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Examples of mislocalization to the phantom limb (shaded area) on the first, the second and the third examinations in Patient T48 following touch stimulation ( A ), and on the first and second examinations in Patient T58 following painful stimulation ( B ).
Source publication
We report a follow-up study on seven arm amputees in whom magnetic source imaging had originally revealed a strong correlation between the amount of cortical invasion of the deafferented cortex and the amount of pain evoked sensation mislocalized to the phantom limb. This re-examination was performed in order to corroborate the phenomenon of misloc...
Contexts in source publication
Context 1
... both the first and the second examination, stimulation in each of the somaesthetic modalities tested resulted in sensation referred to the phantom limb in at least some individuals. Results from stimulation in single modalities are illustrated in Fig. 1 for two patients (T58, T48). Points from which mislocalization could be elicited were located ipsilateral and contralateral to the amputation side. They involved the face, the ventral trunk and the opposite shoulder. In neither of the examinations was an exact topographic mapping detected involving a strict one-to-one relation between ...
Context 2
... rise to mislocalization in the first examination (Table 1). All other stimulation sites that elicited mislocalization in either the first or the second sensory evaluation were different in the two examinations. The same held true for the third examination of one patient (T48) after 1.5 years. As indicated in the diagrams of individual cases in Fig. 1A and B, even in those few cases where stimulation of a site elicited sensations referred to the phantom in both the first and the second (or third) examination, the quality of that perception was quite variable across these examinations. For example, in subject T58 (Fig. 1B) painful stimulation at the right side of the forehead produced ...
Context 3
... (T48) after 1.5 years. As indicated in the diagrams of individual cases in Fig. 1A and B, even in those few cases where stimulation of a site elicited sensations referred to the phantom in both the first and the second (or third) examination, the quality of that perception was quite variable across these examinations. For example, in subject T58 (Fig. 1B) painful stimulation at the right side of the forehead produced a sensation of intense touch in the whole phantom hand in the first examination and a sensation of pressure radiating into the phantom hand as well as a feeling of extending phantom fingers in the second ...
Context 4
... that nociceptive processing itself is subject to modulations of central excitability (Hillman and Wall, 1969;Cook et al., 1987) and that the mechanisms may be similar to those that influence the extent of cortical invasion on magnetic source imaging. The perceived modality of referred sensation frequently differed from the modality of stimulation (Fig. 1A and B). Mostly, the referred sensation in the phantom limb was felt as a tingling or a pressure. Therefore, reorganized sensory processing seems to be inaccurate, not only with respect to localization but also with respect to ...
Citations
... Il trend promettente in direzione di una riduzione dell'intensità del dolore a seguito dell'implementazione della RV potrebbe essere legato in parte al ripristino della rappresentazione compromessa dell'arto che determinava l'incongruenza tra feedback sensoriale atteso e reale (Ambron et al., 2021). In effetti, il dolore da arto fantasma sembrerebbe indotto da un'integrazione sensomotoria incongruente associata a un arto mancante o non attivo (McCabe et al., 2005;Mc Cabe et al., 2007) e strettamente legato alla riorganizzazione della corteccia cerebrale (Knecht et al., 1998;Lotze et al., 2001). A causa del legame funzionale riscontrato tra la riorganizzazione corticale e il dolore da arto fantasma, gli approcci terapeutici come la realtà virtuale che mirano a modificare la prima influenzano probabilmente anche il secondo (Birbaumer et al., 1997). ...
Introduction
The therapeutic approach to post-amputation phantom limb pain is very complex; several treatments are available but none is widely accepted or clearly superior to the others. One of the most recent and innovative therapies is virtual reality (VR). There is growing interest that immersive VR can reduce chronic persistent pain including phantom limb pain.
Purpose
To evaluate the effectiveness of VR on phantom limb pain in amputees
Methods
Systematic review of clinical trials by querying six biomedical databases (Cochrane library, PubMed, EMBASE, CINAHL, Web of Science, Scopus). Screening of records for title/abstract reading and of eligible studies for full text reading. Methodological quality assessment with RoB 2. Analysis of key study characteristics and narrative summary of results.
Results
Five clinical trials (N=117 participants) with a high risk of bias met the inclusion criteria. In studies whose participants had undergone upper limb (3 studies, n=35) or lower limb (2 studies, n=82) amputation, VR reduced pain intensity statistically significantly (p < 0.05) or non-significantly (p > 0.05), respectively.
Discussion and Conclusions
Due to the high risk of bias and the limitations manifested by the available trials, the results obtained are scarcely generalisable and to be considered with great caution due to the low confidence in their reliability. The VR intervention at present costs much more than alternative interventions. However, it cannot be ruled out that in the future it may have an increasing diffusion in clinical practice and an increasingly intrusive role in the field of algology in general and in the management of chronic pain, including phantom limb pain, specifically.
Key words
virtual reality, amputation, phantom limb pain
... Shortly after, Flor and others (1995) extended this finding by demonstrating a strong correlation between the extent of functional reorganization in S1 and the intensity of PLP. Since then, several studies confirmed this association using different types of measurement: electroencephalography (Flor and others 2001;Grüsser and others 2001), magnetoencephalography (Flor and others 1998;Knecht and others 1996), and fMRI (Lotze and others 2001;MacIver and others 2008;Raffin and others 2016). Moreover, the link between S1 reorganization and PLP was affirmed for lower limb amputees (Huse and others 2001;Meyer and others 2012;Zheng and others 2021). ...
... In hand amputees, for instance, studies demonstrate that the stimulation of the lip results not exclusively in the expected lip representation but in additional activation of central representations of the hand (Elbert and others 1994;Flor and others 1995). Moreover, stimulation at different body locations can result in feelings of the amputated fingers (Knecht and others 1996;Knecht and others 1998), sometimes even with an ordered representation of the fingers at the face (Ramachandran and others 1992). Specifically, others (1996, 1998) are among the researchers who investigated this consequently. ...
... However, the locations from which they were able to evoke referred sensations were constant for only a short period, at least a day, but differed considerably 4 wk or 1.5 y later. Even more critical in this context, the number of locations correlates with the reported strength of PLP (Knecht and others 1996;Knecht and others 1998). This activation within an unpredicted cortical somatosensory representation should result in a prediction error. ...
There is an ongoing discussion on the relevance of brain reorganization following amputation for phantom limb pain. Recent attempts to provide explanations for seemingly controversial findings—specifically, maladaptive plasticity versus persistent functional representation as a complementary process—acknowledged that reorganization in the primary somatosensory cortex is not sufficient to explain phantom limb pain satisfactorily. Here we provide theoretical considerations that might help integrate the data reviewed and suppose a possible additional driver of the development of phantom limb pain—namely, an error in interoceptive predictions to somatosensory sensations and movements of the missing limb. Finally, we derive empirically testable consequences based on our considerations to guide future research.
... It is well established that the human brain has substantial capacity for plasticity as a function of experience (Draganski and May, 2008). Use-dependent structural reorganization of human S1 has been observed after deprivation of afferent input because of limb amputation (Elbert et al., 1994;Flor et al., 1995;Knecht, 1998) or peripheral nerve lesion (Henderson et al., 2011). Whether or not the human genital field is capable to structurally adapt to its normal use is entirely unknown. ...
The precise location of the human female genital representation field in the primary somatosensory cortex (S1) is controversial and its capacity for use-associated structural variation as a function of sexual behavior remains unknown. We used a functional magnetic resonance imaging (fMRI)-compatible sensory-tactile stimulation paradigm to functionally map the location of the female genital representation field in 20 adult women. Neural response to tactile stimulation of the clitoral region (vs right hand) identified individually-diverse focal bilateral activations in dorsolateral areas of S1 (BA1–BA3) in alignment with anatomic location. We next used cortical surface analyses to assess structural thickness across the 10 individually most activated vertices per hemisphere for each woman. We show that frequency of sexual intercourse within 12 months is correlated with structural thickness of the individually-mapped left genital field. Our results provide a precise functional localization of the female genital field and provide support for use-associated structural variation of the human genital cortex.
SIGNIFICANCE STATEMENT We provide a precise location of the human female genital field in the somatosensory cortex and, for the first time, provide evidence in support of structural variation of the human genital field in association with frequency of genital contact. Our study represents a significant methodological advance by individually mapping genital fields for structural analyses. On a secondary level, our results suggest that any study investigating changes in the human genital field must map the field individually to achieve sufficient precision. Our results pave the way for future research into the plasticity of the human genital cortex as a function of normal or adverse experience as well as changes in pathologic conditions, i.e., sexual dysfunction, sexual deviation, or sexual risk-taking behavior.
... However, subsequent studies using more systematic stimulation paradigms found that phantom referred sensations could be evoked by touches on various body-parts. This includes body-parts that have not been considered to invade the missing hand cortical area, such as the feet, trunk, and neck, in some cases even contralateral to the missing hand [3,[15][16][17][18][19]. These reports, as well as recent fMRI studies that dispute the existence of a large-scale S1 facial remapping post-amputation in humans [20][21][22][23], challenge the perceptual remapping hypothesis. ...
... Here we used vibrotactile stimulation (used to evoke reliable referred sensations in previous reports, e.g., [15,17,18]) of ten body-parts in a group of upper-limb amputees experiencing spontaneous phantom sensations. We also tested two control groups who do not report feelings of phantom sensations: two-handed individuals and individuals born with one hand. ...
Background
Some amputees have been prominently reported to perceive touch applied to their face as coming from their phantom hand. These referred sensations have been classically interpreted as the perceptual correlate of cortical remapping of the face into the neighbouring missing- hand territory in primary somatosensory cortex (S1). We investigated whether referred sensations reports are associated with S1 remapping or can instead be attributed to demand characteristics (e.g., compliance, expectation, and suggestion), which were uncontrolled in previous studies.
Methods
Unilateral upper-limb amputees (N=18), congenital one-handers (N=19), and two-handers (N=20) were repeatedly stimulated with PC-controlled vibrations on ten body-parts and asked to report on each trial the occurrence of any concurrent sensations on their hand(s). To further manipulate expectations, we gave participants the suggestion that some of these vibrations had a higher probability to evoke referred sensations. To evaluate remapping, we analysed fMRI data in S1 from two tasks involving movement of facial and whole-body parts, using univariate and multivariate approaches.
Results
The frequency and distribution of reported referred sensations were similar across groups, with higher frequencies in the high expectancy condition. In amputees, referred sensations were evoked by stimulation of multiple body-parts and reported in both the intact and phantom hand. The group profiles for referred sensations reports were not consistent with the observed patterns of S1 remapping.
Conclusions
These findings weaken the interpretation of referred sensations as a perceptual consequence of post-amputation S1 remapping and reveal the need to account for demand characteristics when evaluating anomalous perceptual and germane phenomena.
... Several studies have showed that the referred sensation might not be observed in all amputees. Moreover, in some patients, it might gradually fade away while the other patients continue to perceive referred sensations (Borsook et al. 1998;Halligan et al. 1994;Htut et al. 2006;Knecht et al. 1998). Furthermore, an uncommon phenomenon called 'Mitempfindung' (sympathy) described as the perceived sensation created by the same stimulus in different body regions can occur in healthy individuals, and may reflect abnormal central connectivity (Bean 1981;Evans 1976;Richter 1977;Schott 1988;Sterling 1973). ...
The aim of this study is to examine cortical plasticity and to analyze cortical reorganization following hand and facial transplantation, using functional magnetic resonance imaging. Patients who had undergone full-face transplantation, hand transplantation and scapular arm replantation, as well as healthy controls, participated in the study. The perioral area and volar surfaces of the index finger and thumb were stimulated and images were acquired using 3 T functional MRI. The areas of the somatosensory cortex representing the hand and face are different in size and shape due to experience-dependent plasticity. Therefore, a new and more adaptive volume of interest analysis was created whereby the radiuses of the VOI masks were defined by the peak intensity of subsequent clusters. For each control subject, the distribution of activated voxels was observed for various cluster defining thresholds in order to determine the mean number of activated voxels for each stimulation inside the defined region. The determined numbers of voxels per subject were extracted from the defined regions using a binary search algorithm. Subsequently, the distances between the weighted centers of the extracted regions were calculated and compared. In transplant patients, the weighted centers of the hand and face clusters were separated at same-sized volumes. Two of the rehabilitated full-face transplant patients converge to the range of the controls. As a result, the weighted distribution of somatotopy indicated previous and present cortical reorganization. Additionally, referred sensation was assessed in two full-face transplant and one replant patient with activation clusters partially in BA40 in the Inferior Parietal Lobule.
... Because the present study aimed to minimize patients' burden and fatigue, we used a simplified procedure to determine RSAs. A previous study used a standardized procedure involving multiple sensory modalities, such as heat and vibration (Knecht et al., 1998). Future studies should implement a standardized procedure. ...
Background:
Patients with brachial plexus avulsion (BPA) usually experience phantom sensations and phantom limb pain (PLP) in the deafferented limb. It has been suggested that evoking the sensation of touch in the deafferented limb by stimulating referred sensation areas (RSAs) on the cheek or shoulder might alleviate PLP. However, feasible rehabilitation techniques using this approach have not been reported.
Objective:
The present study sought to examine the analgesic effects of simple electrical stimulation of RSAs in BPA patients with PLP.
Methods:
Study 1: Electrical stimulation of RSAs for 60 minutes was conducted for six BPA patients suffering from PLP to examine short-term analgesic effects. Study 2: A single case design experiment was conducted with two BPA patients to investigate whether electrical stimulation of RSAs was more effective for alleviating PLP than control electrical stimulation (electrical stimulation of sites on side opposite to the RSAs), and to elucidate the long-term effects of electrical stimulation of RSAs.
Results:
Study 1: Electrical stimulation of RSAs evoked phantom touch sensations in the deafferented limb, and significantly alleviated PLP (p < 0.05). Study 2: PLP was alleviated more after electrical stimulation on RSAs compared with control electrical stimulation (p < 0.05). However, the analgesic effects of electrical stimulation on RSAs were observed only in the short term, not in the long term (p > 0.05).
Conclusions:
Electrical stimulation of RSAs not only evoked phantom touch sensation but also alleviated PLP in the short term. The results indicate that electrical stimulation of RSAs may provide a useful practical rehabilitation technique for PLP. Future studies will be required to clarify the mechanisms underlying immediate PLP alleviation via electrical stimulation of RSAs.
... The lack of afferent input from an amputated limb after surgery leads to shrinking of the corresponding area in the somatosensory cortex. Neighbouring cortical areas (representing other anatomical regions) expand as a result [11,12]. These changes present clinically with the patient not only experiencing phantom limb pain after amputation, but the phantom pain also being produced by touching a completely different part of the body sometimes (for example, feeling pain in the amputated arm when the face is touched) [13]. ...
... It is unclear how phantom limb pain occurs, although there are a number of competing theories including sensory-motor incongruence (similar to motion sickness) (Harris, 1999), cortical reorganization (Flor et al., 1995;Knecht et al., 1998;Lotze et al., 1999Lotze et al., , 2001Grüsser et al., 2001), reduced functional connectivity (Makin et al., 2013), and stochastic entanglement (Ortiz-Catalan, 2018). The latter theory, which is also the most recent one, postulates that stochastic entanglement can occur between networks responsible for sensorimotor processing and paint perception. ...
This manuscript reviews historical and recent studies that focus on supplementary sensory feedback for use in upper limb prostheses. It shows that the inability of many studies to speak to the issue of meaningful performance improvements in real-life scenarios is caused by the complexity of the interactions of supplementary sensory feedback with other types of feedback along with other portions of the motor control process. To do this, the present manuscript frames the question of supplementary feedback from the perspective of computational motor control, providing a brief review of the main advances in that field over the last 20 years. It then separates the studies on the closed-loop prosthesis control into distinct categories, which are defined by relating the impact of feedback to the relevant components of the motor control framework, and reviews the work that has been done over the last 50+ years in each of those categories. It ends with a discussion of the studies, along with suggestions for experimental construction and connections with other areas of research, such as machine learning.
... Moreover, one study revealed a positive association between sensory input and cortical activation (Fornander et al., 2010). Therefore, an initial increase in the activated volume may alter the return of sensory function after a nerve injury, which indicates an important and potential mechanism for neurological rehabilitation (Knecht et al., 1998). ...
Importance: To develop a practical program in the early phase after nerve repair for more rapid return of function.
Objective: To investigate the effects of touch-observation and task-based mirror therapy on the sensorimotor outcomes of patients with nerve repair.
Design: An assessor-blinded study with a randomized controlled design.
Setting: University hospital.
Participants: We recruited 12 patients with median or ulnar nerve repair between the level of midpalm and elbow referred by the plastic surgeons.
Intervention: The patients were randomized into touch-observation and task-based mirror therapy or control groups, and both groups received training for 12 wk.
Outcomes and Measures: The Semmes–Weinstein monofilament (SWM) test, two-point discrimination test, Purdue Pegboard Test (PPT), Minnesota Manual Dexterity Test (MMDT), and pinch-holding-up activity test were assessed at pretreatment, immediately after treatment, and 12 wk after the last treatment.
Results: The experimental group showed greater improvements in the results of the pinch-holding-up activity test and the PPT Unilateral Pin Insertion, Bilateral Pin Insertion, and Assembly subtests. However, change on the SWM test revealed no significant difference between the two groups.
Conclusions and Relevance: Touch-observation and task-based mirror therapy is an effective but low-cost treatment protocol to optimize sensorimotor control and functional capability of the upper limb in patients with peripheral nerve injury.
... Le traumatisme crânien se révèle être la première cause de handicap neurologique chez le sujet jeune (Ghajar, 2000). (Pons et al., 1991) et chez des patients après amputation (Flor et al., 1995 ;Knecht et al., 1998), ces auteurs suggèrent que la taille des représentations corticales des parties du corps chez l'Homme adulte dépend de la quantité d'utilisation de ces parties. ...
La thèse présentée a pour objectif d’analyser dans le cadre de l’approche dynamique du contrôle moteur la coordination motrice de participants sains et cérébrolésés évoluant sur un nouvel outil de rééducation, le cheval mécanique. L’analyse de ces coordinations spontanément adoptées par les individus sur ce cheval, ou modifiées suite à l’apprentissage d’une nouvelle coordination grâce à l’ajout d’un biofeedback visuel en temps réel, conduit à participer à (i) déterminer l’utilité du biofeedback dans ce type de tâche et (ii) à évaluer l’intérêt d’un protocole de 24 séances prescrites par nos soins et réalisées sur cet outil. L’objectif final est alors de participer à l’élaboration d’un protocole de rééducation posturale pour une population de patients cérébrolésés. La première étude a permis de mettre en avant le rôle joué par l’expertise dans l’évolution des coordinations posturales des individus sur le cheval mécanique amenant les cavalières expertes vers une coordination posturale plus adaptée (i.e. maintien des patterns en phase et en antiphase), en comparaison aux novices. Par ces analyses, la coordination tronc/cheval mesurée en antiphase, a été mise en lumière, correspondant ainsi à la coordination retrouvée dans l’activité équestre réelle. Par ailleurs, la mise en place d’une méthode d’apprentissage (étude 2) a permis de modifier le comportement postural des individus après seulement 3 séances, selon les conditions d’apprentissage prescrites. La fréquence d’oscillation du cheval avait un impact important sur la coordination des participants, qui adoptaient une coordination en antiphase (fort attracteur) lorsque la contrainte environnementale était élevée. Toutefois, ces observations n’ont pas permis de démontrer le réel intérêt de l’ajout d’un biofeedback visuel dans l’apprentissage d’une nouvelle coordination posturale chez des sujets sains. Enfin, la troisième étude réalisée chez des patients cérébrolésés a montré l’intérêt de cette nouvelle méthode de rééducation sur la coordination posturale de ces patients. Après 24 séances, leur coordination était différente de celle du groupe témoin, permettant de mettre en avant leur capacité à s’adapter aux contraintes et à développer des modes de coordinations posturales spécifiques (tronc/cheval en antiphase) à l’activité afin d’optimiser au mieux leur posture.
