Kozo Ueta

Negative body image associated with changes in the visual body appearance increases pain perception.

Changing the visual body appearance by use of as virtual reality system, funny mirror, or binocular glasses has been reported to be helpful in rehabilitation of pain. However, there are interindividual differences in the analgesic effect of changing the visual body image. We hypothesized that a negative body image associated with changing the visual body appearance causes interindividual differences in the analgesic effect although the relationship between the visual body appearance and analgesic effect has not been clarified. We investigated whether a negative body image associated with changes in the visual body appearance increased pain. Twenty-five healthy individuals participated in this study. To evoke a negative body image, we applied the method of rubber hand illusion. We created an “injured rubber hand” to evoke unpleasantness associated with pain, a “hairy rubber hand” to evoke unpleasantness associated with embarrassment, and a “twisted rubber hand” to evoke unpleasantness associated with deviation from the concept of normality. We also created a “normal rubber hand” as a control. The pain threshold was measured while the participant observed the rubber hand using a device that measured pain caused by thermal stimuli. Body ownership experiences were elicited by observation of the injured rubber hand and hairy rubber hand as well as the normal rubber hand. Participants felt more unpleasantness by observing the injured rubber hand and hairy rubber hand than the normal rubber hand and twisted rubber hand (p<0.001). The pain threshold was lower under the injured rubber hand condition than with the other conditions (p<0.001). We conclude that a negative body appearance associated with pain can increase pain sensitivity.

Factors associated with the modulation of pain by visual distortion of body size

Modulation of pain using visual distortion of body size (VDBS) has been the subject of various reports. However, the mechanism underlying the effect of VDBS on pain has been less often studied. In the present study, factors associated with modulation of pain threshold by VDBS were investigated. Visual feedback in the form of a magnified image of the hand was provided to 44 healthy adults to examine changes in pain. In participants with a higher pain threshold when visual feedback of a magnified image of the hand was provided, the two-point discrimination threshold decreased. In contrast, participants with a lower pain threshold with visual feedback of a magnified image of the hand experienced unpleasant emotions toward the magnified image of the hand. Interestingly, this emotional reaction was strongly associated with negative body consciousness in several subjects. These data suggested an analgesic effect of visual feedback in the form of a magnified image of the hand is only when tactile perception is vivid and the emotional reaction toward the magnified image is moderate. The results also suggested that negative body consciousness is important for the modulation of pain using VDBS.

Changes in electroencephalographic activity during observation, preparation, and execution of a motor learning task

This study aimed to compare electroencephalographic (EEG) activity between high- and low-motor learning groups (n = 10 each) during observation of, preparation for, and execution of a motor learning task. The subjects performed a ball rotation task in which two balls were rotated clockwise with the right hand. Each trial started with a rest period (5 s), subjects then observed the task action on a computer screen (30 s), this was followed by another rest (5 s), preparation for performing the action (5 s), and finally action execution (30 s); five trials were performed. The number of rotations during execution and EEG activities during observation, preparation, and execution were recorded. The EEG data of the high-motor learning group were compared with those of the low-motor learning group and were analyzed using exact low-resolution electromagnetic tomography (eLORETA). The left sensorimotor and parietal areas of the high-motor learning group showed a greater decrease in the alpha-2 (10.5–12.0 Hz) and beta-2 (18.5–21.0 Hz) rhythms than those of the low-motor learning group during all three phases of the trials. The study results suggest that the decreases in the alpha-2 and beta-2 rhythms in these areas during observation, preparation, and execution are associated with motor skill improvement.

Brain Activity during the Observation, Imagery, and Execution of Tool Use: An fNIRS/EEG Study

This study used a functional near-infrared spectroscopy (fNIRS)/electroencephalogram (EEG) system to investigate brain activity during a daily living situation where subjects are engaged in the observation, imagery, and execution of tool use. The subjects were 24 healthy adults who signed an agreement to participate in the present study. All subjects were right-handed according to the Edinburgh Handedness Inventory. The subjects sat on a chair and participated in the observation, imagery, and execution of chopstick and hammer movements. Each trial consisted of observation, imagery, and execution and the trials were performed in triplicate. The timing protocol was 15.0, 15.0, 15.0, 15.0, and 15.0 s for rest, task, rest, task, and rest, respectively, and brain activity was measured during these periods. fNIRS and EEG were used to measure brain activity. Optical fibers of fNIRS were positioned over the frontoparietal area. Oxyhemoglobin served as a parameter, and NIRS-statistical parametric mapping (SPM) was used for data analysis. EEG measurements were made using 32 electrodes with an international 10–20 system. The event-related desynchronization of the Mu frequency band (8-12 Hz) was calculated by power spectrum analysis. The brain regions activated during the imagery and execution of the chopsticks movement were the dorsolateral prefrontal cortex, inferior frontal gyrus, premotor cortex, and primary somatosensory cortex, while the mu ERD values were obtained under both conditions. The brain regions that were mainly activated under all three conditions of the hammer movement, i.e., observation, imagery, and execution, were the dorsolateral prefrontal cortex, inferior frontal gyrus, and premotor cortex, while the mu ERD values were obtained under all three conditions. These results suggest that brain activity during the observation, imagery, and execution of tool use differed according to the sensory modality linked to a tool.

Effects of Voluntary and Automatic Control of Center of Pressure Sway During Quiet Standing

ABSTRACT The authors investigated the effects of voluntary and automatic control on the spatial variables (envelope area, maximal amplitude, and root mean square [RMS]) of center of pressure (COP) displacement during quiet standing and identified differences in their postural control strategies (mean velocity [MV], mean power frequency [MPF], and power density). COP data were recorded under relaxed (experimental control), still (voluntary control), and dual (automatic control) conditions. RMS was significantly lower in the still and dual conditions than in the relaxed condition. MV, MPF, and power density were significantly higher in the still condition than in the dual condition. These results indicate that both voluntary and automatic control decrease the spatial variables of COP displacement; however, their postural control strategies are different.

Tactile localization training for pain, sensory disturbance, and distorted body image: a case study of complex regional pain syndrome

This report presents a case of complex regional pain syndrome. The patient presented with severe pain, sensory disturbance, and distorted body image at the site of initial injury and other body sites. Tactile localization training (TLT) at only the site of initial injury decreased severe pain at the site of initial injury and the secondary affected sites, whereas TLT at secondary affected sites had no effect. These results highlighted the importance of assessing changes in patients’ pain processes to determine the part of the body where TLT should be applied.

Effect of a plantar perceptual learning task on walking stability in the elderly: a randomized controlled trial

Objective: To determine whether the plantar perceptual learning task, using a hardness discrimination training, efficiently improves walking stability in the elderly. Design: A randomized controlled trial. Setting: Elder day-care center. Participants: Eighty-six elderly people (73.84 SD 5.98 years) who went to an elder day-care center were randomly assigned evenly to either an intervention or a control group. Intervention: The intervention group performed a task to discriminate hardness differences while standing on sponge mats of different levels of hardness. The control group underwent the same task except that they were not instructed to discriminate hardness levels of the mats. The tasks were carried out over a four-week period for 10 days for both groups. Outcome measures: Outcome was assessed by determining root mean squares of trunk acceleration during walking. Results: Plantar perception was significantly improved in the intervention group after training (F = 26.24, p < 0.01). In addition, changes in root mean square values of acceleration were significantly greater after training in the intervention group (medial–lateral, 0.36 SD 0.26; vertical, 0.32 SD 0.24; anterio–posterior, 0.26 SD 0.24) than in the control group (medial–lateral, 0.14 SD 0.28, vertical, 0.16 SD 0.35, anterio–posterior, 0.12 SD 0.29) (p < 0.05). Changes in walking speed were not significantly different (p = 0.13) between the intervention (0.06 SD 0.13) and control groups (0.02 SD 0.14). Conclusion: The plantar perceptual learning task might efficiently stabilize postural control during walking in the elderly.

Effects of vestibular rehabilitation on gait performance in poststroke patients: a pilot randomized controlled trial

The effects of vestibular rehabilitation on poststroke patients are unknown. This study aimed to investigate whether or not vestibular rehabilitation would improve both the vestibulo–ocular reflex and gait performance of patients with poststroke hemiparesis. Twenty-eight patients with stroke were assigned randomly to either an experimental group (N=14) or a control group (N=14). The experimental group performed the conventional physical therapy for 40 min and vestibular rehabilitation for 20 min, as a 60 min session, during the first 3 weeks and then completed only the conventional intervention for 60 min for the following 3 weeks. The control group performed only the 60 min conventional physical therapy for 6 weeks. Both groups were measured using the gaze stabilization test, the 10 m walking test, the timed up and go test, and the dynamic gait index. Patients were assessed at baseline, and at 3 and 6 weeks. Although the control group showed no significant difference in any outcome measures, the experimental group showed an improvement in gaze stabilization test scoring, which increased significantly after 3 weeks compared with the baseline (P=0.030). The dynamic gait index was also significantly increased after 3 and 6 weeks compared with the baseline (P=0.049 and 0.024, respectively). This study indicated that vestibular rehabilitation might improve poststroke patients’ vestibulo–ocular reflex. Moreover, patients might show improved gait performance at least up to 3 weeks after the vestibular intervention by the sensory reweight to coordinate vestibular input.

Poor gait performance is influenced with decreased vestibulo-ocular reflex in poststroke patients

The vestibulo-ocular reflex (VOR) exerts a significant influence on gait performance. Therefore, a decrease in VOR function could worsen gait impairments in patients with poststroke hemiparesis. The effects of decreased VOR function on gait performance could be further exacerbated by aging-related physical weakness and impaired motor function of the hemiparetic lower limb. The aim of our study was to evaluate the possible synergistic effect of aging and impairment in lower extremity function and the VOR on walking ability of poststroke hemiplegic patients. The VOR was evaluated, using the gaze-stabilization test (GST), in 75 patients with a poststroke hemiplegia. Lower extremity function was assessed using the Fugl-Meyer assessment (FMA-LE). Gait performance was evaluated using the 10-m walking test, the timed up-and-go, and the dynamic gait index (DGI). The relationships between gait performance and age, FMA-LE and GST, as well as whether age, FMA-LE, and/or GST were significant predictors of gait performance were evaluated. The 10-m walking test, timed up-and-go and DGI were significantly correlated to the FMA-LE and GST (P<0.05). On stepwise multiple regression analysis, the GST remained a significant predictor of the DGI (P<0.001). The present study indicates that decreased VOR function after stroke contributes to impairments in gait both in simple and in dual-task walking tests.

Early Intervention with a Tactile Discrimination Task for Phantom Limb Pain Related to Superficial Pain

[Purpose] We report the outcome of an early intervention with a tactile discrimination task for 2 patients with phantom limb pain related to superficial pain, after qualitative assessment. [Subjects] Two patients who experienced phantom limb pain related to superficial pain after amputation for diabetic gangrene. [Method] The 2 patients were asked to discriminate the region of tactile sensation when a cushion was held to the amputation stump. [Results] At the beginning of the discrimination task, the patients could not discriminate the region of tactile sensation accurately. However, after the discrimination task, the subjects could discriminate the region of tactile sensation, and the phantom limb pain improved. [Conclusion] This result shows the importance of an immediate decision regarding intervention, after the qualitative assessment of phantom limb pain.