Does use of a myoelectric prosthesis prevent cortical reorganization and phantom limb pain?
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Adult↗
Biomedical subjects
H Flor
Publications and source records attributed to H Flor.
Conditioned stress-induced analgesia in humans.
The purpose of this experiment was the demonstration of conditioned stress-induced analgesia in humans. Following a baseline day (day 1), two groups of 10 subjects were each exposed to green light as the conditioned stimulus (CS) and mental arithmetic plus noise as the unconditioned stimulus (US) for 5 days (days 2-6), a third group of 10 subjects was only exposed to the US. On the test day (day 7), pain threshold and pain tolerance were tested, while groups 1 and 3 received the green light CS and group 2 received no CS. Group 1 showed a significantly higher pain threshold and higher pain tolerance on the test day, whereas the two control groups did not have altered pain perception. Heart rate data confirmed successful stress induction. Heart rate and blood pressure were unaltered on the test day, thus making cardiovascular mediation of the conditioning effect unlikely. Conditioned stress analgesia might be useful in the understanding of chronic pain-syndromes. Copyright 1999 European Federation of Chapters of the International Association for the Study of Pain.
Journal Article↗
Activation of cortical and cerebellar motor areas during executed and imagined hand movements: an fMRI study.
Brain activation during executed (EM) and imagined movements (IM) of the right and left hand was studied in 10 healthy right-handed subjects using functional magnetic resonance imagining (fMRI). Low electromyographic (EMG) activity of the musculi flexor digitorum superficialis and high vividness of the imagined movements were trained prior to image acquisition. Regional cerebral activation was measured by fMRI during EM and IM and compared to resting conditions. Anatomically selected regions of interest (ROIs) were marked interactively over the entire brain. In each ROI activated pixels above a t value of 2.45 (p<0.01) were counted and analyzed. In all subjects the supplementary motor area (SMA), the premotor cortex (PMC), and the primary motor cortex (M1) showed significant activation during both EM and IM; the somatosensory cortex (S1) was significantly activated only during EM. Ipsilateral cerebellar activation was decreased during IM compared to EM. In the cerebellum, IM and EM differed in their foci of maximal activation: Highest ipsilateral activation of the cerebellum was observed in the anterior lobe (Larsell lobule H IV) during EM, whereas a lower maximum was found about 2-cm dorsolateral (Larsell lobule H VII) during IM. The prefrontal and parietal regions revealed no significant changes during both conditions. The results of cortical activity support the hypothesis that motor imagery and motor performance possess similar neural substrates. The differential activation in the cerebellum during EM and IM is in accordance with the assumption that the posterior cerebellum is involved in the inhibition of movement execution during imagination.
Adult↗
Magnetoencephalographic investigations of cortical reorganization in humans.
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Humans↗
Learned maintenance of pain: muscle tension reduces central nervous system processing of painful stimulation in chronic and subchronic pain patients.
The effect of level of muscle tension on the perception of painful stimuli was assessed in 13 chronic back pain patients, 14 subjects at high risk for chronic back pain, and 14 matched healthy controls. Subjects received painful intracutaneous electric stimuli to the forearm or the lower back while they produced either high or low muscle tension levels. Visual analog scale (VAS) ratings of acute pain were obtained after each trial. Electroencephalograms, electromyograms, skin conductance levels, and blood pressure were measured during the trials. Although subjective pain ratings were not significantly affected by muscle tension levels, the chronic pain patients displayed elevated N150 and N150/P260 amplitudes of the somatosensory-evoked potentials in the low as compared to the high muscle tension condition. The high risk group showed a trend toward higher N150 amplitudes in the low as compared to the high tension condition. The results of this study partially support the hypothesis that increases in muscle tension might serve as a pain-reducing mechanism in chronic pain patients and those at risk for chronicity, thus leading to a vicious pain-tension cycle.
Adult↗
Reorganization of auditory cortex in tinnitus.
Magnetic source imaging was used to determine whether tonotopy in auditory cortex of individuals with tinnitus diverges from normative functional organization. Ten tinnitus subjects and 15 healthy controls were exposed to four sets of tones while magnetoencephalographic recordings were obtained from the two cortical hemispheres in sequence. A marked shift of the cortical representation of the tinnitus frequency into an area adjacent to the expected tonotopic location was observed. The Euclidean distance of the tinnitus frequency from the trajectory of the tonotopic map was 5.3 mm (SD = 3.1) compared with a distance of 2.5 mm (SD = 1.3) of a corresponding frequency in the healthy controls (t = 3.13, P < 0.01). In addition, a strong positive correlation was found between the subjective strength of the tinnitus and the amount of cortical reorganization (r = 0.82, P < 0.01). These results demonstrate that tinnitus is related to plastic alterations in auditory cortex. Similarities between these data and the previous demonstrations that phantom limb pain is highly correlated with cortical reorganization suggest that tinnitus may be an auditory phantom phenomenon.
Acoustic Stimulation↗
fMRI reveals amygdala activation to human faces in social phobics.
Functional magnetic resonance imaging was used to determine the activation of the amygdala while seven social phobics and five healthy controls were exposed to slides of neutral faces as well as aversive odor stimuli. The amygdala was selectively activated in the social phobics during presentation of the face stimuli. The data show for the first time that the amygdala is active in human phobics when they are exposed to potentially fear-relevant stimuli. Further research is needed to determine the extent to which overactivation of the amygdala precedes or is a consequence of phobia.
Adult↗
Cortical reorganization and phantom phenomena in congenital and traumatic upper-extremity amputees.
The relationship between phantom limb phenomena and cortical reorganization was examined in five subjects with congenital absence of an upper limb and nine traumatic amputees. Neuromagnetic source imaging revealed minimal reorganization of primary somatosensory cortex in the congenital amputees (M=0.69 cm, SD 0.24) and the traumatic amputees without phantom limb pain (M=0.27 cm, SD 0.25); the amputees with phantom limb pain showed massive cortical reorganization (M=2.22 cm, SD 0.78). Phantom limb pain and nonpainful phantom limb phenomena were absent in the congenital amputees. Whereas phantom limb pain was positively related to cortical reorganization (r=0.87), nonpainful phantom phenomena were not significantly correlated with cortical reorganization (r=0.34). Sensory discrimination was normal and mislocalization (referral of stimulation-induced sensation to a phantom limb) was absent in the congenital amputees. The role of peripheral and central factors in the understanding of phantom limb pain and phantom limb phenomena is discussed in view of these findings.
Adult↗
The cortical somatotopic map and phantom phenomena in subjects with congenital limb atrophy and traumatic amputees with phantom limb pain.
The extent of the cortical somatotopic map and its relationship to phantom phenomena was tested in five subjects with congenital absence of an upper limb, four traumatic amputees with phantom limb pain and five healthy controls. Cortical maps of the first and fifth digit of the intact hand, the lower lip and the first toe (bilaterally) were obtained using neuroelectric source imaging. The subjects with congenital upper limb atrophy showed symmetric positions of the left and right side of the lower lip and the first toe, whereas the traumatic amputees with pain showed a significant shift (about 2.4 cm) of the cortical representation of the lower lip towards the hand region contralateral to the amputation side but no shift for the toe representation. In healthy controls, no significant hemispheric differences between the cortical representation of the digits, lower lip or first toe were found. Phantom phenomena were absent in the congenital but extensive in the traumatic amputees. These data confirm the assumption that congenital absence of a limb does not lead to cortical reorganization or phantom limbs whereas traumatic amputations that are accompanied by phantom limb pain show shifts of the cortical areas adjacent to the amputation zone towards the representation of the deafferented body part.
Adult↗
Plasticity of plasticity? Changes in the pattern of perceptual correlates of reorganization after amputation.
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 mislocalization. On follow-up examination for mislocalization 4 weeks later, a close correlation had remained between the original amount of cortical representational reorganization of the amputation zone (at the first examination) and the number of sites from where painful stimuli evoked sensations referred to the phantom limb, i.e. the amount of perceptual mislocalization, at the second examination. However, contrary to our expectation, the topography of referred sensation had completely changed in every patient. These results suggest that while the overall extent of reorganization is a rather stable phenomenon, the concomitant changes in the pattern of sensory processing are not. This may be due to the fact that alterations of sensory processing are not hardwired, but are rather mediated by an extensive and interconnected neural network with fluctuating synaptic strengths. This mechanism may be of importance for neurological rehabilitation.
Accidents↗
Effects of regional anesthesia on phantom limb pain are mirrored in changes in cortical reorganization.
The causes underlying phantom limb pain are still unknown. Recent studies on the consequences of nervous system damage in animals and humans reported substantial reorganization of primary somatosensory cortex subsequent to amputation, and one study showed that cortical reorganization is positively correlated with phantom limb pain. This paper examined the hypothesis of a functional relationship between cortical reorganization and phantom limb pain. Neuroelectric source imaging was used to determine changes in cortical reorganization in somatosensory cortex after anesthesia of an amputation stump produced by brachial plexus blockade in six phantom limb pain patients and four pain-free amputees. Three of six phantom limb subjects experienced a virtual elimination of current phantom pain attributable to anesthesia (mean change: 3.8 on an 11-point scale; Z = -1.83; p < 0.05) that was mirrored by a very rapid elimination of cortical reorganization in somatosensory cortex (change = 19.8 mm; t(2) = 5.60; p < 0.05). Cortical reorganization remained unchanged (mean change = 1.6 mm) in three phantom limb pain amputees whose pain was not reduced by brachial plexus blockade and in the phantom pain-free amputation controls. These findings suggest that cortical reorganization and phantom limb pain might have a causal relationship. Methods designed to alter cortical reorganization should be examined for their efficacy in the treatment of phantom limb pain.
Adult↗
Enhanced dimensional complexity of the EEG during memory for personal pain in chronic pain patients.
Associative connections between cortical cell assemblies representing pain-related memories should be stronger and more extensive in subjects with chronic pain. To test this hypothesis, the dimensional complexity of the electroencephalograph (EEG) was examined during the actual experience as well as during memory for pain. Nine chronic pain patients and nine matched healthy controls participated in the study. During acute pain induction, acute pain recall, personal stress and pain recall, the EEG was recorded from 15 scalp sites. Non-linear analysis, based on the theory of deterministic chaos, revealed higher and more widespread EEG complexity in the patients compared to the healthy controls only during the recall of the personal pain scene. The personal stress scene was rated equally aversive but did not induce more EEG complexity. These more extensive and more readily accessible pain memories may be instrumental for the persistence of chronic pain.
Adult↗
Extensive reorganization of primary somatosensory cortex in chronic back pain patients.
The hypothesis of reorganization of the primary somatosensory cortex in states of chronic pain was assessed in 10 low back pain patients and nine matched healthy controls. Intracutaneous electric stimuli were applied to the left back and index finger at a standard, a non-painful and a painful intensity. Magnetic fields were recorded by a 37-channel BTi biomagnetometer from the hemisphere contralateral to the site of stimulation. The power of the early evoked magnetic field (< 100 ms) elicited by painful stimulation of the painful back in very chronic patients was elevated relative to that elicited by painful back stimulation of healthy controls and showed a linear increase with chronicity (r = 0.74). The maximum activity elicited in primary somatosensory cortex was shifted more medially in the very chronic back pain subjects. These data suggest that chronic pain is accompanied by cortical reorganization and may serve an important function in the persistence of the pain experience.
Adult↗
Input-increase and input-decrease types of cortical reorganization after upper extremity amputation in humans.
A plastic remodeling of regions in somatosensory cortex has previously been observed to occur in separate experimental paradigms in response to loss of somatosensory input and to increase in input. In this study, both types of cortical reorganization have been observed to occur concurrently in the same adult human nervous system as a result of a single intervention. Following upper extremity amputation, magnetic source imaging revealed that tactile stimulation of the lip evoked responses not only in the area of the somatosensory cortex corresponding to the face, but also within the cortical region that would normally correspond to the now absent hand. This "invasion" of the cortical amputation zone was accompanied by a significant increase in the size of the representation of the digits of the intact hand, presumably as a result of an increased importance of sensory stimulation consequent to increased dependence on that hand imposed by the loss of the contralateral extremity.
Adolescent↗
The Arm Motor Ability Test: reliability, validity, and sensitivity to change of an instrument for assessing disabilities in activities of daily living.
OBJECTIVE: To continue and expand determination of the reliability, validity, and sensitivity to change of the Arm Motor Ability Test (AMAT), an instrument for assessing deficits in activities of daily living (ADL). DESIGN: The AMAT was administered twice to patients, with an interest interval of either 1 or 2 weeks, by one of two examiners assigned to patients in counterbalanced order. Patients' interest intervals and scores on the arm portion of the Motricity Index was unknown to the raters. SETTING: A referral inpatient neurological rehabilitation center. PATIENTS: Thirty-three subacute stroke inpatients with moderate to mild upper extremity motor deficit: median Motricity-Index-Arm score = 89, median chronicity = 43d, median age = 66yr; 12 were women. MAIN OUTCOME MEASURE AND RESULTS: The AMAT was developed in 1987, and interrater reliabilities at that time were found to range from .95 to .99. The present values for interrater reliability (2 scales) from videotaped test performance were: kappas = .68 to .77. Spearman correlations = .97 to .99. For performance time, interscorer reliability from videotaped test performance was .99. Homogeneities for the three AMAT measures for the total sample (Cronbach's alpha and split-half reliability) were .93 to .99. The test-retest reliabilities for the total sample were .93 to .99. The correlations to the Motricity-Index-Arm score were .45 to .61. The AMAT detected the difference in change occurring as a result of the passage of 1 versus 2 weeks in these subacute inpatients, presumably as a result of intensive therapy and/or spontaneous recovery, confirming the results of an earlier intervention study. CONCLUSION: The AMAT is an instrument with high interrater reliability, internal consistency, and sensitivity to change, as well as having satisfactory concurrent validity.
Activities of Daily Living↗
The relationship of phantom limb pain to other phantom limb phenomena in upper extremity amputees.
In thirty-two unilateral upper extremity amputees with and without phantom limb pain, various phantom limb phenomena were investigated. In general, the incidence of non-painful phantom limb sensations was higher in patients with phantom limb pain than in pain-free amputees. Kinesthetic and kinetic phantom limb sensations were reported more frequently than exteroceptive cutaneous sensations. There was a significant positive correlation between phantom limb pain and stump pain. Patients more frequently assigned sensory than affective pain qualities to their phantom limb pain, whereas no differences between pain qualities were observed for stump pain. No support was found for a relationship between the presence of telescoping (i.e., shrinkage of the phantom limb) and phantom limb pain. These findings point to central as well as to peripheral factors contributing to phantom limb pain.
Adult↗
Behavioral and neurophysiological evidence for altered processing of anxiety-related words in panic disorder.
Body-related and nonsomatic words were presented tachistoscopically to 15 panic patients and 15 healthy controls at each participant's threshold for correctly identifying 50% of neutral words. Behavioral (proportion of words correctly recognized) and electrocortical (event-related brain potentials [ERPs]) measures were registered. Panic patients recognized more body-related than nonsomatic words, and body-related as compared with nonsomatic words elicited, in these patients, significantly larger P300 amplitudes and enhanced positive slow waves (600 to 800 ms after stimulus presentation). In healthy controls, the number of correct recognized words and the ERPs were not differentially affected by the 2 word types. These results are grossly consistent with cognitive models of panic disorders, assuming that certain bodily sensation are perceived and processed in an affective manner that differentiates panic patients from healthy controls.
Adult↗
Biofeedback treatment for pediatric migraine: prediction of treatment outcome.
Despite a growing number of studies showing good effectiveness of nonpharmacological treatments such as thermal biofeedback (TBF) for pediatric migraine, little is known about psychosocial variables that might be predictive of treatment outcome. The identification of predictors appears especially important when children are treated in a home-based treatment format that tends to be somewhat less effective than a therapist-administered treatment. A total of 32 children between the ages 8 and 16 years completed a home-based TBF treatment program with treatment outcome being of similar magnitude as previously reported in the literature. Multiple regression analysis revealed externalizing behavior tendencies, initial level of psychosomatic complaints, and the child's age to be highly predictive of outcome, whereas dimensions of family functioning failed to exert a direct influence. The implications of these findings for the development and evaluation of future treatment programs are discussed.
Adolescent↗