30% from baseline to the end of Intervention 2, and only one maintained his gains after 6 months. Group analyses confirmed that average pain levels were lower after intervention than at baseline and had returned to baseline after 6 months. Social support, degree of functionality, and perception of control about their lives prior to the intervention correlated significantly with pain reduction.

CONCLUSIONS

Persons with phantom limb pain may benefit from this novel intervention combining observation and motor imagery. Additional studies are needed to confirm our findings, elucidate mechanisms, and identify patients likely to respond.

Event-Related Functional Magnetic Resonance Images during the Perception of Phantom Limb. A Brushing Task

The phantom limb phenomenon has been used in amputee patients as a paradigm to study plasticity, mainly of the sensorimotor cortex. Nevertheless, most functional studies have been done in upper limb amputee patients using magnetoencephalography and functional magnetic resonance image imaging (fMRI). In addition, the actual experience of phantom limb sensation has not been widely used to study the neural mechanism of the human brain as a conscious knowledge of the phantom limb perception like the integration of the body image in amputee patients. fMRI studies of patients with lower limb amputation have recently been published, but none of these used an event-related design to try to observe only the stimulus application, correlating images with the subject's indication of phantom perception and discarding images with no phantom perception. In this work, we used the event-related fMRI design in two right-handed patients with identical right, transfemoral amputations, performing the same sensitive stimulation in a 3.0 T MR scanner. For comparison, we applied the same paradigm to six control subjects to compare the resulting functional maps. We found areas with statistical significance in the sensorimotor cortex contralateral to the site of stimulation, in the parietal lobe in Brodmann areas 3 in both cases (Patients and Control Subjects), but we also found activation in the Brodmann areas 6, 40, and 5 with stimulation of the stump. We observed a specific activation of the frontoparietal circuit during phantom limb perception in both amputee patients.

Supernumerary phantom limbs in spinal cord injury

STUDY DESIGN AND OBJECTIVES

Case report and review of supernumerary phantom limbs in patients suffering from spinal cord injury (SCI).

SETTING

SCI rehabilitation centre.

CASE REPORT

After a ski accident, a 71-year-old man suffered an incomplete SCI (level C3; AIS C, central cord syndrome), with a C3/C4 dislocation fracture. From the first week after injury, he experienced a phantom duplication of both upper limbs that lasted for 7 months. The supernumerary limbs were only occasionally related to painful sensation, specifically when they were perceived as crossed on his trunk. Although the painful sensations were responsive to pain medication, the presence of the illusory limb sensations were persistent. During neurological recovery, the supernumerary limbs gradually disappeared. A rubber hand illusion paradigm was used twice during recovery to monitor the patient's ability to integrate visual, tactile and proprioceptive stimuli.

CONCLUSION

Overall, the clinical relevance of supernumerary phantom limbs is not clear, specific treatment protocols have not yet been developed, and the underlying neural mechanisms are not fully understood. Supernumerary phantom limbs have been previously reported in patients with (sub)cortical lesions, but might be rather undocumented in patients suffering from traumatic SCI. For the appropriate diagnosis and treatment after SCI, supernumerary phantoms should be distinguished from other phantom sensations and pain syndromes after SCI.

Behavioral and Electrophysiological Evidence of Motor Cortex Activation Related to an Amputated Limb: A Multisensorial Approach

Phantom limb sensations may be linked to motor activities in the deafferented cortices of amputees, with artificial visual feedback of an amputated limb leading to enhanced phantom sensations. The present study was designed to verify if cortical motor activity related to an amputated limb can be triggered by visual input using an objective behavioral measure and with a neurophysiological correlate. Trauma amputees and normally limbed subjects showed superior performance in a mirror-drawing task when the mirror was placed sagittally (giving visual feedback of the amputated/inactive limb) compared with when it was placed frontally. Measurement of lateralized movement-related brain potentials showed that, under the lateral mirror condition, contralateral motor activity of the viewed hand was observed in both normal subjects and trauma amputees. In contrast, this activity was not observed in subjects with congenital limb absence. These findings suggest that, in traumatic amputees, motor enhancement due to visualization of the movements of the missing limb reflects the effectiveness of motor commands to the missing limb, strengthening the hypothesis of the functional survival of deafferented cortical motor areas.

Seeing the phantom: a functional magnetic resonance imaging study of a supernumerary phantom limb

OBJECTIVE

Supernumerary phantom limb (SPL) is a rare neurological manifestation where patients with a severe stroke-induced sensorimotor deficit experience the illusory presence of an extra limb that duplicates a real one. The illusion is most often experienced as a somesthetic phantom, but rarer SPLs may be intentionally triggered or seen. Here, we report the case of a left visual, tactile, and intentional SPL caused by right subcortical damage in a nondeluded woman.

METHODS

Using functional magnetic resonance imaging, we investigated the multimodal nature of this phantom, which the patient claimed to be able see, use, and move intentionally. The patient participated in a series of sensorimotor and motor imagery tasks involving the right, the left plegic, and the SPL's hand.

RESULTS

Right premotor and motor regions were engaged when she imagined that she was scratching her left cheek with her left plegic hand, whereas when she performed the same task with the SPL, additional left middle occipital areas were recruited. Moreover, comparison of responses induced by left cheek (subjectively feasible) versus right cheek scratching (reportedly unfeasible movement) with the SPL demonstrated significant activation in right somesthetic areas.

INTERPRETATION

These findings demonstrate that intentional movements of a seen and felt SPL activate premotor and motor areas together with visual and sensory cortex, confirming its multimodal dimension and the reliability of the patient's verbal reports. This observation, interpreted for cortical deafferentation/disconnection caused by subcortical brain damage, constitutes a new but theoretically predictable entity among disorders of bodily awareness.

Motor control over the phantom limb in above-elbow amputees and its relationship with phantom limb pain

Recent evidence shows that the primary motor cortex continues to send motor commands when amputees execute phantom movements. These commands are retargeted toward the remaining stump muscles as a result of motor system reorganization. As amputation-induced reorganization in the primary motor cortex has been associated with phantom limb pain we hypothesized that the motor control of the phantom limb would differ between amputees with and without phantom limb pain. Eight above-elbow amputees with or without pain were included in the study. They were asked to produce cyclic movements with their phantom limb (hand, wrist, and elbow movements) while simultaneously reproducing the same movement with the intact limb. The time needed to complete a movement cycle and its amplitude were derived from the kinematics of the intact limb. Electromyographic (EMG) activity from different stump muscles and from the homologous muscles on the intact side was recorded. Different EMG patterns were recorded in the stump muscles depending on the movement produced, showing that different phantom movements are associated with distinct motor commands. Phantom limb pain was associated with some aspects of phantom limb motor control. The time needed to complete a full cycle of a phantom movement was systematically shorter in subjects without phantom limb pain. Also, the amount of EMG modulation recorded in a stump muscle during a phantom hand movement was positively correlated with the intensity of phantom limb pain. Since phantom hand movement-related EMG patterns in above-elbow stump muscles can be considered as a marker of motor system reorganization, this result indirectly supports the hypothesis that amputation-induced plasticity is associated with phantom limb pain severity. The discordance between the (amputated) hand motor command and the feedback from above-elbow muscles might partially explain why subjects exhibiting large EMG modulation during phantom hand movement have more phantom limb pain.

Selective activation of human finger muscles after stroke or amputation

Individuated finger movements of the human hand require selective activation of particular sets of muscles. Such selective activation is controlled primarily by the motor cortex via the corticospinal tract. Is this selectivity therefore lost when lesions damage the corticospinal tract? Or when the motor cortex reorganizes after amputation? We studied finger movements in normal human subjects and in patients who had recovered substantially from pure motor hemiparesis caused by lacunar strokes, which damage the corticospinal tract without affecting other pathways. Even after substantial recovery from these strokes, individuation of finger movements remained reduced-both for flexion/extension and for adduction/ abduction motion of the fingers. Stroke subjects regained the ability to move the instructed digit through a normal range, but unintentional motion of other digits was increased. This increase did not result from a change in the passive biomechanical coupling of the fingers. Rather, voluntary contractions of muscles that move the intended digit were accompanied by inappropriate contractions in muscles acting on additional digits. These observations suggest that the normal corticospinal system produces individuated finger movements not only by selectively activating certain muscles, but also by suppressing activation of other muscles during voluntary effort to move a given digit. In a separate experiment, reversible amputation of the hand was produced in normal subjects by ischemic nerve block at the wrist. Motor output to the intrinsic muscles and sensory input both become blocked under these conditions, effectively amputating the hand from the nervous system. But the long extrinsic muscles that flex and extend the digits remain normally innervated, and thus flexion forces still can be generated at the fingertips. During reversible amputation of the hand produced by ischemic nerve block, the ability of subjects to activate subdivisions of extrinsic muscles and to exert flexion force at individual fingertips continued to show essentially normal selectivity. Voluntary activation of the remaining muscles thus continues to be selective after amputation, in spite of both the loss of sensory input from the amputated hand, and reorganization within the primary motor cortex. During cortical reorganization after amputation, then, voluntary patterns of motor output intended for finger muscles may not be lost. We therefore examined activity in the stump muscles of above-elbow amputees, who have no remaining hand muscles. Different movements of the phantom hand were accompanied by different patterns of EMG in remaining proximal muscles, distinct from the EMG patterns associated with movement of the phantom elbow. We infer that voluntary motor output patterns that normally control finger movements after amputation may become diverted to remaining proximal muscles.

Upper limb amputees can be induced to experience a rubber hand as their own

We describe how upper limb amputees can be made to experience a rubber hand as part of their own body. This was accomplished by applying synchronous touches to the stump, which was out of view, and to the index finger of a rubber hand, placed in full view (26 cm medial to the stump). This elicited an illusion of sensing touch on the artificial hand, rather than on the stump and a feeling of ownership of the rubber hand developed. This effect was supported by quantitative subjective reports in the form of questionnaires, behavioural data in the form of misreaching in a pointing task when asked to localize the position of the touch, and physiological evidence obtained by skin conductance responses when threatening the hand prosthesis. Our findings outline a simple method for transferring tactile sensations from the stump to a prosthetic limb by tricking the brain, thereby making an important contribution to the field of neuroprosthetics where a major goal is to develop artificial limbs that feel like a real parts of the body.

Selectivity of voluntary finger flexion during ischemic nerve block of the hand

During ischemic nerve block of an extremity the cortical representations of muscles proximal to the block are known to expand, increasing the overlap of different muscle representations. Such reorganization mimics that seen in actual amputees. We investigated whether such changes degrade voluntary control of muscles proximal to the block. Nine subjects produced brief, isometric flexion force selectively with each fingertip before, during, and after ischemic block at the wrist. We recorded the isometric force exerted at the distal phalanx of each digit, along with electromyographic (EMG) activity from intrinsic and extrinsic finger muscles. Despite paralysis of the intrinsic hand muscles, and associated decrements in the flexion forces exerted by the thumb, index, and little fingers, the selectivity of voluntary finger flexion forces and of EMG activity in the extrinsic finger muscles that generated these forces remained unchanged. Our observations indicate that during ischemic nerve block reorganization does not eliminate or degrade motor representations of the temporarily deafferented and paralyzed fingers.

Mechanisms underlying embodiment, disembodiment and loss of embodiment

Bodily experience is a complex, mostly unconscious, process that requires the integration of multiple sensory inputs. This paper reviews the sensory systems involved in internal representations of the body--primarily the proprioceptive, motor, vestibular, and visual systems. Various neurological disorders are defined by aberrations in bodily experience--including the perceptual ablation or disembodiment of body parts, "filling in" of amputated body parts, or reduplication of body parts. These perceptual aberrations are discussed and their implications for the central and peripheral systems involved in updating and retrieving internal representations of the body are highlighted. Bodily perception and egocentric frames of reference can be experimentally manipulated through visual capture (e.g., using rubber limbs), functional adaptation and embodiment of tools and prostheses, and changes in afferent sensory feedback (e.g., through stimulation of muscle spindles). These perceptual illusions are described, and discussed for their implications for the mechanisms underlying bodily perception.

The motor cortex and its role in phantom limb phenomena

Limb amputation results in plasticity of connections between the brain and muscles; the cortical motor representation of the missing limb seemingly disappears. The disappearance of the hand's motor representation is, however, difficult to reconcile with evidence that a perceptual representation of the missing limb persists in the form of a phantom limb endowed with sensory and motor qualities. Here, we argue that despite considerable reorganization within the motor cortex of upper-limb amputees, the representation of the amputated hand does not disappear. We hypothesize that two levels of hand-movement representation coexist within the primary motor cortex; at one level, limb movements are specified in terms of arm and hand motor commands, and at another level, limb movements are specified as muscles synergies. We propose that primary motor cortex reorganization after amputation concerns primarily the upper limb's muscular map but not its motor command map and that the integrity of the motor command map underlies the existence of the phantom limb.

Cerebral blood flow associated with creative performance: A comparative study

Creativity is important for social survival and individual wellbeing; science, art, philosophy and technology have been enriched and expanded by this trait. To our knowledge this is the first study probing differences in brain cerebral blood flow (CBF) between highly creative individuals (scientists and/or artists socially recognized for their contributions to their fields with creativity indexes corresponding to the 99% percentile) and average control subjects while performing a verbal task from the Torrance Tests of Creative Thinking. Additionally, we correlated CBF with creativity dimensions such as fluency, originality and flexibility. Subjects with a high creative performance showed greater CBF activity in right precentral gyrus, right culmen, left and right middle frontal gyrus, right frontal rectal gyrus, left frontal orbital gyrus, and left inferior gyrus (BA 6, 10, 11, 47, 20), and cerebellum; confirming bilateral cerebral contribution. These structures have been involved in cognition, emotion, working memory, and novelty response. The score on the three creativity dimensions--fluency, originality, and flexibility--correlated with CBF activation in right middle frontal gyrus and right rectal gyrus (Brodmann Area 6, 11). Moreover, fluency and flexibility strongly correlated with CBF in left inferior frontal gyrus and originality correlated with CBF in left superior temporal gyrus and cerebellar tonsil. These findings suggest an integration of perceptual, volitional, cognitive and emotional processes in creativity. The higher CBF found in particular brain regions of highly creative individuals during the performance of a creative task provides evidence of a specific neural network related to the creative process.

Examining the influence of the cerebral cortex in range of motion exercise using MEG

In rehabilitating stroke patients, many therapists use range of motion exercise (ROM-ex) at early post onset. There are three general types of ROM-ex: passive, active, and active-assistive ROM-ex is used to prevent joint contracture in paralyzed limbs and to assist in recovery of the central nervous system (CNS). However, its effect on CNS recovery is unclear. Therefore, this study compared the influence of different tasks, including passive and active ROM-ex and imagined extension/flexion at the elbow, on the cerebral cortex. The subjects were six healthy volunteers. We used a magnetoencephalogram (MEG) to measure cerebral cortex activity. In the active ROM-ex task, we confirmed a dipole in the motor area in all subjects. It has been suggested that this dipole is activity of the motor-related field (MRF). By contrast, in the passive ROM-ex experiment, we did not confirm a dipole in the cortex. In addition, in the experiment with no joint motion, in which the subject only imagined moving the elbow joint from flexion to extension, it was possible to estimate a dipole in the motor area. Therefore, an imaginary task might be a possible method of activation when voluntary movement is impossible.

Brain–machine interfaces: past, present and future

Since the original demonstration that electrical activity generated by ensembles of cortical neurons can be employed directly to control a robotic manipulator, research on brain-machine interfaces (BMIs) has experienced an impressive growth. Today BMIs designed for both experimental and clinical studies can translate raw neuronal signals into motor commands that reproduce arm reaching and hand grasping movements in artificial actuators. Clearly, these developments hold promise for the restoration of limb mobility in paralyzed subjects. However, as we review here, before this goal can be reached several bottlenecks have to be passed. These include designing a fully implantable biocompatible recording device, further developing real-time computational algorithms, introducing a method for providing the brain with sensory feedback from the actuators, and designing and building artificial prostheses that can be controlled directly by brain-derived signals. By reaching these milestones, future BMIs will be able to drive and control revolutionary prostheses that feel and act like the human arm.

Cortical correlates of TMS-induced phantom hand movements revealed with concurrent TMS-fMRI

We studied an amputee patient who experiences a conscious sense of movement (SoM) in her phantom hand, without significant activity in remaining muscles, when transcranial magnetic stimulation (TMS) is applied at appropriate intensity over the corresponding sector of contralateral motor cortex. We used the novel methodological combination of TMS during fMRI to reveal the neural correlates of her phantom SoM. A critical contrast concerned trials at intermediate TMS intensities: low enough not to produce overt activity in remaining muscles; but high enough to produce a phantom SoM on approximately half such trials. Comparing trials with versus without a phantom SoM reported phenomenally, for the same intermediate TMS intensities, factored out any non-specific TMS effects on brain activity to reveal neural correlates of the phantom SoM itself. Areas activated included primary motor cortex, dorsal premotor cortex, anterior intraparietal sulcus, and caudal supplementary motor area, regions that are also involved in some hand movement illusions and motor imagery in normals. This adds support to proposals that a conscious sense of movement for the hand can be conveyed by activity within corresponding motor-related cortical structures.

Cortical ensemble adaptation to represent velocity of an artificial actuator controlled by a brain-machine interface

Monkeys can learn to directly control the movements of an artificial actuator by using a brain-machine interface (BMI) driven by the activity of a sample of cortical neurons. Eventually, they can do so without moving their limbs. Neuronal adaptations underlying the transition from control of the limb to control of the actuator are poorly understood. Here, we show that rapid modifications in neuronal representation of velocity of the hand and actuator occur in multiple cortical areas during the operation of a BMI. Initially, monkeys controlled the actuator by moving a hand-held pole. During this period, the BMI was trained to predict the actuator velocity. As the monkeys started using their cortical activity to control the actuator, the activity of individual neurons and neuronal populations became less representative of the animal's hand movements while representing the movements of the actuator. As a result of this adaptation, the animals could eventually stop moving their hands yet continue to control the actuator. These results show that, during BMI control, cortical ensembles represent behaviorally significant motor parameters, even if these are not associated with movements of the animal's own limb.

Clinical applicability of functional MRI

Functional MRI (fMRI) has become the most widely used modality for examining human brain function in basic and clinical neuroscience. As compared to the application of fMRI in basic neuroscience research, clinical fMRI presents unique challenges. A growing body of literature supports the feasibility of clinical fMRI, with the best-studied applications being localization of motor cortex and lateralization of language. While it may be tempting to assume that fMRI will supercede prior approaches, it may turn out that fMRI will be used to complement more difficult or invasive methods rather than replace them entirely. This article focuses on fMRI studies in patients and patient populations. Specific considerations for such applications include pathophysiological effects on functional physiology, brain-behavior correlations in the presence of cognitive or sensorimotor deficits, and test-retest reliability for longitudinal studies.